Search

Understory forest plants are often limited by shade from the canopy above them. Many such species therefore make use of a shade avoidance strategy referred to as "phenological escape" to access ephemeral light availability during periods when the canopy above them is open (e.g., in early spring). In this primer, we review past literature on phenological escape and related topics. We discuss (1) the physiological importance of this shade avoidance strategy, (2) the effects that climate change may have on species performance via changes in phenological escape, (3) the potential for climate change to result in phenological mismatch related to shade avoidance, and (4) the potential avenues of future research in this area of study. Phenological escape is an important strategy used by spring-active plant species ranging from spring ephemeral wildflowers to deciduous tree seedlings, allowing them to assimilate 50%–100% of their annual carbon budgets before the canopy closes above them. Access to spring light, and thus success of this shade avoidance strategy, is projected to change in response to climate change. Change in access to light, and therefore change in spring performance, likely depends on functional group (woody vs. nonwoody plants), continent, and other geographic and environmental drivers. [ABSTRACT FROM AUTHOR]

Drought, heat, and their combined stress have increasingly become common phenomena in horticulture, significantly reducing chili production worldwide. The current study aimed to phenotype Akabare chili landraces (Capsicum spp.) in climate chambers subjected to drought and heat treatments during their early generative stage, focusing on PSII efficacy (Fv/Fm), net photosynthetic rate (PN), stomatal conductance (gs), leaf cooling, and biomass production. Six landraces were examined under heat and control conditions at 40/32 °C for 4 days and at 30/22 °C under drought and control conditions followed by a 5-day recovery under control conditions (30/22 °C, irrigated). Two landraces with higher (>0.77) and two with lower (

Urbanization creates novel ecosystems comprised of species assemblages and environments with no natural analogue. Moreover, irrigation can alter plant function compared to non-irrigated systems. However, the capacity of irrigation to alter functional trait patterns across multiple species is unknown but may be important for the dynamics of urban ecosystems. We evaluated the hypothesis that urban irrigation influences plasticity in functional traits by measuring carbon-gain and water-use traits of 30 tree species planted in Southern California, USA spanning a coastal-to-desert gradient. Tree species respond to irrigation through increasing the carbon-gain trait relationship of leaf nitrogen per specific leaf area compared to their native habitat. Moreover, most species shift to a water-use strategy of greater water loss through stomata when planted in irrigated desert-like environments compared to coastal environments, implying that irrigated species capitalize on increased water availability to cool their leaves in extreme heat and high evaporative demand conditions. Therefore, irrigated urban environments increase the plasticity of trait responses compared to native ecosystems, allowing for novel response to climatic variation. Our results indicate that trees grown in water-resource-rich urban ecosystems can alter their functional traits plasticity beyond those measured in native ecosystems, which can lead to plant trait dynamics with no natural analogue.

To determine the invasiveness of invasive plants, many studies have compared photosynthetic traits or strategies between invasive and native species. However, few studies have compared the photosynthetic dynamics between invasive and native species during light fluctuations. We compared photosynthetic induction, relaxation dynamics and leaf traits between the invasive species, Tithonia diversifolia and two native species, Clerodendrum bungei and Blumea balsamifera, in full-sun and shady habitats. The photosynthetic dynamics and leaf traits differed among species. T. diversifolia showed a slower induction speed and stomatal opening response but had higher average intrinsic water-use efficiency than the two native species in full-sun habitats. Thus, the slow induction response may be attributed to the longer stomatal length in T. diversifolia. Habitat had a significant effect on photosynthetic dynamics in T. diversifolia and B. balsamifera but not in C. bungei. In shady habitat, T. diversifolia had a faster photosynthetic induction response than in full-sun habitat, leading to a higher average stomatal conductance during photosynthetic induction in T. diversifolia than in the two native species. In contrast, B. balsamifera had a larger stomatal length and slower photosynthetic induction and relaxation response in shady habitat than in full-sun habitat, resulting in higher carbon gain during photosynthetic relaxation. Nevertheless, in both habitats, T. diversifolia had an overall higher carbon gain during light fluctuations than the two native species. Our results indicated that T. diversifolia can adopt more effective response strategies under fluctuating light environments to maximize carbon gain, which may contribute to its successful invasion.

