Depletion Of Available Soil Water Research Articles

Assessment of trunk microtensiometer as a novel biosensor to continuously monitor plant water status in nectarine trees.

The objective of this work was to validate the trunk water potential (Ψtrunk), using emerged microtensiometer devices, as a potential biosensor to ascertain plant water status in field-grown nectarine trees. During the summer of 2022, trees were subjected to different irrigation protocols based on maximum allowed depletion (MAD), automatically managed by real-time soil water content values measured by capacitance probes. Three percentages of depletion of available soil water (α) were imposed: (i) α=10% (MAD=27.5%); (ii) α=50% (MAD=21.5%); and (iii) α=100%, no-irrigation until Ψstem reached -2.0 MPa. Thereafter, irrigation was recovered to the maximum water requirement of the crop. Seasonal and diurnal patterns of indicators of water status in the soil-plant-atmosphere continuum (SPAC) were characterised, including air and soil water potentials, pressure chamber-derived stem (Ψstem) and leaf (Ψleaf) water potentials, and leaf gas exchange, together with Ψtrunk. Continuous measurements of Ψtrunk served as a promising indicator to determine plant water status. There was a strong linear relationship between Ψtrunk vs. Ψstem (R2 = 0.86, p<0.001), while it was not significant between Ψtrunk vs. Ψleaf (R2 = 0.37, p>0.05). A mean gradient of 0.3 and 1.8 MPa was observed between Ψtrunk vs.Ψstem and Ψleaf, respectively. In addition, Ψtrunk was the best matched to the soil matric potential. The main finding of this work points to the potential use of trunk microtensiometer as a valuable biosensor for monitoring the water status of nectarine trees. Also, trunk water potential agreed with the automated soil-based irrigation protocols implemented.

Harvest time explains substantially more variance in yield, essential oil and quality performances of Salvia officinalis than irrigation and putrescine application.

Elicitors, irrigation regimes and harvest times influence the content, yield and compound of the essential oil (EO) in Salvia officinalis (sage), through changes in biomass dynamics and biosynthetic pathways. A two-year field experiment was conducted to determine if foliar application of putrescine under optimum and deficit stress conditions would favorably affect EO yield, content and profile of sage harvested in spring and summer. The response of dry weight, EO yield and content, myrcene and borneol concentrations to irrigation regime and putrescine concentration can be expressed by a quadratic model. The maximum dry weight (182.63gm-2) and EO yield (1.68gm-2) were predicted under irrigation regimes of 9.06% and 27.75% available soil water depletion (ASWD), respectively.The highest EO content (1.05%) was predicted under 3.04mM of putrescine. Based on results obtained from GC/MS analyses, 25 compounds (mostly monoterpenes) were identified in the EO of sage. Among EO compounds, α-thujone (54.08%), 1, 8-cineole (17.87%), pinocarvone (14.30%), β-thujone (7.97%) and camphor (8.76%) in turn were the most abundant. The concentration of myrcene was higher in spring than summer under the irrigation regimes of 60% and 80% ASWD. The myrcene concentration reached its maximum (4.53%) under the irrigation regime of 86.5% ASWD. The irrigation regimes of 48.03% and 45.6% ASWD caused the highest borneol concentrations of 1.47% and 1.41% by application of 1.5mM and 2.25mM putrescine, respectively. All treatments tested on sage, particularly harvest time, can play an important role in the improvement of EO quality and quantity. Averaged over both years, the irrigation regime of nearly 30% ASWD resulted in the highest EO yield harvested with greater quantity and better quality in summer. The EO content and quality changed slightly with the application of putrescine, without significant effect on yield.

