North America’s oldest boreal trees are more efficient water users due to increased [CO2], but do not grow faster

Due to anthropogenic emissions and changes in land use, trees are now exposed to atmospheric levels of [CO2] that are unprecedented for 650,000 y [Lüthi et al. (2008) Nature 453:379–382] (thousands of tree generations). Trees are expected to acclimate by modulating leaf–gas exchanges and alter water use efficiency which may result in forest productivity changes. Here, we present evidence of one of the strongest, nonlinear, and unequivocal postindustrial increases in intrinsic water use efficiency (iWUE) ever documented (+59%). A dual-isotope tree-ring analysis (δ13C and δ18O) covering 715 y of growth of North America’s oldest boreal trees (Thuja occidentalis L.) revealed an unprecedented increase in iWUE that was directly linked to elevated assimilation rates of CO2 (A). However, limited nutrient availability, changes in carbon allocation strategies, and changes in stomatal density may have offset stem growth benefits awarded by the increased iWUE. Our results demonstrate that even in scenarios where a positive CO2 fertilization effect is observed, other mechanisms may prevent trees from assimilating and storing supplementary anthropogenic emissions as above-ground biomass. In such cases, the sink capacity of forests in response to changing atmospheric conditions might be overestimated.

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Incontinence in aging leaves: deteriorating water relations with leaf age in Agastachys odorata (Proteaceae), a shrub with very long-lived leaves

Functional Plant Biology ◽

10.1071/fp07166 ◽

2007 ◽

Vol 34 (10) ◽

pp. 918 ◽

Cited By ~ 12

Author(s):

Gregory J. Jordan ◽

Timothy J. Brodribb

Keyword(s):

Water Use Efficiency ◽

Water Use ◽

Stomatal Density ◽

Leaf Age ◽

Carbon Assimilation ◽

Leaf Damage ◽

Evergreen Species ◽

Intrinsic Water Use Efficiency ◽

Use Efficiency ◽

Cuticle Thickness

This paper examines physiological characteristics of the leaves of Agastachys odorata R.Br., a wet-climate sclerophyllous shrub with very long-lived leaves. It addresses the hypothesis that cuticles become leakier to water vapour as leaves age. Astomatous cuticular conductance, whole-leaf minimum epidermal conductance, leaf damage and accumulation of epiphylls all increased several-fold with leaf age from first year growth to 10 years of age. Maximum carbon assimilation peaked 1 year after full leaf expansion, then declined. Intrinsic water use efficiency was highest in mid-aged leaves and declined markedly in the oldest leaves. Stomatal density, stomatal size and cuticle thickness did not vary significantly among ages. The older leaves were less effective at controlling water loss, resulting in decreases in water use efficiency. A differential increase in the conductance of the stomatal surface of the leaves relative to astomatous surface suggested that stomatal leakiness was significant in leaves over five years old. Although data for other species is ambiguous, the deterioration in A. odorata appears to be consistent with changes in the oldest leaves of other species. Thus, decreasing ability to use water efficiently appears to be a consequence of accumulated damage and may contribute to the need for leaf senescence in evergreen species with little self shading.

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Intrinsic water use efficiency depends on stomatal aperture rather than stomatal density in C3 and C4 grasses grown at glacial CO2 and low light

10.1101/2021.07.22.453465 ◽

2021 ◽

Author(s):

Walter K Israel ◽

Alex Watson-Lazowski ◽

Zhong-Hua Chen ◽

Oula Ghannoum

Keyword(s):

Stomatal Conductance ◽

Water Use Efficiency ◽

Water Use ◽

Stomatal Density ◽

Stomatal Aperture ◽

C4 Grasses ◽

Low Light ◽

Influx Rate ◽

Intrinsic Water Use Efficiency ◽

Use Efficiency

We investigated how stomatal morphology and physiology control intrinsic leaf water use efficiency (iWUE) in grasses. Two C3 and six C4 grasses were grown at ambient (400 μl L-1) or glacial CO2 (180 μl L-1) and high (1000 μmol m-2 s-1) or low light intensity (200 μmol m-2 s-1). C4 grasses tended to have higher iWUE and CO2 assimilation rates, and lower stomatal conductance (gs), operational stomatal aperture (aop) and guard cell K+ influx rate relative to C3 grasses, while stomatal size (SS) and stomatal density (SD) did not vary according to the photosynthetic type. Overall, iWUE and gs depended most on aop and density of open stomata. In turn, aop correlated with K+ influx, stomatal opening speed on transition to high light and SS. Species with higher SD had smaller and faster-opening stomata. Although C4 grasses operated with lower gs and aop at ambient CO2, they showed a greater potential to open stomata relative to maximal stomatal conductance (gmax), indicating heightened stomatal sensitivity and control. We uncover novel links between aop, gs, iWUE and K+ influx amongst grasses and differential K+ influx responses of C4 guard cells to low light, revealing molecular targets for breeding crops with high iWUE.

