Plant Water Use Efficiency Research Articles

Exogenous application of liquiritin alleviated salt stress and improved growth of Chinese kale plants

Current research was designed to evaluate the role of exogenous liquiritin (750 ppm) in alleviation of salt stress in Chinese kale (Brassica oleracea var. alboglabra). Salt stress (2.5 and 5 dS m−1) caused ionic phytotoxicity through enhancing sodium content and decreasing plant nutrients such as potassium, calcium and magnesium. The 5 dS m−1 salinity treatment significantly declined the root length, shoot length, total chlorophyll, total soluble proteins, leaf relative water content, water use efficiency, total glucosinolates, and ascorbic acid of Chinese kale plants by 39%, 35%, 28%, 15%, 26%, 29%, 35%, and 19% respectively as compared to untreated control. Neverthless, liquiritin supplemented plants showed obvious augmentation in the values of these growth parameters under toxic and non toxic regimes. Similarly, salinized plants showed higher amount of hydrogen peroxide (H2O2), malondialdehyde (MDA), flavonoids, total soluble proteins, proline phenolics and free amino acids in addition to activity of antioxidant enzymes including super oxidase, catalase and peroxidase. Nevertheless, liquiritin alleviated salt induced oxidative stress through decreasing MDA and H2O2 level besides improving antioxidative machinery in treated plants. The salt stress assuagement in liquiritin treated plants was correlated to the elevated biosynthesis of total free amino acids, proline, and total glucosinolate content besides well-organized antioxidant system.

Exogenous Myo-Inositol Alleviates Salt Stress by Enhancing Antioxidants and Membrane Stability via the Upregulation of Stress Responsive Genes in Chenopodium quinoa L.

Myo-inositol has gained a central position in plants due to its vital role in physiology and biochemistry. This experimental work assessed the effects of salinity stress and foliar application of myo-inositol (MYO) on growth, chlorophyll content, photosynthesis, antioxidant system, osmolyte accumulation, and gene expression in quinoa (Chenopodium quinoa L. var. Giza1). Our results show that salinity stress significantly decreased growth parameters such as plant height, fresh and dry weights of shoot and root, leaf area, number of leaves, chlorophyll content, net photosynthesis, stomatal conductance, transpiration, and Fv/Fm, with a more pronounced effect at higher NaCl concentrations. However, the exogenous application of MYO increased the growth and photosynthesis traits and alleviated the stress to a considerable extent. Salinity also significantly reduced the water potential and water use efficiency in plants under saline regime; however, exogenous application of myo-inositol coped with this issue. MYO significantly reduced the accumulation of hydrogen peroxide, superoxide, reduced lipid peroxidation, and electrolyte leakage concomitant with an increase in the membrane stability index. Exogenous application of MYO up-regulated the antioxidant enzymes’ activities and the contents of ascorbate and glutathione, contributing to membrane stability and reduced oxidative damage. The damaging effects of salinity stress on quinoa were further mitigated by increased accumulation of osmolytes such as proline, glycine betaine, free amino acids, and soluble sugars in MYO-treated seedlings. The expression pattern of OSM34, NHX1, SOS1A, SOS1B, BADH, TIP2, NSY, and SDR genes increased significantly due to the application of MYO under both stressed and non-stressed conditions. Our results support the conclusion that exogenous MYO alleviates salt stress by involving antioxidants, enhancing plant growth attributes and membrane stability, and reducing oxidative damage to plants.

MdHB-7 Regulates Water Use Efficiency in Transgenic Apple (Malus domestica) Under Long-Term Moderate Water Deficit.