Understanding understory seedling regeneration mechanisms is important for the sustainable development of temperate primary forests in the context of increasingly intense climate warming events. The poor regeneration of dominant tree species, however, is one of the biggest challenges it faces at the moment. Especially, the regeneration of the shade-intolerant Quercus mongolica seedling is difficult in primary forests, which contrasts with the extreme abundance of understory seedlings in secondary forests. The mechanism behind the interesting phenomenon is still unknown. This study used in-situ monitoring and nursery-controlled experiment to investigate the survival rate, growth performance, as well as nonstructural carbohydrate (NSC) concentrations and pools of various organ tissues of seedlings for two consecutive years, further analyze the understory light availability and simulate the foliage carbon (C) gain in the secondary and primary forest. Results suggested that seedlings in the secondary forest had greater biomass allocation aboveground, height and specific leaf area (SLA) in summer, which allowed the seedling to survive longer in the canopy closure period. High light availability and positive C gain in early spring and late autumn are key factors affecting the growth and survival of understory seedlings in the secondary forest, whereas seedlings in the primary forest had annual negative carbon gain. Through the growing season, the total NSC concentrations of seedlings gradually decreased, whereas those of seedlings in the secondary forest increased significantly in autumn, and were mainly stored in roots for winter consumption and the following year's summer shade period, which was verified by the nursery-controlled experiment that simulated autumn enhanced light availability improved seedling survival rate and NSC pools. In conclusion, our results revealed the survival trade-off strategies of Quercus mongolica seedlings and highlighted the necessity of high light availability during the spring and autumn phenological periods for shade-intolerant tree seedling recruitment.

The study aimed to show that droughts are increasing in frequency and intensity in the Dinghushan Biosphere Reserve and to illustrate the effects of seasonal droughts on carbon gain in a subtropical forest. This is in response to the threat posed by increased droughts due to global climate change. We used four drought indices to accurately determine periods of drought and periods of increased precipitation. Thereafter, the measured eddy flux and soil moisture content data collected from 2003 to 2014 were compared between the droughts and wet periods to determine drought impacts on the ecosystem carbon gain. Drought accounted for about 20% of the 12-year study period, with the highest drought events and severity occurring between 2012 and 2013. The average annual precipitation and air temperature during the study period were 1404.57 ± 43.2 mm and 22.65 ± 0.1 °C, respectively, showing a decrease of 523 mm in precipitation and an increase of 2.55 °C in temperature, compared with the 30-year records (1990–2020). Contrary to most published data for most forest ecosystems globally, Dinghushan Biosphere Reserve recorded significant carbon gain during 60% of the drought period. [ABSTRACT FROM AUTHOR]

Simple Summary: Temperatures are increasing globally, but polar regions (including Antarctica) are warming much faster than the rest of the globe. Increased temperatures in Antarctica can impact the distribution and performance of plants, the majority of which on this continent are mosses. This study aims to investigate whether Bryum argenteum var. muticum, a moss species found in Antarctica, is capable of acclimation (adjustment of its physiology, specifically photosynthesis and respiration) to increased temperatures. We used short-term warming experiments that mimicked heatwaves and compared them to seasonal rates of photosynthesis and respiration in order to better understand how resilient this important moss species is to climate change. We found that this moss can acclimate very quickly (within 7 days) by increasing its photosynthesis (carbon gain). This shows that B. argenteum is highly resilient, and it may potentially benefit from short- and long-term climatic changes. Climate warming in Antarctica involves major shifts in plant distribution and productivity. This study aims to unravel the plasticity and acclimation potential of Bryum argenteum var. muticum, a cosmopolitan moss species found in Antarctica. By comparing short-term, closed-top chamber warming experiments which mimic heatwaves, with in situ seasonal physiological rates from Cape Hallett, Northern Victoria Land, we provide insights into the general inherent resilience of this important Antarctic moss and into its adaptability to longer-term threats and stressors associated with climate change. Our findings show that B. argenteum can thermally acclimate to mitigate the effects of increased temperature under both seasonal changes and short-term pulse warming events. Following pulse warming, this species dramatically increased its carbon uptake, measured as net photosynthesis, while reductions in carbon losses, measured as dark respiration, were not observed. Rapid growth of new shoots may have confounded the effects on respiration. These results demonstrate the high physiological plasticity of this species, with acclimation occurring within only 7 days. We show that this Antarctic moss species appears to have a high level of resilience and that fast acclimation processes allow it to potentially benefit from both short-term and long-term climatic changes. [ABSTRACT FROM AUTHOR]