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Coordination of stomata and vein patterns with leaf width underpins water use efficiency in a C4 crop

10.22541/au.162009415.55042548/v1 ◽

2021 ◽

Author(s):

Ling Pan ◽

Barbara George-Jaeggli ◽

Andrew Borrell ◽

David Jordan ◽

Fiona Koller ◽

...

Keyword(s):

Energy Balance ◽

Water Use Efficiency ◽

Water Use ◽

Stomatal Density ◽

Leaf Gas Exchange ◽

Crop Productivity ◽

Stomatal Aperture ◽

Leaf Width ◽

Intrinsic Water Use Efficiency ◽

Use Efficiency

Despite its importance for crop productivity in drought-affected environments, the underlying mechanisms of variation in intrinsic water use efficiency (iWUE) are not well understood, especially in C4 plants. Recently, Cano et al. (2019) discovered that leaf width (LW) correlated negatively with iWUE and positively with stomatal conductance for water vapour (gsw) across several C4 grasses. Here, we analysed these relationships within 48 field-grown genotypes that cover a broad range of variation in LW in Sorghum bicolor, a well-adapted C4 crop to xeric and hot conditions, by measuring and modelling leaf gas exchange and leaf energy balance three times a day, using anatomical traits as potential drivers for iWUE. LW correlated negatively with iWUE and stomatal density, but positively with gsw, interveinal distance of longitudinal veins (IVDL) and the percentage of stomatal aperture relative to maximum. Energy balance modelling showed that wider leaves opened the stomata more to generate a more negative leaf-to-air temperature difference especially at midday, when air temperatures exceeded 40ºC. These results highlight the important role that LW plays in shaping iWUE through modification of vein and stomatal traits and by regulating stomatal aperture. Therefore, LW could be used as a predictor for higher iWUE among sorghum genotypes.

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The effects of sodium sulphate and sodium chloride on growth, morphology, photosynthesis, and water use efficiency of Chenopodium rubrum

Canadian Journal of Botany ◽

10.1139/b90-126 ◽

1990 ◽

Vol 68 (5) ◽

pp. 999-1006 ◽

Cited By ~ 21

Author(s):

Patricia Warne ◽

R. D. Guy ◽

Lorna Rollins ◽

D. M. Reid

Keyword(s):

Sodium Chloride ◽

Water Use Efficiency ◽

Water Use ◽

Stomatal Density ◽

Stable Carbon Isotope ◽

Dry Weight ◽

Sodium Sulphate ◽

Chenopodium Rubrum ◽

Intrinsic Water Use Efficiency ◽

Use Efficiency

The effects of sodium sulphate and sodium chloride salinity on the anatomy, water relations, and photosynthesis of Chenopodium rubrum L. were compared. Low concentrations of either salt stimulated growth, but higher concentrations resulted in large decreases in dry weight and leaf area. Leaf succulence and the number of layers of palisade cells were increased, but these effects were more pronounced with NaCl than with Na2SO4. Stomatal density was reduced at low to moderate salinities, but then increased again at high salinity. Stomatal size was reduced at all salinities. Increasing salinity had no great effect on photosynthetic rates except with older plants grown at the highest level of Na2SO4. Stomatal conductance decreased at all salinities. This reduced transpiration and led to increased intrinsic water use efficiency. Total tissue stable carbon isotope ratios also indicated that water use efficiency was improved. Chenopodium rubrum adjusted osmotically by accumulating electrolytes from the nutrient solution and by synthesizing glycinebetaine. Plants in NaCl limited osmotic adjustment more than those growing in Na2SO4. Despite this, Na2SO4 was more damaging than NaCl and caused earlier leaf senescence at high concentrations.