Improved water use efficiency (WUE) promotes plant survival and crop yield under water deficit conditions. Although the plant-specific HD-Zip I transcription factors have important roles in plant adaptation to various abiotic stresses, including water deficit, their functions in regulating WUE of apple (Malus domestica) are poorly understood. We characterized the role of MdHB-7 in WUE regulation by subjecting MdHB-7 transgenic plants to long-term moderate soil water deficit. The long-term WUE (WUEL) of transgenic apple plants with MdHB-7 overexpression or MdHB-7 RNA interference (RNAi) differed significantly from that of control plants. Upregulation of MdHB-7 caused reduced stomatal density, whereas the suppression of MdHB-7 increased stomatal density under both normal and long-term moderate soil water deficit conditions. Moderate reduction in stomatal density helped to improve the WUE of MdHB-7 overexpression transgenic plants, especially under water deficit conditions. MdHB-7 overexpression plants maintained high rates of photosynthesis that were conducive to the accumulation of biomass and the improvement of WUEL. MdHB-7 overexpression also alleviated the inhibition of root growth caused by long-term moderate soil water deficit and improved root vitality and hydraulic conductivity, which were essential for improving plant WUEL. By contrast, MdHB-7 RNA interference reduced the WUEL of transgenic plants by inhibiting these factors under normal and long-term moderate soil water deficit conditions. Taken together, our results provide solid evidence for a crucial role of MdHB-7 in the regulation of apple WUEL and provide new insights for improving the WUE of apple plants under moderate soil water deficit.

The Cretaceous physiological adaptation of angiosperms to a declining <i>p</i>CO<sub>2</sub>: a modeling approach emulating paleo-traits

Abstract. The Cretaceous evolution of angiosperm leaves towards higher vein densities enables unprecedented leaf stomatal conductance. Still, simulating and quantifying the impact of such change on plant productivity and transpiration in the specific environmental conditions of the Cretaceous remain challenging. Here, we address this issue by combining a paleo proxy-based model with a full atmosphere–vegetation model that couples stomatal conductance to carbon assimilation. Based on the fossil record, we build and evaluate three consistent proto-angiosperm vegetation parameterizations under two end-member scenarios of pCO2 (280 and 1120 ppm) for the mid-Cretaceous: a reduction of leaf hydraulic or photosynthetic capacity and a combination of both, supported by a likely coevolution of stomatal conductance and photosynthetic biochemistry. Our results suggest that decreasing leaf hydraulic and/or photosynthetic capacities always generates a reduction of transpiration that is predominantly the result of plant productivity variations modulated by light, water availability in the soil, atmospheric evaporative demand and pCO2. The high pCO2 acts as a fertilizer on plant productivity that strengthens plant transpiration and water-use efficiency. However, we show that proto-angiosperm physiology does not allow vegetation to grow under low pCO2 because of a positive feedback between leaf stomatal conductance and leaf area index. Our modeling approach stresses the need to better represent paleovegetation physiological traits. It also confirms the hypothesis of a likely evolution of angiosperms from a state of low leaf hydraulic and photosynthetic capacities at high pCO2 to a state of high leaf hydraulic and photosynthetic capacities linked to leaves with more and more veins together with a more efficient biochemistry at low pCO2.

Soil Ventilation Benefited Strawberry Growth via Microbial Communities and Nutrient Cycling Under High-Density Planting

In order to increase O2 concentration in the rhizosphere and reduce the continuous cropping obstacles under high-density cultivation, ventilation is often used to increase soil aeration. Yet, the effect of ventilation on soil microbial communities and nutrient cycling and, further, the extent to which they influence strawberry growth under greenhouse conditions are still poorly understood. Thus, four treatments—no ventilation + low planting density (LD), ventilation + LD, no ventilation + high planting density (HD), and ventilation + HD—of strawberry “Red cheeks” (Fragaria × ananassa Duch. cv. “Benihopp”) were studied in a greenhouse for 3 years. The ventilation pipe (diameter = 10 cm) was buried in the soil at a depth of 15 cm from the surface and fresh air was sent to the root zone through the pipe by a blower. Ten pipes (one pipeline in a row) were attached to a blower. Soil samples were collected using a stainless-steel corer (five-point intra-row sampling) for the nutrient and microbial analyses. The composition and structure of the soil bacterial and fungal communities were analyzed by high-throughput sequencing of the 16S and 18S rRNA genes, and functional profiles were predicted using PICRUSt and FUNGuild, respectively. The results showed that soil ventilation increased the net photosynthetic rate (Pn), transpiration rate (Tr), and water use efficiency (WUE) of strawberry plants across two growth stages [vegetative growth stage (VGS) and fruit development stage (FDS)]. Soil ventilation increased its available nutrient contents, but the available nutrient contents were reduced under the high planting density compared with low planting density. Both the O2 concentration and O2:CO2 ratio were increased by ventilation; these were positively correlated with the relative abundance of Bacilli, Gamma-proteobacteria, Blastocatella, as well as Chytridiomycota and Pezizomycetes. Conversely, ventilation decreased soil CO2 concentration and the abundance of Beta-proteobacteria and Gemmatimonadetes. The greater planting density increased the relative abundance of Acidobacteria (oligotrophic group). Ventilation altered soil temperature and pH along with carbon and nitrogen functional profiles in the VGS (more nitrogen components) and FDS (more carbon components), which benefited strawberry plant growth under high planting density. The practice of soil ventilation provides a strategy to alleviate hypoxia stress and continuous cropping obstacles for improving crop production in greenhouse settings.

