Greater Photosynthetic Capacity Research Articles

Clonal Transgenerational Effects of Parental Grazing Environment on Offspring Shade Avoidance

Grassland plants that endure livestock grazing exhibit a dwarf phenotype, which can be transmitted to clonal offspring. Yet to date, it remains poorly understood whether such transgenerational dwarf effects alter the plants’ response to shade. Here, we conducted a common garden experiment under sunlight and shade conditions with clonal Leymus chinensis offspring, the parents of which had endured livestock overgrazing (OG) and non-grazing (NG) in the field, respectively. Plant morphological, physiological, and transcriptomic analyses were carried out. The results indicated that NG offspring showed greater shade avoidance than OG offspring. That is, NG offspring exhibited greater plasticity of vegetative height and leaf width, which may be contributed to their greater photosynthetic capacity and gibberellin (GA3) content compared with OG offspring when treated with shade. In addition, RNA-Seq profiling showed that differentially expressed genes in NG offspring were mainly enriched in RNA modification and metabolic processes, which facilitated rapid response to shade. Phytochrome interacting factors (PIFs) promoted downstream shade marker genes in NG offspring by significantly downregulating the expression of PHYC, SPY, and DELLA. Our findings suggest that light conditions should be taken into account to better understand transgenerational dwarf effects induced by livestock grazing on grassland ecosystems. These results provide new insights into the inducible factors of phenotypic variations in grassland plants that experience grazing.

Selection for drought tolerance in backcross populations derived from interspecific crosses of Solanum lycopersicum × Solanum pennellii

AbstractDrought strongly limits tomato yield, and the introgression of genes from wild tomatoes is a powerful tool to obtain drought‐tolerant progenies. The aim of this study was to select drought‐tolerant transgressive progeny obtained from interspecific crosses between drought‐susceptible tomatoes (Solanum lycopersicum) × drought‐tolerant wild species (Solanum pennellii) under in vitro and greenhouse conditions. BC1F2 populations were advanced from backcrosses between F1 × Jumbo AG‐592 (cultivar for fresh consumption) and F1 × BRS Tospodoro (cultivar for industrial processing). For this, BC1F2 seeds were germinated in vitro and evaluated for tolerance to drought. Then, eight genotypes from each BC1F2 were selected and submitted to 14 days of drought (0% of water supply) or well‐watered (100% of water supply) in greenhouse conditions and evaluated for growth, water balance and gas exchanges. Using in vitro assays with mannitol‐induced drought proved to be effective for the initial screening of drought‐tolerant BC1F2 plants, while greenhouse experiments showed that drought decreased photosynthesis in all genotypes, but almost all the BC1F2 progenies had greater photosynthetic capacity, water balance and growth than their commercial parents. As a result, we selected six progenies for fresh consumption and six progenies for industrial processing with increased drought tolerance.

Leaf and wood functional traits explain the strategies developed by Byrsonima sericea (Malpighiaceae) to survive in Atlantic Forest ecosystems under water and light variations

The Atlantic Forest is a heterogeneous biome comprised of different phytophysiognomies with contrasting microclimatic and edaphic characteristics, such as sandbanks and forests. Sandbanks are ecosystems with low water availability and high irradiance, requiring leaf and wood specific adjustments from species to survive. On the other hand, tropical rain forests lack a pronounced dry season, providing enough resources to allow competition from light-demanding trees and sustaining a spectrum of shade tolerance for understory species. To better understand how functional traits are determined, it is necessary to evaluate variables that are site-specific, i.e. that are displayed within an organism in different environments. We aimed to assess how does variation in the functional traits of the leaf and wood of Byrsonima sericea influence the survival abilities of this species to thrive under contrasting scenarios of light and water availability. Also, which set of morpho-anatomical and physiological traits are considered to be site-specific responses that are affecting positively the capacity of the species to adapt in these contrasting scenarios of the Atlantic Forest? The high irradiance in sandbank shaped functional traits of B. sericea leaves that allowed an allocation strategy of the available resources, with investment in leaf mass rather than in trunk biomechanics and hydraulic efficiency. The higher leaf density through smaller and numerous cells along with higher stomatal density and area, facilitating CO2 diffusion, were associated with a greater photosynthetic capacity and greater intrinsic water use efficiency. As in the forest, light is a limiting factor for species to grow, the fluctuating light over a short timescale can influence whole plant performance, thus requiring an investment in trunk biomechanics. Additionally, a set of wood traits in the forest was related to water availability favoring wider vessel elements with thicker walls, increasing the theoretical hydraulic conductivity, even though it implicated a higher vulnerability to cavitation. Our study has demonstrated that variation of traits of different plant structures, such as the leaf and wood, within a species has direct implications in the survival strategies at each environmental conditions of light and water availability. It is also stated that there are different sets of functional traits which are responsible for allocation strategies, leading to specific trade-offs that allow the species to display site-specific responses in order to survive.

