Photosynthetic efficiency of three C species is maintained under low light and high vapour pressure deficit.

The photosynthetic efficiency of C plants could be impaired in environments with low light and high vapour pressure deficit (VPD). However, the interactive effect of low light and high VPD on C photosynthetic efficiency remains unexplored. We grew three C species, Setaria viridis L.

The response of mesophyll conductance to short-term CO variation is related to stomatal conductance.

The response of mesophyll conductance (g) to CO plays a key role in photosynthesis and ecosystem carbon cycles under climate change. Despite numerous studies, there is still debate about how g responds to short-term CO variations. Here we used multiple methods and looked at the relationship between stomatal conductance to CO (g) and g to address this aspect.

Half of the O enrichment of leaf sucrose is conserved in leaf cellulose of a C grass across atmospheric humidity and CO levels.

The O enrichment (ΔO) of cellulose (ΔO) is recognized as a unique archive of past climate and plant function. However, there is still uncertainty regarding the proportion of oxygen in cellulose (p) that exchanges post-photosynthetically with medium water of cellulose synthesis. Particularly, recent research with C grasses demonstrated that the ΔO of leaf sucrose (ΔO, the parent substrate for cellulose synthesis) can be much higher than predicted from daytime ΔO of leaf water (ΔO), which could alter conclusions on photosynthetic versus post-photosynthetic effects on ΔO via p.

Temperature responses of leaf respiration in light and darkness are similar and modulated by leaf development.

Our ability to predict temperature responses of leaf respiration in light and darkness (R and R ) is essential to models of global carbon dynamics. While many models rely on constant thermal sensitivity (characterized by Q ), uncertainty remains as to whether Q of R and R are actually similar. We measured short-term temperature responses of R and R in immature and mature leaves of two evergreen tree species, Castanopsis carlesii and Ormosia henry in an open field.

δ13C of bulk organic matter and cellulose reveal post-photosynthetic fractionation during ontogeny in C4 grass leaves.

The 13C isotope composition (δ13C) of leaf dry matter is a useful tool for physiological and ecological studies. However, how post-photosynthetic fractionation associated with respiration and carbon export influences δ13C remains uncertain. We investigated the effects of post-photosynthetic fractionation on δ13C of mature leaves of Cleistogenes squarrosa, a perennial C4 grass, in controlled experiments with different levels of vapour pressure deficit and nitrogen supply.

Photosynthetic resource-use efficiency trade-offs triggered by vapour pressure deficit and nitrogen supply in a C species.

Trade-offs in resource-use efficiency (including water-, nitrogen-, and light-use efficiency, i.e., WUE, NUE, and LUE) are an important acclimation strategy of plants to environmental stresses.

Estimation of intrinsic water-use efficiency from δC signature of C leaves: Assumptions and uncertainty.

Carbon isotope composition (δC) has been widely used to estimate the intrinsic water-use efficiency (iWUE) of plants in ecosystems around the world, providing an ultimate record of the functional response of plants to climate change. This approach relies on established relationships between leaf gas exchange and isotopic discrimination, which are reflected in different formulations of C-based iWUE models. In the current literature, most studies have utilized the simple, linear equation of photosynthetic discrimination to estimate iWUE.

Short- and long-term responses of leaf day respiration to elevated atmospheric CO2.

Evaluating leaf day respiration rate (RL), which is believed to differ from that in the dark (RDk), is essential for predicting global carbon cycles under climate change. Several studies have suggested that atmospheric CO2 impacts RL. However, the magnitude of such an impact and associated mechanisms remain uncertain.

Overestimated gains in water-use efficiency by global forests.

Increases in terrestrial water-use efficiency (WUE) have been reported in many studies, pointing to potential changes in physiological forcing of global carbon and hydrological cycles. However, gains in WUE are of uncertain magnitude over longer (i.e.

[Influence of ball milling with PTFE plastic tube on carbon isotope ratio measurement of C4 plants.].

Before the measurement of stable carbon isotope signatures (δC), plant samples should be well homogenized. Using a ball-mill fitted with poly tetra fluoroethylene (PTFE) plastic tubes is one of the most efficient and convenient methods. However, sample-tube plastic might contaminate plant samples during milling.

Accounting for mesophyll conductance substantially improves C-based estimates of intrinsic water-use efficiency.

Carbon isotope discrimination (Δ) has been used widely to infer intrinsic water-use efficiency (iWUE) of C plants, a key parameter linking carbon and water fluxes. Despite the essential role of mesophyll conductance (g ) in photosynthesis and Δ, its effect on Δ-based predictions of iWUE has generally been neglected. Here, we derive a mathematical expression of iWUE as a function of Δ that includes g (iWUE ) and exploits the g -stomatal conductance (g ) relationship across drought-stress levels and plant functional groups (deciduous or semideciduous woody, evergreen woody and herbaceous species) in a global database.

[Mesophyll conductance to CO: Methods and current knowledge].

Mesophyll conductance (g), the total conductance of CO diffusion from substomatal cavity to the site of carboxylation within chloroplast, is a major limiting factor for photosynthesis and a key parameter for improving photosynthetic resource use efficiency of crops. Online C discrimination method is an important method for plant eco-physiological studies and a well-established method for measuring g of C3 plants, although it has not been widely used due to challenges in methodology and high demands on experimental facilities. In this review, we summarized the characteristics of commonly used methods for g, introduced the basic theory of the online C discrimination method, namely Farquhar's photosynthetic C discrimination model; systematically introduced the practical measurements, equations and the components of facilities; and reviewed the drivers for variation in g of C3 plants.

