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Yin H, Perera-Castro AV, Randall KL, Turnbull JD, Waterman MJ, Dunn J, Robinson SA. Basking in the sun: how mosses photosynthesise and survive in Antarctica. PHOTOSYNTHESIS RESEARCH 2023; 158:151-169. [PMID: 37515652 PMCID: PMC10684656 DOI: 10.1007/s11120-023-01040-y] [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: 02/15/2023] [Accepted: 07/10/2023] [Indexed: 07/31/2023]
Abstract
The Antarctic environment is extremely cold, windy and dry. Ozone depletion has resulted in increasing ultraviolet-B radiation, and increasing greenhouse gases and decreasing stratospheric ozone have altered Antarctica's climate. How do mosses thrive photosynthetically in this harsh environment? Antarctic mosses take advantage of microclimates where the combination of protection from wind, sufficient melt water, nutrients from seabirds and optimal sunlight provides both photosynthetic energy and sufficient warmth for efficient metabolism. The amount of sunlight presents a challenge: more light creates warmer canopies which are optimal for photosynthetic enzymes but can contain excess light energy that could damage the photochemical apparatus. Antarctic mosses thus exhibit strong photoprotective potential in the form of xanthophyll cycle pigments. Conversion to zeaxanthin is high when conditions are most extreme, especially when water content is low. Antarctic mosses also produce UV screening compounds which are maintained in cell walls in some species and appear to protect from DNA damage under elevated UV-B radiation. These plants thus survive in one of the harshest places on Earth by taking advantage of the best real estate to optimise their metabolism. But survival is precarious and it remains to be seen if these strategies will still work as the Antarctic climate changes.
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Affiliation(s)
- Hao Yin
- Securing Antarctica's Environmental Future, University of Wollongong, Wollongong, NSW, 2522, Australia
- Centre for Sustainable Ecosystem Solutions, School of Earth, Atmospheric and Life Sciences, University of Wollongong, Wollongong, NSW, 2522, Australia
| | | | - Krystal L Randall
- Securing Antarctica's Environmental Future, University of Wollongong, Wollongong, NSW, 2522, Australia
- Centre for Sustainable Ecosystem Solutions, School of Earth, Atmospheric and Life Sciences, University of Wollongong, Wollongong, NSW, 2522, Australia
| | - Johanna D Turnbull
- Securing Antarctica's Environmental Future, University of Wollongong, Wollongong, NSW, 2522, Australia
- Centre for Sustainable Ecosystem Solutions, School of Earth, Atmospheric and Life Sciences, University of Wollongong, Wollongong, NSW, 2522, Australia
| | - Melinda J Waterman
- Securing Antarctica's Environmental Future, University of Wollongong, Wollongong, NSW, 2522, Australia
- Centre for Sustainable Ecosystem Solutions, School of Earth, Atmospheric and Life Sciences, University of Wollongong, Wollongong, NSW, 2522, Australia
| | - Jodie Dunn
- Securing Antarctica's Environmental Future, University of Wollongong, Wollongong, NSW, 2522, Australia
- Centre for Sustainable Ecosystem Solutions, School of Earth, Atmospheric and Life Sciences, University of Wollongong, Wollongong, NSW, 2522, Australia
| | - Sharon A Robinson
- Securing Antarctica's Environmental Future, University of Wollongong, Wollongong, NSW, 2522, Australia.
- Centre for Sustainable Ecosystem Solutions, School of Earth, Atmospheric and Life Sciences, University of Wollongong, Wollongong, NSW, 2522, Australia.