BBX21 reduces abscisic acid sensitivity, mesophyll conductance and chloroplast electron transport capacity to increase photosynthesis and water use efficiency in potato plants cultivated under moderated drought.

The B-box (BBX) proteins are zinc-finger transcription factors with a key role in growth and developmental regulatory networks mediated by light. AtBBX21 overexpressing (BBX21-OE) potato (Solanum tuberosum) plants, cultivated in optimal water conditions, have a higher photosynthesis rate and stomatal conductance without penalty in water use efficiency (WUE) and with a higher tuber yield. In this work, we cultivated potato plants in two water regimes: 100 and 35% field capacity of water restriction that imposed leaf water potentials between -0.3 and -1.2 MPa for vegetative and tuber growth during 14 or 28 days, respectively. We found that 42-day-old plants of BBX21-OE were more tolerant to water restriction with higher levels of chlorophylls and tuber yield than wild-type spunta (WT) plants. In addition, the BBX21-OE lines showed higher photosynthesis rates and WUE under water restriction during the morning. Mechanistically, we found that BBX21-OE lines were more tolerant to moderated drought by enhancing mesophyll conductance (gm ) and maximum capacity of electron transport (Jmax ), and by reducing abscisic acid (ABA) sensitivity in plant tissues. By RNA-seq analysis, we found 204 genes whose expression decreased by drought in WT plants and expressed independently of the water condition in BBX21-OE lines as SAP12, MYB73, EGYP1, TIP2-1 and DREB2A, and expressions were confirmed by quantitative polymerase chain reaction. These results suggest that BBX21 interplays with the ABA and growth signaling networks, improving the photosynthetic behavior in suboptimal water conditions with an increase in potato tuber yield.

Effects of elevated CO2 and nitrogen supply on leaf gas exchange, plant water relations and nutrient uptake of tomato plants exposed to progressive soil drying

The effects of nitrogen (N) supply on the response of leaf gas exchange, leaf water relations and plant nutrient uptake of tomato plants exposed to progressive soil drying under elevated CO2 (e[CO2], 800 ppm) were investigated. Two tomato genotypes differing in their endogenous abscisic acid (ABA) level, i.e. Ailsa Craig and its ABA-deficient mutant (flacca) were grown in pots in greenhouse cells with either ambient CO2 (a[CO2], 400 ppm) or e[CO2]. Two N levels, i.e., N1, 0.5 g pot−1 and N2, 1.0 g pot−1 were used and the N fertilizer (NH4NO3) was applied with the irrigation water before transplanting. The results showed that e[CO2] and N2 increased photosynthesis and water use efficiency (WUE) of tomato plants. N2 improved plant water relations by sensitizing the decline of transpiration rate during soil drying. The plant N acquisition and major ionic concentrations in xylem sap were lowered under e[CO2], such negative effect was compensated by increasing N supply. For WT, the ABA concentrations in leaf ([ABA]leaf) and xylem sap ([ABA]xylem) were increased with the decrease of the fraction of transpirable soil water, whereas, for flacca this was only observed in [ABA]leaf. Compared to WT, flacca had lower xylem sap ionic concentrations and WUE. Collectively, the responses of tomato plants to e[CO2] and N supply under progressive soil drying were genotypic-dependent, and endogenous ABA level could play an important role in modulating the responses.

