Statistical Analysis of Leaf Water Use Efficiency and Physiology Traits of Winter Wheat Under Drought Condition

Five statistical methods including simple correlation, multiple linear regression, stepwise regression, principal components, and path analysis were used to explore the relationship between leaf water use efficiency （WUE） and physiological traits （photosynthesis rate, stomatal conductance, transpiration rate, intercellular CO2 concentration, etc.） of 29 wheat cultivars. The results showed that photosynthesis rate, stomatal conductance, and transpiration rate were the most important leaf WUE parameters under drought condition. Based on the results of statistical analyses, principal component analysis could be the most suitable method to ascertain the relationship between leaf WUE and relative physiological traits. It is reasonable to assume that high leaf WUE wheat could be obtained by selecting breeding materials with high photosynthesis rate, low transpiration rate, and stomatal conductance under dry area.

Variations in Composition and Water Use Efficiency of Plant Functional Groups Based on Their Water Ecological Groups in the Xilin River Basin

Major plant species in the Xilin River Basin were grouped into six plant functional groups (PFGs) based on their water ecological groups: xerophytes, mesoxerophytes, xeromesophytes, mesophytes, hygromesophytes and hygrophytes. We surveyed the composition, delta(13)C values and proline concentration of PFGs in eight different plant communities along a soil moisture gradient. Results show that: (1) PFGs occurred variously in eight steppe communities with different soil moisture status. In wetter habitats, hygromesophytes and hygrophytes were more abundant and accounted for the majority of aboveground biomass, whereas xerophytes and mesoxerophytes became more conspicuous in dryer habitats; (2) the numerical order of the mean delta(13)C values of PFGs is as follows: xerophytes (-26.38parts per thousand) = mesoxerophytes (-26.51parts per thousand) > xeromesophytes (-27.02parts per thousand) > mesophytes (-27.56parts per thousand) = hygromesophytes and hygrophytes (-27.80parts per thousand); (3) xerophytes maintained relative higher delta(13)C values and water use efficiency (WUE) in habitats of different water availability, whereas delta(13)C values of xeromesophytes were more sensitive to change in soil water availability; (4) From xerophytes to hygrophytes, their proline content markedly increased. Significantly positive correlations existed between proline and biomass or delta(13)C values of different water ecological groups.

Photosynthetic Water Use Efficiency of Heritage and Modern Potatoes under Limited and Unlimited Water Environments

Photosynthetic capacity for heritage (Taewa) and modern potato cultivars were compared at different water and nitrogenregimes in the glasshouse and field. The glasshouse was 2*2*4 factorial design with two irrigation: 100% ET and 60% ET;two applied N: 50 kg N ha-1 and 200 kg N ha-1, two Taewa (Moe Moe, Tutaekuri) and two modern potatoes (Moonlight, Agria). The 2009/2010 field experiment was a split-plot, with irrigation and rain-fed regimes as the main treatments: four potatoes above were sub-treatments. The 2010/2011 field experiment was a split-split-plot, with three water regimes as the main treatments: three cultivars (Moe Moe, Tutaekuri, and Agria) were subplots;two N rates were sub-sub-treatments. Gaseous exchange was measured by CIRAS-2 at different days from emergence. Leaf water potential was measured using pressure chamber method. Taewa achieved high photosynthetic WUE in glasshouse and 2010/2011 experiment by maintaining high An, low gs and low Ci compared to modern cultivars (p The An, gs and T increased with irrigation and N increase while decreasing Ci (p < 0.01). Water stress significantly increased VPD resulting in low An and photosynthetic WUE in Moonlight in the glasshouse. The leaf water potential for Taewa was very tolerant while modern potatoes were weakened by water stress. The study indicated that Taewa can be scheduled at partial irrigation without more detrimental effects on photosynthetic capacity while modern potatoes need full irrigation to avoid detrimental effects on photosynthetic capacity.

