Effect of irrigation on the relationships between leaf gas exchange related traits and yield in dwarf dry bean grown under Mediterranean conditions
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Keywords:
Water Use Efficiency
Stomatal Conductance
Water use
Specific leaf area
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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Water use efficiency (WUE) increment and reduction in amount of irrigation are important role played by deficit irrigation. Deficit irrigation is a well-accepted practice to optimize increase water use, thereby saving cost, by allowing crops to withstand mild water stress with no or only marginal decreases in yield and quality. Greenhouse experiments were conducted using a deficit irrigation program on cucumber crops under drip irrigation during 2018–2019 growing season, to determine the crop water requirements in greenhouse and WUE of cucumber crop using a deficit irrigation program at different stages of growth. Irrigation treatments consisted of 12 levels of ETc (20%-100%), deficit irrigation tested at different growth stages (initial, mid and late stage of growth) for a total of 12 treatments at each experiment. The maximum amount of water applied to the crop was 455 mm for the 20% ETc treatment while the minimum water applied was 247 mm for 100% ETc treatment. The ETc ranges between 223 and 407 mm for the different treatments. The results indicated that, cucumber could stand a shortage of water during the growth and water use efficiency (WUE) and water productivity (WP) values increased when water amounts decreased; these values decreased to 45.6 and 24 kg/m3, respectively. Water resource management under water scarcity bring about different policies aim at reducing the non-beneficial water uses, particularly those corresponding to water consumption and to the non-reusable fraction of the diverted water.
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Growing season
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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.
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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.
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Stomatal density
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Stomatal Conductance
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Photosynthetically active radiation
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Almond yields vary between rainfed and intensively irrigated systems, but how to match irrigation to potential productivity is unclear. Hence, we compared almond physiology under deficit (600 mm) and full (1300 mm) irrigation to identify stress indices and determine the production overheads of mismanaged watering. We hypothesized that trees alter their growth to conserve resources during drought and mitigate their hydraulic stress responses. Thus, we monitored stem water potential and stomatal conductance to characterize the hydraulic responses of trees to deficient and hydrated water conditions. Adapting the seasonal relationship between irrigation coefficients and tree water potential was also tested. Finally, soil water status and trunk development were considered physical stress indices for field conditions. Soil water depletion in deficit irrigation reduced stem water potential below − 2 MPa and checked stomatal conductance at 0.15 mol m-2 s-1 for most of the growing season. An empirical productivity model determined that, under deficit irrigation, almond trees suffer from chronic stress that limits their photosynthetic capacity to ∼14 µmol m-2 s-1. Consequently, nominal assimilation limitations (10%) in early summer manifested to 4 kg C tree-1 metabolic losses by autumn. The inter-annual vegetative limitations in deficit irrigation resulted in significant yield reductions (35%) by the second experimental season. Temporal changes in the correlations between stem water potential, stomatal conductance, and trunk contractions made it difficult to use water stress indices to make irrigation decisions. However, normalizing tree performance by phenology indicated a 960 mm irrigation that supported high yields. Further, integrating the variability in soil water with trunk dendrometry illustrated that trees could maintain constant growth between irrigation days under well-watered conditions. Hence, in commercial operations, variable growth rates and trunk contraction measures signal insufficient irrigation and could guide practical irrigation adaptations.
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Growing season
Water use
Water potential
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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.
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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.
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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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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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