Variation in shoot architecture traits and their relationship to canopy coverage and light interception in soybean (Glycine max)

BACKGROUND

In soybeans, faster canopy coverage (CC) is a highly desirable trait but a fully covered canopy is unfavorable to light interception at lower levels in the canopy with most of the incident radiation intercepted at the top of the canopy. Shoot architecture that influences CC is well studied in crops such as maize and wheat, and altering architectural traits has resulted in enhanced yield. However, in soybeans the study of shoot architecture has not been as extensive.

RESULTS

This study revealed significant differences in CC among the selected soybean accessions. The rate of CC was found to decrease at the beginning of the reproductive stage (R1) followed by an increase during the R2-R3 stages. Most of the accessions in the study achieved maximum rate of CC between R2-R3 stages. We measured Light interception (LI), defined here as the ratio of Photosynthetically Active Radiation (PAR) transmitted through the canopy to the incoming PAR or the radiation above the canopy. LI was found to be significantly correlated with CC parameters, highlighting the relationship between canopy structure and light interception. The study also explored the impact of plant shape on LI and CO2 assimilation. Plant shape was characterized into distinct quantifiable parameters and by modeling the impact of plant shape on LI and CO2 assimilation, we found that plants with broad and flat shapes at the top maybe more photosynthetically efficient at low light levels, while conical shapes were likely more advantageous when light was abundant. Shoot architecture of plants in this study was described in terms of whole plant, branching and leaf-related traits. There was significant variation for the shoot architecture traits between different accessions, displaying high reliability. We found that that several shoot architecture traits such as plant height, and leaf and internode-related traits strongly influenced CC and LI.

CONCLUSION

In conclusion, this study provides insight into the relationship between soybean shoot architecture, canopy coverage, and light interception. It demonstrates that novel shoot architecture traits we have defined here are genetically variable, impact CC and LI and contribute to our understanding of soybean morphology. Correlations between different architecture traits, CC and LI suggest that it is possible to optimize soybean growth without compromising on light transmission within the soybean canopy. In addition, the study underscores the utility of integrating low-cost 2D phenotyping as a practical and cost-effective alternative to more time-intensive 3D or high-tech low-throughput methods. This approach offers a feasible means of studying basic shoot architecture traits at the field level, facilitating a broader and efficient assessment of plant morphology.

Technologies used in ruminant grazing management: an integrative review

The objective of this study was to identify the main technologies used in the management of ruminant grazing. We developed a review protocol in which the search terms were previously tested and based on the PVO strategy to determine the guiding question (population [P]: domestic ruminants; variables [V] of interest: grazing management technologies; and outcomes [O]: intake, performance, and productivity of animals raised exclusively on pasture). The guiding question was the following: What technologies are used in the grazing management of domestic ruminants on pasture? The databases used were SCOPUS (Elsevier), SciELO Citation Index, Science Direct, and Wiley Online Library, and the search was carried out until October 15, 2021. The search identified 2683 research articles; however, only 43 were considered eligible and included due to their methodological robustness for data extraction. The most commonly used species were Lolium multiflorum and Lolium perenne (20%), Panicum maximum (18%), and Brachiaria brizantha (14%). The most widely used grazing methods were continuous grazing (53.4%) and intermittent grazing (39.5%). Among the technologies, the most widely adopted were pasture height (55.8%) and herbage allowance (11.6%). The most frequent sampling methods were the use of a ruler (37.2%) and measuring stick (13.9%) to measure the height, and clipping with a frame (18.6%) to measure herbage allowance. The animals used in the included studies were cattle (n = 1335), sheep (n = 839), and goats (n = 41). Pasture height and herbage allowance were the most widely used grazing management technologies, with the data concentrated mainly in Brazil, in studies with continuous grazing by cattle.

Green manuring effects on crop morpho-physiological characters, rice yield and soil properties

A field experiment was carried out to evaluate the effect of green manure and nitrogen fertilizer on morpho-physiological traits, yield and post-harvest nutrient status of the soil during kharif season of 2017. The experiment was laid out with a randomized complete block design with twelve treatments, and was replicated thrice. The treatments were T1 [Control (no green manure + no fertilizer)], T2 (Sesbania aculeata + N0), T3 (Sesbania aculeata + N15), T4 (Sesbania aculeata + N30), T5 (Sesbania aculeata + N45), T6 (Sesbania aculeata + N60), T7 (Crotalaria juncea + N0), T8 (Crotalaria juncea + N15), T9 (Crotalaria juncea + N30), T10 (Crotalaria juncea + N45), T11 (Crotalaria juncea + N60), and T12 (N60). Incorporation of green manure with nitrogen fertilizer generated consistently positive responses in important morpho-physiological traits such as chlorophyll content (SPAD value), leaf area index (LAI), light interception percent (%LI), and net assimilation rate (NAR), which may result in higher grain yield compared to control, and N60 due to greater contribution of yield determining traits. Treatment comprising green manure with N60 produced significantly the higher grain yield even over the N60. The results of this research indicated that balanced nutrients supply increased leaf chlorophyll content, LAI, %LI, NAR, and finally led to higher dry matter production and yield of rice. Incorporation of green manure also had significantly increased the macro- and micronutrient content of post-harvest soil. These results suggest that continuous use of fertilizer might lead to a yield loses of rice, and that situation could be escaped by a combined application of green manure and judicial nitrogen fertilizer management.