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Beltrán-Sanz N, Raggio J, Pintado A, Dal Grande F, García Sancho L. Physiological Plasticity as a Strategy to Cope with Harsh Climatic Conditions: Ecophysiological Meta-Analysis of the Cosmopolitan Moss Ceratodon purpureus in the Southern Hemisphere. PLANTS (BASEL, SWITZERLAND) 2023; 12:499. [PMID: 36771584 PMCID: PMC9919500 DOI: 10.3390/plants12030499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Revised: 12/22/2022] [Accepted: 12/29/2022] [Indexed: 06/18/2023]
Abstract
Determining the physiological tolerance ranges of species is necessary to comprehend the limits of their responsiveness under strong abiotic pressures. For this purpose, the cosmopolitan moss Ceratodon purpureus (Hedw.) Brid. is a good model due to its wide geographical distribution throughout different biomes and habitats. In order to disentangle how this species copes with stresses such as extreme temperatures and high radiation, we designed a meta-analysis by including the main photosynthetic traits obtained by gas exchange measurements in three contrasting habitats from the Southern Hemisphere. Our findings highlight that traits such as respiration homeostasis, modulation of the photosynthetic efficiency, adjustment of the optimal temperature, and switching between shade and sun-adapted forms, which are crucial in determining the responsiveness of this species. In fact, these ecophysiological traits are in concordance with the climatic particularities of each habitat. Furthermore, the photosynthetic trends found in our study point out how different Livingston Island (Maritime Antarctica) and Granite Harbour (Continental Antarctica) are for plant life, while the population from the Succulent Karoo Desert (South Africa) shares traits with both Antarctic regions. Altogether, the study highlights the high resilience of C. purpureus under abrupt climate changes and opens new perspectives about the wide spectrum of physiological responses of cryptogams to cope with climate change scenarios.
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Affiliation(s)
- Núria Beltrán-Sanz
- Department of Pharmacology, Pharmacognosy and Botany, Complutense University of Madrid, 28040 Madrid, Spain
| | - José Raggio
- Department of Pharmacology, Pharmacognosy and Botany, Complutense University of Madrid, 28040 Madrid, Spain
| | - Ana Pintado
- Department of Pharmacology, Pharmacognosy and Botany, Complutense University of Madrid, 28040 Madrid, Spain
| | | | - Leopoldo García Sancho
- Department of Pharmacology, Pharmacognosy and Botany, Complutense University of Madrid, 28040 Madrid, Spain
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Perera-Castro AV, González-Rodríguez ÁM, Fernández-Marín B. When time is not of the essence: constraints to the carbon balance of bryophytes. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:4562-4575. [PMID: 35298628 DOI: 10.1093/jxb/erac104] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 03/10/2022] [Indexed: 06/14/2023]
Abstract
The data available so far indicate that the photosynthetic and relative growth rates of bryophytes are 10% of those reported for tracheophytes. By examining the existing literature and reanalysing data published in over 100 studies, this review examines the ecophysiological, biochemical, and structural reasons behind this phenomenon. The limiting Rubisco content and surface for gas exchange are the internal factors that can explain the low photosynthetic and growth rates of bryophytes. The role of the thicker cell walls of bryophytes in limiting CO2 diffusion is unclear, due to the current uncertainties regarding their porosity and permeability to CO2. From this review, it is also evident that, despite bryophytes having low photosynthetic rates, their positive carbon balance is tightly related to their capacity to deal with extreme conditions. Contributing factors include their capacity to deal with large daily temperature oscillations, and their capacity to delay the cessation of photosynthesis under water deficit (or to tolerate desiccation in extreme situations). Although further studies on bryophytes are needed before more solid conclusions can be drawn, it seems that their success relies on their remarkable tolerance to a highly variable environment, possibly at the expense of their maximum photosynthetic rate.