Comparative Study of Cypripedium Plant Photosynthetic Characteristics from Changbai Mountain

This study reports on extensive and in-depth investigations into the morphological, photosynthetic, and physiological indices of 10 different types of Cypripedium plant introduced from Changbai Mountain. It is an important prerequisite for the ex situ conservation of Cypripedium plants to provide new insights into their photosynthesis. This result can not only promote the production of vegetative plants but also promote the production of plants with lots of flowers and the physiological characteristics of Cypripedium plants for promoting the artificial introduction and cultivation of wild resources. A critical comparison of the results showed that high light intensity is one of the causes of the reduction in photosynthesis in the samples. Cypripedium macranthum had the most morphological advantages, while Cypripedium guttatum, the smallest plant type, had the lowest plant morphogenesis. Photoinhibition began daily at 12:00 pm and reached a second peak at 14:00 pm in all 10 types. C. macranthum, Cypripedium ventricosum, and Cypripedium calceolus had greater photosynthetic capacity than the other types. Using principal component analysis, the order of photosynthetic physiological characteristics of the 10 Cypripedium plants was CCMY > CVPP > CCRY > CMPP > CVRR > CSPY > CMWW > CMLL > CMDD > CGWW. These results lay the groundwork for future research on Cypripedium resource distribution and artificial conservation.

Exogenous Application of Glycine Betaine on Sweet Cherry Tree (Prunus avium L.): Effects on Tree Physiology and Leaf Properties.

Biostimulants, such as glycine betaine (GB), are a sustainable way to boost productivity and quality in fruit crops, even in adverse environment conditions. Sweet cherry (Prunus avium L.) is an important crop, which is very sensitive to abiotic stress. Known primarily for its fruits, its leaves are also rich in bioactive substances, which, however, still have no commercial value. There are no studies about the effects of GB exogenous application on biochemical parameters of sweet cherry leaves and few studies about effects in sweet cherry tree physiology. This study was conducted in a Portuguese sweet cherry commercial orchard. Lapins sweet cherry trees were treated with a commercial product based on GB, at two different concentrations (0.25% and 0.40%). The applications were performed at three different phenological stages, according to the BBCH (Biologische Bundesanstalt, Bundessortenamt und Chemische Industrie) scale: 77, 81 and 86 BBCH. Both GB treatments improved leaf water status, photosynthetic pigments, soluble solids content, total phenolic contents, and antioxidant activity, resulting in better leaf water status regulation, greater photosynthetic capacity, and higher antioxidant activity. These results shows that GB can benefit sweet cherry tree physiology and provide new opportunities for sweet cherry leaves valorisation.

Restoring the iconic Ulmus americana to urban landscapes: Early tree growth responds to aboveground conditions

Native trees provide a range of benefits, from supporting native wildlife to climate regulation, and many urban natural resource managers prioritize native tree planting and restoration. Ulmus americana (American elm) was once widely planted in American cities but has been decimated by Dutch elm disease (DED; Ophiostoma ulmi). Our study evaluated U. americana establishment and growth across urban landscapes. We planted ramets from three DED-tolerant U. americana genotypes (RV16, RV474, and Sunfield) along an urbanization gradient in Newark, DE and Philadelphia, PA, and assessed physiological and morphological responses. We analyzed how U. americana clone growth, chlorophyll fluorescence, and foliar chemistry relate to impervious surface area, ozone (O3) concentrations, and soil characteristics. The one-year post planting mortality rate was low (4%) demonstrating these elms can withstand urban environmental conditions when provided ample water supply and protection from deer. As expected, the elms differed in growth rate, chlorophyll fluorescence, and foliar chemistry between the cities. Elms planted in Philadelphia had greater photosynthetic capacity in July (Fv/Fm = 0.76) and September (Fv/Fm = 0.75), while Newark elms had greater photosynthetic capacity in August (Fv/Fm = 0.78). Depleted foliar δ13C signatures in Philadelphia suggest elms are experiencing greater fossil-fuel derived atmospheric CO2 than in Newark, possibly contributing to the greater growth rates observed in Philadelphia compared to Newark. Enriched foliar δ15N and greater foliar %N in Philadelphia clones suggest they are experiencing greater N deposition from NOx-derived sources compared to Newark clones. Clones growing in Philadelphia had greater foliar nutrient concentrations despite growing in soils with greater heavy metal concentrations. These foliar-soil chemistry patterns suggest that clones growing in Philadelphia respond positively to urban environmental conditions in a large city, whereas clones growing in Newark may be experiencing N limitation in the first year of growth after planting.