Higher photosynthetic capacity and different functional trait scaling relationships in erect bryophytes compared with prostrate species

Ecophysiological studies of bryophytes have generally been conducted at the shoot or canopy scale. However, their growth forms are diverse, and knowledge of whether bryophytes with different shoot structures have different functional trait levels and scaling relationships is limited. We collected 27 bryophyte species and categorised them into two groups based on their growth forms: erect and prostrate species. Twenty-one morphological, nutrient and photosynthetic traits were quantified. Trait levels and bivariate trait scaling relationships across species were compared between the two groups. The two groups had similar mean values for shoot mass per area (SMA), light saturation point and mass-based nitrogen (N(mass)) and phosphorus concentrations. Erect bryophytes possessed higher values for mass-based chlorophyll concentration (Chl(mass)), light-saturated assimilation rate (A(mass)) and photosynthetic nitrogen/phosphorus use efficiency. N(mass), Chl(mass) and A(mass) were positively related, and these traits were negatively associated with SMA. Furthermore, the slope of the regression of N(mass) versus Chl(mass) was steeper for erect bryophytes than that for prostrate bryophytes, whereas this pattern was reversed for the relationship between Chl(mass) and A(mass). In conclusion, erect bryophytes possess higher photosynthetic capacities than prostrate species. Furthermore, erect bryophytes invest more nitrogen in chloroplast pigments to improve their light-harvesting ability, while the structure of prostrate species permits more efficient light capture. This study confirms the effect of growth form on the functional trait levels and scaling relationships of bryophytes. It also suggests that bryophytes could be good models for investigating the carbon economy and nutrient allocation of plants at the shoot rather than the leaf scale.

Petiole mechanics, leaf inclination, morphology, and investment in support in relation to light availability in the canopy of Liriodendron tulipifera

To determine the role of leaf mechanical properties in altering foliar inclination angles, and the nutrient and carbon costs of specific foliar angle variation patterns along the canopy, leaf structural and biomechanical characteristics, biomass partitioning into support, and foliar nitrogen and carbon concentrations were studied in the temperate deciduous species Liriodendron tulipifera L., which possesses large leaves on long petioles. We used beam theory to model leaf lamina as a uniform load, and estimated both the lamina and petiole flexural stiffness, which characterizes the resistance to bending of foliar elements at a common load and length. Petiole and lamina vertical inclination angles with respect to horizontal increased with increasing average daily integrated photon flux density (Q _int). Yet, the light effects on lamina inclination angle were primary determined by the petiole inclination angle. Although the petioles and laminas became longer, and the lamina loads increased with increasing Q _int, the flexural stiffness of both lamina and petiole increased to compensate for this, such that the lamina vertical displacement was only weakly related to Q _int. In addition, increases and decreases in the petiole inclination angle with respect to the horizontal effectively reduced the distance of lamina load from the axis of rotation, thereby reducing the bending moments and lamina inclination due to gravity. We demonstrate that large investments, up to 30% of total leaf biomass, in petiole and large veins are necessary to maintain the lamina at a specific position, but also that light has no direct effect on the fractional biomass investment in support. However, we provide evidence that apart from light availability, structural and chemical characteristics of the foliage may also be affected by water stress, magnitude of which scales positively with Q _int.

Koch in a partially shaded forest environment

Leaf orientations and light environments were recorded for 40 juvenile Pseudopanax crassifolius trees growing in New Zealand in a partially shaded, secondary forest environment. Efficiencies of interception of diffuse and direct light by the observed leaf arrangments were calculated relative to those of three hypothetical leaf arrangements. Canopy gaps above the study plants were unevenly distributed with respect to azimuth and elevation above the horizon. Our results indicate that photosynthetically active radiation (PAR) received from the sides is more important than that received from directly above. In 33 of the plants leaf orientation was found to be significantly clustered towards one azimuth. The mean azimuth and the mean angle of declination were different for each plant. Leaves were steeply declined, and oriented towards the largest canopy gap at each site. Steep leaf angles reduced interception of direct and diffuse PAR when compared to interception by plant with a hypothetical horizontal leaf arrangement. When compared to a hypothetical arrangement with steep leaf declination and a uniform azimuth distribution, the observed leaf arrangement increased the efficiency of interception of diffuse PAR, but had a variable effect on the interception of direct PAR. Results indicate that the developing leaves of juvenile P. crassifolius orient towards the strongest sources of diffuse light, regardless of their value as a source of direct light. By maximising diffuse light interception while reducing direct light interception, leaf orientation may be a partial determinant of the types of habitats exploited by this species. This study emphasises the importance of considering diffuse light interception for plants growing in partially shaded environments.

Petiole mechanics, light interception by Lamina, and "Economy in Design"

Computer simulations were used to assess the influence of palmate leaf morphology, decussate phyllotaxy, and the elastic moduli of petioles on the capacity of turgid and wilted twigs ofAesculus hippocastanum to intercept direct solar radiation. Leaf size, morphology, orientation, and the Young's and shear moduli (E and G) of petioles were measured and related to leaf position on 8 twigs whose cut ends were placed in water ("turgid" twigs) and 8 twigs dried for 8 h at room temperature ("wilted" twigs). Petioles mechanically behaved as elastic cantilevered beams; the loads required to shear petioles at their base from twigs were correlated with the cross-sectional areas of phyllopodia but not with petiole length or tissue volume. Empirically determined morphometric and biomechanical data were used to construct "average" turgid and wilted twigs. The diurnal capacity to intercept direct sunlight for each was simulated for vertically oriented twigs for 15 h of daylight, 40° N latitude. The daily integrated irradiance (DII) of the wilted twig was roughly 3% less than that of the otherwise comparable twig bearing turgid leaves. Simulations indicated that the orientation of turgid leaves did not maximize DII. More decumbent (wilted) petioles increased DII by as much as 4%. Reduction in the girth, E, or G of petioles, or an increase in petiole length or the surface area of laminae (with attending increase in laminae weight), increased petiolar deflections and DII. Thus, the mechanical design of petioles ofA. hippocastanum was found not to be "economical" in terms of investing biomass for maximum light interception.