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.

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.

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.

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.

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 .