Row Spacing and the Use of Plant-Available Water in Sugarcane Cultivation in Water-Abundant Louisiana

Optimizing row spacing can potentially improve yields when resources such as light and water are limited. Sugarcane in Louisiana is principally grown on rows spaced 1.8 m apart, but interest in planting on 2.4 m rows is increasing. In this study, we hypothesized that wider row spacing would have greater water availability. Soil moisture sensors were placed at 15, 30, and 45 cm depths in treatments: 1.8 and 2.4 m row spacings, two varieties (L 01-299 and HoCP 04-838), and two planting dates. Soil moisture was monitored in 15-min intervals from 2017 to 2020. Mean volumetric water content was slightly greater in 2.4 m than 1.8 m row spacing at 15 and 45 cm, but the biggest difference was observed when soil water content reached its lowest levels where 2.4 m rows had 1.1, 3.1, and 9.8 times more water available at 15, 30, and 45 cm, respectively, compared to 1.8 m row spacing. However, in both row spacings, plant-available water was always present in the top 45 cm, even during periods of low rainfall. Potentially, high water availability provides an opportunity to increase photosynthesis in sugarcane varieties by selecting for greater photosynthetic capacity and CO2 uptake through increasesd stomatal conductance.

Harnessing genetic variation at regulatory regions to fine-tune traits for climate-resilient crops

Climate change is making it more challenging to meet the food demands of a growing global population. Increased food production relies on continual crop improvements to generate higher and more stable yields, especially with increasingly unpredictable environments and less arable land. The improvement of traits that promote climate resilience and resource utilization, for example, greater photosynthetic capacity, increased nitrogen use efficiency, and optimized root and shoot architecture, represents a promising avenue for engineering crops to yield more with less (Evans and Lawson, 2020).

Effect of irrigation water pH on the agronomic development of hops in protected cultivation

The hydrogenionic potential (pH) is one of the parameters that characterize the quality of water for irrigation, and can influence soil microbiology and the cation exchange process between soil and plant. However, there are few studies related to the pH of irrigation water for hop culture. According to this, our work aimed to evaluate the irrigation effect with different water pH ranges on the agronomic development of hops grown in a greenhouse, in Botucatu, state of São Paulo, Brazil. It was used a completely randomized design (CRD), with three treatments (pH levels) and ten replications. The treatments consisted of three water pH levels: T1 – 6 to 6.5, T2 – 6.5 to 7, and T3 – 7 to 7.5. To obtain the different pH ranges were used solutions of 0,1 mol L−1 of sodium hydroxide (NaOH), and phosphoric acid (H3PO4). Gas exchanges, nutritional content in plant leaf tissue, yield, and alpha and beta-acids concentration were evaluated. The results obtained allowed us to conclude that the pH range 6.5 to 7 promotes greater availability, absorption, and accumulation of K in plant leaf tissue, as well as greater photosynthetic capacity, in addition to greater yield between treatments. The preliminary values of alpha and beta-acids were higher in plants irrigated with the water pH of T1, indicating that possible stress may favor the production of these compounds.

