1
|
Ocheltree TW, Gleason SM. Grass veins are leaky pipes: vessel widening in grass leaves explain variation in stomatal conductance and vessel diameter among species. THE NEW PHYTOLOGIST 2024; 241:243-252. [PMID: 37964665 DOI: 10.1111/nph.19368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Accepted: 09/26/2023] [Indexed: 11/16/2023]
Abstract
The widening of xylem vessels from tip to base of trees is an adaptation to minimize the hydraulic resistance of a long pathway. Given that parallel veins of monocot leaves do not branch hierarchically, vessels should also widen basipetally but, in addition to minimizing resistance, should also account for water volume lost to transpiration since they supply water to the lamina along their lengths, that is 'leakiness'. We measured photosynthesis, stomatal conductance, and vessel diameter at five locations along each leaf of five perennial grass species. We found that the rate of conduit widening in grass leaves was larger than the widening exponent required to minimize pathlength resistance (0.35 vs c. 0.22). Furthermore, variation in the widening exponent among species was positively correlated with maximal stomatal conductance (r2 = 0.20) and net CO2 assimilation (r2 = 0.45). These results suggest that faster rates of conduit widening (> 0.22) were associated with higher rates of water loss. Taken together, our results show that the widening exponent is linked to plant function in grass leaves and that natural selection has favored parallel vein networks that are constructed to meet transpiration requirements while minimizing hydraulic resistance within grass blades.
Collapse
Affiliation(s)
- Troy W Ocheltree
- Department of Forest and Rangeland Stewardship, Colorado State University, Fort Collins, CO, 80523, USA
| | - Sean M Gleason
- Water Management and Systems Research Unit, United States Department of Agriculture, Agricultural Research Service, Fort Collins, CO, 80526, USA
| |
Collapse
|
2
|
Gao C, Marker SJV, Gundlach C, Poulsen HF, Bohr T, Schulz A. Tracing the opposing assimilate and nutrient flows in live conifer needles. JOURNAL OF EXPERIMENTAL BOTANY 2023; 74:6677-6691. [PMID: 37668473 DOI: 10.1093/jxb/erad334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Accepted: 08/28/2023] [Indexed: 09/06/2023]
Abstract
The vasculature along conifer needles is fundamentally different from that in angiosperm leaves as it contains a unique transfusion tissue inside the bundle sheath. In this study, we used specific tracers to identify the pathway of photoassimilates from mesophyll to phloem, and the opposing pathway of nutrients from xylem to mesophyll. For symplasmic transport we applied esculin to the tip of attached pine needles and followed its movement down the phloem. For apoplasmic transport we let detached needles take up a membrane-impermeable contrast agent and used micro-X-ray computed tomography to map critical water exchange interfaces and domain borders. Microscopy and segmentation of the X-ray data enabled us to render and quantify the functional 3D structure of the water-filled apoplasm and the complementary symplasmic domain. The transfusion tracheid system formed a sponge-like apoplasmic domain that was blocked at the bundle sheath. Transfusion parenchyma cell chains bridged this domain as tortuous symplasmic pathways with strong local anisotropy which, as evidenced by the accumulation of esculin, pointed to the phloem flanks as the preferred phloem-loading path. Simple estimates supported a pivotal role of the bundle sheath, showing that a bidirectional movement of nutrient ions and assimilates is feasible and emphasizing the role of the bundle sheath in nutrient and assimilate exchange.
Collapse
Affiliation(s)
- Chen Gao
- Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark
| | - Sean J V Marker
- Department of Physics, Technical University of Denmark. Fysikvej, 2800 Kgs. Lyngby, Denmark
| | - Carsten Gundlach
- Department of Physics, Technical University of Denmark. Fysikvej, 2800 Kgs. Lyngby, Denmark
| | - Henning F Poulsen
- Department of Physics, Technical University of Denmark. Fysikvej, 2800 Kgs. Lyngby, Denmark
| | - Tomas Bohr
- Department of Physics, Technical University of Denmark. Fysikvej, 2800 Kgs. Lyngby, Denmark
| | - Alexander Schulz
- Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark
| |
Collapse
|
3
|
Boudina M, Elfring GJ. Capillary Imbibition in a Diverging Flexible Channel. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:12174-12181. [PMID: 37594738 DOI: 10.1021/acs.langmuir.3c01488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/19/2023]
Abstract
We study the imbibition of a wetting liquid between flexible sheets that are fixed at both ends. Assuming a narrow gap between the sheets, we solve the lubrication equation coupled with a slender body deformation. When the sheets are parallel, we find that the deformation initially speeds up the flow, as shown in previous studies, but only up to the middle of the channel. As the channel contracts, the hydrodynamic resistance increases and ultimately slows down the filling process. Below a threshold stiffness, the channel collapses and imbibition stops. We propose a scaling of the filling duration near this threshold. Next, we show that if the sheets are initially tilted with a minimal angle, the channel avoids collapse. The liquid front pulls the diverging sheets and spreads in a nearly parallel portion, which maintains the capillary propulsion and enhances the wicking. Therefore, while it is established that diverging rigid plates imbibe liquids slower than parallel ones do, we show that elasticity reverses this principle: diverging flexible sheets imbibe liquids faster than parallel ones. We find an optimal tilt angle that gives the shortest filling time.
Collapse
Affiliation(s)
- Mouad Boudina
- Department of Mechanical Engineering, University of British Columbia, Vancouver V6T 1Z4, British Columbia, Canada
| | - Gwynn J Elfring
- Department of Mechanical Engineering, University of British Columbia, Vancouver V6T 1Z4, British Columbia, Canada
| |
Collapse
|
4
|
Liesche J, Vincent C, Han X, Zwieniecki M, Schulz A, Gao C, Bravard R, Marker S, Bohr T. The mechanism of sugar export from long conifer needles. THE NEW PHYTOLOGIST 2021; 230:1911-1924. [PMID: 33638181 DOI: 10.1111/nph.17302] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 02/17/2021] [Indexed: 06/12/2023]
Abstract
The green leaves of plants are optimised for carbon fixation and the production of sugars, which are used as central units of carbon and energy throughout the plant. However, there are physical limits to this optimisation that remain insufficiently understood. Here, quantitative anatomical analysis combined with mathematical modelling and sugar transport rate measurements were used to determine how effectively sugars are exported from the needle-shaped leaves of conifers in relation to leaf length. Mathematical modelling indicated that phloem anatomy constrains sugar export in long needles. However, we identified two mechanisms by which this constraint is overcome, even in needles longer than 20 cm: (1) the grouping of transport conduits, and (2) a shift in the diurnal rhythm of sugar metabolism and export in needle tips. The efficiency of sugar transport in the phloem can have a significant influence on leaf function. The constraints on sugar export described here for conifer needles are likely to also be relevant in other groups of plants, such as grasses and angiosperm trees.