Horticultural Performance of Greenhouse Cherry Tomatoes Irrigated Automatically Based on Soil Moisture Sensor Readings

Precision irrigation is essential to improve water use efficiency (WUE), defined as the amount of biomass produced per unit of water used by plants. Our objective is to evaluate the effect of different soil volumetric water content (VWC) in plant growth, fruit yield, quality, and WUE of cherry tomatoes grown in a greenhouse. We tested four VWC thresholds (0.23, 0.30, 0.37, and 0.44 m3 m−3) to trigger a drip irrigation system in two tomato cultivars (‘Sweet Heaven’ and ‘Mascot F1’). The experiment was arranged in a split-plot design with four replications. We used capacitance sensors connected to an open-source, low-cost platform to monitor and control the irrigation in real-time based on demand. Plants were watered every time the soil VWC dropped below the set thresholds. The treatment with VWC 0.44 m3 m−3 resulted in the highest fruit yield, with 102.10% higher WUE when compared to the VWC 0.23 m3 m−3 in both cultivars. Fruit quality traits such as longitudinal and equatorial diameter increased asymptotically with soil water content. In contrast, treatments with deficit irrigation increased the fruit soluble solids by 15.73% in both cultivars. These results strongly suggest that accurate control of the soil VWC is essential to modulate the fruit yield and quality attributes in tomatoes produced in the greenhouse.

Feeding the world in a narrowing safe operating space

Feeding the world in a narrowing safe operating space

2,4-Epibrassinolide mechanisms regulating water use efficiency and fruit production in tomato plants

2,4-Epibrassinolide mechanisms regulating water use efficiency and fruit production in tomato plants

Trichoderma-Enriched Vermicompost Extracts Reduces Nematode Biotic Stress in Tomato and Bell Pepper Crops

Root-knot nematode (RKN) is a serious threat to crops worldwide due to the difficulty in controlling it and the limited eco-friendly alternatives to deal with the biotic stress it causes. In the present work, water-extractable fractions obtained from vermicompost (WSFv), vermicompost enriched with Trichoderma asperellum (WSFta) and T. virens (WSFtv) were tested as biotechnological tools to reduce the impacts of RKN on gas exchange, water use efficiency (WUE) and nutrient concentration in tomato and bell pepper plants. The plants were infected with 5000 eggs and eventual J2 of RKN and then treated with the water-extractable fractions for seven weeks. It was observed that the addition of WSFta, WSFtv and WSFv increased the CO2 assimilation, stomatal conductance and WUE in the tomato plants. In the bell pepper plants, WSFta, WSFtv, WSFv increased the stomatal conductance, while WUE was higher in the treatment with WSFtv. In fact, the parameters associated with the gas exchange were usually higher in the bell pepper than in the tomato plants. Overall, higher contents of N, Mg, B and Mn were detected when the extracts were applied in both bell pepper and tomato plants. The application of the water-extractable fractions, inoculated or not with Trichoderma, attenuates the RKN damage on the gas exchange parameters and successfully enhanced the nutrient concentration in the infected tomato and bell pepper plants, showing that it could be an important and promising tool for reducing the damage caused by this pathogen. We suggest that both the tomato and pepper plants can cope with the dilemma between growth and stress response via stomata regulation that are modulated by the WSF and Trichoderma.

Assessment of bias in carbon isotope composition of organic leaf matter due to pre-analysis milling methods.