Influence of nitrogen supply on gas exchange, chlorophyll fluorescence and grain yield of breeding lines of common bean evaluated in the Amazon region of Colombia

The common bean (Phaseolus vulgaris L.) is a food crop that provides fiber, vitamins and carbohydrates and it is produced by smallholders in developing countries under nitrogen (N)-depleted and low-fertility soil conditions. Soil acidity and the associated aluminum toxic and phosphorus deficient conditions are known to reduce symbiotic N-fixing ability of common bean. Breeding lines of common bean have been developed to adapt to acid-soil and high-temperature conditions in the Amazon region but the response of these lines to N application was not determined. The present study was conducted with an objective to identify genotypic differences among ten common bean breeding lines (4 Andean, 5 Mesoamerican, 1 interspecific) in their physiological characteristics (gas exchange, chlorophyll fluorescence and photosynthetic efficiency) and their contribution to superior agronomic performance under three different levels of N (0, 60 and 120 kg N ha−1; N0, N60 and N120) supply. We tested the hypothesis that common bean genotypes that combine greater capacity to assimilate carbon with improved ability to mobilize photosynthates to developing pods and seeds could enhance their agronomic performance at different levels of N supply under high-temperature and acid soil-stress conditions in the field. A randomized complete block design with factorial arrangement (3 levels of N × 10 genotypes) in three replications was used for the study. Measurements included photosynthetic gas exchange characteristics (light and CO2-saturated photosynthesis), chlorophyll fluorescence, viability of pollen, leaf N concentration, photosynthetic N use efficiency and grain yield. The increase in supply of N had a significant effect on grain yield and on different photosynthetic characteristics. Results showed that lines with indeterminate growth habit responded better to increase in N supply through their physiological response in improving grain yield. Among the genotypes evaluated, two lines (BFS 10 and SEF 10) were outstanding in their agronomic performance due to greater photosynthetic capacity combined with greater ability to mobilize photosynthates to grain with increase in N supply. These two lines can serve as parents for further improvement in resource use efficiency and multiple-stress resistance of common bean in the tropics.

FUNCTIONAL TRAITS IN THE ARBOREAL COMPONENT OF THE CERRADO VEGETABLE COMMUNITY

The current study aimed to describe functional attributes of arboreal species in fragments of sensu stricto Cerrado areas with a transition to Cerradão in Ipameri – GO to describe which characteristics are more representative in these phytophysiognomies. Ten individuals were sampled for each of the twenty arboreous species most commonly found in the region. Functional attributes related to the architecture of the aerial part of the tree and functional leaf traits were collected. Once the functional traits were evaluated, an analysis of variance and a posterior Tukey test at 0.5% were performed. Then, the data were standardized, and the species were functionally grouped. The results showed great variability of the functional characteristics forming two groups of species with similar characteristics. Group 1 was constituted by species with functional traits proper to survival in adverse environmental conditions, such as poor soils, seasonality, and natural or provoked incidents, like fire. Group 2, on the other hand, apparently points to functional traits related to success and investment in height growth, as well as greater photosynthetic capacity and adaptations to shading conditions. The functional traits studied indicated the occurrence of a great diversity of adaptations between species. Therefore, it is possible to say that both groups of species are important for maintaining these phytophysiognomies in the landscape.

Heat stress resistance drives coordination of emissions of suites of volatiles after severe heat stress and during recovery in five tropical crops

Severe heat stress leads to a major reduction in foliage photosynthetic characteristics and the initial reduction and degree of recovery depend on species heat resistance. However, how the emissions of biogenic volatile organic compounds (BVOC) from different biochemical pathways are coordinated with photosynthetic modifications from the initial stress response through recovery are poorly understood, and the data are especially limited for short-living tropical crop species. We exposed leaves of five tropical crop species (A. cruentus, A. hybridus, S. aethiopicum, T. occidentalis and V. unguiculata) to severe heat treatment of 49 °C and a control treatment of 25 °C for 5 min and studied the modifications in foliage photosynthetic characteristics and constitutive BVOC emissions and elicitation of stress-induced volatiles through a 48 h recovery period upon return to non-stressed conditions. Overall, heat shock application resulted in a major inhibition of net assimilation rate similarly in all species indicating cellular damage and photosynthetic decay. However, species strongly varied in photosynthetic recovery with A. hybridus recovering the most and S. aethiopicum the least. Heat shock stress led to enhancement of emissions characterizing increased leaf oxidative status, in particular to enhanced emissions of lipoxygenase pathway volatiles (LOX). Surprisingly, LOX emissions were not associated with species heat resistance, but were greater in physiologically more active species with greater photosynthetic capacity. Species with greater constitutive isoprenoid emission capacity were generally more heat resistant, but terpenoid emissions were induced to a greater degree in less heat resistant species that likely suffered the most from the applied level of stress. Heat stress affected different groups of terpenoids - isoprene, monoterpenes and sesquiterpenes - to a different degree in different species, resulting in unique species-specific emission blends at different times of recovery. Heat stress had relatively minor effects on benzenoid emissions with moderately enhanced emissions primarily in V. unguiculata that differed from the other species by lower constitutive terpenoid emissions correspondent to its relatively high heat resistance. The results collectively demonstrate that species heat resistance is associated with the quantitative and qualitative characteristics of heat stress-dependent volatile emissions in different tropical crop species. We argue that these species-specific patterns need consideration in simulating volatile emissions under heat stress.