Collapse
Affiliation(s)
- Johannes Liesche
- College of Life Sciences & Biomass Energy Center for Arid and Semi-arid Lands, Northwest A&F University, Taicheng Road 3, Yangling, 712100, China
- Cluster of Excellence on Plant Sciences (CEPLAS), Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, Düsseldorf, 40225, Germany
| | - Christopher Vincent
- Department of Horticultural Sciences, University of Florida, 700 Experiment Station Road, Lake Alfred, FL, 33850, USA
| | - Xiaoyu Han
- College of Life Sciences & Biomass Energy Center for Arid and Semi-arid Lands, Northwest A&F University, Taicheng Road 3, Yangling, 712100, China
| | - Maciej Zwieniecki
- Department of Plant Sciences, University of California, Davis One Shields Avenue, Davis, CA, 95616, USA
| | - Alexander Schulz
- Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg, 1871, Denmark
| | - Chen Gao
- Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg, 1871, Denmark
| | - Rodrigue Bravard
- Department of Physics, Technical University of Denmark, Kgs. Lyngby, DK-2800, Denmark
| | - Sean Marker
- Department of Physics, Technical University of Denmark, Kgs. Lyngby, DK-2800, Denmark
| | - Tomas Bohr
- Department of Physics, Technical University of Denmark, Kgs. Lyngby, DK-2800, Denmark
| |
Collapse
|
5
|
Sakurai G, Miklavcic SJ. On the Efficacy of Water Transport in Leaves. A Coupled Xylem-Phloem Model of Water and Solute Transport. FRONTIERS IN PLANT SCIENCE 2021; 12:615457. [PMID: 33613602 PMCID: PMC7889512 DOI: 10.3389/fpls.2021.615457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 01/05/2020] [Indexed: 06/12/2023]
Abstract
In this paper, we present and use a coupled xylem/phloem mathematical model of passive water and solute transport through a reticulated vascular system of an angiosperm leaf. We evaluate the effect of leaf width-to-length proportion and orientation of second-order veins on the indexes of water transport into the leaves and sucrose transport from the leaves. We found that the most important factor affecting the steady-state pattern of hydraulic pressure distribution in the xylem and solute concentration in the phloem was leaf shape: narrower/longer leaves are less efficient in convecting xylem water and phloem solutes than wider/shorter leaves under all conditions studied. The degree of efficiency of transport is greatly influenced by the orientation of second-order veins relative to the main vein for all leaf proportions considered; the dependence is non-monotonic with efficiency maximized when the angle is approximately 45° to the main vein, although the angle of peak efficiency depends on other conditions. The sensitivity of transport efficiency to vein orientation increases with increasing vein conductivity. The vein angle at which efficiency is maximum tended to be smaller (relative to the main vein direction) in narrower leaves. The results may help to explain, or at least contribute to our understanding of, the evolution of parallel vein systems in monocot leaves.
Collapse
Affiliation(s)
- Gen Sakurai
- Institute for Agro-Environmental Sciences, National Agriculture and Food Research Organization, Tsukuba, Japan
| | - Stanley J. Miklavcic
- Phenomics and Bioinformatics Research Centre, University of South Australia, Mawson Lakes, SA, Australia
| |
Collapse
|
6
|
Jung Y, Park K, Jensen KH, Kim W, Kim HY. A design principle of root length distribution of plants. J R Soc Interface 2019; 16:20190556. [PMID: 31795862 DOI: 10.1098/rsif.2019.0556] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Shaping a plant root into an ideal structure for water capture is increasingly important for sustainable agriculture in the era of global climate change. Although the current genetic engineering of crops favours deep-reaching roots, here we show that nature has apparently adopted a different strategy of shaping roots. We construct a mathematical model for optimal root length distribution by considering that plants seek maximal water uptake at the metabolic expenses of root growth. Our theory finds a logarithmic decrease of root length density with depth to be most beneficial for efficient water uptake, which is supported by biological data as well as our experiments using root-mimicking network systems. Our study provides a tool to gauge the relative performance of root networks in transgenic plants engineered to endure a water deficit. Moreover, we lay a fundamental framework for mechanical understanding and design of water-absorptive growing networks, such as medical and industrial fluid transport systems and soft robots, which grow in porous media including soils and biotissues.
Collapse
Affiliation(s)
- Yeonsu Jung
- Department of Mechanical and Aerospace Engineering, Seoul National University, Seoul 08826, Korea
| | - Keunhwan Park
- Department of Physics, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Kaare H Jensen
- Department of Physics, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Wonjung Kim
- Department of Mechanical Engineering, Sogang University, Seoul 04107, Korea
| | - Ho-Young Kim
- Department of Mechanical and Aerospace Engineering, Seoul National University, Seoul 08826, Korea
| |
Collapse
|
7
|
Boyce CK, Zwieniecki MA. The prospects for constraining productivity through time with the whole-plant physiology of fossils. THE NEW PHYTOLOGIST 2019; 223:40-49. [PMID: 30304562 DOI: 10.1111/nph.15446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Accepted: 02/26/2018] [Indexed: 06/08/2023]
Abstract
Anatomically preserved fossils allow estimation of hydraulic parameters, potentially providing constraints on interpreting whole-plant physiology. However, different organ systems have typically been considered in isolation - a problem given common mismatches of high and low conductance components coupled in the hydraulic path of the same plant. A recent paper addressed the issue of how to handle resistance mismatches in fossil plant hydraulics, focusing on Carboniferous medullosan seed plants and arborescent lycopsids. Among other problems, however, a fundamental error was made: the transpiration stream consists of resistances in series (where resistances are additive and the component with the largest resistance can dominate the behavior of the system), but emphasis was instead placed on the lowest resistance, effectively treating the system as resistances in parallel (where the component with the smallest resistance will dominate the behavior). Instead of possessing high assimilation capacities to match high specific stem conductances, it is argued here that individual high conductance components in these Paleozoic plants are nonetheless associated with low whole-plant productivity, just as can be commonly seen in living plants. Resolution of how to handle these issues may have broad implications for the Earth system including geobiological feedbacks to rock weathering, atmospheric composition, and climate.
Collapse
Affiliation(s)
- C Kevin Boyce
- Geological Sciences, Stanford University, Stanford, CA, 94305, USA
| | | |
Collapse
|
8
|
Wang N, Palmroth S, Maier CA, Domec JC, Oren R. Anatomical changes with needle length are correlated with leaf structural and physiological traits across five Pinus species. PLANT, CELL & ENVIRONMENT 2019; 42:1690-1704. [PMID: 30684950 DOI: 10.1111/pce.13516] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Revised: 12/22/2018] [Accepted: 12/27/2018] [Indexed: 06/09/2023]
Abstract
The genus Pinus has wide geographical range and includes species that are the most economically valued among forest trees worldwide. Pine needle length varies greatly among species, but the effects of needle length on anatomy, function, and coordination and trade-offs among traits are poorly understood. We examined variation in leaf morphological, anatomical, mechanical, chemical, and physiological characteristics among five southern pine species: Pinus echinata, Pinus elliottii, Pinus palustris, Pinus taeda, and Pinus virginiana. We found that increasing needle length contributed to a trade-off between the relative fractions of support versus photosynthetic tissue (mesophyll) across species. From the shortest (7 cm) to the longest (36 cm) needles, mechanical tissue fraction increased by 50%, whereas needle dry density decreased by 21%, revealing multiple adjustments to a greater need for mechanical support in longer needles. We also found a fourfold increase in leaf hydraulic conductance over the range of needle length across species, associated with weaker upward trends in stomatal conductance and photosynthetic capacity. Our results suggest that the leaf size strongly influences their anatomical traits, which, in turn, are reflected in leaf mechanical support and physiological capacity.