Stable isotope analysis of leaf material has many applications including assessment of plant water-use efficiency and palaeoclimatology. To facilitate interpretations of small shifts in the carbon isotope composition (δ13 C) of leaves, accurate and repeatable results are required. Pre-sample homogenisation is essential to ensure a representative sample is analysed, but can also introduce error. We investigate how different grinding methods (freezer-milling and ball-milling) affect the carbon content and δ13 C of tree leaves from a wetland in Queensland, Australia, commenting on how increased temperature, sample contamination, sample loss or poor homogenisation may impact results. No alteration of leaf δ13 C is observed due to different milling methods, although there may be a significant increase in %C of samples processed using ball-milling. We suggest %C variability is possibly due to contamination from abraded plastic vials or insufficient homogenisation during ball-milling, with no significant impact on δ13 C. Overall, we suggest that intermittent ball-milling may be the best solution to reduce costs, preparation time and use of liquid nitrogen, aiming to achieve complete homogenisation using the shortest possible duration of milling.

Modelling rice yield from biochar-inorganic fertilizer amended fields

Rice yield is vulnerable to climatic changes. High concentrations of atmospheric CO 2 is noted to increase yield by improving upon nutrient uptake and water use efficiency of plants. Temperature variations also affect plant growth and eventually crop yield as it has an effect on respiration and photosynthesis. Soil fertility is an important parameter affecting the production of most crops and rice is not an exception. The cost as well as the environmental consequences of using inorganic fertilizers makes it necessary to use other soil amendments such as biochar. Field experiments are often time consuming and involves a lot of drudgery. This research was therefore conducted to model the quantities of biochar-inorganic fertilizer combinations that give optimum yields of rice and assess the effect of changes in climatic parameters on the yield of rice. CERES-Rice model was used to simulate the yield of rice using different combinations of biochar-inorganic fertilizer as soil amendments. Effects of changes in climatic parameters on the yield of rice were also simulated. The yield of rice from the simulations were sensitive to the soil amendments especially the biochar. Treatments with no biochar had relatively low rice yields compared with those with biochar. The average simulated yields were 1.5 t/ha, 5.6 t/ha and 5.5 t/ha for treatments with 0 t/ha, 20 t/ha and 30 t/ha of biochar respectively. Increasing or decreasing rainfall resulted in reduction in the yield of rice. Increasing carbon dioxide concentrations generally led to an increase in the simulated yields of rice. On the other hand, decreasing the carbon dioxide concentrations resulted in decreased simulated rice yields. It was observed that increasing temperature resulted in a reduction in rice yield for the various treatments. The reduction in the yield of rice ranged from 7.64% to 34 .67%. • Biochar-inorganic fertilizer improve upon simulated rice yield. • Increase in temperature results in a decrease in simulated rice yield. • Increase in carbon dioxide results in an increase in simulated rice yield. • An increase in solar radiation results in an increase in rice yield.

Chloride Changes Soil–Plant Water Relations in Potato (Solanum tuberosum L.)

There is evidence that chloride (Cl―) can lead to both an improved hydration and water use efficiency in plants due to its osmotic properties. The potato crop is widely assumed to be sensitive to Cl―. This is based on studies which found tuber yield or tuber starch reductions following a Cl― fertilization. However, there are also contradictory reports which could not find any detrimental effect of Cl― fertilization on potato plant development. As potato is inefficient in the use of water, we aimed to test if it is possible to improve the hydration status of potato without reducing tuber yield and dry matter by means of Cl― fertilization. We conducted a pot experiment with four different Cl― doses and investigated soil–plant water relations, biomass, tuber yield and dry matter development. Our findings deliver an indication that the potato crop is much less sensitive to Cl― than previously assumed and, more importantly, that a Cl― supply can indeed improve the potato shoot water status. This happened without impairing tuber yield and dry matter. Since potato is very sensitive to drought stress, we assume that Cl― fertilization is a promising measure to improve the drought resilience of potato.