Fatty Acid Composition and Eco-agronomical Traits of Lallemantia Species Modulated upon Exposed to Arbuscular Mycorrhizal Fungi and Nano-iron Chelate Fertilizers under Water Deficit Conditions

The main objectives of the current study were to investigate the effect of arbuscular mycorrhizal fungi (AMF) and nano-iron chelate fertilizer under water deficit conditions on grain yield, root colonization, leaf chlorophyll concentration, oil percentage, and fatty acid profile of Lallemantia species. The experiment was carried out as a factorial based on a complete randomized block design consisting of three factors of irrigation levels of 30, 60, and 90% depletion of available soil water (ASW)), fertilizer levels of control (without fertilizer), AMF inoculation, and nano-iron chelate, and plant species of Lallemantia (L. iberica and L. royleana). The results showed that increasing water deficit stress significantly decreased the above traits, while applying nano-iron and AMF fertilizers significantly increased them across water treatments. AMF fertilizer inoculation significantly improved yield of both Lallemantia species. Higher root colonization by AMF inoculation enhanced seed oil production with all major fatty acid moieties improved. In contrast, applying nano-iron chelate by increasing chlorophyll concentration in any irrigation regime could enhance seed oil of L. royleana and some fatty acids such as palmitoleic acid. Water deficit stress and application of fertilizers had different effects on both species. L. iberica, compared with L. royleana, had the most tolerance to water deficit stress and the highest dependence on AMF inoculation. Overall, these results demonstrated that the application of AMF could improve major features of Lallemantia species under irrigation deficit conditions, especially at the 60% depletion of ASW.

Withdrawn: Effects of water‐deficit stress and putrescine on performances, photosynthetic gas exchange, and chlorophyll fluorescence parameters of Salvia officinalis in two cutting times

A 2‐year (2017–2018) field experiment was performed to specify if the foliar application of putrescine (PUT) under optimum and water‐deficit stress (WDS) conditions would favorably affect leaf gas exchange, greenness, chlorophyll fluorescence parameters, pigments, sodium (Na), potassium (K), as well as yield and content of the essential oil (EO) relationships in Salvia officinalis L. (sage) in spring (cutting 1) and summer (cutting 2). Based on the results analysis of variance, the effects of WDS, PUT, and cutting time were significant for the dry weight, leaf area index (LAI), EO content, EO yield, chlorophyll (Chl) t, carotenoid, Na, and K of sage. According to regression results, the response of EO content, EO yield, non‐photochemical quenching (NPQ), spad, Chl a, Chl t, K, and K/Na to WDS can be expressed by a quadratic model, indicating that they would attain their maximum in 75.5%, 34.86%, 38.33%, 84.13% 60%, 70%, 50.40%, and 40.28% available soil water depletion (ASWD), respectively. The response of dry weight, LAI, EO content, EO yield, Fv/Fm, spad, ΦpsII, Chl a, Chl b, Chl t, carotenoid, K, and K/Na to PUT can be expressed by a quadratic model, showing that they would attain their most under 0.98, 1.14, 1.34, 1.16, 1.27, 1.18, 1.17, 1.25, 1.17, 1.27, 1.31, 1.21, and 1.19 mM of PUT, respectively. These findings suggest that, probably, the functions and structures of the photosynthetic system were further enhanced with PUT, thereby they can be promoting primary electron transfer in PSII. Also, stomatal and photosynthetic activity improved with increasing K levels with PUT.

Improving water deficit tolerance of Salvia officinalis L. using putrescine

To study the effects of foliar application of putrescine (distilled water (0), 0.75, 1.5, and 2.25 mM) and water deficit stress (20%, 40%, 60%, and 80% available soil water depletion (ASWD)) on the physiological, biochemical, and molecular attributes of Salvia officinalis L., a factorial experiment was performed in a completely randomized design with three replications in the growth chamber. The results of Real-Time quantitative polymerase chain reaction (qRT-PCR) analysis showed that putrescine concentration, irrigation regime, and the two-way interaction between irrigation regime and putrescine concentration significantly influenced cineole synthase (CS), sabinene synthase (SS), and bornyl diphosphate synthase (BPPS) relative expression. The highest concentration of 1,8-cineole, camphor, α-thujone, β-thujone, CS, SS, and BPPS were obtained in the irrigation regime of 80% ASWD with the application of 0.75 mM putrescine. There was high correlation between expression levels of the main monoterpenes synthase and the concentration of main monoterpenes. The observed correlation between the two enzyme activities of ascorbate peroxidase (APX) and catalase (CAT) strongly suggests they have coordinated action. On the other hand, the highest peroxidase (PO) and superoxide dismutase (SOD) concentrations were obtained with the application of 0.75 mM putrescine under the irrigation regime of 40% ASWD. Putrescine showed a significant increase in LAI and RWC under water deficit stress. There was an increasing trend in endogenous putrescine when putrescine concentration was increased in all irrigation regimes. Overall, the results suggest that putrescine may act directly as a stress-protecting compound and reduced H2O2 to moderate the capacity of the antioxidative system, maintain the membrane stability, and increase secondary metabolites under water deficit stress.