Collapse
Affiliation(s)
- Na Wang
- School of Forestry, Northeast Forestry University, Harbin, 150040, China
- Nicholas School of the Environment, Duke University, Durham, NC, 27708, USA
| | - Sari Palmroth
- Nicholas School of the Environment, Duke University, Durham, NC, 27708, USA
| | | | - Jean-Christophe Domec
- Nicholas School of the Environment, Duke University, Durham, NC, 27708, USA
- Bordeaux Sciences Agro, UMR 1391 INRA-ISPA, 33175 Gradignan Cedex, France
| | - Ram Oren
- Nicholas School of the Environment, Duke University, Durham, NC, 27708, USA
- Department of Forest Sciences, University of Helsinki, Helsinki, Finland
| |
Collapse
|
9
|
Jubery TZ, Ganapathysubramanian B, Gilbert ME, Attinger D. In silico design of crop ideotypes under a wide range of water availability. Food Energy Secur 2019. [DOI: 10.1002/fes3.167] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
| | - Baskar Ganapathysubramanian
- Department of Mechanical Engineering
- Department of Electrical and Computer Engineering Iowa State University Ames Iowa
| | | | | |
Collapse
|
10
|
Jankowski A, Wyka TP, Żytkowiak R, Danusevičius D, Oleksyn J. Does climate-related in situ variability of Scots pine (Pinus sylvestris L.) needles have a genetic basis? Evidence from common garden experiments. TREE PHYSIOLOGY 2019; 39:573-589. [PMID: 30715504 DOI: 10.1093/treephys/tpy145] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 11/28/2018] [Accepted: 12/17/2018] [Indexed: 06/09/2023]
Abstract
The correlations of phenotypic traits with environmental drivers suggest that variability of these traits is a result of natural selection, especially if such trait correlations are based on genetic variability. We hypothesized that in situ correlations of structural needle traits of Scots pine (Pinus sylvestris L) with minimal winter temperature (Tmin) reported previously from a temperate/boreal transect would be conserved when plants are cultivated under common conditions. We tested this hypothesis by analyzing needles from two common gardens located in the temperate zone, one including adult trees and the other juvenile seedlings. The majority of adult needle traits for which correlations with Tmin were found in the field turned out to be under environmental influence. In contrast, the majority of traits studied in juvenile needles were correlated with the original Tmin suggesting the role of past natural selection in shaping their variability. Juvenile needles thus appeared to be inherently less plastic than adult needles, perhaps reflecting the stronger selective pressure acting during juvenile, as compared with adult, ontogenetic stage. Genetically based cold-climate adaptation in either juvenile or adult needles, or both, involved an increase in leaf mass per area and leaf density, decrease in needle length, reduction in the amount of xylem and phloem, increase in thickness of epidermis, decrease in tracheid diameter and increase in tracheid density, and increase in diameter and volume fraction of resin ducts. We also show that at least some traits, such as transverse xylem and phloem areas and number of fibers, scale with needle length, suggesting that climate-related trait variation may also be mediated by changes in needle length. Moreover, slopes of these allometric relationships may themselves be plastically modified. The phenotypic syndrome typical of needles from cold environments may thus be under environmental, genetic and allometric control.
Collapse
Affiliation(s)
- Artur Jankowski
- General Botany Laboratory, Adam Mickiewicz University, Faculty of Biology, Institute of Experimental Biology, Umultowska 89, Poznań, Poland
- Polish Academy of Sciences, Institute of Dendrology, Parkowa 5, Kórnik, Poland
| | - Tomasz P Wyka
- General Botany Laboratory, Adam Mickiewicz University, Faculty of Biology, Institute of Experimental Biology, Umultowska 89, Poznań, Poland
| | - Roma Żytkowiak
- Polish Academy of Sciences, Institute of Dendrology, Parkowa 5, Kórnik, Poland
| | - Darius Danusevičius
- Aleksandras Stulginskis University, Faculty of Forest Science and Ecology, Studentų str. 11, Akademija, Kaunas reg., Lithuania
| | - Jacek Oleksyn
- Polish Academy of Sciences, Institute of Dendrology, Parkowa 5, Kórnik, Poland
- Department of Forest Resources, University of Minnesota, St Paul, MN, USA
| |
Collapse
|
11
|
Baresch A, Crifò C, Boyce CK. Competition for epidermal space in the evolution of leaves with high physiological rates. THE NEW PHYTOLOGIST 2019; 221:628-639. [PMID: 30216453 DOI: 10.1111/nph.15476] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Accepted: 08/27/2018] [Indexed: 06/08/2023]
Abstract
Leaves with high photosynthetic capacity require high transpiration capacity. Consequently, hydraulic conductance, stomatal conductance, and assimilation capacities should be positively correlated. These traits make independent demands on anatomical space, particularly due to the propensity for veins to have bundle sheath extensions that exclude stomata from the local epidermis. We measured density and area occupation of bundle sheath extensions, density and size of stomata and subsidiary cells, and venation density for a sample of extant angiosperms and fossil and living nonangiosperm tracheophytes. For most nonangiosperms, even modest increases in vein density and stomatal conductance would require substantial reconfigurations of anatomy. One characteristic of the angiosperm syndrome (e.g. small cell sizes, etc.) is hierarchical vein networks that allow expression of bundle sheath extensions in some, but not all veins, contrasting with all-or-nothing alternatives available with the single-order vein networks in most nonangiosperms. Bundle sheath modulation is associated with higher vein densities in three independent groups with hierarchical venation: angiosperms, Gnetum (gymnosperm) and Dipteris (fern). Anatomical and developmental constraints likely contribute to the stability in leaf characteristics - and ecophysiology - seen through time in different lineages and contribute to the uniqueness of angiosperms in achieving the highest vein densities, stomatal densities, and physiological rates.
Collapse
Affiliation(s)
- Andrés Baresch
- Department of Geological Sciences, Stanford University, Stanford, CA, 94305, USA
- Smithsonian Tropical Research Institute, Box 0843-03092, Balboa, Ancón, Republic of Panamá
| | - Camilla Crifò
- Smithsonian Tropical Research Institute, Box 0843-03092, Balboa, Ancón, Republic of Panamá
- Department of Biology, University of Washington, Seattle, WA, 98195, USA
| | - C Kevin Boyce
- Department of Geological Sciences, Stanford University, Stanford, CA, 94305, USA
| |
Collapse
|
12
|
Jankowski A, Wyka TP, Żytkowiak R, Nihlgård B, Reich PB, Oleksyn J. Cold adaptation drives variability in needle structure and anatomy in
P
inus sylvestris
L. along a 1,900 km temperate–boreal transect. Funct Ecol 2017. [DOI: 10.1111/1365-2435.12946] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Artur Jankowski
- General Botany LaboratoryFaculty of BiologyAdam Mickiewicz University Poznan Poland
- Institute of DendrologyPolish Academy of Sciences Kornik Poland
| | - Tomasz P. Wyka
- General Botany LaboratoryFaculty of BiologyAdam Mickiewicz University Poznan Poland
| | - Roma Żytkowiak
- Institute of DendrologyPolish Academy of Sciences Kornik Poland
| | | | - Peter B. Reich
- Hawkesbury Institute for the EnvironmentUniversity of Western Sydney Penrith NSW Australia
- Department of Forest ResourcesUniversity of Minnesota St. Paul MN USA
| | - Jacek Oleksyn
- Institute of DendrologyPolish Academy of Sciences Kornik Poland
- Department of Forest ResourcesUniversity of Minnesota St. Paul MN USA
| |
Collapse
|
13
|
Carvalho MR, Turgeon R, Owens T, Niklas KJ. The hydraulic architecture of Ginkgo leaves. AMERICAN JOURNAL OF BOTANY 2017; 104:1285-1298. [PMID: 29885239 DOI: 10.3732/ajb.1700277] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 08/31/2017] [Indexed: 05/24/2023]
Abstract
PREMISE OF THE STUDY The hydraulics of xylem has been widely studied in numerous species and organ types. However, comparatively little is known about how phloem and xylem are hydraulically coupled or about many of the basic structural properties of phloem (such as conducting cell numbers and conductive areas), which nevertheless have direct bearing on understanding phloem loading and unloading. METHODS Using a combination of light, epifluorescence, confocal, and transmission electron microscopy, we quantified the hydraulic architecture of Ginkgo biloba leaf laminae and examined the scaling relationships between phloem and xylem in five fully mature leaves. KEY RESULTS The conductive areas and lengths of sieve cells and tracheids increase basipetally toward the petiole in a manner that is consistent with Münch's pressure flow hypothesis for phloem transport. This trend holds true for individual veins, the sum of conductive areas across all veins at any distance from the petiole, and for individual sieve cells and tracheids. Further, the conductive areas of phloem and xylem are isometrically correlated across the entire vasculature of the leaf lamina. The data for conducting cell areas do not conform with the predictions of the hydraulic models of da Vinci and Murray. CONCLUSIONS The scaling of Ginkgo lamina hydraulics complies with that observed in leaves of other gymnosperms and most angiosperms and is inconsistent with theoretical models that assume that the volume of transported incompressible fluids is conserved.