Impact of air drought on photosynthesis efficiency of the Siberian crabapple(Malus baccata L. Borkh.) in the forest-steppe zone of Transbaikalia, Russia

The adaption of photosynthesis, being a key metabolic process, plays an important role in plant resistance to air drought. In this study, the Siberian crabapple(Malus baccata L. Borkh.) in the forest-steppe zone of Transbaikalia region, Russia, was subjected to air drought stress and its photosynthesis characteristics were analyzed. The results show that air drought and sufficient soil moisture supply lead to the decrease in the total chlorophyll(Chl) content, while the ratio of Chls to carotenoids is constant in the Siberian crabapple tree. The function of photosystem II(PS-II) in the crabapple trees is characterized by a decrease in the fraction of absorbed light energy spent on the photochemical work and an increase in the proportion of non-photosynthetic thermal quenching. These changes indicate the photosynthetic down-regulation that acts as a universal photoprotective mechanism. During the midday hours, the combination of high air temperature and low air humidity leads to the decrease in the maximum photochemical quantum yield of photosystem II(Fv/Fm) and the efficiency of photosynthesis(PABS). The parameters of leaf gas exchange show the significant differences in these values between the control and experimental variants. During the morning hours, the Siberian crabapple, growing in the Irkutsk City,assimilates carbon dioxide more intensively. Due to the higher air humidity, the stomata are kept open and the necessary amount of carbon dioxide entries the sites of carboxylation. The low air humidity combined with wind in the experimental variants leads to the unreasonably high water loss in the crabapple leaves by more than 27% as compared to the control variant(Irkutsk City). However, water use efficiency in the morning hours increases during plant photosynthetic processes, i.e., 42% higher than that of control. This,apparently, is a reflection of the adaptation processes of the Siberian crabapple to the air drought and parching wind.

Contrasting Drought Tolerance in Two Apple Cultivars Associated with Difference in Leaf Morphology and Anatomy

Apple is one of the most important fruit trees in temperate zones, and is cultivated widely throughout the world. Drought stress affects the normal growth of apple tree, and further affects fruit yield and quality. The present study examined the effects of drought on photosynthesis and water use efficiency (WUE) of two apple cultivars (Honeycrisp and Yanfu 3) that differ in drought tolerance. The results showed that the photosynthetic rate decreased in response to drought stress for both cultivars, with significant differences in intensity. Values for net photosynthetic rate (Pn) in stressed Yanfu 3 remained significantly lower than in the controls, while, for Honeycrisp, only a slight drop in photosynthesis. Similarly, stomatal conductance (Gs), intercellular CO2 concentration (Ci), transpiration rate (Tr) were markedly reduced in Yanfu 3 under drought stress. However, Honeycrisp showed only minor changes. Under drought stress, the contents of Chl a, Chl b and Chl t in Yanfu 3 were all decreased significantly compared with the control. However, little difference in Honeycrisp was noted between stressed plants and controls. Values for WUE in stressed Yanfu 3 remained higher than in the controls from day 3 until the end of the experiment, while no significant difference was observed in Honeycrisp. Furthermore, Honeycrisp also exhibited superior physiological traits, as indicated by its anatomical and morphological characteristics. Therefore, we conclude that the superior drought tolerance of Honeycrisp was due to its anatomical and morphological characteristics, which possibly contributed to the maintenance of higher photosynthetic capacity than Yanfu 3.

Comparison study on water use efficiency of wheat flag leaf

wild species and cultivars were planted under irrigated and dryland field condition. LCA\|3 model photosynthesis apparatus was employed to measure flag leaf WUE. The results show that WUE of diploid and tetraploid increases as the wild species became cultivated species. WUE of flag leaf increases as the chromosome ploid increases (2\%n\%→4\%n\%→6\%n\%) in the wheat evolution. Among modern cultivars, WUE of most irrigated varieties is higher than that of dryland varieties.