Capacidad fotosintética de 15 clones de café robusta (Coffea canephora)

Con el fin de obtener información de la capacidad fotosintética de café robusta (Coffea canephora), se evaluó la tasa de fotosíntesis (A), Transpiración (E), conductancia estomática (gs), concentración intercelular de CO2 (Ci) y eficiencia de uso de agua (EUA= A/E) de 15 diferentes clones de café. Se cuantificó la respuesta de la fotosíntesis (A) a la densidad de flujo fotónico (DFF; A vs DFF) y a la Ci (A vs Ci) de 6 clones: SICA 1, 2, 3, 4, CONILON 1 y ECU ROBUSTA 01 cultivados en un umbráculo, en un diseño estadístico completamente aleatorizado en el jardín Botánico de la Estación Experimental Mutile. Las plántulas de café se regaron cada tres días y fertilizaron durante el experimento para mantener las plantas con vigor, garantizando el buen desempeño fisiológico. Se encontraron diferencias significativas entre los clones estudiados en el intercambio gaseoso: la A varió entre 9,5 y 15 mmol m-2 s-1, la gs entre 198 y 375 mmol m-2 s-1 y la EUA vario entre 2,6 y 5,8 mmol CO2 mol H2O-1. Los clones (ECU ROBUSTA 01, CONILON 1 y CONILON 2) mostraron las mayores A y EUA. Se observaron diferencias significativas en la curvas A/DFF y A/Ci entre los clones ECU ROBUSTA 01, CONILON 1 y los SICA. En conclusión, se encontraron diferencias significativas entre clones de café robusta estudiados, siendo los clones ECU ROBUSTA 01, CONILON 1 y SICA 1 por su mayor capacidad fotosintética, los que podrían tener una mayor productividad en Esmeraldas.

Seasonal variation in the leaf physiology of co-occurring invasive (Hakea sericea) and native (Pinus pinaster) woody species in a Mediterranean-type ecosystem

Physiological traits are critical factors in species invasion success. It is generally accepted that invasive alien species (IAS) are more efficient at resource acquisition and/or use than are native species. However, in the case of the invasive Hakea sericea, the importance of such mechanisms remains unexplained. This gap in extant knowledge has prompted the present study, in which the main objective was contrasting the physiological performance of Hakea sericea with the native Pinus pinaster in Mediterranean-climate ecosystems. Leaf gas exchange, photosynthetic pigments, metabolites and water relationships were measured seasonally during one year, revealing a pronounced seasonal variation in all parameters. Overall, stomatal conductance (gs) peaked in spring, whereas intrinsic water use efficiency (WUE) reached its maximum in autumn. The highest photosynthetic rate (A) was detected in autumn and summer. Across the year, Hakea sericea displayed higher relative water content (RWC), A and WUE values than Pinus pinaster. Moreover, the IAS presented higher leaf total chlorophyll and soluble sugars. In turn, leaves of the native species had values of starch and proteins higher than the IAS. Therefore, compared with Pinus pinaster, Hakea sericea exhibits superior physiological performance mainly supported by an efficient use of resources and greater photosynthetic capacity. These characteristics are likely responsible for its invasion success in Mediterranean ecosystems. In addition, they could confer a significant competitive advantage in a changing climate, as well as enable this species to outcompete native species, resulting in increased abundance and more significant impact on ecosystems.