Collapse
Affiliation(s)
- Mónica R Carvalho
- Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, New York 14853 USA
- Smithsonian Tropical Research Institute, Box 0843-03092, Balboa, Ancon Republic of Panama
| | - Robert Turgeon
- Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, New York 14853 USA
| | - Thomas Owens
- Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, New York 14853 USA
| | - Karl J Niklas
- Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, New York 14853 USA
| |
Collapse
|
14
|
Abstract
Plants provide unmatched opportunities to evaluate long debated evolutionary patterns in terms of the detailed biology of the fossil organisms. Leaves serve here as an example of how those advantages can be exploited. Over the history of vascular plants, three important transitions in leaf evolution—the origin of laminate leaves, the progressive loss of seed plant morphological diversity, and the evolution of more angiosperm-like leaves—also represent major shifts in leaf development and physiology. These transitions often occurred in parallel in different lineages, such as the evolution of marginal growth in each of at least four independent origins of laminate leaves during the Devonian and Carboniferous. Each also entailed dramatic reorganizations of leaf hydraulics. For example, the length of the finest distributary vein order varies from up to tens of centimeters down to hundreds of microns in successive groups of dominant seed plants. Angiosperms impose an additional trend upon these patterns with the evolution of their uniquely high vein densities. Vein density strongly influences and can provide a proxy for other physiological characteristics, such as assimilation and transpiration rates. The large increase in transpiration capacity accompanying the evolution of angiosperm leaf traits may even play an important role in feeding precipitation and thereby altering local climate.
Collapse
|
15
|
Rademaker H, Zwieniecki MA, Bohr T, Jensen KH. Sugar export limits size of conifer needles. Phys Rev E 2017; 95:042402. [PMID: 28505712 DOI: 10.1103/physreve.95.042402] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Indexed: 06/07/2023]
Abstract
Plant leaf size varies by more than three orders of magnitude, from a few millimeters to over one meter. Conifer leaves, however, are relatively short and the majority of needles are no longer than 6 cm. The reason for the strong confinement of the trait-space is unknown. We show that sugars produced near the tip of long needles cannot be exported efficiently, because the pressure required to drive vascular flow would exceed the greatest available pressure (the osmotic pressure). This basic constraint leads to the formation of an inactive region of stagnant fluid near the needle tip, which does not contribute to sugar flow. Remarkably, we find that the size of the active part does not scale with needle length. We predict a single maximum needle size of 5 cm, in accord with data from 519 conifer species. This could help rationalize the recent observation that conifers have significantly smaller leaves than angiosperms, and provide a biophysical explanation for this intriguing difference between the two largest groups of plants.
Collapse
Affiliation(s)
- Hanna Rademaker
- Department of Physics, Technical University of Denmark, DK 2800 Kgs. Lyngby, Denmark
| | - Maciej A Zwieniecki
- Department of Plant Sciences, University of California at Davis, Davis, California 95616, USA
| | - Tomas Bohr
- Department of Physics, Technical University of Denmark, DK 2800 Kgs. Lyngby, Denmark
| | - Kaare H Jensen
- Department of Physics, Technical University of Denmark, DK 2800 Kgs. Lyngby, Denmark
| |
Collapse
|
16
|
Zhang YJ, Rockwell FE, Graham AC, Alexander T, Holbrook NM. Reversible Leaf Xylem Collapse: A Potential "Circuit Breaker" against Cavitation. PLANT PHYSIOLOGY 2016; 172:2261-2274. [PMID: 27733514 PMCID: PMC5129713 DOI: 10.1104/pp.16.01191] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Accepted: 10/10/2016] [Indexed: 05/02/2023]
Abstract
We report a novel form of xylem dysfunction in angiosperms: reversible collapse of the xylem conduits of the smallest vein orders that demarcate and intrusively irrigate the areoles of red oak (Quercus rubra) leaves. Cryo-scanning electron microscopy revealed gradual increases in collapse from approximately -2 MPa down to -3 MPa, saturating thereafter (to -4 MPa). Over this range, cavitation remained negligible in these veins. Imaging of rehydration experiments showed spatially variable recovery from collapse within 20 s and complete recovery after 2 min. More broadly, the patterns of deformation induced by desiccation in both mesophyll and xylem suggest that cell wall collapse is unlikely to depend solely on individual wall properties, as mechanical constraints imposed by neighbors appear to be important. From the perspective of equilibrium leaf water potentials, petioles, whose vessels extend into the major veins, showed a vulnerability to cavitation that overlapped in the water potential domain with both minor vein collapse and buckling (turgor loss) of the living cells. However, models of transpiration transients showed that minor vein collapse and mesophyll capacitance could effectively buffer major veins from cavitation over time scales relevant to the rectification of stomatal wrong-way responses. We suggest that, for angiosperms, whose subsidiary cells give up large volumes to allow large stomatal apertures at the cost of potentially large wrong-way responses, vein collapse could make an important contribution to these plants' ability to transpire near the brink of cavitation-inducing water potentials.
Collapse
Affiliation(s)
- Yong-Jiang Zhang
- Department of Organismic and Evolutionary Biology (Y.-J.Z., F.E.R., T.A., N.M.H.) and Center for Nanoscale Systems (A.C.G.), Harvard University, Cambridge, Massachusetts 02138
| | - Fulton E Rockwell
- Department of Organismic and Evolutionary Biology (Y.-J.Z., F.E.R., T.A., N.M.H.) and Center for Nanoscale Systems (A.C.G.), Harvard University, Cambridge, Massachusetts 02138
| | - Adam C Graham
- Department of Organismic and Evolutionary Biology (Y.-J.Z., F.E.R., T.A., N.M.H.) and Center for Nanoscale Systems (A.C.G.), Harvard University, Cambridge, Massachusetts 02138
| | - Teressa Alexander
- Department of Organismic and Evolutionary Biology (Y.-J.Z., F.E.R., T.A., N.M.H.) and Center for Nanoscale Systems (A.C.G.), Harvard University, Cambridge, Massachusetts 02138
| | - N Michele Holbrook
- Department of Organismic and Evolutionary Biology (Y.-J.Z., F.E.R., T.A., N.M.H.) and Center for Nanoscale Systems (A.C.G.), Harvard University, Cambridge, Massachusetts 02138
| |
Collapse
|
17
|
Chin ARO, Sillett SC. Phenotypic plasticity of leaves enhances water-stress tolerance and promotes hydraulic conductivity in a tall conifer. AMERICAN JOURNAL OF BOTANY 2016; 103:796-807. [PMID: 27208348 DOI: 10.3732/ajb.1600110] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Accepted: 03/30/2016] [Indexed: 06/05/2023]
Abstract
PREMISE OF THE STUDY Leaves respond to environmental signals and acclimate to local conditions until their ecological limits are reached. Understanding the relationships between anatomical variation in leaves and the availability of water and light improves our ability to predict ecosystem-level impacts of foliar response to climate change, as it expands our knowledge of tree physiology. METHODS We examined foliar anatomy and morphology of the largest plant species, Sequoiadendron giganteum, from leafy shoot samples collected throughout crowns of trees up to 95 m tall and assessed the functionality of within-crown variation with a novel drought/recovery experiment. KEY RESULTS We found phenotypic variation in response to water availability in 13 anatomical traits of Sequoiadendron leaves. Shoot expansion was constrained by the hydrostatic gradient of maximum water potential, while functional traits supporting succulence and toughness were associated with sites of peak hydraulic limitation. Water-stress tolerance in experimental shoots increased dramatically with height. CONCLUSION We propose a heat-sink function for transfusion tissue and uncover a suite of traits suggesting rapid hydraulic throughput and flexibility in water-stress tolerance investments as strategies that help this montane species reach such enormous size. Responses to water stress alter the amount of carbon stored in foliage and the rate of the eventual release of carbon.