Application of zeolite improves water and nitrogen use efficiency while increasing essential oil yield and quality of Salvia officinalis under water-deficit stress

Soil moisture and nitrogen (N) are two of the most important factors affecting the production of medicinal plants. So, the management strategy of these factors is critical and to be identified. In order to study the application of zeolite (Z) (0 and 10 ton ha−1) in S. officinalis culture medium under different irrigation regimes (30 % depletion of available soil water (ASW)) and 60 % depletion of ASW) and N (0, 75 and 150 kg N ha−1) a split-factorial experiment was carried out with three replicates in 2018. The highest fresh and dry weight were achieved at irrigation after 30 % depletion of ASW while using 150 kg N ha−1 and 10 ton Z ha−1. Maximum water use efficiency (WUE) (22.10 g.L-1) was obtained after 60 % depletion of ASW and 150 kg N ha−1 and 10 ton Z ha−1. Besides, the maximum nitrogen use efficiency (NUE) was obtained after 60 % depletion of ASW and 75 kg N ha−1 and 10 ton Z ha−1 (14.25 kg.kg-1N). Maximum essential oil (EO) content (1.06%) and cis-Thujone were obtained from plants subjected to 60 % depletion of ASW and, application of 75 kg N ha−1 and 10 ton Z ha−1. Applying Z with N, in different irrigation regimes did improve soil conditions for achieving higher, WUE and NUE, increased the EO content and yield while decreasing the negative effects from water-deficit stress and has provided a direction towards a stable system.

Water use efficiency of green gram (Vigna radiata L.) impacted by paddy straw mulch and irrigation regimes in north-western India

A multilocation field experiment was conducted at Students’ Research Farm, Department of Agronomy, Punjab Agricultural University (PAU), Ludhiana and PAU, Regional Research Station (RRS), Bathinda, during summer 2019. The experiment was conducted in RCBD with 15 treatment combinations with 3 replications. The treatments comprised of 3 mulch levels i.e., M0, M6, and M12 i.e., no mulch, 6 and 12 t ha−1, respectively, and 5 irrigation schedules i.e., I10, I20, I30, and I40 with 10%, 20%, 30% and 40% depletion of available soil water (ASW), respectively, and IR (PAU recommendation as 4 irrigations). The growth parameters (plant height, dry matter accumulation and leaf area index), yield attributing characters namely pods per plant, number of seeds per pod and thousand-grain weight, seed and straw yield were significantly higher in M12 than M6 and no mulch (M0). The growth parameters, yield attributes, seed and straw yield were significantly higher for I10 due to increased irrigation frequency (5–6 irrigations). Both M0I10 (seven irrigations without mulch) and M6I30 (3 irrigations with straw mulch (6 t ha−1)) treatments observed comparable seed yield (1.06 t ha−1). Therefore, the substantial increase in seed yield with lower crop water use with the usage of straw mulch saves a considerable amount of water. Subsequently, the use of 6 t ha−1 of straw mulch with 3 irrigations (30% depletion from available soil water) facilitated a higher seed yield. The crop water use (CWU) was highest for M0 as due to bare soil, resulted in more evapotranspiration. The bio-physical productivity (BPWP) and water use efficiency was found to be maximum for mulch treatments. The I10 reported maximum CWU, whereas, Bio-physical water productivity (BPWP) were higher for I40 treatment where only one irrigation was given in this treatment. The WUE was maximum in I30 treatment at Ludhiana and in I20 at Bathinda location.