Photosynthetic pigments and gas exchange in red and green cabbage under no-tillage and conventional systems

The aim of the present study was to verify changes in the levels of photosynthetic pigments as well as gas exchange in the Fuyutoyo and Red Cabbage cultivars, grown under no-tillage (NT) and conventional (CT) systems. A randomised block design with four replications was used, in a 2 x 2 factorial scheme, where the Fuyutoyo and Red Cabbage cultivars were evaluated under two tillage systems. The levels of chlorophyll a, chlorophyll b, total chlorophyll and anthocyanins in the leaves were evaluated in triplicate. Localised gas exchange was measured at different times of the day, together with different photosynthetic photon flux density curves (PPFD). The Fuyutoyo cultivar showed a higher mean value for chlorophyll a (34.58%), chlorophyll b (35.09%) and total chlorophyll (34.76%), however, no difference was seen between cultivars for the levels of anthocyanin. Greater mean values for chlorophyll a (76.07%), chlorophyll b (77.87%), total chlorophyll (76.74%) and anthocyanin (72.24%) were found under CT compared to the cultivars grown under NT. The relative chlorophyll content of the Red Cabbage plants was influenced by adoption of the no-till system, showing a higher value for the SPAD index. The Fuyutoyo cabbage cultivar showed greater photosynthetic capacity during the day, promoting greater instantaneous carboxylation efficiency. All the cultivars and tillage systems gave a linear reduction in water use efficiency during this period. Under the conventional system, despite presenting higher rates of stomatal conductance, the Red Cabbage cultivar achieved lower values for net photosynthesis when submitted to light-curve analysis.

Overexpression of S-nitrosoglutathione reductase alleviated iron-deficiency stress by regulating iron distribution and redox homeostasis

Iron (Fe) is an essential micronutrient element for plant growth. The S-nitrosoglutathione reductase (GSNOR) gene’s functions under Fe-deficiency conditions are not well understood. Here, GSNOR expression was induced by Fe deficiency in tomato (Solanum lycopersicum L.) leaves and roots, while its overexpression alleviated chlorosis under Fe-deficiency conditions. GSNOR overexpression positively regulated the Fe distribution from root to shoot, which might result from the transcriptional regulation of genes involved in Fe metabolism. Additionally, the overexpression of GSNOR maintained redox homeostasis and protected chloroplasts from Fe-deficiency-related damage, resulting in a greater photosynthetic capacity. As a nitric oxide regulator, GSNOR’s overexpression decreased the excessive accumulation of nitric oxide and S-nitrosothiols during the Fe deficiency, and maintained the homeostases of reactive oxygen species and reactive nitrogen species. Moreover, GSNOR overexpression, probably at the level of genes and proteins, along with protein S-nitrosylation, promoted Fe uptake and regulated the shoot/root Fe ratio under Fe-deficiency conditions.

How root traits would be affected by soybean yield improvement? An examination of historical cultivars grafted with record-yield cultivar scion

During historical yield improvement in soybean, breeders have seldom considered selection for root traits, generally focusing selection on yield traits. Yet, it is not known how root traits of historical cultivars would be altered if their shoot functions and grain yields were largely improved. Here we investigated the influence of record-yield soybean cultivars L14 and Z35 as scions on root traits of historical cultivars. A total of 11 cultivars, released in different decades, were used to graft with L14 or Z35 scions. Some morphological and physiological traits were measured in the pot-culture experiments. During grain-filling stage, the scions of L14 and Z35 had greater photosynthetic capacity, seed biomass and seed starch accumulation than those of other cultivars. Grafting of cultivars with L14 and Z35 scions resulted in significant decreases in root biomass, root-shoot ratio, root starch accumulation and root morphological traits compared with non-grafts or self-grafts. The genetic gain for these root traits of cultivars released from 1966 to 2006 increased by grafting record-yield cultivars scions, while that of grain yield and nutrient accumulation decreased. Our results revealed the uncoordinated improvement between roots and shoots during historical breeding in soybean.

Drivers of leaf carbon exchange capacity across biomes at the continental scale.