Collapse
Affiliation(s)
- Alana R O Chin
- Department of Natural Resources, American River College, 4700 College Oak Drive, Sacramento, California 95841 USA
| | - Stephen C Sillett
- Department of Forestry and Wildland Resources, Humboldt State University, 1 Harpst Street, Arcata, California 95521 USA
| |
Collapse
|
18
|
Gorce JB, Hewitt IJ, Vella D. Capillary Imbibition into Converging Tubes: Beating Washburn's Law and the Optimal Imbibition of Liquids. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:1560-7. [PMID: 26784118 DOI: 10.1021/acs.langmuir.5b04495] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We consider the problem of capillary imbibition into an axisymmetric tube for which the tube radius decreases in the direction of increasing imbibition. For tubes with constant radius, imbibition is described by Washburn's law (referred to here as the BCLW law to recognize the contributions of Bell, Cameron, and Lucas that predate Washburn). We show that imbibition into tubes with a power-law relationship between the radius and axial position generally occurs more quickly than imbibition into a constant-radius tube. By a suitable choice of the shape exponent, it is possible to decrease the time taken for the liquid to imbibe from one position to another by a factor of 2 compared to the BCLW law. We then show that a further small decrease in the imbibition time may be obtained by using a tube consisting of a cylinder joined to a cone of 3 times the cylinder length. For a given inlet radius, this composite shape attains the minimum imbibition time possible. We confirm our theoretical results with experiments on the tips of micropipettes and discuss the possible significance of these results for the control of liquid motion in microfluidic devices.
Collapse
Affiliation(s)
- Jean-Baptiste Gorce
- Mathematical Institute, Andrew Wiles Building, Woodstock Road, Oxford OX2 6GG, U.K
| | - Ian J Hewitt
- Mathematical Institute, Andrew Wiles Building, Woodstock Road, Oxford OX2 6GG, U.K
| | - Dominic Vella
- Mathematical Institute, Andrew Wiles Building, Woodstock Road, Oxford OX2 6GG, U.K
| |
Collapse
|
19
|
Roden J, Kahmen A, Buchmann N, Siegwolf R. The enigma of effective path length for (18) O enrichment in leaf water of conifers. PLANT, CELL & ENVIRONMENT 2015; 38:2551-2565. [PMID: 26037826 DOI: 10.1111/pce.12568] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2015] [Revised: 05/02/2015] [Accepted: 05/04/2015] [Indexed: 06/04/2023]
Abstract
The Péclet correction is often used to predict leaf evaporative enrichment and requires an estimate of effective path length (L). Studies to estimate L in conifer needles have produced unexpected patterns based on Péclet theory and leaf anatomy. We exposed seedlings of six conifer species to different vapour pressure deficits (VPD) in controlled climate chambers to produce steady-state leaf water enrichment (in (18) O). We measured leaf gas exchange, stable oxygen isotopic composition (δ(18) O) of input and plant waters as well as leaf anatomical characteristics. Variation in bulk needle water δ(18) O was strongly related to VPD. Conifer needles had large amounts of water within the vascular strand that was potentially unenriched (up to 40%). Both standard Craig-Gordon and Péclet models failed to accurately predict conifer leaf water δ(18) O without taking into consideration the unenriched water in the vascular strand and variable L. Although L was linearly related to mesophyll thickness, large within-species variation prevented the development of generalizations that could allow a broader use of the Péclet effect in predictive models. Our results point to the importance of within needle water pools and isolating mechanisms that need further investigation in order to integrate Péclet corrections with 'two compartment' leaf water concepts.
Collapse
Affiliation(s)
- John Roden
- Department of Biology, Southern Oregon University, Ashland, OR, 97520, USA
| | - Ansgar Kahmen
- Department of Environmental Sciences - Botany, University of Basel, 4056, Basel, Switzerland
| | - Nina Buchmann
- Department of Environmental Systems Science, Eidgenössische Technische Hochschule, 8092, Zürich
| | - Rolf Siegwolf
- Laboratory of Atmospheric Chemistry, Paul Scherrer Institut, 5232, Villigen, Switzerland
| |
Collapse
|
20
|
Drobnitch ST, Jensen KH, Prentice P, Pittermann J. Convergent evolution of vascular optimization in kelp (Laminariales). Proc Biol Sci 2015; 282:20151667. [PMID: 26423844 PMCID: PMC4614777 DOI: 10.1098/rspb.2015.1667] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Accepted: 09/02/2015] [Indexed: 11/12/2022] Open
Abstract
Terrestrial plants and mammals, although separated by a great evolutionary distance, have each arrived at a highly conserved body plan in which universal allometric scaling relationships govern the anatomy of vascular networks and key functional metabolic traits. The universality of allometric scaling suggests that these phyla have each evolved an 'optimal' transport strategy that has been overwhelmingly adopted by extant species. To truly evaluate the dominance and universality of vascular optimization, however, it is critical to examine other, lesser-known, vascularized phyla. The brown algae (Phaeophyceae) are one such group--as distantly related to plants as mammals, they have convergently evolved a plant-like body plan and a specialized phloem-like transport network. To evaluate possible scaling and optimization in the kelp vascular system, we developed a model of optimized transport anatomy and tested it with measurements of the giant kelp, Macrocystis pyrifera, which is among the largest and most successful of macroalgae. We also evaluated three classical allometric relationships pertaining to plant vascular tissues with a diverse sampling of kelp species. Macrocystis pyrifera displays strong scaling relationships between all tested vascular parameters and agrees with our model; other species within the Laminariales display weak or inconsistent vascular allometries. The lack of universal scaling in the kelps and the presence of optimized transport anatomy in M. pyrifera raises important questions about the evolution of optimization and the possible competitive advantage conferred by optimized vascular systems to multicellular phyla.
Collapse
Affiliation(s)
- Sarah Tepler Drobnitch
- Department of Ecology and Evolutionary Biology, University of California, 1156 High Street, Santa Cruz, CA 95040, USA
| | - Kaare H Jensen
- Department of Physics, Technical University of Denmark, Kongens Lyngby 2800, Denmark
| | - Paige Prentice
- Department of Ecology and Evolutionary Biology, University of California, 1156 High Street, Santa Cruz, CA 95040, USA
| | - Jarmila Pittermann
- Department of Ecology and Evolutionary Biology, University of California, 1156 High Street, Santa Cruz, CA 95040, USA
| |
Collapse
|
21
|
Ferris KG, Rushton T, Greenlee AB, Toll K, Blackman BK, Willis JH. Leaf shape evolution has a similar genetic architecture in three edaphic specialists within the Mimulus guttatus species complex. ANNALS OF BOTANY 2015; 116:213-23. [PMID: 26070644 PMCID: PMC4512191 DOI: 10.1093/aob/mcv080] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Revised: 03/06/2015] [Accepted: 04/24/2015] [Indexed: 05/13/2023]
Abstract
BACKGROUND AND AIMS The genetic basis of leaf shape has long interested botanists because leaf shape varies extensively across the plant kingdom and this variation is probably adaptive. However, knowledge of the genetic architecture of leaf shape variation in natural populations remains limited. This study examined the genetic architecture of leaf shape diversification among three edaphic specialists in the Mimulus guttatus species complex. Lobed and narrow leaves have evolved from the entire, round leaves of M. guttatus in M. laciniatus, M. nudatus and a polymorphic serpentine M. guttatus population (M2L). METHODS Bulk segregant analysis and next-generation sequencing were used to map quantitative trait loci (QTLs) that underlie leaf shape in an M. laciniatus × M. guttatus F2 population. To determine whether the same QTLs contribute to leaf shape variation in M. nudatus and M2L, F2s from M. guttatus × M. nudatus and lobed M2L × unlobed M. guttatus crosses were genotyped at QTLs from the bulk segregant analysis. KEY RESULTS Narrow and lobed leaf shapes in M. laciniatus, M. nudatus and M. guttatus are controlled by overlapping genetic regions. Several promising leaf shape candidate genes were found under each QTL. CONCLUSIONS The evolution of divergent leaf shape has taken place multiple times in the M. guttatus species complex and is associated with the occupation of dry, rocky environments. The genetic architecture of elongated and lobed leaves is similar across three species in this group. This may indicate that parallel genetic evolution from standing variation or new mutations is responsible for the putatively adaptive leaf shape variation in Mimulus.