Drought, heat, and their combined stress have increasingly become common phenomena in horticulture, significantly reducing chili production worldwide. The current study aimed to phenotype Akabare chili landraces ( Capsicum spp.) in climate chambers subjected to drought and heat treatments during their early generative stage, focusing on PSII efficacy (F v /F m ), net photosynthetic rate ( P N ), stomatal conductance ( g s ), leaf cooling, and biomass production. Six landraces were examined under heat and control conditions at 40/32 °C for 4 days and at 30/22 °C under drought and control conditions followed by a 5-day recovery under control conditions (30/22 °C, irrigated). Two landraces with higher (>0.77) and two with lower (<0.763) F v /F m during the stress treatments were later evaluated in the field under 55-day-long drought stress at the fruiting stage. In both treatments, stress-tolerant landraces maintained high F v /F m , P N , and better leaf cooling leading to improved biomass compared to the sensitive landraces. Agro-morpho-physiological responses of the tolerant and sensitive landraces during the early generative stage echoed those during the fruiting stage in the field. A climate chamber experiment revealed a 13.9 % decrease in total biomass under heat stress, a further 21.5 % reduction under drought stress, and a substantial 38.7 % decline under combine stress. In field conditions, drought stress reduced total biomass by 28.1 % and total fruit dry weight by 26.2 %. Tolerant landraces showed higher F v /F m , demonstrated better wilting scores, displayed a higher chlorophyll content index (CCI), and accumulated more biomass. This study validated lab-based results through field trials and identified two landraces, C44 and DKT77, as potential stress-tolerant genotypes. It recommends F v /F m , P N , and CCI as physiological markers for the early detection of stress tolerance., Competing Interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:All authors have equally contributed to the work entitled “Insights into the responses of Akabare chili landraces to drought, heat, and their combined stress during pre-flowering and fruiting stages.” The authors declare that the manuscript as submitted has not been published or accepted for publication, nor is being considered for publication elsewhere, either in whole or substantial part. We wish to confirm that there are no known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome. We confirm that the manuscript has been read and approved by all named authors and that there are no other people who satisfied the criteria for authorship but are not listed. We further confirm that the order of authors listed in the manuscript has been approved by all of us. We confirm that we have considered the protection of intellectual property associated with this work and that there are no impediments to publication, including the timing of publication, concerning intellectual property. In so doing we confirm that we have followed the regulations of our institutions concerning intellectual property. We further confirm none of our work or its part has involved either experimental animals or human patients and has been conducted with the ethical approval of all relevant bodies and that such approvals are acknowledged within the manuscript. Authors conform to the legal requirements of Denmark and Nepal where the work was conducted. We understand that the Corresponding Author is the sole contact for the Editorial process (including the Editorial Manager and direct communications with the office). He is responsible for communicating with the other authors about progress, submissions of revisions, and final approval of proofs. We confirm that we have provided a current, correct email address which is accessible by the Corresponding Author., (© 2024 The Authors.)

Climate warming in Antarctica involves major shifts in plant distribution and productivity. This study aims to unravel the plasticity and acclimation potential of Bryum argenteum var. muticum, a cosmopolitan moss species found in Antarctica. By comparing short-term, closed-top chamber warming experiments which mimic heatwaves, with in situ seasonal physiological rates from Cape Hallett, Northern Victoria Land, we provide insights into the general inherent resilience of this important Antarctic moss and into its adaptability to longer-term threats and stressors associated with climate change. Our findings show that B. argenteum can thermally acclimate to mitigate the effects of increased temperature under both seasonal changes and short-term pulse warming events. Following pulse warming, this species dramatically increased its carbon uptake, measured as net photosynthesis, while reductions in carbon losses, measured as dark respiration, were not observed. Rapid growth of new shoots may have confounded the effects on respiration. These results demonstrate the high physiological plasticity of this species, with acclimation occurring within only 7 days. We show that this Antarctic moss species appears to have a high level of resilience and that fast acclimation processes allow it to potentially benefit from both short-term and long-term climatic changes.

Traits are the primary attributes that distinguish a species niche. Species and higher taxa are part of a structured phylogeny, and variation in plant traits depends on lineage as well as on environmental conditions. Therefore, it is crucial to investigate linkages between taxonomic identity, shared ancestry, and environment for understanding the variation in leaf traits. We investigated the evolutionary relationships, based on multiple gene sequences among 26 plant species sampled along an elevational gradient from 650 to 3600 m a.s.l. in the central Himalaya. We tested for the phylogenetic signal based on three different measures in 10 leaf traits having a significant association with the resource acquisition-conservation trade-offs axis and influencing plant growth, development, and ecological performance. We further assessed the role of elevation and growth forms as the potential drivers of leaf traits variation while controlling for phylogeny. 5 out of 10 leaf traits showed significant phylogenetic signal. Plant species clustered more often by growth forms at the tips of the phylogeny indicating multiple instances of independent evolution. Evergreen taxa showed niche separation with deciduous and incorporated larger trait variation. Trait variations were guided by both growth forms and elevation when accounted for phylogeny. Growth form has a higher contribution to trait variation compared to elevation. Trade-offs were detected between resource conservation and resource acquisition machinery traits (that would maximise carbon gain), differing between growth forms and along elevation. [ABSTRACT FROM AUTHOR]

