CO2 Elevation and Nitrogen Supply Alter the Growth and Physiological Responses of Tomato and Barley Plants to Drought Stress
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Global climate change will modify plants in terms of growth and physiology. To better understand the consequences of this effect, the responses of the leaf water relations and nitrogen (N) use efficiency of barley and tomato plants to elevated CO2 (e[CO2], 800 ppm) combined with progressive drought stress at two levels of N supply (N1, 0.5 g N pot−1 and N2, 1.0 g N pot−1) were studied. The plants were grown in two separate phytotrons at ambient CO2 (a[CO2], 400 ppm) and e[CO2], respectively. The leaf physiological parameters as well as carbon (C) and N concentrations were determined; plant growth, water and N use efficiencies were evaluated. The results showed that e[CO2] increased photosynthesis and water use efficiency (WUE) while decreased specific leaf area (SLA) in both species, whereas N supply level differentially influenced WUE in barley and tomato plants. The abscisic acid (ABA)-induced stomatal closure during progressive soil drying varied between the two species where the stomatal conductance (gs) of barley plants was more sensitive to leaf ABA than tomato plants, though CO2 environment did not affect the response in both species. Compared to a[CO2], e[CO2] reduced plant transpiration rate (Tplant) in barley but not in tomato. e[CO2] increased the leaf C:N ratio ([C:N]leaf) in plants by enhancing leaf C concentration ([C]leaf) in barley and by dilution of leaf N concentration ([N]leaf) in tomato, respectively, but N2 substantially decreased [C:N]leaf, and thus, N treatment was the dominant factor controlling [C:N]leaf. Collectively, appropriate N supply may modulate the acclimation of plants to e[CO2] and soil water deficits. This study provides some novel insights into N management of different plant species for adapting to future drier and CO2-enriched environment.Keywords:
Water Use Efficiency
Stomatal Conductance
Plant Physiology
Specific leaf area
Drought Tolerance
Stomatal Conductance
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Leaf functional traits are important because they reflect physiological functions, such as transpiration and carbon assimilation. In particular, morphological leaf traits have the potential to summarize plants strategies in terms of water use efficiency, growth pattern and nutrient use. The leaf economics spectrum (LES) is a recognized framework in functional plant ecology and reflects a gradient of increasing specific leaf area (SLA), leaf nitrogen, phosphorus and cation content, and decreasing leaf dry matter content (LDMC) and carbon nitrogen ratio (CN). The LES describes different strategies ranging from that of short-lived leaves with high photosynthetic capacity per leaf mass to long-lived leaves with low mass-based carbon assimilation rates. However, traits that are not included in the LES might provide additional information on the species' physiology, such as those related to stomatal control. Protocols are presented for a wide range of leaf functional traits, including traits of the LES, but also traits that are independent of the LES. In particular, a new method is introduced that relates the plants' regulatory behavior in stomatal conductance to vapor pressure deficit. The resulting parameters of stomatal regulation can then be compared to the LES and other plant functional traits. The results show that functional leaf traits of the LES were also valid predictors for the parameters of stomatal regulation. For example, leaf carbon concentration was positively related to the vapor pressure deficit (vpd) at the point of inflection and the maximum of the conductance-vpd curve. However, traits that are not included in the LES added information in explaining parameters of stomatal control: the vpd at the point of inflection of the conductance-vpd curve was lower for species with higher stomatal density and higher stomatal index. Overall, stomata and vein traits were more powerful predictors for explaining stomatal regulation than traits used in the LES.
Stomatal Conductance
Specific leaf area
Water Use Efficiency
Stomatal density
Photosynthetic capacity
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Abstract Ground-level ozone (O3) pollution affects the plant carbon and water balance, but the relative contributions of impaired photosynthesis and the loss of stomatal functioning to the O3-induced reductions in water-use efficiency (WUE) remain unclear. We combined the leaf stable dual isotopic signatures of carbon (δ13C) and oxygen (δ18O) with related instantaneous gas exchange performance to determine the effects of O3 dose on the net photosynthetic rate (An), stomatal conductance (gs) and intrinsic WUE (iWUE = An/gs) in four tree species (one being a hybrid) exposed to five O3 levels. The iWUE declined for each step increase in O3 level, reflecting progressive loss of the coupling between leaf carbon gain and water loss. In ambient compared with charcoal-filtered air, the decreased iWUE was associated with reductions in both An and gs (i.e., decreased δ13C and increased δ18O). In elevated O3 treatments, however, the iWUE declines were caused by reduced An at constant or increased gs. The results show that the dual isotope approach provides a robust way to gather time-integrated information on how O3 pollution affects leaf gas exchange. Our study highlights that O3-induced decoupling between photosynthesis and stomatal regulation causes large and progressive declines in the WUE of forest trees, demonstrating the need for incorporating this hitherto unaccounted for effect into vegetation models.