Collapse
Affiliation(s)
- Kathleen G Ferris
- Department of Biology, Duke University, 125 Science Drive, Durham, NC 27705, USA and
| | - Tullia Rushton
- Department of Biology, Duke University, 125 Science Drive, Durham, NC 27705, USA and
| | - Anna B Greenlee
- Department of Biology, University of Virginia, 485 McCormick Road Charlottesville, VA 22904, USA
| | - Katherine Toll
- Department of Biology, Duke University, 125 Science Drive, Durham, NC 27705, USA and
| | - Benjamin K Blackman
- Department of Biology, University of Virginia, 485 McCormick Road Charlottesville, VA 22904, USA
| | - John H Willis
- Department of Biology, Duke University, 125 Science Drive, Durham, NC 27705, USA and
| |
Collapse
|
22
|
Ronellenfitsch H, Liesche J, Jensen KH, Holbrook NM, Schulz A, Katifori E. Scaling of phloem structure and optimality of photoassimilate transport in conifer needles. Proc Biol Sci 2015; 282:20141863. [PMID: 25567645 PMCID: PMC4308992 DOI: 10.1098/rspb.2014.1863] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Accepted: 12/04/2014] [Indexed: 12/22/2022] Open
Abstract
The phloem vascular system facilitates transport of energy-rich sugar and signalling molecules in plants, thus permitting long-range communication within the organism and growth of non-photosynthesizing organs such as roots and fruits. The flow is driven by osmotic pressure, generated by differences in sugar concentration between distal parts of the plant. The phloem is an intricate distribution system, and many questions about its regulation and structural diversity remain unanswered. Here, we investigate the phloem structure in the simplest possible geometry: a linear leaf, found, for example, in the needles of conifer trees. We measure the phloem structure in four tree species representing a diverse set of habitats and needle sizes, from 1 (Picea omorika) to 35 cm (Pinus palustris). We show that the phloem shares common traits across these four species and find that the size of its conductive elements obeys a power law. We present a minimal model that accounts for these common traits and takes into account the transport strategy and natural constraints. This minimal model predicts a power law phloem distribution consistent with transport energy minimization, suggesting that energetics are more important than translocation speed at the leaf level.
Collapse
Affiliation(s)
- Henrik Ronellenfitsch
- Max Planck Institute for Dynamics and Self-Organization, Am Faßberg 17, 37077 Göttingen, Germany
| | - Johannes Liesche
- Department of Plant and Environmental Sciences, University of Copenhagen, 1871 Frederiksberg C, Denmark
| | - Kaare H Jensen
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA Department of Physics, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - N Michele Holbrook
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
| | - Alexander Schulz
- Department of Plant and Environmental Sciences, University of Copenhagen, 1871 Frederiksberg C, Denmark
| | - Eleni Katifori
- Max Planck Institute for Dynamics and Self-Organization, Am Faßberg 17, 37077 Göttingen, Germany
| |
Collapse
|
23
|
Leigh A, Hill R, Ball MC. Leaf shape influences spatial variation in photosynthetic function in Lomatia tinctoria. FUNCTIONAL PLANT BIOLOGY : FPB 2014; 41:833-842. [PMID: 32481037 DOI: 10.1071/fp13334] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Accepted: 02/25/2014] [Indexed: 06/11/2023]
Abstract
A relationship exists between the two-dimensional shape of leaves and their venation architecture, such that broad or broad-lobed leaves can have leaf tissue far from major veins, potentially creating stronger gradients in water potential - and associated photosynthetic function - than found across narrow counterparts. We examined the spatial patterns of photosynthetic efficiency (ΔF/Fm') and non-photochemical quenching (NPQ) in response to increased vapour pressure deficit (VPD) using two morphs of Lomatia tinctoria (Labill.) R.Br: those with broad-lobed and those with narrow-lobed leaves. Stomatal conductance (gs), instantaneous water use efficiency (WUE), stomatal and minor veins density also were measured. ΔF/Fm' decreased with stress but was higher and less spatially heterogeneous across broad than narrow lobes. The strongest depression in ΔF/Fm' in broad lobes was at the edges and in narrow lobes, the tips. Non-photochemical quenching was spatially more varied in broad lobes, increasing at the edges and tips. Variation in photosynthetic function could not be explained by gs, WUE or minor vein density, whereas proximity to major veins appeared to mitigate water stress at the tips only for broad lobes. Our findings indicate that the relationship between venation architecture and water delivery alone can partially explain the spatial pattern of photosynthetic function.
Collapse
Affiliation(s)
- Andrea Leigh
- School of the Environment, University of Technology, Sydney, PO Box 123, Broadway, NSW 2007, Australia
| | - Ross Hill
- Centre for Marine Bio-Innovation and Sydney Institute of Marine Science, School of Biological, Earth and Environmental Sciences, The University of New South Wales, Sydney, NSW 2052, Australia
| | - Marilyn C Ball
- Plant Science Division, Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia
| |
Collapse
|
24
|
Sack L, Scoffoni C. Leaf venation: structure, function, development, evolution, ecology and applications in the past, present and future. THE NEW PHYTOLOGIST 2013; 198:983-1000. [PMID: 23600478 DOI: 10.1111/nph.12253] [Citation(s) in RCA: 313] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2012] [Accepted: 02/18/2013] [Indexed: 05/18/2023]
Abstract
The design and function of leaf venation are important to plant performance, with key implications for the distribution and productivity of ecosystems, and applications in paleobiology, agriculture and technology. We synthesize classical concepts and the recent literature on a wide range of aspects of leaf venation. We describe 10 major structural features that contribute to multiple key functions, and scale up to leaf and plant performance. We describe the development and plasticity of leaf venation and its adaptation across environments globally, and a new global data compilation indicating trends relating vein length per unit area to climate, growth form and habitat worldwide. We synthesize the evolution of vein traits in the major plant lineages throughout paleohistory, highlighting the multiple origins of individual traits. We summarize the strikingly diverse current applications of leaf vein research in multiple fields of science and industry. A unified core understanding will enable an increasing range of plant biologists to incorporate leaf venation into their research.
Collapse
Affiliation(s)
- Lawren Sack
- Department of Ecology and Evolution, University of California Los Angeles, 621 Charles E. Young Drive South, Los Angeles, CA, 90095, USA
| | - Christine Scoffoni
- Department of Ecology and Evolution, University of California Los Angeles, 621 Charles E. Young Drive South, Los Angeles, CA, 90095, USA
| |
Collapse
|
25
|
Charra-Vaskou K, Badel E, Burlett R, Cochard H, Delzon S, Mayr S. Hydraulic efficiency and safety of vascular and non-vascular components in Pinus pinaster leaves. TREE PHYSIOLOGY 2012; 32:1161-1170. [PMID: 22907978 DOI: 10.1093/treephys/tps071] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Leaves, the distal section of the soil-plant-atmosphere continuum, exhibit the lowest water potentials in a plant. In contrast to angiosperm leaves, knowledge of the hydraulic architecture of conifer needles is scant. We investigated the hydraulic efficiency and safety of Pinus pinaster needles, comparing different techniques. The xylem hydraulic conductivity (k(s)) and embolism vulnerability (P(50)) of both needle and stem were measured using the cavitron technique. The conductance and vulnerability of whole needles were measured via rehydration kinetics, and Cryo-SEM and 3D X-ray microtomographic observations were used as reference tools to validate physical measurements. The needle xylem of P. pinaster had lower hydraulic efficiency (k(s) = 2.0 × 10(-4) m(2) MPa(-1) s(-1)) and safety (P(50) = - 1.5 MPa) than stem xylem (k(s) = 7.7 × 10(-4) m(2) MPa(-1) s(-1); P(50) = - 3.6 to - 3.2 MPa). P(50) of whole needles (both extra-vascular and vascular pathways) was - 0.5 MPa, suggesting that non-vascular tissues were more vulnerable than the xylem. During dehydration to - 3.5 MPa, collapse and embolism in xylem tracheids, and gap formation in surrounding tissues were observed. However, a discrepancy in hydraulic and acoustic results appeared compared with visualizations, arguing for greater caution with these techniques when applied to needles. Our results indicate that the most distal parts of the water transport pathway are limiting for hydraulics of P. pinaster. Needle tissues exhibit a low hydraulic efficiency and low hydraulic safety, but may also act to buffer short-term water deficits, thus preventing xylem embolism.