Spring greening has been widely observed across the Northern Hemisphere (NH) using a remotely sensed vegetation index (e.g., the normalized difference vegetation index, NDVI). However, there is still a debate on the ecological effects of spring greening on seasonal carbon and water budgets. This study jointly investigated the concurrent and lagged effects of spring greening on carbon gain (gross primary productivity, GPP) and water loss (evapotranspiration, ET) in the summer-active ecosystems at mid and high latitudes of NH using remote sensing and multimodel ensemble data during 1982–2013. The results showed that the collective promotion of spring greening to concurrent GPP and ET is widespread despite variations in magnitude and significance. Both beneficial and adverse lagged effects of spring greening on summer GPP commonly appear with an obvious spatial heterogeneity and difference among climate-plant types. However, the expected significant suppression of spring greening to summer GPP was rarely observed even in the areas where spring ET was significantly promoted by spring greening. Nevertheless, when drought was taken into account, the response patterns of spring water use to spring greening varied to some extent, and the adverse lagged effect of spring greening to summer GPP appeared or strengthened in some regions, especially during the years with dry summer. Given the predicted warming of the climate and more frequent climatic extremes, the adverse effect of spring greening should be given more attention. [ABSTRACT FROM AUTHOR]

Summary: Optimal stomatal control models have shown great potential in predicting stomatal behavior and improving carbon cycle modeling. Basic stomatal optimality theory posits that stomatal regulation maximizes the carbon gain relative to a penalty of stomatal opening. All models take a similar approach to calculate instantaneous carbon gain from stomatal opening (the gain function). Where the models diverge is in how they calculate the corresponding penalty (the penalty function). In this review, we compare and evaluate 10 different optimization models in how they quantify the penalty and how well they predict stomatal responses to the environment. We evaluate models in two ways. First, we compare their penalty functions against seven criteria that ensure a unique and qualitatively realistic solution. Second, we quantitatively test model against multiple leaf gas‐exchange datasets. The optimization models with better predictive skills have penalty functions that meet our seven criteria and use fitting parameters that are both few in number and physiology based. The most skilled models are those with a penalty function based on stress‐induced hydraulic failure. We conclude by proposing a new model that has a hydraulics‐based penalty function that meets all seven criteria and demonstrates a highly predictive skill against our test datasets. [ABSTRACT FROM AUTHOR]

This study intended to clarify whether low irradiance, high temperature or both acted as a trigger inducing summer dormancy in Daphne pseudomezereum (Dpm), a wintergreen shrub native to Japanese mixed forests. A 2-year growth chamber experiment was conducted in Otsu, Japan where, in the first year, 3 provenances of Dpm were raised in two irradiance levels by two temperature regimes to observe their effects on leaf phenology. The results showed a clear effect of temperature, but not irradiance, on leaf phenology. In the second year, the experiment was repeated using different Dpm plants and applying only the two temperature regimes. The results confirmed those obtained in the first year, where the temperature regime that tracked normal field condition induced summer dormancy similar to field populations. In both years, when plants were kept over the summer under a cool temperature regime mimicking field conditions in April, most plants did not undergo summer dormancy (i.e., becoming "evergreen"). In contrast to phenology, leaf morphology (i.e., LMA), and photosynthetic capacity (e.g., Amax) did respond to irradiance levels consistent with shade adaptive changes, but were not affected by temperature. Simulated carbon gain using previously determined parameters for Dpm and the chamber microclimate data found that only plants in the warm treatment experienced carbon deficit in mid-summer. These findings suggest that summer temperature alone and the attendant rise in respiration can alter internal carbon balance and trigger the onset of summer dormancy in Dpm. [ABSTRACT FROM AUTHOR]

Xylem density is a physical property of wood that varies between individuals, species and environments. It reflects the physiological strategies of trees that lead to growth, survival and reproduction. Measurements of branch xylem density, ρx, were made for 1653 trees representing 598 species, sampled from 87 sites across the Amazon basin. Measured values ranged from 218 kg m−3for a Cordia sagotii (Boraginaceae) from Mountagne de Tortue, French Guiana to 1130 kg m−3 for an Aiouea sp. (Lauraceae) from Caxiuana, Central Pará, Brazil. Analysis of variance showed significant differences in average ρx across regions and sampled plots as well as significant differences between families, genera and species. A partitioning of the total variance in the dataset showed that species identity (family, genera and species) accounted for 33% with environment (geographic location and plot) accounting for an additional 26%; the remaining "residual" variance accounted for 41% of the total variance. Variations in plot means, were, however, not only accountable by differences in species composition because xylem density of the most widely distributed species in our dataset varied systematically from plot to plot. Thus, as well as having a genetic component, branch xylem density is a plastic trait that, for any given species, varies according to where the tree is growing in a predictable manner. Within the analysed taxa, exceptions to this general rule seem to be pioneer species belonging for example to the Urticaceae whose branch xylem density is more constrained than most species sampled in this study. These patterns of variation of branch xylem density across Amazonia suggest a large functional diversity amongst Amazonian trees which is not well understood.