Overexpression of MdATG8i improves water use efficiency in transgenic apple by modulating photosynthesis, osmotic balance, and autophagic activity under moderate water deficit

Water deficit is one of the major limiting factors for apple (Malus domestica) production on the Loess Plateau, a major apple cultivation area in China. The identification of genes related to the regulation of water use efficiency (WUE) is a crucial aspect of crop breeding programs. As a conserved degradation and recycling mechanism in eukaryotes, autophagy has been reported to participate in various stress responses. However, the relationship between autophagy and WUE regulation has not been explored. We have shown that a crucial autophagy protein in apple, MdATG8i, plays a role in improving salt tolerance. Here, we explored its biological function in response to long-term moderate drought stress. The results showed that MdATG8i-overexpressing (MdATG8i-OE) apple plants exhibited higher WUE than wild-type (WT) plants under long-term moderate drought conditions. Plant WUE can be increased by improving photosynthetic efficiency. Osmoregulation plays a critical role in plant stress resistance and adaptation. Under long-term drought conditions, the photosynthetic capacity and accumulation of sugar and amino acids were higher in MdATG8i-OE plants than in WT plants. The increased photosynthetic capacity in the OE plants could be attributed to their ability to maintain optimal stomatal aperture, organized chloroplasts, and strong antioxidant activity. MdATG8i overexpression also promoted autophagic activity, which was likely related to the changes described above. In summary, our results demonstrate that MdATG8i-OE apple lines exhibited higher WUE than WT under long-term moderate drought conditions because they maintained robust photosynthesis, effective osmotic adjustment processes, and strong autophagic activity.

Meta-analysis of the effect of the overexpression of aquaporin family genes on the drought stress response

Aquaporin (AQP) plays an essential role in water uptake and transport in plants, especially in the response to drought stress, which suggests the use of AQP expression to regulate plant water-use efficiency. The overexpression of various AQP genes in a variety of plants has been reported, but inconsistencies in the experimental variables (such as stress type, gene donor, and recipient genus) and physiological parameters used to evaluate transgenic plants have made it difficult to elucidate the complex mechanisms by which AQPs affect drought tolerance. In this study, we performed a meta-analysis to categorize the responses of physiological parameters involved in drought tolerance in AQP-overexpressing plants and to evaluate the experimental variables that affect transgenic plant performance. The results of various studies indicated that two primary physiological processes (osmotic adjustment and alleviation of oxidative damage) were significantly affected by AQP overexpression. Among the examined experimental variables, treatment media (soil), stress type (no watering), stress duration (long-term), recipient genus (Nicotiana), donor species (Musaceae), and gene family (PIP2) had positive impacts on drought tolerance in transgenic plants. These findings may help to guide future studies investigating the function of AQPs in the response of plants to water deficit stress.

Water requirement and nutrient management of guava (cv. Arka amulya) using drip under high density plantation in coastal Odisha

In the experimental farm, the vegetative characteristics and yield characteristics of the 3-year-old guava were observed at various fertigation doses. Four levels of fertigation i. e. 100%, 80% and 60% of the recommended dose of fertilizer (RDF) by drip irrigation and 100% of the recommended dose of fertilizer by soil application were studied in a Randomized block design (RBD). The results showed a significant effect on the plant height, girth of trunk & number of primary branches in vegetative parameters. Canopy spread has shown insignificant effect on various fertigation levels. Yield characteristics viz., number of fruits per plant, weight of the fruit, equatorial and polar diameter of the fruit and yield per hectare affected significantly across various fertigation levels and higher doses resulted in better values. Water use efficiency (WUE) & Fertilizer use efficiency (FUE) were varied with fertigation levels. The results revealed that drip-fertigation can play a positive role in increasing yield, WUE of guava plants with additional benefit of saving in fertilizer cost and fruit quality improvement.

Multiple environmental factors regulate the large-scale patterns of plant water use efficiency and nitrogen availability across China’s forests

