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.

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.

O enrichment of sucrose and photosynthetic and nonphotosynthetic leaf water in a C grass-atmospheric drivers and physiological relations.

The O enrichment (Δ O) of leaf water affects the Δ O of photosynthetic products such as sucrose, generating an isotopic archive of plant function and past climate. However, uncertainty remains as to whether leaf water compartmentation between photosynthetic and nonphotosynthetic tissue affects the relationship between Δ O of bulk leaf water (Δ O ) and leaf sucrose (Δ O ). We grew Lolium perenne (a C grass) in mesocosm-scale, replicated experiments with daytime relative humidity (50% or 75%) and CO level (200, 400 or 800 μmol mol ) as factors, and determined Δ O , Δ O and morphophysiological leaf parameters, including transpiration (E ), stomatal conductance (g ) and mesophyll conductance to CO (g ).

Do H and O in leaf water reflect environmental drivers differently?

We compiled hydrogen and oxygen stable isotope compositions (δ H and δ O) of leaf water from multiple biomes to examine variations with environmental drivers. Leaf water δ H was more closely correlated with δ H of xylem water or atmospheric vapour, whereas leaf water δ O was more closely correlated with air relative humidity. This resulted from the larger proportional range for δ H of meteoric waters relative to the extent of leaf water evaporative enrichment compared with δ O.

Endophytic fungi and drought tolerance: ecophysiological adjustment in shoot and root of an annual mesophytic host grass.

Epichloid endophytic fungi, vertically transmitted symbionts of grasses, can increase plant tolerance to biotic and abiotic stress. Our aim was to identify ecophysiological mechanisms by which the endophyte Epichloë occultans confers drought tolerance to the annual grass Lolium multiflorum Lam. Endophyte-associated or endophyte-free plants were either well-watered or subjected to water deficit.

Time Course of Root Axis Elongation and Lateral Root Formation in Perennial Ryegrass ( L.).

Grasses have a segmental morphology. Compared to leaf development, data on root development at the phytomer level are scarce. Leaf appearance interval was recorded over time to allow inference about the age of segmental sites that later form roots.

Stomatal conductance limited the CO response of grassland in the last century.

Background: The anthropogenic increase of atmospheric CO concentration (c) is impacting carbon (C), water, and nitrogen (N) cycles in grassland and other terrestrial biomes. Plant canopy stomatal conductance is a key player in these coupled cycles: it is a physiological control of vegetation water use efficiency (the ratio of C gain by photosynthesis to water loss by transpiration), and it responds to photosynthetic activity, which is influenced by vegetation N status. It is unknown if the c-increase and climate change over the last century have already affected canopy stomatal conductance and its links with C and N processes in grassland.

Temperature-sensitive biochemical O-fractionation and humidity-dependent attenuation factor are needed to predict δ O of cellulose from leaf water in a grassland ecosystem.

We explore here our mechanistic understanding of the environmental and physiological processes that determine the oxygen isotope composition of leaf cellulose (δ O ) in a drought-prone, temperate grassland ecosystem. A new allocation-and-growth model was designed and added to an O-enabled soil-vegetation-atmosphere transfer model (MuSICA) to predict seasonal (April-October) and multi-annual (2007-2012) variation of δ O and O-enrichment of leaf cellulose (Δ O ) based on the Barbour-Farquhar model. Modelled δ O agreed best with observations when integrated over c.

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.

Atmospheric CO and VPD alter the diel oscillation of leaf elongation in perennial ryegrass: compensation of hydraulic limitation by stored-growth.

We explored the effects of atmospheric CO concentration (C ) and vapor pressure deficit (VPD) on putative mechanisms controlling leaf elongation in perennial ryegrass. Plants were grown in stands at a C of 200, 400 or 800 μmol mol combined with high (1.17 kPa) or low (0.

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).

Abscisic Acid Receptors and Coreceptors Modulate Plant Water Use Efficiency and Water Productivity.

Improving the water use efficiency (WUE) of crop plants without trade-offs in growth and yield is considered a utopic goal. However, recent studies on model plants show that partial restriction of transpiration can occur without a reduction in CO uptake and photosynthesis. In this study, we analyzed the potentials and constraints of improving WUE in Arabidopsis () and in wheat ().

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.

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.

Model explanation of the seasonal variation of δO in cow (Bos taurus) hair under temperate conditions.

Oxygen isotopes (δO) in animal and human tissues are expected to be good recorders of geographical origin and migration histories. However, seasonal variation of δO may diminish the origin information in the tissues. Here the seasonality of δO in tail hair was investigated in a domestic suckler cow (Bos taurus) that underwent different ambient conditions, physiological states, keeping and feeding during five years.

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 .

Leveraging abscisic acid receptors for efficient water use in Arabidopsis.

Plant growth requires the influx of atmospheric CO2 through stomatal pores, and this carbon uptake for photosynthesis is inherently associated with a large efflux of water vapor. Under water deficit, plants reduce transpiration and are able to improve carbon for water exchange leading to higher water use efficiency (WUE). Whether increased WUE can be achieved without trade-offs in plant growth is debated.

Carbon dynamics in aboveground biomass of co-dominant plant species in a temperate grassland ecosystem: same or different?

Understanding the role of individual organisms in whole-ecosystem carbon (C) fluxes is probably the biggest current challenge in C cycle research. Thus, it is unknown whether different plant community members share the same or different residence times in metabolic (τmetab ) and nonmetabolic (i.e.

Grassland biodiversity bounces back from long-term nitrogen addition.

The negative effect of increasing atmospheric nitrogen (N) pollution on grassland biodiversity is now incontrovertible. However, the recent introduction of cleaner technologies in the UK has led to reductions in the emissions of nitrogen oxides, with concomitant decreases in N deposition. The degree to which grassland biodiversity can be expected to 'bounce back' in response to these improvements in air quality is uncertain, with a suggestion that long-term chronic N addition may lead to an alternative low biodiversity state.