Individual leaves have a unique instantaneous photosynthetic photon flux density (PPFD) at which net photosynthetic light use efficiency (εL, the ratio between net photosynthesis and PPFD) is maximised (PPFDεmax). When PPFD is above or below PPFDεmax, efficiency declines. Thus, we hypothesised that heterogeneous PPFD conditions should increase the amount of time leaves photosynthesise at a PPFD different than PPFDεmax and result in reduced growth. To date, this prediction has not been rigorously tested. Here, we exposed seedlings of Abatia parviflora Ruiz & Pav to light regimes of equal total daily irradiance but with three different daily time courses of PPFD: constant PPFD (No_H), low heterogeneity (Low_H) and high heterogeneity (High_H). Mean εL, leaf daily photosynthesis and plant growth were all significantly higher in No_H and Low_H plants than in High_H plants, supporting our hypothesis. In addition, mean εL was positively related to final plant biomass. Unexpectedly, High_H plants had more etiolated stems and more horizontal leaves than No_H and Low_H plants, possibly due to exposure to low PPFD in the morning and afternoon. In conclusion, PPFD heterogeneity had an important effect on average εL, photosynthesis and growth, but also on allocation and plant morphology. In theory, plants have evolved to maximise the efficiency with which they use light (maximise photosynthesis per unit light), yet there is limited empirical evidence to show that efficiency can have strong effects on plant growth. By exposing plants to different distributions of light in the day, we demonstrated that low efficiency can reduce plant growth by nearly 50%. Thus, we found clear support for the general expectation that light use efficiency is a central determinant of plant performance. [ABSTRACT FROM AUTHOR]

Interacting species can respond differently to climate change, causing unexpected consequences. Many understorey wildflowers in deciduous forests leaf out and flower in the spring when light availability is the highest before overstorey canopy closure. Therefore, different phenological responses by understorey and overstorey species to increased spring temperature could have significant ecological implications. Pairing contemporary data with historical observations initiated by Henry David Thoreau (1850s), we found that overstorey tree leaf out is more responsive to increased spring temperature than understorey wildflower phenology, resulting in shorter periods of high light in the understorey before wildflowers are shaded by tree canopies. Because of this overstorey–understorey mismatch, we estimate that wildflower spring carbon budgets in the northeastern United States were 12–26% larger during Thoreau's era and project a 10–48% reduction during this century. This underappreciated phenomenon may have already reduced wildflower fitness and could lead to future population declines in these ecologically important species. [ABSTRACT FROM AUTHOR]

Highlights • We digitized leaf canopies of individual plants that had grown in dense stands, contrasting a two wild Australian rice lines with cultivated rice. • The densest canopies were observed in one wild accession, where self-shading compromised the efficiency of light capture. • However, this self-shading in dense canopies was compensated by larger leaf canopies that captured more light. • As a result, calculated rates of carbon gain per day - and actual dry biomass - were highest when canopies were densest. • Elevated carbon dioxide atmospheres made denser crowns but did not affect the rank of species performance. • Simulation of seasons indicated a peak of light capture during the Summer Solstice. Abstract Oryza sativa has many wild relatives that exhibit a wide range of canopy architectures. Two fast-growing ecotypes of an Australian wild rice ( O. meridionalis ) were compared with cultivated O. sativa to analyze the efficiency of light interception in mature vegetative canopies and how well light capture predicts biomass production. Canopies of individual plants were digitized and analyzed with YplantQMC. Plants were also grown at 700 ppm CO 2 as a means of increasing the canopy density and assessing the relative impact of rising CO 2 levels on photosynthesis, light interception and biomass. Simulations of light interception for these morphologically diverse canopies were combined with photosynthetic light response curves to estimate theoretical carbon gain. Both O. meridionalis genotypes had more tillers and leaves, and denser canopies, than O. sativa but one (‘Howard Springs’) intercepted more light than the other two genotypes, resulting in the highest simulated carbon gains. Photosynthesis per unit leaf area ( A max ) was enhanced by 20–50% in 700 ppm CO 2 in all genotypes but the proportion of total leaf area intercepting light decreased as a result of denser leaf canopies in these plants. Estimated total shoot carbon gain increased strongly at elevated CO 2 despite these denser canopies and increased self-shading, reaching a peak in ‘Howard Springs’ at 700 ppm CO 2. Thus, while high crown density and low leaf dispersion reduced the efficiency of light interception by the canopy, elevated CO 2 still enhanced growth through consistently higher assimilation rates. Simulations showed that during the Summer Solstice, carbon gain was predicted to be greater than at the Equinox through superior light capture, particularly in ‘Howard Springs’. However, the relationship between light interception and carbon gain was broadly maintained, regardless of genotype, CO 2 concentration and season. [ABSTRACT FROM AUTHOR]