Adaptability of High-Yielding Rice Cultivars in Relation to Biomass Productivity under Moderately Water Stressed Upland Conditions

Recent studies have focused on the improvement of rice productivity under aerobic conditions for times when water resources and food production are limited. This study aimed to evaluate the adaptability of high-yielding rice cultivars to moderately water-stressed upland conditions in order to contribute breeding. A three-year field experiment in the temperate climate of Kyoto, Japan, indicated that the decrease in yield was mainly derived from a decrease in above-ground total dry matter (TDM) rather than a decrease in harvest index (HI). Although the decrease in TDM was mostly caused by a decrease in radiation use efficiency (RUE), we determined that the key to adapting high-yielding cultivars to upland conditions is intercepted radiation per day (IRPD), governed by leaf area index (LAI). Although the effect was not robust, LAI growth under upland conditions was associated with root length density. RUE was dependent on leaf water potential (LWP), indicating that a plant’s ability to maintain LWP under water-stressed conditions is important. The results also suggest the necessity of a canopy analyzer to evaluate LAI, as well as an infrared radiation thermometer to evaluate RUE. Performing such measurements during breeding efforts allows us to select for genotypes that are suitable for less stressed aerobic conditions.

Review on Leaf Water Use Efficiency of Major Trees Species in Arid and Semi-Arid Area

The tree specie selection is the critical part in the process of vegetation restoration and reconstruction in arid and semi-arid areas.As a reliable indicator of drought resistance and water use characteristics of tree species,water use efficiency（WUE） has become a hotspot in the research on tree specie selection.This paper introduced the concept and correspondingly research method of leaf WUE and summarized the research progress of leaf WUE in terms of the variation in leaf WUE between species,positions in the canopy,and characteristics of temporal and spatial variation,its influence on environmental factors like illumination,moisture,temperature, CO2 and O3 concentrations.Furthermore,it put forward the problems currently existing in the research and prospected the trend of future research on leaf WUE.

Effect of Limited Single Irrigation on Yield of Winter Wheat and Spring Maize Relay Intercropping

A field experiment was conducted during the 2002/2003 cropping season of winter wheat （Triticum aestivum） and spring maize （Zea mays） to evaluate the effect of limited single drip irrigation on the yield and water use of both crops under relay intercropping in a semi-arid area of northwestern China. A controlled 35 mm single irrigation, either early or late, was applied to each crop at a certain growth stage. Soil water, leaf area, final grain yield and yield components such as the thousand-grain weight, length of spike, fertile spikelet number, number of grains per spike, and grain weight per spike were measured, and water use efficiency and leaf area index were calculated for the irrigated and non-irrigated relay intercropping treatments and sole cropping controls. The results showed that yield, yield components, water use efficiency, and leaf area index in the relay intercropping treatments were affected by limited single drip irrigation during various growth stages of wheat and maize. The total yields in the relay intercropping treatment irrigated during the heading stage of wheat and the heading and anthesis stage of maize were the highest among all the treatments, followed by that irrigated during the anthesis stage of wheat and silking stage of maize; so was the water use efficiency. Significant differences occurred in most yield components between the irrigated and non-irrigated relay-intercropping treatments. The dynamics of the leaf area index in the relay-intercropped or solely cropped wheat and maize showed a type of single-peak pattern, whereas that of the relay intercropping treatments showed a type of double-peak pattern. Appropriately, limited single irrigation and controlled soil water content level could result in higher total yield, water use efficiency, and leaf area index, and improved yield components in relay intercropping. This practice saved the amount of water used for irrigation and also increased the yield. Therefore, heading stage of wheat and heading and anthesis stage of maize were suggested to be the optimum limited single irrigation time for relay-intercropped wheat and maize in the semi-arid area.