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Affiliation(s)
- Alicia V Perera-Castro
- Department of Botany, Ecology and Plant Physiology, Universidad de La Laguna, 38200 La Laguna, Canary Islands, Spain
| | - Águeda M González-Rodríguez
- Department of Botany, Ecology and Plant Physiology, Universidad de La Laguna, 38200 La Laguna, Canary Islands, Spain
| | - Beatriz Fernández-Marín
- Department of Botany, Ecology and Plant Physiology, Universidad de La Laguna, 38200 La Laguna, Canary Islands, Spain
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Carbon dioxide isotopic compositions during tundra ecosystem respiration and photosynthesis in relation to environmental variables in maritime Antarctica. Polar Biol 2021. [DOI: 10.1007/s00300-021-02829-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Osaki S, Nakatsubo T. Effects of climate warming on the production of the pioneer moss Racomitrium japonicum: seasonal and year-to-year variations. JOURNAL OF PLANT RESEARCH 2021; 134:115-126. [PMID: 33433707 DOI: 10.1007/s10265-020-01240-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Accepted: 11/13/2020] [Indexed: 06/12/2023]
Abstract
Pioneer mosses are among the dominant vegetation in the early stages of xeric successions. Recent climate warming may have a significant effect on the productivity of these mosses, thereby affecting successional processes. In this study, we investigated the effects of temperature changes on the productivity of Racomitrium japonicum, a pioneer moss species commonly found on open ground in Japan. We examined the microclimate (moss temperature and water content) of a natural R. japonicum stand in Higashi-Hiroshima City, western Japan, and related them to the climate records of the weather station to create a model for estimating microclimate from past climatic data. We also examined the effects of environmental factors (light, temperature, and water) on photosynthesis in the laboratory to construct a production model. Using these models, we estimated the net primary production (NPP) over the last 10 years (2009-2018) based on the climatic data (air temperature and precipitation) recorded at the weather station of Higashi-Hiroshima City. The estimated NPP showed negative values in summer, which indicated that respiratory carbon loss exceeded photosynthetic carbon gain. In contrast, NPP was positive in the spring and winter seasons throughout the 10 years. Autumn NPP varied widely, showing both positive and negative values. The annual NPP also showed considerable year-to-year variations. Additionally, we examined the effects of temperature conditions on NPP assuming annual temperature changes of 0 °C (present temperature), + 1 °C, and + 2 °C. The results indicated that NPP decreased with increasing temperature, except in the winter season. The findings of this study suggest that climate warming has a large impact on the NPP of R. japonicum; however, the impact can be both positive and negative depending on the season. The results also suggest that future climate warming is likely to decrease NPP on an annual basis.
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Affiliation(s)
- Soshi Osaki
- Graduate School of Integrated Sciences for Life, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, 739-8521, Japan.
| | - Takayuki Nakatsubo
- Graduate School of Integrated Sciences for Life, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, 739-8521, Japan
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Perera-Castro AV, Waterman MJ, Turnbull JD, Ashcroft MB, McKinley E, Watling JR, Bramley-Alves J, Casanova-Katny A, Zuniga G, Flexas J, Robinson SA. It Is Hot in the Sun: Antarctic Mosses Have High Temperature Optima for Photosynthesis Despite Cold Climate. FRONTIERS IN PLANT SCIENCE 2020; 11:1178. [PMID: 32922412 PMCID: PMC7457050 DOI: 10.3389/fpls.2020.01178] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Accepted: 07/21/2020] [Indexed: 05/05/2023]
Abstract
The terrestrial flora of Antarctica's frozen continent is restricted to sparse ice-free areas and dominated by lichens and bryophytes. These plants frequently battle sub-zero temperatures, extreme winds and reduced water availability; all influencing their ability to survive and grow. Antarctic mosses, however, can have canopy temperatures well above air temperature. At midday, canopy temperatures can exceed 15°C, depending on moss turf water content. In this study, the optimum temperature of photosynthesis was determined for six Antarctic moss species: Bryum pseudotriquetrum, Ceratodon purpureus, Chorisodontium aciphyllum, Polytrichastrum alpinum, Sanionia uncinata, and Schistidium antarctici collected from King George Island (maritime Antarctica) and/or the Windmill Islands, East Antarctica. Both chlorophyll fluorescence and gas exchange showed maximum values of electron transport rate occurred at canopy temperatures higher than 20°C. The optimum temperature for both net assimilation of CO2 and photoprotective heat dissipation of three East Antarctic species was 20-30°C and at temperatures below 10°C, mesophyll conductance did not significantly differ from 0. Maximum mitochondrial respiration rates occurred at temperatures higher than 35°C and were lower by around 80% at 5°C. Despite the extreme cold conditions that Antarctic mosses face over winter, the photosynthetic apparatus appears optimised to warm temperatures. Our estimation of the total carbon balance suggests that survival in this cold environment may rely on a capacity to maximize photosynthesis for brief periods during summer and minimize respiratory carbon losses in cold conditions.