In nature, crops such as soybean are concurrently exposed to temperature (T) stress and phosphorus (P) deficiency. However, there is a lack of reports regarding soybean response to T × P interaction. To fill in this knowledge-gap, soybean was grown at four daily mean T of 22, 26, 30, and 34°C (moderately low, optimum, moderately high, and high temperature, respectively) each under sufficient (0.5 mM) and deficient (0.08 mM) P nutrition for the entire season. Phosphorus deficiency exacerbated the low temperature stress, with further restrictions on growth and net photosynthesis. For P deficient soybean at above optimum temperature (OT) regimes, growth, and photosynthesis was maintained at levels close to those of P sufficient plants, despite a lower tissue P concentration. P deficiency consistently decreased plant tissue P concentration ≈55% across temperatures while increasing intrinsic P utilization efficiency of canopy photosynthesis up to 147%, indicating a better utilization of tissue P. Warmer than OTs delayed the time to anthesis by 8–14 days and pod development similarly across P levels. However, biomass partitioning to pods was greater under P deficiency. There were significant T × P interactions for traits such as plant growth rates, total leaf area, biomass partitioning, and dry matter production, which resulted a distinct T response of soybean growth between sufficient and deficient P nutrition. Under sufficient P level, both lower and higher than optimum T tended to decrease total dry matter production and canopy photosynthesis. However, under P-deficient condition, this decrease was primarily observed at the low T. Thus, warmer than optimum T of this study appeared to compensate for decreases in soybean canopy photosynthesis and dry matter accumulation resulting from P deficiency. However, warmer than OT appeared to adversely affect reproductive structures, such as pod development, across P fertilization. This occurred despite adaptations, especially the increased P utilization efficiency and biomass partitioning to pods, shown by soybean under P deficiency.

In nature, crops such as soybean are concurrently exposed to temperature (T) stress and phosphorus (P) deficiency. However, there is a lack of reports regarding soybean response to T × P interaction. To fill in this knowledge-gap, soybean was grown at four daily mean T of 22, 26, 30, and 34°C (moderately low, optimum, moderately high, and high temperature, respectively) each under sufficient (0.5 mM) and deficient (0.08 mM) P nutrition for the entire season. Phosphorus deficiency exacerbated the low temperature stress, with further restrictions on growth and net photosynthesis. For P deficient soybean at above optimum temperature (OT) regimes, growth, and photosynthesis was maintained at levels close to those of P sufficient plants, despite a lower tissue P concentration. P deficiency consistently decreased plant tissue P concentration ≈55% across temperatures while increasing intrinsic P utilization efficiency of canopy photosynthesis up to 147%, indicating a better utilization of tissue P. Warmer than OTs delayed the time to anthesis by 8–14 days and pod development similarly across P levels. However, biomass partitioning to pods was greater under P deficiency. There were significant T × P interactions for traits such as plant growth rates, total leaf area, biomass partitioning, and dry matter production, which resulted a distinct T response of soybean growth between sufficient and deficient P nutrition. Under sufficient P level, both lower and higher than optimum T tended to decrease total dry matter production and canopy photosynthesis. However, under P-deficient condition, this decrease was primarily observed at the low T. Thus, warmer than optimum T of this study appeared to compensate for decreases in soybean canopy photosynthesis and dry matter accumulation resulting from P deficiency. However, warmer than OT appeared to adversely affect reproductive structures, such as pod development, across P fertilization. This occurred despite adaptations, especially the increased P utilization efficiency and biomass partitioning to pods, shown by soybean under P deficiency. [ABSTRACT FROM AUTHOR]

Water-use efficiency ( WUE ) at the whole-plant level plays as an important role as an indicator of both the water-use strategy of the plant, and the ecophysiological processes linking the carbon and water cycles. However, the variation in the annual pattern of WUE , the interannual trends, and the regulating factors of WUE in rubber plantations remain poorly understood. Here, we used a four-year (2013–2016) continuous biometric survey along with sap flow data recorded at a monthly resolution to examine the annual and interannual dynamics of WUE and the relationships of WUE with environmental and biological factors in rubber ( Hevea brasiliensis ) plantations in Southwest China. The results showed that (1) there was no definitive pattern in WUE between April and December, but the peak WUE values generally occurred around August; (2) the multi-year mean WUE was 2.34 ± 0.19 g C·kg −1 H 2 O, and a negative correlation of WUE to photosynthetically active radiation was found at the interannual scale ( r  = −0.962, P  < 0.05); and (3) a moderate, significant and parabolic relationship of WUE with air temperature ( R 2  = 0.40), net radiation ( R 2  = 0.37) and growth rate of the diameter at breast height ( R 2  = 0.35) was observed at the monthly scale during the growing season ( P  < 0.001). These findings indicate that WUE might be regulated by factors affecting the carbon sequestration rather than water consumption, and it will provide a deeper understanding of the ecohydrological and coupled processes between the carbon and water cycles of rubber plants. [ABSTRACT FROM AUTHOR]