Traits mediate drought effects on wood carbon fluxes.

CO fluxes from wood decomposition represent an important source of carbon from forest ecosystems to the atmosphere, which are determined by both wood traits and climate influencing the metabolic rates of decomposers. Previous studies have quantified the effects of moisture and temperature on wood decomposition, but these effects were not separated from the potential influence of wood traits. Indeed, it is not well understood how traits and climate interact to influence wood CO fluxes.

Gross and net nitrogen export from leaves of a vegetative C grass.

Nitrogen (N) mobilization from mature leaves plays a key role in supplying amino acids to vegetative and reproductive sinks. However, it is unknown if the mobilized N is predominantly sourced by net N-export (a senescence-related process) or other source of N-export from leaves. We used a new approach to partition gross and net N-export from leaf blades at different developmental stages in Cleistogenes squarrosa (a perennial C grass).

Determination of leaf respiration in the light: comparison between an isotopic disequilibrium method and the Laisk method.

Quantification of leaf respiration is important for understanding plant physiology and ecosystem biogeochemical processes. Leaf respiration continues in the light (R ) but supposedly at a lower rate than in the dark (R ). However, there is no method for direct measurement of R and the available methods require nonphysiological measurement conditions.

Leaf day respiration: low CO flux but high significance for metabolism and carbon balance.

Contents 986 I. 987 II. 987 III.

An oxygen isotope chronometer for cellulose deposition: the successive leaves formed by tillers of a C perennial grass.

Multiannual time series of (palaeo)hydrological information can be reconstructed from the oxygen isotope composition of cellulose (δ O ) in biological archives, for example, tree rings, but our ability to temporally resolve information at subannual scale is limited. We capitalized on the short and predictable leaf appearance interval (2.4 d) of a perennial C grass (Cleistogenes squarrosa), to assess its potential for providing highly time-resolved δ O records of vapour pressure deficit (VPD).

The δ O and δ H of water in the leaf growth-and-differentiation zone of grasses is close to source water in both humid and dry atmospheres.

The oxygen and hydrogen isotope composition of water in the leaf growth-and-differentiation zone, LGDZ, (δ O , δ H ) of grasses influences the isotopic composition of leaf cellulose (oxygen) and wax (hydrogen) - important for understanding (paleo)environmental and physiological information contained in these biological archives - but is presently unknown. This work determined δ O and δ H , O- and H-enrichment of LGDZ (∆ O and ∆ H ), and the O- and H-enrichment of leaf blade water (∆ O ∆ H ) in two C and three C grasses grown at high and low vapor pressure deficit (VPD). The proportion of unenriched water (p ) in the LGDZ ranged from 0.

Effects of resource addition on recovery of production and plant functional composition in degraded semiarid grasslands.

Degradation of semiarid ecosystems from overgrazing threatens a variety of ecosystem services. Rainfall and nitrogen commonly co-limit production in semiarid grassland ecosystems; however, few studies have reported how interactive effects of precipitation and nitrogen addition influence the recovery of grasslands degraded by overgrazing. We conducted a 6-year experiment manipulating precipitation (natural precipitation and simulated wet year precipitation) and nitrogen (0, 25 and 50 kg N ha) addition at two sites with different histories of livestock grazing (moderately and heavily grazed) in Inner Mongolian steppe.

Atmospheric CO mole fraction affects stand-scale carbon use efficiency of sunflower by stimulating respiration in light.

Plant carbon-use-efficiency (CUE), a key parameter in carbon cycle and plant growth models, quantifies the fraction of fixed carbon that is converted into net primary production rather than respired. CUE has not been directly measured, partly because of the difficulty of measuring respiration in light. Here, we explore if CUE is affected by atmospheric CO .

Bundle-sheath leakiness and intrinsic water use efficiency of a perennial C4 grass are increased at high vapour pressure deficit during growth.

Bundle-sheath leakiness (ϕ) is a key parameter of the CO-concentrating mechanism of C photosynthesis and is related to leaf-level intrinsic water use efficiency (WUE). This work studied short-term dynamic responses of ϕ to alterations of atmospheric CO concentration in Cleistogenes squarrosa, a perennial grass, grown at high (1.6 kPa) or low (0.

Effects of nitrogen and vapour pressure deficit on phytomer growth and development in a C4 grass.

Phytomers are basic morphological units of plants. Knowledge of phytomer development is essential for understanding morphological plasticity, functional-structural modelling of plant growth and the usage of leaf characteristics to indicate growth conditions at the time of production (e.g.

Nitrogen fertilization and δ O of CO have no effect on O-enrichment of leaf water and cellulose in Cleistogenes squarrosa (C ) - is VPD the sole control?

The oxygen isotope composition of cellulose (δ O ) archives hydrological and physiological information. Here, we assess previously unexplored direct and interactive effects of the δ O of CO (δ O ), nitrogen (N) fertilizer supply and vapour pressure deficit (VPD) on δ O , O-enrichment of leaf water (Δ O ) and cellulose (Δ O ) relative to source water, and p p , the proportion of oxygen in cellulose that exchanged with unenriched water at the site of cellulose synthesis, in a C grass (Cleistogenes squarrosa). δ O and N supply, and their interactions with VPD, had no effect on δ O , Δ O , Δ O and p p .