Stomatal Conductance
Water Use Efficiency
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Summary Improvement in crop water‐use efficiency ( WUE ) is a critical priority for regions facing increased drought or diminished groundwater resources. Despite new tools for the manipulation of stomatal development, the engineering of plants with high WUE remains a challenge. We used Arabidopsis epidermal patterning factor ( EPF ) mutants exhibiting altered stomatal density to test whether WUE could be improved directly by manipulation of the genes controlling stomatal density. Specifically, we tested whether constitutive overexpression of EPF 2 reduced stomatal density and maximum stomatal conductance ( g w(max) ) sufficiently to increase WUE . We found that a reduction in g w(max) via reduced stomatal density in EPF 2 ‐overexpressing plants ( EPF 2 OE ) increased both instantaneous and long‐term WUE without altering significantly the photosynthetic capacity. Conversely, plants lacking both EPF 1 and EPF 2 expression ( epf1epf2 ) exhibited higher stomatal density, higher g w(max) and lower instantaneous WUE , as well as lower (but not significantly so) long‐term WUE . Targeted genetic modification of stomatal conductance, such as in EPF 2 OE , is a viable approach for the engineering of higher WUE in crops, particularly in future high‐carbon‐dioxide ( CO 2 ) atmospheres.
Stomatal Conductance
Water Use Efficiency
Stomatal density
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Stomatal Conductance
Water Use Efficiency
Photosynthetically active radiation
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In growth chamber experiments the authors compared the water-use efficiency (WUE) and drought tolerance (DT - retention of dry mass vegetative yield when droughted) of the drought intolerant common tomato, L. esculentum and the ostensibly drought tolerant tomato, L. pennellii. Drought treatment was imposed as two severe episodes of drought, each episode lasting until all leaves on the plant were silted, with a period of recovery between treatments. They measured up to 20 performance attributes to WUE and DT, including: root:shoot ratio, leaf internal CO2/ambient CO2, {delta}{sup 13}C, leaf photosynthetic rate, specific leaf mass, leaf water potential, leaf osmotic potential, and stomatal density. Water-use efficiency is negatively correlated with drought tolerance; drought tolerance is positively correlated with plants' ability to increase WUE under stress. Few other attributes are correlated with drought tolerance, and some are conspicuous by their absence. They find evidence for substantial genetic linkage among attributes that confer drought tolerance; and interplant rankings in drought tolerance depend strongly upon the type of drought stress experienced (episodic vs. continuous).
Drought Tolerance
Water Use Efficiency
Lycopersicon
Drought stress
Drought Resistance
Stomatal Conductance
Water Stress
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Populus deltoids is a fast growing and high water-consuming species.It is necessary to choose clones with high water use efficiency when they are introduced to China.In our test,long-term water use efficiency (WUEL),instantaneous water use efficiency (WUEi),foliar carbon isotope composition (δ13C),photosynthesis,stomatal density and stomatal conductance(Gs) of three P.deltoids clones(DN2,P.deltoides×P.nigra;R-270,P.deltoides×P.nigra;NE-19,P.nigra×(P.deltoides×P.nigra)) were studied under different water treatments.The results showed that significant differences in these parameters were detected among three clones,indicating the variation of water use efficiency among three clones.NE-19 was the best clone,with the highest WUEL,WUEi,δ13 C and net photosynthetic rate(Pn) and the lowest stomatal density and Gs.Therefore,we make a conclusion that stomatal density and conductance are the major factors which could lead to the variation of Pn and WUE i and in turn affect WUEL and δ13C.δ13 C could be a good indicator to evaluate the WUEL of clones,which was correlated with WUEL under sufficient water supply;however,the correlation decreased under water stress.ERECTA gene is the first gene which could regulate plant transpiration efficiency in Arabidopsis.A cDNA clone,designated PdERECTA,was isolated from P.deltoids.RT-PCR indicated that PdERECTA gene may have the similar function in P.deltoids.