Abstract: From 2011 to 2013, Texas experienced its worst drought in recorded history. This event provided a unique natural experiment to assess species‐specific responses to extreme drought and mortality of four co‐occurring woody species: Quercus fusiformis, Diospyros texana, Prosopis glandulosa, and Juniperus ashei. We examined hypothesized mechanisms that could promote these species' diverse mortality patterns using postdrought measurements on surviving trees coupled to retrospective process modelling. The species exhibited a wide range of gas exchange responses, hydraulic strategies, and mortality rates. Multiple proposed indices of mortality mechanisms were inconsistent with the observed mortality patterns across species, including measures of the degree of iso/anisohydry, photosynthesis, carbohydrate depletion, and hydraulic safety margins. Large losses of spring and summer whole‐tree conductance (driven by belowground losses of conductance) and shallower rooting depths were associated with species that exhibited greater mortality. Based on this retrospective analysis, we suggest that species more vulnerable to drought were more likely to have succumbed to hydraulic failure belowground. [ABSTRACT FROM AUTHOR]

Multiple studies have examined the effects of clouds on shoot and canopy-level microclimate and physiological processes; none have yet done so on the scale of individual plant crowns. We compared incident photosynthetically active radiation (PAR), leaf temperatures, chlorophyll fluorescence, and photosynthetic gas exchange of shoots in three different spatial locations of Abies fraseri crowns on sunny (clear to partly cloudy) versus overcast days. The field site was a Fraser fir farm (1038 m elevation) in the Appalachian mountains, USA. Ten saplings of the same age class were marked and revisited for all measurements. Sunny conditions corresponded with 5-10× greater sunlight incidence on south-facing outer shoots compared to south-facing inner and north-facing outer shoots, which were shaded and received only indirect (diffuse) sunlight. Differences in spatial distribution of irradiance were mirrored in differences in shoot temperatures, photosynthesis, and transpiration, which were all greater in south-facing outer shoots compared to more shaded crown locations. In contrast, overcast conditions corresponded with more homogeneous sunlight distribution between north and south-facing outer shoots, and similar shoot temperatures, chlorophyll fluorescence (ΦPSII), photosynthesis, and transpiration; these effects were observed in south-facing inner shoots as well, but to a lesser extent. There was no significant difference in conductance between different crown locations on sunny or overcast days, indicating spatial differences in transpiration under sunny conditions were likely driven by leaf temperature differences. We conclude that clouds can affect spatial distribution of sunlight and associated physiological parameters not only within forest communities, but within individual crowns as well. [ABSTRACT FROM AUTHOR]

Wetlands have an inordinate influence on the global greenhouse gas budget, but how global changes may alter wetland contribution to future greenhouse gas fluxes is poorly understood. We determined the greenhouse gas balance of a tidal marsh exposed to nine years of experimental carbon dioxide (CO) and nitrogen (N) manipulation. We estimated net carbon (C) gain rates by measuring changes in plant and soil C pools over nine years. In wetland soils that accrete primarily through organic matter inputs, long-term measurements of soil elevation, along with soil C density, provide a robust estimate of net soil C gain. We used net soil C gain along with methane and nitrous oxide fluxes to determine the radiative forcing of the marsh under elevated CO and N addition. Nearly all plots exhibited a net gain of C over the study period (up to 203 g C m year), and C gain rates were greater with N and CO addition. Treatment effects on C gain and methane emissions dominated trends in radiative forcing while nitrous oxide fluxes in all treatments were negligible. Though these soils experience salinities that typically suppress methane emissions, our results suggest that elevated CO can stimulate methane emissions, overcoming positive effects of elevated CO on C gain, converting brackish marshes that are typically net greenhouse gas sinks into sources. Adding resources, either CO or N, will likely increase 'blue carbon' accumulation rates in tidal marshes, but importantly, each resource can have distinct influences on the direction of total greenhouse forcing. [ABSTRACT FROM AUTHOR]