Gas exchange of Populus euphratica leaves in a riparian zone

Riparian vegetation belts in arid regions of Central Asia are endangered to lose their ecosystem services due to intensified land use.For the development of sustained land use,management knowledge of plant performance in relation to resource supply is needed.We estimated productivity related functional traits at the edges of the habitat of Populus euphratica Oliv.Specific leaf area （SLA） and carbon/nitrogen （C/N） ratio of P.euphratica leaves growing near a former river bank and close to moving sand dunes in the Ebinur Lake National Nature Reserve in Xinjiang,Northwest China （near Kazakhstan） were determined and daily courses of CO2 net assimilation （PN）,transpiration （E）,and stomatal conductance （gs） of two consecutive seasons were measured during July-August 2007 and June-July 2008.Groundwater level was high （1.5-2.5 m below ground） throughout the years and no flooding occurred at the two tree stands.SLA was slightly lower near the desert than at the former river bank and leaves contained less N in relation to C.Highest E and gs of P.euphratica were reached in the morning before noon on both stands and a second low maximum occurred in the afternoon despite of the unchanged high levels of air to leaf water vapor pressure deficit （ALVPD）.Decline of gs in P.euphratica was followed by decrease of E.Water use efficiency （WUE） of leaves near the desert were higher in the morning and the evening,in contrast to leaves from the former river bank that maintained an almost stable level throughout the day.High light compensation points and high light saturation levels of PN indicated the characteristics of leaves well-adapted to intensive irradiation at both stands.In general,leaves of P.euphratica decreased their gs beyond 20 Pa/kPa ALVPD in order to limit water losses.Decrease of E did not occur in both stands until 40 Pa/kPa ALVPD was reached.Full stomatal closure of P.euphratica was achieved at 60 Pa/kPa ALVPD in both stands.E through the leaf surface amounted up to 30％ of the highest E rates,indicating dependence on water recharge from the ground despite of obviously closed stomata.A distinct leaf surface temperature （Tleaf） threshold of around 30℃ also existed before stomata started to close.Generally,the differences in gas exchange between both stands were small,which led to the conclusion that micro-climatic constraints to E and photosynthesis were not the major factors for declining tree density with increasing distance from the river.

Ecophysiological response to irrigation of two olive cultivars grown in a high-density orchard

High-density oliveculture system needs irrigation and introduces new cultivars in new environments. So the evaluation of varietal ecophysiological response to irrigation is a crucial topic. For this reason it was planned a research on two cultivars, Coratina and Arbequina, trained according to high-density system. In 2009 the irrigation was conducted according to the conventional management by applying an irrigation frequency of 4 days. The leaf water potentials reached values similar to the limits reported for the recovery within 48 hours. However, plants showed a leaf water status and gas exchange recovery just after 24 hours from watering. The results highlighted some varietal differences: Arbequina showed a better response to irrigation, while Coratina performed a higher water use efficiency by a lower leaf transpiration.

Impact of soil conditions on the physiological characteristics of maize plants in an arid region, Northwest China

Overuse of irrigation water to ensure the crop yield of maize plants has caused serious water shortage problems in the middle reach of Heihe River, China. Thus, further research on the physiological characteristics, i.e., photosynthetic rate and leaf transpiration rate, are urgently needed to develop an efficient irrigation management system. In this paper, we selected two common soil textures （sandy loam, sand） and three one-time irrigation volumes （60 mm, 20 mm, 0 mm） in order to analyze the impact of soil conditions on the physiological characteristics of maize plants. Physiological and meteorological factors, soil water content and plant growing parameters were synchronously monitored on Jun. 30, Jul. 25 and Aug. 27 of 2012. The results indicate that sandy loam is better than sand for the growth of maize plants and single irrigation may provide limited influence on the physiological characteristics. Thus, increasing irrigation times and decreasing one-time volume is suggested for an efficient irrigation system.

Effects of planting dates, densities, and varieties on ecophysiology of pigeonpea in the Southeastern United States

Pigeonpea [Cajanus cajan (L.) Millsp.] is an important legume crop widely cultivated in tropical and subtropical climates of the world. Interest in this crop is growing in many countries because of its multiple uses as a source of food, feed, fuel, and fertilizer. However, the performance of pigeonpea in Southeastern US has not been well investigated. We conducted an experiment in Nashville, Tennessee to test the effects of two planting dates, three densities, and four varieties on pigeonpea ecophysiology that included leaf photosynthesis, stomatal conductance, transpiration, water use efficiency (WUE), leaf area index (LAI) and soil respiration. Results indicated that the plants in the late planting plots had higher photosynthetic rate, stomatal conductance and transpiration. There were significant differences in the levels of leaf photosynthesis, stomatal conductance, transpiration, WUE and LAI among all four varieties. W3 and G1 showed higher photosynthetic rate and LAI than W1, and W3 had higher WUE than G2 and W1. Planting densities had no significant effect on all variables studied. This study indicated that late planting of variety G1 or W3 resulted in higher WUE and yield, but did no significant influence soil CO2 emission.