Water Use Efficiency
Stomatal Conductance
Stomatal density
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Elevated atmospheric CO2 is not only a reaction caused by a series of climate change,but also has a significant impact on plant physiological process and growth.This article analyses the research progress on the leaf stomatal density,stomatal conductance,plant photosynthesis,transpiration and water use efficiency under the condition of high atmospheric CO2 enrichment.It is found out that under such condition stomatal density decreases significantly,and stomatal conductance also decreases significantly(30%).Plant photosynthesis increases by 50%～100% in general.The decreased rate of transpiration may differ on different plant,about 10%～70%.The water use efficiency(WUE) increases,and its increasing rate under adequate nitrogen treatment is more obvious than that under inadequate treatment.And analysis is made of the interrelationship between them.The conclusion can be used as theoretical basis for breeding crop varieties with high water use and water-saving efficiency.
Stomatal Conductance
Water Use Efficiency
Stomatal density
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Intrinsic water use efficiency (WUE(intr)), the ratio of photosynthesis to stomatal conductance to water, is often used as an index for crop water use in breeding projects. However, WUE(intr) conflates variation in these two processes, and thus may be less useful as a selection trait than knowledge of both components. The goal of the present study was to determine whether the contribution of photosynthetic capacity and stomatal conductance to WUE(intr) varied independently between soybean genotypes and whether this pattern was interactive with mild drought. Photosynthetic capacity was defined as the variation in WUE(intr) that would occur if genotypes of interest had the same stomatal conductance as a reference genotype and only differed in photosynthesis; similarly, the contribution of stomatal conductance to WUE(intr) was calculated assuming a constant photosynthetic capacity across genotypes. Genotypic differences in stomatal conductance had the greatest effect on WUE(intr) (26% variation when well watered), and was uncorrelated with the effect of photosynthetic capacity on WUE(intr). Thus, photosynthetic advantages of 8.3% were maintained under drought. The maximal rate of Rubisco carboxylation, generally the limiting photosynthetic process for soybeans, was correlated with photosynthetic capacity. As this trait was not interactive with leaf temperature, and photosynthetic capacity differences were maintained under mild drought, the observed patterns of photosynthetic advantage for particular genotypes are likely to be consistent across a range of environmental conditions. This suggests that it is possible to employ a selection strategy of breeding water-saving soybeans with high photosynthetic capacities to compensate for otherwise reduced photosynthesis in genotypes with lower stomatal conductance.
Water Use Efficiency
Stomatal Conductance
Photosynthetic capacity
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Citations (181)
Leaf functional traits are important because they reflect physiological functions, such as transpiration and carbon assimilation. In particular, morphological leaf traits have the potential to summarize plants strategies in terms of water use efficiency, growth pattern and nutrient use. The leaf economics spectrum (LES) is a recognized framework in functional plant ecology and reflects a gradient of increasing specific leaf area (SLA), leaf nitrogen, phosphorus and cation content, and decreasing leaf dry matter content (LDMC) and carbon nitrogen ratio (CN). The LES describes different strategies ranging from that of short-lived leaves with high photosynthetic capacity per leaf mass to long-lived leaves with low mass-based carbon assimilation rates. However, traits that are not included in the LES might provide additional information on the species' physiology, such as those related to stomatal control. Protocols are presented for a wide range of leaf functional traits, including traits of the LES, but also traits that are independent of the LES. In particular, a new method is introduced that relates the plants' regulatory behavior in stomatal conductance to vapor pressure deficit. The resulting parameters of stomatal regulation can then be compared to the LES and other plant functional traits. The results show that functional leaf traits of the LES were also valid predictors for the parameters of stomatal regulation. For example, leaf carbon concentration was positively related to the vapor pressure deficit (vpd) at the point of inflection and the maximum of the conductance-vpd curve. However, traits that are not included in the LES added information in explaining parameters of stomatal control: the vpd at the point of inflection of the conductance-vpd curve was lower for species with higher stomatal density and higher stomatal index. Overall, stomata and vein traits were more powerful predictors for explaining stomatal regulation than traits used in the LES.
Stomatal Conductance
Specific leaf area
Water Use Efficiency
Stomatal density
Photosynthetic capacity
Leaf size
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Citations (33)