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Modelling the climatic drivers determining photosynthesis and carbon allocation in evergreen Mediterranean forests using multiproxy long time series

Biogeosciences Discussions ◽

10.5194/bgd-12-2745-2015 ◽

2015 ◽

Vol 12 (3) ◽

pp. 2745-2786

Author(s):

G. Gea-Izquierdo ◽

F. Guibal ◽

R. Joffre ◽

J. M. Ourcival ◽

G. Simioni ◽

...

Keyword(s):

Time Series ◽

Water Use Efficiency ◽

Water Use ◽

Carbon Allocation ◽

Climatic Variability ◽

Mediterranean Forests ◽

Intrinsic Water Use Efficiency ◽

Climatic Drivers ◽

Use Efficiency

Abstract. Climatic drivers limit several important physiological processes involved in ecosystem carbon dynamics including gross primary productivity (GPP) and carbon allocation in vegetation. Climatic variability limits these two processes differently. We developed an existing mechanistic model to analyse photosynthesis and variability in carbon allocation in two evergreen species at two Mediterranean forests. The model was calibrated using a combination of eddy covariance CO2 flux data, dendrochronological time series of secondary growth and forest inventory data. The model was modified to be climate explicit in the key processes addressing acclimation of photosynthesis and allocation. It succeeded to fit both the high- and the low-frequency response of stand GPP and carbon allocation to the stem. This would support its capability to address both carbon source and sink limitations. Simulations suggest a decrease in mean stomatal conductance in response to environmental changes and an increase in mean annual intrinsic water use efficiency (iWUE) in both species during the last 50 years. However, this was not translated on a parallel increase in ecosystem water use efficiency (WUE). A long-term decrease in annual GPP matched the local trend in precipitation since the 1970s observed in one site. In contrast, GPP did not show a negative trend and the trees buffered the climatic variability observed at the site where long-term precipitation remained stable. In our simulations these temporal changes would be partly related to increasing [CO2] because the model includes biochemical equations where photosynthesis is directly linked to [CO2]. Long-term trends in GPP did not match those in growth, in agreement with the C-sink hypothesis. There is a great potential to use the model with abundant dendrochronological data and analyse forest performance under climate change. This would help to understand how different interfering environmental factors produce instability in the climatic signal expressed in tree-rings.

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The use of physiological, biochemical and morpho-anatomical traits in tree breeding for improved water-use efficiency of Quercus robur L.

Forest Systems ◽

10.5424/fs/2019283-15233 ◽

2019 ◽

Vol 28 (3) ◽

pp. e017

Author(s):

Srđan Stojnić ◽

Branislav Kovačević ◽

Marko Kebert ◽

Erna Vaštag ◽

Mirjana Bojović ◽

...

Keyword(s):

Water Use Efficiency ◽

Water Use ◽

Stepwise Regression ◽

Stomatal Density ◽

Common Garden ◽

Path Coefficient ◽

Common Garden Experiment ◽

Intrinsic Water Use Efficiency ◽

Use Efficiency ◽

One Year

Aim of study: In the present paper we studied the nature and level of co-dependence between leaf functional traits and intrinsic water-use efficiency (WUEi)in one-year-old Quercus roburL. seedlings, grown in a common garden experiment under moderate drought conditions. The study aimed to identify those traits that might be potentially utilized to improve leaf-level WUEi, and therefore be used in breeding programmes to enhance drought adaptation of Q. roburtree species.Area of study: The study was carried out at the common garden experiment established within UNESCO Biosphere Reserve Mura-Drava-Danube.Material and methods: The study involved one-year-old seedlings of eight half-sib lines of Q. robur. We analyzed 18 leaf parameters; i.e. physiological, biochemical, morphological and anatomical. Data were processed using multivariate statistical methods: a) principal component analysis, b) stepwise regression analysis, and c) path coefficient analysis.Main results: The results evidenced that leaf stomatal traits, particularly stomatal density (SD),and leaf dry mass per unit leaf area (LMA) were the most important traits associated closely with WUEi.Stomatal density achieved the highest score on PC1 (0.825), in which WUEihad the highest loading (0.920), as well. SDwas also included first in stepwise regression model. Research highlights: The results demonstrated that under moderate water stressWUEiin Q. robur half-sib lines were mainly the result of the plants’ structural acclimation to surrounding environmental conditions.

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