Sexual dimorphism in water and nitrogen use strategies in Honckenya peploides: timing matters

Aims Sexes of dimorphic species often differ in ecophysiological traits and display spatial segregation.These differences have been interpreted as an evolved response of the sexes to meet the specific resource demands associated with reproduction.Sexes may differ not only in the amount of resources allocated to reproduction but also in the tim-ing of allocation to reproduction.In this study,we hypothesize that as a consequence of their specific resource demands for reproduction,the sexes of the dune plant Honckenya peploides differ in terms of tempo-ral patterns of water use efficiency and nitrogen use and acquisition.Methods Water use efficiency,as inferred from leaf carbon isotope discrimi-nation(Δ^(13)C),nitrogen use,estimated by leaf nitrogen isotope com-position(δ^(15)N),and the foliar carbon and nitrogen contents were measured in males and females at three different points in time.Important Findings Females had greater water use efficiency than males,regardless of time.The ratio of N^(15) to N^(14) did not change with time in males,but significantly decreased in August for females.The total N content in the leaf tissues of females decreased as the season progressed,while in males a decrease was only found from April to June and then it remained constant from June to August.A similar pattern,but reversed,was followed by the foliar C/N ratio.Additionally,nega-tive relationships between leafΔ^(13)C and N content were found at all times for males and only at the end of the season for females.Thus,our hypothesis that sex-specific patterns of nitrogen and water use efficiency will depend on time was supported.Overall,our results highlight the importance of including time in studies of sex-ual dimorphism,and also the role that physiological specialization plays in meeting the specific demands associated with reproduction.

A global meta-analysis of woody plant responses to elevated CO_(2):implications on biomass,growth,leaf N content,photosynthesis and water relations

Background:Atmospheric CO_(2)may double by the year 2100,thereby altering plant growth,photosynthesis,leaf nutrient contents and water relations.Specifically,atmospheric CO_(2)is currently 50%higher than pre-industrial levels and is projected to rise as high as 936μmol mol^(−1)under worst-case scenario in 2100.The objective of the study was to investigate the effects of elevated CO_(2)on woody plant growth,production,photosynthetic characteristics,leaf N and water relations.Methods:A meta-analysis of 611 observations from 100 peer-reviewed articles published from 1985 to 2021 was conducted.We selected articles in which elevated CO_(2)and ambient CO_(2)range from 600–1000 and 300–400μmol mol^(−1),respectively.Elevated CO_(2)was categorized into<700,700 and>700μmol mol^(−1)concentrations.Results:Total biomass increased similarly across the three elevated CO_(2)concentrations,with leguminous trees(LTs)investing more biomass to shoot,whereas non-leguminous trees(NLTs)invested to root production.Leaf area index,shoot height,and light-saturated photosynthesis(A_(max))were unresponsive at<700μmol mol^(−1),but increased significantly at 700 and>700μmol mol^(−1).However,shoot biomass and A_(max)acclimatized as the duration of woody plants exposure to elevated CO_(2)increased.Maximum rate of photosynthetic Rubisco carboxylation(V_(cmax))and apparent maximum rate of photosynthetic electron transport(J_(max))were downregulated.Elevated CO_(2)reduced stomatal conductance(g_(s))by 32%on average and increased water use efficiency by 34,43 and 63%for<700,700 and>700μmol mol^(−1),respectively.Leaf N content decreased two times more in NLTs than LTs growing at elevated CO_(2)than ambient CO_(2).Conclusions:Our results suggest that woody plants will benefit from elevated CO_(2)through increased photosyn-thetic rate,productivity and improved water status,but the responses will vary by woody plant traits and length of exposure to elevated CO_(2).