Abies fabri is a typical subalpine dark coniferous forest in southwestern China. Air temperature increases more at high elevation areas than that at low elevation areas in mountainous regions, and climate change ratio is also uneven in different seasons. Carbon gain and the response of water use efficiency (WUE) to annual and seasonal increases in temperature with or without CO fertilization were simulated in Abies fabri using the atmospheric-vegetation interaction model (AVIM2). Four future climate scenarios (RCP2.6, RCP4.5, RCP6.0 and RCP8.5) from the Coupled Model Intercomparison Project Phase 5 (CMIP5) were selectively investigated. The results showed that warmer temperatures have negative effects on gross primary production (GPP) and net primary production (NPP) in growing seasons and positive effects in dormant seasons due to the variation in the leaf area index. Warmer temperatures tend to generate lower canopy WUE and higher ecosystem WUE in Abies fabri. However, warmer temperature together with rising CO concentrations significantly increase the GPP and NPP in both growing and dormant seasons and enhance WUE in annual and dormant seasons because of the higher leaf area index (LAI) and soil temperature. The comparison of the simulated results with and without CO fertilization shows that CO has the potential to partially alleviate the adverse effects of climate warming on carbon gain and WUE in subalpine coniferous forests. [ABSTRACT FROM AUTHOR]

To determine the invasiveness of invasive plants, many studies have compared photosynthetic traits or strategies between invasive and native species. However, few studies have compared the photosynthetic dynamics between invasive and native species during light fluctuations. We compared photosynthetic induction, relaxation dynamics and leaf traits between the invasive species, Tithonia diversifolia and two native species, Clerodendrum bungei and Blumea balsamifera , in full-sun and shady habitats. The photosynthetic dynamics and leaf traits differed among species. T. diversifolia showed a slower induction speed and stomatal opening response but had higher average intrinsic water-use efficiency than the two native species in full-sun habitats. Thus, the slow induction response may be attributed to the longer stomatal length in T. diversifolia . Habitat had a significant effect on photosynthetic dynamics in T. diversifolia and B. balsamifera but not in C. bungei . In shady habitat, T. diversifolia had a faster photosynthetic induction response than in full-sun habitat, leading to a higher average stomatal conductance during photosynthetic induction in T. diversifolia than in the two native species. In contrast, B. balsamifera had a larger stomatal length and slower photosynthetic induction and relaxation response in shady habitat than in full-sun habitat, resulting in higher carbon gain during photosynthetic relaxation. Nevertheless, in both habitats, T. diversifolia had an overall higher carbon gain during light fluctuations than the two native species. Our results indicated that T. diversifolia can adopt more effective response strategies under fluctuating light environments to maximize carbon gain, which may contribute to its successful invasion., (© 2023 Kunming Institute of Botany, Chinese Academy of Sciences. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co., Ltd.)

Reductions in snow cover over winter can increase frost exposure in herbaceous plants. Nevertheless, increased exposure to light can potentially increase plant carbon gain during periods of reduced snow cover. We used a combined field and growth chamber experiment to examine how variation in the timing and cumulative duration of light exposure over winter (from one to four 1-week incubation periods at 5 °C) affected subsequent summer growth in the grass Poa pratensis . We also measured net photosynthetic rates, dark respiration and chlorophyll fluorescence both 48 h and 120 h after the start of each winter light exposure period. Summer biomass increased by up to 50% for tillers exposed to light during the final winter incubation period (mid-late February), and the timing of light exposure, not the cumulative duration, was the most influential factor in increasing biomass. In contrast, for tillers incubated in the dark, multiple weeks of incubation at 5 °C resulted in the largest reductions in summer biomass. Leaf-level net photosynthetic rates were highest for the earliest and latest light exposure periods over winter, whereas dark respiration rates were highest in early winter and lowest in late winter. Thus, the gas exchange and biomass results were consistent in revealing that the last period of light exposure promoted the highest carbon gain. Overall, our results reveal that naturally occurring periods of snow melt over winter, or scenarios where snow is removed or melted as an experimental treatment, have the potential to benefit plant growth substantially, as opposed to simply rendering plants vulnerable to frost damage. [ABSTRACT FROM AUTHOR]

Premise of research. More detailed studies are required to evaluate the distribution of N among leaves and the whole-plant carbon gain in the absence of a light gradient. This study assessed the effect of leaf age on photosynthetic capacity and leaf N content simultaneously with the calculation of leaf demographic parameters in plants of Wedelia trilobata growing horizontally at three levels of nitrogen availability. Methodology. Leaf production, leaf death rates, leaf life span, and the decline in maximum photosynthetic rate with age were measured. With these data, the structure of leaf age population in whole plants was constructed, and their effect on the distribution of N among leaves and the whole-plant carbon gain was projected. Pivotal results. In allNtreatments, leaf age regulated the photosynthetic capacity along the life of the leaf and established a nonuniform distribution of leaf N content in the leaves present in the plant. Leaf age structure showed that with the increase in N availability, the leaf population tends to be younger. The major contribution of carbon took place in the early life of the leaf, but the relative importance of the older leaves was different among treatments. Conclusions. The use of traditional demographic approaches allowed the scaling up of leaf carbon gain from leaf to whole plant in a species with horizontally oriented branches and demonstrated that an optimal leaf age structure at different N availabilities may be important to maximize whole-plant carbon gain under the same light condition. [ABSTRACT FROM AUTHOR]