Realistic representations of plant carbon exchange processes are necessary to reliably simulate biosphere-atmosphere feedbacks. These processes are known to vary over time and space, though the drivers of the underlying rates are still widely debated in the literature. Here, we measured leaf carbon exchange in >500 individuals of 98 species from the Neotropics to high boreal biomes to determine the drivers of photosynthetic and dark respiration capacity. Covariate abiotic (long- and short-term climate) and biotic (plant type, plant size, ontogeny, water status) data were used to explore significant drivers of temperature-standardized leaf carbon exchange rates. Using model selection, we found the previous week's temperature and soil moisture at the time of measurement to be a better predictor of photosynthetic capacity than long-term climate, with the combination of high recent temperatures and low soil moisture tending to decrease photosynthetic capacity. Non-trees (annual and perennials) tended to have greater photosynthetic capacity than trees, and, within trees, adults tended to have greater photosynthetic capacity than juveniles, possibly as a result of differences in light availability. Dark respiration capacity was less responsive to the assessed drivers than photosynthetic capacity, with rates best predicted by multi-year average site temperature alone. Our results suggest that, across large spatial scales, photosynthetic capacity quickly adjusts to changing environmental conditions, namely light, temperature, and soil moisture. Respiratory capacity is more conservative and most responsive to longer-term conditions. Our results provide a framework for incorporating these processes into large-scale models and a data set to benchmark such models.

Sex-specific responses of Populus deltoides to defoliation

There has been an increasing interest in understanding the differential effects of sexual dimorphism on plant stress responses. However, there is no clear pattern in the responses of the sexes to defoliation. In this study, the effects of different severity of artificial defoliation on biomass production, total nonstructural carbohydrate (NSC) concentration, and photosynthetic rate (<em>P</em><sub>N</sub>) of male and female <em>Populus deltoides</em> were examined. We used half and full defoliation to observe the differences between the sexes in three harvest dates (1 week, 4 weeks, and 8 weeks after treatments). We hypothesized that female and male <em>P. deltoides</em> compared with an undefoliated control would have compensatory growth in response to defoliation treatments. Results showed that half and full defoliation reduced the growth of both sexes. Following half defoliation, root growth was reduced, especially in males, at T2 (4 weeks after defoliation) and T3 (8 weeks after defoliation), while males showed an increase in height increment under the half defoliation compared with the nondefoliation treatments. By contrast, females were more negatively affected by defoliation than males in terms of biomass after 8 weeks. One week after defoliation, <em>P</em><sub>N</sub> increased significantly in females and males under half defoliation (+30%, +32%, respectively) and full defoliation (+58%, +56%, respectively). However, 8 weeks after defoliation, there was little difference in <em>P</em><sub>N</sub> between defoliated and undefoliated female cuttings. Increases in stomatal conductance (g<sub>s</sub>) and leaf nitrogen were observed under fully defoliated female and male cuttings. Moreover, males had less NSC concentrations following half defoliation compared with females. Our results indicate that leaf compensatory growth in male cuttings of <em>P. deltoides</em> was maintained by obtaining greater photosynthetic capacity, higher leaf nitrogen, and lower NSC concentration following half and full defoliation. Our results highlight that females suffered from greater negative effects than did males following half defoliation, but under full defoliation, the differences between both sexes were subtle.

Nitrogen Distribution in Leaf Canopies of High‐Yielding Rice Cultivar Takanari

Takanari, an indica cultivar of rice (Oryza sativa L.), is one of the Japanese cultivars with the highest yield. Although previous studies have indicated that Takanari has a greater photosynthetic capacity in canopy top leaves, which is achieved partly by its higher nitrogen (N) content per leaf area, N distribution at the whole‐canopy level has not been studied. We addressed following questions: (i) Does Takanari have a higher N uptake rate? (ii) Does Takanari have more leaf N in the whole canopy? (iii) Does Takanari have higher leaf N content per leaf area in the whole canopy? (iv) Does Takanari reallocate more N from old to canopy top leaves? We studied N distribution in stands of Takanari and a popular japonica rice cultivar Koshihikari. Difference in the total plant N and leaf N per plant between Takanari and Koshihikari was small. Whereas Takanari had a lower leaf N per plant N than Koshihikari, Takanari had a steeper vertical gradient of leaf N content than Koshihikari. The slope of vertical distribution of leaf N content (KN) was positively correlated with the light extinction coefficient (KL) in each cultivar. Whereas the KN–KL relationship of Koshihikari was similar to that of the general trend found in a recent meta‐analysis, Takanari had a significantly higher KN value than others when compared at a given KL. The KN values in Takanari were considered to be closer to the optimal KN than those in other species, which may contribute to higher productivity and higher N use efficiency in canopy photosynthesis.