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Affiliation(s)
- Alicia V. Perera-Castro
- Department of Biology, Universitat de les Illes Balears, INAGEA, Palma de Mallorca, Spain
- Centre for Sustainable Ecosystem Solutions, School of Earth, Atmosphere and Life Sciences, University of Wollongong, Wollongong, NSW, Australia
| | - Melinda J. Waterman
- Centre for Sustainable Ecosystem Solutions, School of Earth, Atmosphere and Life Sciences, University of Wollongong, Wollongong, NSW, Australia
| | - Johanna D. Turnbull
- Centre for Sustainable Ecosystem Solutions, School of Earth, Atmosphere and Life Sciences, University of Wollongong, Wollongong, NSW, Australia
| | - Michael B. Ashcroft
- Centre for Sustainable Ecosystem Solutions, School of Earth, Atmosphere and Life Sciences, University of Wollongong, Wollongong, NSW, Australia
| | - Ella McKinley
- School of Biological Sciences, The University of Adelaide, Adelaide, SA, Australia
| | - Jennifer R. Watling
- School of Biological Sciences, The University of Adelaide, Adelaide, SA, Australia
- Manchester Metropolitan University, Manchester, United Kingdom
| | - Jessica Bramley-Alves
- Centre for Sustainable Ecosystem Solutions, School of Earth, Atmosphere and Life Sciences, University of Wollongong, Wollongong, NSW, Australia
| | - Angelica Casanova-Katny
- Laboratorio de Ecofisiología Vegetal y Cambio Climático y Núcleo de Estudios Ambientales (NEA), Facultad de Recursos Naturales, Universidad Católica de Temuco, Temuco, Chile
| | - Gustavo Zuniga
- Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile
| | - Jaume Flexas
- Department of Biology, Universitat de les Illes Balears, INAGEA, Palma de Mallorca, Spain
| | - Sharon A. Robinson
- Centre for Sustainable Ecosystem Solutions, School of Earth, Atmosphere and Life Sciences, University of Wollongong, Wollongong, NSW, Australia
- Global Challenges Program, University of Wollongong, Wollongong, NSW, Australia
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Royles J, Amesbury MJ, Roland TP, Jones GD, Convey P, Griffiths H, Hodgson DA, Charman DJ. Moss stable isotopes (carbon-13, oxygen-18) and testate amoebae reflect environmental inputs and microclimate along a latitudinal gradient on the Antarctic Peninsula. Oecologia 2016; 181:931-45. [PMID: 27003701 PMCID: PMC4912596 DOI: 10.1007/s00442-016-3608-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Accepted: 03/08/2016] [Indexed: 11/27/2022]
Abstract
The stable isotope compositions of moss tissue water (δ(2)H and δ(18)O) and cellulose (δ(13)C and δ(18)O), and testate amoebae populations were sampled from 61 contemporary surface samples along a 600-km latitudinal gradient of the Antarctic Peninsula (AP) to provide a spatial record of environmental change. The isotopic composition of moss tissue water represented an annually integrated precipitation signal with the expected isotopic depletion with increasing latitude. There was a weak, but significant, relationship between cellulose δ(18)O and latitude, with predicted source water inputs isotopically enriched compared to measured precipitation. Cellulose δ(13)C values were dependent on moss species and water content, and may reflect site exposure to strong winds. Testate amoebae assemblages were characterised by low concentrations and taxonomic diversity, with Corythion dubium and Microcorycia radiata types the most cosmopolitan taxa. The similarity between the intra- and inter-site ranges measured in all proxies suggests that microclimate and micro-topographical conditions around the moss surface were important determinants of proxy values. Isotope and testate amoebae analyses have proven value as palaeoclimatic, temporal proxies of climate change, whereas this study demonstrates that variations in isotopic and amoeboid proxies between microsites can be beyond the bounds of the current spatial variability in AP climate.