Global changes, e.g. global warming, elevated nitrogen deposition, and shifts of precipitation regime, exert a major influence on forests via affecting plant water use efficiency (WUE) and plant nitrogen (N) availability. Large-scale ecological sampling can help us to better understand variation across regions and provide opportunities to investigate the potential impacts of multiple aspects of global change on forest ecosystem responses. Here, we determine the geographical patterns of key isotopic measures of ecosystem function—plant WUE (calculated from foliar δ 13C values) and plant N availability (assessed by foliar δ 15N values)—across China’s forests covering ∼21 latitude (∼22–43°N) and ∼28 longitude (∼93–121°E) degree, and investigate how a suite of soil, plant, and atmospheric factors regulate them. We found that plant WUE increased but N availability decreased with latitude, while plant WUE and N availability did not vary with longitudinal gradient. Different factors regulate the large-scale patterns in WUE and N availability. The mean annual temperature, atmospheric N deposition, and soil water content exhibit considerable effects on plant WUE over both the north-to-south and east-to-west transects, while the mean annual precipitation, soil potassium content, foliar N, and precipitation seasonality considerably affect the latitudinal patterns of plant N availability. In addition, the east-to-west spatial pattern in plant N availability is associated with the variation in solar radiation. Our results suggest that key forest ecological functions respond to an array of environmental factors, and imply that changes in many different environmental attributes need to be considered in order to successfully assess plant WUE and N availability responses to global changes this century.

Endogenous ABA level modulates the effects of CO2 elevation and soil water deficit on growth, water and nitrogen use efficiencies in barley and tomato plants

Atmospheric CO2 elevation (e[CO2]) could alleviate the impact of soil water deficit, yet the underlying mechanisms remains largely elusive. This study aimed to investigate whether different endogenous abscisic acid (ABA) level modulates the response of barley and tomato plants to soil water deficit combined with e[CO2]. Wild type (WT) genotypes (Steptoe barley and AC tomato) and their corresponding ABA-deficient mutants (Az34 barley and AC-flacca) were grown in pots separately in greenhouse cells with ambient (a[CO2], 400 ppm) and e[CO2] (800 ppm) and were either well-watered or exposed to soil water deficit. The results showed that, compared to well-watered regime, soil water deficit decreased aboveground dry matter (ADM), leaf area (LA) and specific leaf area (SLA) while enhanced water use efficiency (WUE) in all genotypes. e[CO2] increased ADM and LA in tomato genotypes. Moreover, it reduced SLA, leaf N concentration while improved WUE and nitrogen use efficiency (NUE) in WT plants, not in ABA-deficient mutants. These results indicate that endogenous ABA level played an important role in modulating the response of WUE and NUE of barley and tomato to e[CO2] environment, which advances our knowledge on the physiological mechanisms of crop plants adapt to future climate changed scenarios.

Effects of biochar amendment and reduced irrigation on growth, physiology, water-use efficiency and nutrients uptake of tobacco (Nicotiana tabacum L.) on two different soil types

Biochar has shown beneficial effects in agricultural production, yet the combined effects of biochar and reduced irrigation on crop growth and water-use efficiency (WUE) in diverse soil types have not been fully explored. A split-root pot experiment was conducted to investigate the effects of addition of 2% softwood (SWB) and wheat straw biochar (WSB) on growth, physiology, WUE and nutrients uptake of tobacco (Nicotiana tabacum L.) plants grown in a Ferrosol and an Anthrosol, respectively, under three irrigation treatments. The plants were either irrigated daily to 90% of water-holding capacity (FI), or irrigated with 70% volume of water used for FI to the whole root-zone (DI) or alternately to half root-zone (PRD). The results showed that plants grown in Anthrosol possessed greater leaf gas exchange rates, dry biomass and WUE while lower nutrients content compared to those grown in Ferrosol. Despite a negative effect on plant N content and WUE, WSB addition increased water-holding capacity, consequently improved leaf gas exchange, water uptake, biomass and K content resulting in an improved in the leaf quality of tobacco as exemplified by an increased leaf K content and a more appropriate N to K stoichiometric ratio. However, these effects were not evident upon SWB addition. Moreover, these responses to biochar addition were stronger in Ferrosol than in Anthrosol might be associated with its lower pH. Compared to FI, PRD slightly reduced photosynthetic rate but significantly decreased stomatal conductance, transpiration rate and leaf area, leading to a significant increase in intrinsic, instantaneous and plant WUE. Additionally, PRD was superior over DI in improving yield, WUE, N uptake under a same irrigation volume. It was concluded that WSB combined with PRD could be a promising practice to synergistically improve tobacco yield, quality and WUE by improving soil hydro-physical properties and nutrients bioavailability.