Protective mechanism of desiccation tolerance in Reaumuria soongorica: Leaf abscission and sucrose accumulation in the stem

Reaumuria soongorica (Pall.) Maxim., a perennial semi-shrub, is widely found in semi-arid areas in northwestern China and can survive severe desiccation of its vegetative organs. In order to study the protective mechanism of desiccation tolerance in R. soongorica, diurnal patterns of net photosynthetic rate (Pn), water use efficiency (WUE) and chlorophyll fluorescence parameters of Photosystem II (PSII), and sugar content in the source leaf and stem were investigated in 6-year-old plants during progressive soil drought imposed by the cessation of watering. The results showed that R. soongorica was char-acterized by very low leaf water potential, high WUE, photosynthesis and high accumulation of sucrose in the stem and leaf abscission under desiccation. The maximum Pn increased at first and then de-clined during drought, but intrinsic WUE increased remarkably in the morning with increasing drought stress. The maximal photochemical efficiency of PSII (Fv/Fm) and the quantum efficiency of noncyclic electric transport of PSII(ΦPSII) decreased significantly under water stress and exhibited an obvious phenomenon of photoinhibition at noon. Drought stressed plants maintained a higher capacity of dis-sipation of the excitation energy (measured as NPQ) with the increasing intensity of stress. Conditions of progressive drought promoted sucrose and starch accumulation in the stems but not in the leaves. However, when leaf water potential was less than –21.3 MPa, the plant leaves died and then abscised. But the stem photosynthesis remained and, afterward the plants entered the dormant state. Upon re-watering, the shoots reactivated and the plants developed new leaves. Therefore, R. soongorica has the ability to reduce water loss through leaf abscission and maintain the vigor of the stem cells to survive desiccation.

Alternate partial root-zone irrigation with high irrigation frequency improves root growth and reduces unproductive water loss by apple trees in arid north-west China

Alternate partial root-zone irrigation(APRI)can improve water use efficiency in arid areas. However,the effectiveness and outcomes of different frequencies of APRI on water uptake capacity and physiological water use have not been reported. A two-year field experiment was conducted with two irrigation amounts(400 and500 mm) and three irrigation methods(conventional irrigation, APRI with high and low frequencies). Root length density, stomatal conductance, photosynthetic rate,transpiration rate, leaf water use efficiency, midday stem and leaf water potentials were measured. The results show that in comparison with conventional irrigation, APRI with high frequency significantly increased root length density and decreased water potentials and stomatal conductance.No differences in the above indicators between the two APRI frequencies were detected. A significantly positive relationship between stomatal conductance and root length density was found under APRI. Overall, alternate partial root-zone irrigation with high frequency has a great potential to promote root growth, expand water uptake capacity and reduce unproductive water loss in the arid apple production area.

Precipitation regulates plant gas exchange and its long-term response to climate change in a temperate grassland

Aims Climate change largely impacts ecosystem carbon and water cycles by changing plant gas exchange,which may further cause positive or negative feedback to global climate change.However,long-term global change manipulative experiments are seldom conducted to reveal plant ecophysiological responses to climatic warming and altered precipitation regimes.Methods An 8-year field experiment with both warming and increased precipitation was conducted in a temperate grassland in northern China.We measured leaf gas exchange rates(including plant photosynthesis,transpiration and instantaneous water use efficiency[WUE])of two dominant plant species(Stipa sareptana var.krylovii and Agropyron cristatum)from 2005 to 2012(except 2006 and 2010)and those of other six species from 2011 to 2012.Important Findings Increased precipitation significantly stimulated plant photosynthetic rates(A)by 29.5%and 19.9%and transpiration rates(E)by 42.2%and 51.2%for both dominant species S.sareptana var.krylovii and A.cristatum,respectively,across the 8 years.Similarly,A and E of the six plant functional types were all stimulated by increased precipitation in 2011 and 2012.As the balance of A and E,the instantaneous WUEs of different plant species had species-specific responses to increased precipitation.In contrast,neither warming nor its interaction with increased precipitation significantly affected plant leaf gas exchange rates.Furthermore,A and E of the two dominant species and their response magnitudes to water treatments positively correlated with rainfall amount in July across years.We did not find any significant difference between the short-term versus long-term responses of plant photosynthesis,suggesting the flexibility of leaf gas exchange under climate change.The results suggest that changing precipitation rather than global warming plays a prominent role in determining production of this grassland in the context of climate change.