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Affiliation(s)
- Jessica Royles
- British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET, UK.
- Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EA, UK.
| | - Matthew J Amesbury
- Geography, College of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4RJ, UK
| | - Thomas P Roland
- Geography, College of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4RJ, UK
| | - Glyn D Jones
- Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EA, UK
| | - Peter Convey
- British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET, UK
| | - Howard Griffiths
- Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EA, UK
| | - Dominic A Hodgson
- British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET, UK
| | - Dan J Charman
- Geography, College of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4RJ, UK
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Royles J, Griffiths H. Invited review: climate change impacts in polar regions: lessons from Antarctic moss bank archives. GLOBAL CHANGE BIOLOGY 2015; 21:1041-57. [PMID: 25336089 DOI: 10.1111/gcb.12774] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 09/24/2014] [Accepted: 10/08/2014] [Indexed: 05/13/2023]
Abstract
Mosses are the dominant plants in polar and boreal regions, areas which are experiencing rapid impacts of regional warming. Long-term monitoring programmes provide some records of the rate of recent climate change, but moss peat banks contain an unrivalled temporal record of past climate change on terrestrial plant Antarctic systems. We summarise the current understanding of climatic proxies and determinants of moss growth for contrasting continental and maritime Antarctic regions, as informed by 13C and 18O signals in organic material. Rates of moss accumulation are more than three times higher in the maritime Antarctic than continental Antarctica with growing season length being a critical determinant of growth rate, and high carbon isotope discrimination values reflecting optimal hydration conditions. Correlation plots of 13C and 18O values show that species (Chorisodontium aciphyllum / Polytrichum strictum) and growth form (hummock / bank) are the major determinants of measured isotope ratios. The interplay between moss growth form, photosynthetic physiology, water status and isotope composition are compared with developments of secondary proxies, such as chlorophyll fluorescence. These approaches provide a framework to consider the potential impact of climate change on terrestrial Antarctic habitats as well as having implications for future studies of temperate, boreal and Arctic peatlands. There are many urgent ecological and environmental problems in the Arctic related to mosses in a changing climate, but the geographical ranges of species and life-forms are difficult to track individually. Our goal was to translate what we have learned from the more simple systems in Antarctica, for application to Arctic habitats.
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Affiliation(s)
- Jessica Royles
- British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET, UK; Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EA, UK
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Stanton DE, Merlin M, Bryant G, Ball MC. Water redistribution determines photosynthetic responses to warming and drying in two polar mosses. FUNCTIONAL PLANT BIOLOGY : FPB 2014; 41:178-186. [PMID: 32480977 DOI: 10.1071/fp13160] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2013] [Accepted: 08/14/2013] [Indexed: 05/25/2023]
Abstract
Predicting impacts of climate change requires an understanding of the sensitivity of species to temperature, including conflated changes in humidity. Physiological responses to temperature and clump-to-air vapour pressure difference (VPD) were compared in two Antarctic moss species, Ceratodon purpureus (Hedw.) Brid. and Schistidium antarctici (Cardot) L.I. Savicz & Smirnova. Temperatures from 8 to 24°C had no significant effects on photosynthesis or recovery from drying, whereas high VPD accelerated drying. In Schistidium, which lacks internal conduction structures, shoots dried more slowly than the clump, and photosynthesis ceased at high shoot relative water content (RWC), behaviour consistent with a strategy of drought avoidance although desiccation tolerant. In contrast, shoots of Ceratodon have a central vascular core, but dried more rapidly than the clump. These results imply that cavitation of the hydroid strand enables hydraulic isolation of extremities during rapid drying, effectively slowing water loss from the clump. Ceratodon maintained photosynthetic activity during drying to lower shoot RWC than Schistidium, consistent with a strategy of drought tolerance. These ecophysiological characteristics may provide a functional explanation for the differential distribution of Schistidium and Ceratodon along moisture gradients in Antarctica. Thus, predicting responses of non-vascular vegetation to climate change at high latitudes requires greater focus on VPD and hydraulics than temperature.