Collapse
Affiliation(s)
- Katline Charra-Vaskou
- Department of Botany, University of Innsbruck, Sternwartestr. 15, A-6020 Innsbruck, Austria.
| | | | | | | | | | | |
Collapse
|
26
|
Charra-Vaskou K, Mayr S. The hydraulic conductivity of the xylem in conifer needles (Picea abies and Pinus mugo). JOURNAL OF EXPERIMENTAL BOTANY 2011; 62:4383-4390. [PMID: 21593348 DOI: 10.1093/jxb/err157] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Main resistances of the plant water transport system are situated in leaves. In contrast to angiosperm leaves, knowledge of conifer needle hydraulics and of the partitioning of resistances within needles is poor. A new technique was developed which enabled flow-meter measurements through needles embedded in paraffin and thus quantification of the specific hydraulic conductivity (K(s)) of the needle xylem. In Picea abies, xylem K(s) of needle and axes as well as in needles of different age were compared. In Pinus mugo, resistance partitioning within needles was estimated by measurements of xylem K(s) and leaf conductance (K(leaf), measured via 'rehydration kinetics'). Mean K(s) in P. abies needles was 3.5×10(-4) m(2) s(-1) MPa(-1) with a decrease in older needles, and over all similar to K(s) of corresponding axes xylem. In needles of P. mugo, K(s) was 0.9×10(-4) m(2) s(-1) MPa(-1), and 24% of total needle resistance was situated in the xylem. The results indicate species-specific differences in the hydraulic efficiency of conifer needle xylem. The vascular section of the water transport system is a minor but relevant resistance in needles.
Collapse
Affiliation(s)
- Katline Charra-Vaskou
- Department of Botany, University of Innsbruck, Sternwartestr. 15, A-6020 Innsbruck, Austria
| | | |
Collapse
|
27
|
Nicotra AB, Leigh A, Boyce CK, Jones CS, Niklas KJ, Royer DL, Tsukaya H. The evolution and functional significance of leaf shape in the angiosperms. FUNCTIONAL PLANT BIOLOGY : FPB 2011; 38:535-552. [PMID: 32480907 DOI: 10.1071/fp11057] [Citation(s) in RCA: 203] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Accepted: 05/30/2011] [Indexed: 05/18/2023]
Abstract
Angiosperm leaves manifest a remarkable diversity of shapes that range from developmental sequences within a shoot and within crown response to microenvironment to variation among species within and between communities and among orders or families. It is generally assumed that because photosynthetic leaves are critical to plant growth and survival, variation in their shape reflects natural selection operating on function. Several non-mutually exclusive theories have been proposed to explain leaf shape diversity. These include: thermoregulation of leaves especially in arid and hot environments, hydraulic constraints, patterns of leaf expansion in deciduous species, biomechanical constraints, adaptations to avoid herbivory, adaptations to optimise light interception and even that leaf shape variation is a response to selection on flower form. However, the relative importance, or likelihood, of each of these factors is unclear. Here we review the evolutionary context of leaf shape diversification, discuss the proximal mechanisms that generate the diversity in extant systems, and consider the evidence for each the above hypotheses in the context of the functional significance of leaf shape. The synthesis of these broad ranging areas helps to identify points of conceptual convergence for ongoing discussion and integrated directions for future research.
Collapse
Affiliation(s)
- Adrienne B Nicotra
- Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia
| | - Andrea Leigh
- School of the Environment, University of Technology, Sydney, PO Box 123, Broadway, NSW 2007, Australia
| | - C Kevin Boyce
- Department of the Geophysical Sciences, 5734 S. Ellis Avenue, Chicago, IL 60637, USA
| | - Cynthia S Jones
- Department of Ecology and Evolutionary Biology, University of Connecticut, 75 N. Eagleville Road, Unit-3043, Storrs, CT 06269, USA
| | - Karl J Niklas
- Department of Plant Biology, Cornell University, 412 Mann Library Building, Cornell University, Ithaca, NY 14853, USA
| | - Dana L Royer
- Department of Earth and Environmental Sciences, Wesleyan University, 265 Church Street, Middletown, CT 06459, USA
| | - Hirokazu Tsukaya
- Graduate School of Science, University of Tokyo, Science Build #2, 7-3-1 Hongo, Tokyo 113-0033, Japan
| |
Collapse
|
28
|
Leigh A, Zwieniecki MA, Rockwell FE, Boyce CK, Nicotra AB, Holbrook NM. Structural and hydraulic correlates of heterophylly in Ginkgo biloba. THE NEW PHYTOLOGIST 2011; 189:459-70. [PMID: 20880226 DOI: 10.1111/j.1469-8137.2010.03476.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
This study investigates the functional significance of heterophylly in Ginkgo biloba, where leaves borne on short shoots are ontogenetically distinct from those on long shoots. Short shoots are compact, with minimal internodal elongation; their leaves are supplied with water through mature branches. Long shoots extend the canopy and have significant internodal elongation; their expanding leaves receive water from a shoot that is itself maturing. Morphology, stomatal traits, hydraulic architecture, Huber values, water transport efficiency, in situ gas exchange and laboratory-based steady-state hydraulic conductance were examined for each leaf type. Both structure and physiology differed markedly between the two leaf types. Short-shoot leaves were thinner and had higher vein density, lower stomatal pore index, smaller bundle sheath extensions and lower hydraulic conductance than long-shoot leaves. Long shoots had lower xylem area:leaf area ratios than short shoots during leaf expansion, but this ratio was reversed at shoot maturity. Long-shoot leaves had higher rates of photosynthesis, stomatal conductance and transpiration than short-shoot leaves. We propose that structural differences between the two G. biloba leaf types reflect greater hydraulic limitation of long-shoot leaves during expansion. In turn, differences in physiological performance of short- and long-shoot leaves correspond to their distinct ontogeny and architecture.
Collapse
Affiliation(s)
- A Leigh
- Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia.
| | | | | | | | | | | |
Collapse
|
29
|
Oldham AR, Sillett SC, Tomescu AMF, Koch GW. The hydrostatic gradient, not light availability, drives height-related variation in Sequoia sempervirens (Cupressaceae) leaf anatomy. AMERICAN JOURNAL OF BOTANY 2010; 97:1087-1097. [PMID: 21616861 DOI: 10.3732/ajb.0900214] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
PREMISE OF THE STUDY Leaves at the tops of most trees are smaller, thicker, and in many other ways different from leaves on the lowermost branches. This height-related variation in leaf structure has been explained as acclimation to differing light environments and, alternatively, as a consequence of hydrostatic, gravitational constraints on turgor pressure that reduce leaf expansion. • METHODS To separate hydrostatic effects from those of light availability, we used anatomical analysis of height-paired samples from the inner and outer tree crowns of tall redwoods (Sequoia sempervirens). • KEY RESULTS Height above the ground correlates much more strongly with leaf anatomy than does light availability. Leaf length, width, and mesophyll porosity all decrease linearly with height and help explain increases in leaf-mass-to-area ratio and decreases in both photosynthetic capacity and internal gas-phase conductance with increasing height. Two functional traits-leaf thickness and transfusion tissue-also increase with height and may improve water-stress tolerance. Transfusion tissue area increases enough that whole-leaf vascular volume does not change significantly with height in most trees. Transfusion tracheids become deformed with height, suggesting they may collapse under water stress and act as a hydraulic buffer that improves leaf water status and reduces the likelihood of xylem dysfunction. • CONCLUSIONS That such variation in leaf structure may be caused more by gravity than by light calls into question use of the terms "sun" and "shade" to describe leaves at the tops and bottoms of tall tree crowns.