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Affiliation(s)
- Daniel E Stanton
- Plant Science Division, Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia
| | - Morgane Merlin
- Plant Science Division, Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia
| | - Gary Bryant
- School of Applied Sciences, RMIT, Melbourne Vic. 3001, Australia
| | - Marilyn C Ball
- Plant Science Division, Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia
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Proctor MCF. The Diversification of Bryophytes and Vascular Plants in Evolving Terrestrial Environments. ADVANCES IN PHOTOSYNTHESIS AND RESPIRATION 2014. [DOI: 10.1007/978-94-007-6988-5_4] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Bramley-Alves J, King DH, Robinson SA, Miller RE. Dominating the Antarctic Environment: Bryophytes in a Time of Change. ADVANCES IN PHOTOSYNTHESIS AND RESPIRATION 2014. [DOI: 10.1007/978-94-007-6988-5_17] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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12
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Weber B, Graf T, Bass M. Ecophysiological analysis of moss-dominated biological soil crusts and their separate components from the Succulent Karoo, South Africa. PLANTA 2012; 236:129-139. [PMID: 22278609 DOI: 10.1007/s00425-012-1595-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2011] [Accepted: 01/11/2012] [Indexed: 05/31/2023]
Abstract
Biological soil crusts, formed by an association of soil particles with cyanobacteria, lichens, mosses, fungi and bacteria in varying proportions, live in or directly on top of the uppermost soil layer. To evaluate their role in the global carbon cycle, gas exchange measurements were conducted under controlled conditions. Moss-dominated soil crusts were first analyzed as moss tufts on soil, then the mosses were removed and the soil was analyzed separately to obtain the physiological response of both soil and individual moss stems. Net photosynthetic response of moss stems and complete crusts was decreased by insufficient and excess amounts of water, resulting in optimum curves with similar ranges of optimum water content. Light saturation of both sample types occurred at high irradiance, but moss stems reached light compensation and saturation points at lower values. Optimum temperatures of moss stems ranged between 22 and 27°C, whereas complete crusts reached similar net photosynthesis between 7 and 27°C. Under optimum conditions, moss stems reached higher net photosynthesis (4.0 vs. 2.8 μmol m(-2) s(-1)) and lower dark respiration rates (-0.9 vs. -2.4 μmol m(-2) s(-1)). Respiration rates of soil without moss stems were high (up to -2.0 μmol m(-2) s(-1)) causing by far lower absolute values of NP/DR ratios of soil crusts as compared to moss stems. In carbon balances, it therefore has to be clearly distinguished between measurements of soil crust components versus complete crusts. High rates of soil respiration may be caused by leaching of mosses, creating high-nutrient microsites that favor microorganism growth.
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Affiliation(s)
- Bettina Weber
- Department of Biology, Plant Ecology and Systematics, University of Kaiserslautern, P.O. Box 3049, 67653, Kaiserslautern, Germany.
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Microclimate impacts of passive warming methods in Antarctica: implications for climate change studies. Polar Biol 2011. [DOI: 10.1007/s00300-011-0997-y] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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14
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Proctor MCF, Smirnoff N. Ecophysiology of photosynthesis in bryophytes: major roles for oxygen photoreduction and non-photochemical quenching? PHYSIOLOGIA PLANTARUM 2011; 141:130-40. [PMID: 20969578 DOI: 10.1111/j.1399-3054.2010.01424.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
CO(2) fixation in mosses saturates at moderate irradiances. Relative electron transport rate (RETR) inferred from chlorophyll fluorescence saturates at similar irradiance in shade species (e.g. Plagiomnium undulatum, Trichocolea tomentella), but many species of unshaded habitats (e.g. Andreaea rothii, Schistidium apocarpum, Sphagnum spp. and Frullania dilatata) show non-saturating RETR at high irradiance, with high non-photochemical quenching (NPQ). In P. undulatum and S. apocarpum, experiments in different gas mixtures showed O(2) and CO(2) as interchangeable electron sinks. Nitrogen + saturating CO(2) gave high RETR and depressed NPQ. In S. apocarpum, glycolaldehyde (inhibiting photosynthesis and photorespiration) depressed RETR in air more at low than at high irradiance; in CO(2) -free air RETR was maintained at all irradiances. Non-saturating electron flow was not suppressed in ambient CO(2) with 1% O(2) . The results indicate high capacity for oxygen photoreduction when CO(2) assimilation is limited. Non-saturating light-dependent H(2) O(2) production, insensitive to glycolaldehyde, suggests that electron transport is supported by oxygen photoreduction, perhaps via the Mehler-peroxidase reaction. Consistent with this, mosses were highly tolerant to paraquat, which generates superoxide at photosystem I (PSI). Protection against excess excitation energy in mosses involves high capacity for photosynthetic electron transport to oxygen and high NPQ, activated at high irradiance, alongside high reactive oxygen species (ROS) tolerance.
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Affiliation(s)
- Michael C F Proctor
- School of Biosciences, University of Exeter, Geoffrey Pope Building, Stocker Road, Exeter, EX4 4QG, Devon, UK.
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Block W, Lewis Smith RI, Kennedy AD. Strategies of survival and resource exploitation in the Antarctic fellfield ecosystem. Biol Rev Camb Philos Soc 2009; 84:449-84. [DOI: 10.1111/j.1469-185x.2009.00084.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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16
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Granath G, Wiedermann MM, Strengbom J. Physiological responses to nitrogen and sulphur addition and raised temperature in Sphagnum balticum. Oecologia 2009; 161:481-90. [PMID: 19593588 DOI: 10.1007/s00442-009-1406-x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2008] [Accepted: 06/16/2009] [Indexed: 10/20/2022]
Abstract
Sphagnum, the main genus which forms boreal peat, is strongly affected by N and S deposition and raised temperature, but the physiological mechanisms behind the responses are largely unknown. We measured maximum photosynthetic rate (NP(max)), maximum efficiency of photosystem II [variable fluorescence (F (v))/maximum fluorescence yield (F (m))] and concentrations of N, C, chlorophyll and carotenoids as responses to N and S addition and increased temperature in Sphagnum balticum (a widespread species in the northern peatlands) in a 12-year factorial experiment. NP(max) did not differ between control (0.2 g N m(-2) year(-1)) and high N (3.0 g N m(-2) year(-1)), but was higher in the mid N treatment (1.5 g N m(-2) year(-1)). N, C, carotenoids and chlorophyll concentration increased in shoot apices after N addition. F (v)/F (m) did not differ between N treatments. Increased temperature (+3.6 degrees C) had a small negative effect on N concentration, but had no significant effect on NP(max) or F (v)/F (m). Addition of 2 g S m(-2) year(-1) showed a weak negative effect on NP(max) and F (v)/F (m). Our results suggest a unimodal response of NP(max) to N addition and tissue N concentration in S. balticum, with an optimum N concentration for photosynthetic rate of ~13 mg N g(-1). In conclusion, high S deposition may reduce photosynthetic capacity in Sphagnum, but the negative effects may be relaxed under high N availability. We suggest that previously reported negative effects on Sphagnum productivity under high N deposition are not related to negative effects on the photosynthetic apparatus, but differences in optimum N concentration among Sphagnum species may affect their competitive ability under different N deposition regimes.
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Affiliation(s)
- Gustaf Granath
- Department of Plant Ecology, Evolutionary Biology Centre, Uppsala University, 75236 Uppsala, Sweden.
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