Collapse
Affiliation(s)
- Alana R Oldham
- Department of Biological Sciences, Humboldt State University, Arcata, California 95521 USA
| | | | | | | |
Collapse
|
30
|
Domec JC, Noormets A, King JS, Sun G, McNulty SG, Gavazzi MJ, Boggs JL, Treasure EA. Decoupling the influence of leaf and root hydraulic conductances on stomatal conductance and its sensitivity to vapour pressure deficit as soil dries in a drained loblolly pine plantation. PLANT, CELL & ENVIRONMENT 2009; 32:980-91. [PMID: 19344336 DOI: 10.1111/j.1365-3040.2009.01981.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The study examined the relationships between whole tree hydraulic conductance (K(tree)) and the conductance in roots (K(root)) and leaves (K(leaf)) in loblolly pine trees. In addition, the role of seasonal variations in K(root) and K(leaf) in mediating stomatal control of transpiration and its response to vapour pressure deficit (D) as soil-dried was studied. Compared to trunk and branches, roots and leaves had the highest loss of conductivity and contributed to more than 75% of the total tree hydraulic resistance. Drought altered the partitioning of the resistance between roots and leaves. As soil moisture dropped below 50%, relative extractable water (REW), K(root) declined faster than K(leaf). Although K(tree) depended on soil moisture, its dynamics was tempered by the elongation of current-year needles that significantly increased K(leaf) when REW was below 50%. After accounting for the effect of D on g(s), the seasonal decline in K(tree) caused a 35% decrease in g(s) and in its sensitivity to D, responses that were mainly driven by K(leaf) under high REW and by K(root) under low REW. We conclude that not only water stress but also leaf phenology affects the coordination between K(tree) and g(s) and the acclimation of trees to changing environmental conditions.
Collapse
Affiliation(s)
- Jean-Christophe Domec
- Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC 27695, USA.
| | | | | | | | | | | | | | | |
Collapse
|
31
|
Boyce CK. Seeing the forest with the leaves - clues to canopy placement from leaf fossil size and venation characteristics. GEOBIOLOGY 2009; 7:192-199. [PMID: 19207570 DOI: 10.1111/j.1472-4669.2008.00176.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Although a variety of leaf characteristics appear to be induced by light environment during development, analysis of ontogenetic changes in living broad leaved trees has suggested that a number of other traits also lumped into the classic 'sun' versus 'shade' morphological distinctions, including leaf size, shape, and vein density, are instead controlled largely by local hydraulic environment within the tree canopy. The regularity in how these traits vary with canopy placement suggests a method for addressing a classic paleobotanical quandary: the stature of the source plant - from herb or shrub to canopy tree - is typically unknown for leaf fossils. The study of Ginkgo here complements previous work on Quercus that indicated that leaves throughout the crown are identical in size and venation at the time of bud break and that morphological adaptation to the local microenvironment takes place largely during the expansion phase after the determination of the vascular architecture is complete. Hence, variation in vein density does not reflect differential vein production so much as the distortion of similar vein networks over different final surface areas driven by variation in local hydraulic supply during expansion. Unlike the diffusely growing leaves of the angiosperm, Quercus, the marginally growing leaves of Ginkgo do show some potential for differential vein production, but expansion effects still dominate. The approach suggested here may prove useful for assessing the likelihood that two distinct fossil morphospecies actually represent leaves of the same plant and to gather information concerning canopy structure from disarticulated leaves.
Collapse
Affiliation(s)
- C K Boyce
- Department of the Geophysical Sciences, University of Chicago, Chicago, IL 60637, USA.
| |
Collapse
|
32
|
Coomes DA, Heathcote S, Godfrey ER, Shepherd JJ, Sack L. Scaling of xylem vessels and veins within the leaves of oak species. Biol Lett 2008; 4:302-6. [PMID: 18407890 PMCID: PMC2610058 DOI: 10.1098/rsbl.2008.0094] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2008] [Accepted: 03/19/2008] [Indexed: 11/12/2022] Open
Abstract
General models of plant vascular architecture, based on scaling of pipe diameters to remove the length dependence of hydraulic resistance within the xylem, have attracted strong interest. However, these models have neglected to consider the leaf, an important hydraulic component; they assume all leaves to have similar hydraulic properties, including similar pipe diameters in the petiole. We examine the scaling of the leaf xylem in 10 temperate oak species, an important hydraulic component. The mean hydraulic diameter of petiole xylem vessels varied by 30% among the 10 oak species. Conduit diameters narrowed from the petiole to the midrib to the secondary veins, consistent with resistance minimization, but the power function scaling exponent differed from that predicted for stems. Leaf size was an organizing trait within and across species. These findings indicate that leaf vasculature needs to be included in whole-plant scaling models, for these to accurately reflect and predict whole-plant transport and its implications for performance and ecology.
Collapse
Affiliation(s)
- David A Coomes
- University of Cambridge, Downing Street, Cambridge CB2 3EA, UK.
| | | | | | | | | |
Collapse
|
33
|
Ye Q, Holbrook NM, Zwieniecki MA. Cell-to-cell pathway dominates xylem-epidermis hydraulic connection in Tradescantia fluminensis (Vell. Conc.) leaves. PLANTA 2008; 227:1311-1319. [PMID: 18273638 DOI: 10.1007/s00425-008-0703-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2007] [Accepted: 01/28/2008] [Indexed: 05/25/2023]
Abstract
A steady supply of water is indispensable for leaves to fulfil their photosynthetic function. Understanding water movement in leaves, especially factors that regulate the movement of water flux from xylem to epidermis, requires that the nature of the transport pathway be elucidated. To determine the hydraulic linkage between xylem and epidermis, epidermal cell turgor pressure (P (t)) in leaves of Tradescantia fluminensis was monitored using a cell pressure probe in response to a 0.2 MPa step change in xylem pressure applied at the leaf petiole. Halftime of P (t) changes (T(x)(1/2)) were 10-30 times greater than that of water exchange across an individual cell membrane (T(m)(1/2)) suggesting that cell-to-cell water transport constitutes a significant part of the leaf hydraulic path from xylem to epidermis. Furthermore, perfusion of H(2)O(2) resulted in increases of both T(m)(1/2) and T(x)(1/2) by a factor of 2.5, indicating that aquaporins may play a role in the xylem to epidermis hydraulic link. The halftime for water exchange (T(m)(1/2)) did not differ significantly between cells located at the leaf base (2.5 s), middle (2.6 s) and tip (2.5 s), indicating that epidermal cell hydraulic properties are similar along the length of the leaf. Following the pressure application to the xylem (0.2 MPa), P (t) changed by 0.12, 0.06 and 0.04 MPa for epidermal cells at the base, middle and the tip of the leaf, respectively. This suggests that pressure dissipation between xylem and epidermis is significant, and that the pressure drop along the vein may be due to its structural similarities to a porous pipe, an idea which was further supported by measurements of xylem hydraulic resistance using a perfusion technique.
Collapse
Affiliation(s)
- Qing Ye
- Arnold Arboretum, Harvard University, Cambridge, MA 02138, USA.
| | | | | |
Collapse
|