Self-organizing map estimator for the crop water stress index

Crop water stress index (CWSI) is a reliable, economic and non-destructive method of monitoring the onset of water stress for irrigation scheduling purposes. Its application, however, is limited due to the need of obtaining the baseline canopy temperatures. This study developed a self-organizing map (SOM) based model to predict the CWSI using microclimatic variables, namely air temperature, canopy temperature and relative humidity. The canopy temperature measurements were made from Indian mustard crop grown in a humid sub-tropical agro-climate during the 2017 and 2018 cropping seasons. Eight levels of irrigation treatments (I1 – I8) based on maximum allowable depletion of available soil water were considered in the study. The CWSI for treatments I2 – I7 was computed using the empirical approach based on the experimentally measured baseline canopy temperatures from treatments I1 and I8. The number of data points used was 1260 and 1350 for model training and testing, respectively. The developed SOM model was evaluated using the error indices Nash-Sutcliffe efficiency (NSE), bias error (BE), absolute error (AE), and coefficient of determination (R2). The SOM predicted CWSI presented a good agreement with the baseline computed CWSI values during model training (R2 = 0.98, NSE = 0.97, AE = 0.018, BE = 0.0004) and testing (R2 = 0.98, NSE = 0.98, AE = 0.018, BE = 0.002). Treatment specific analysis was conducted to evaluate the performance of SOM predicted CWSI for different irrigation levels. Results indicated that the presence of zero CWSI values in a significant proportion in the dataset impacted the model prediction performance at low CWSI (<0.1) values, with an R2 of 0.71 during testing. Nonetheless, the model performed exceptionally well in predicting CWSI values between 0.1 and 0.6 (R2 = 0.93–0.98, NSE = 0.92–0.98, AE = 0.013–0.015, BE = −0.002–0.004), which is the commonly observed CWSI range for irrigation scheduling in field crops. For better understanding, the developed SOM model was also analysed through the component planes, U-matrix, clusters and high-low bar planes in the cluster features.

Simulating Maize Yield Response to Depletion of Available Soil Water and Nitrogen Management under Drip Irrigation with the FAO AquaCrop Model

Crop simulation models of different complexity have been developed for predicting the effects of soil, water and nutrients on growth and water productivity of different crops. These models are calibrated and validated for a given region using the data generated from field experiments. Therefore, AquaCrop model was calibrated and validated for grain maize (Single Cross 260) under varying irrigation and nitrogen levels. The experiment was conducted at the research farm of the agricultural college, Islamic Azad University, Shiraz during summer season 2011 and 2012. Irrigation treatments consisted of different levels of depletion of available soil water. The four levels of moisture depletions considered in the study were 20, 40, 60 and 80 percent. Nitrogen application levels were 150 (N1), 200 (N2), 250 (N3) and 300 kg ha–1. Root Mean Square error (RMSE), Prediction error (Pe), coefficient of determination (R2) and normalized root mean square error (RMSEn) were used to test the model performance. The model was calibrated for simulating maize grain and biomass yield for all treatment levels with the prediction error 4 < Pe < 5 per cent, 0.64 < R2 < 0.81 and 469 < RMSE < 786 t ha–1. Upon validation, Pe between 10 and 6; R2 between 0.65 and 0.76 and RMSE between 1062 and 1293 for grain and biomass yield, respectively. The highest and the lowest accuracy to predict yield and biomass under all nitrogen levels was obtained at I1 (MAD: 20%) and I4 (MAD: 80%) treatments, respectively. The results of the present study show that the AquaCrop model simulates aboveground biomass more accurately than grain yield. Also, model cannot provide satisfactory results under severe water stress conditions.

GGE biplot tool to identify melon fruit weight stability under different drought conditions

ABSTRACT It is difficult to identify superior muskmelon (Cucumis melo L.) genotypes due to their interaction in different irrigation regimes, but assessing their interaction with drought is important in identifing stable genotypes. Muskmelon genotypes, procured from the National Plant Gene Bank of Iran, were assessed for response to irrigation level on stability of fruit weight. Irrigation treatment consisted of: 25 (mild), 50 (moderate) and 75% (severe) depletion of available soil water which was indicated as the computational component environment. Performance of genotypes was evaluated as change in fruit weight. Additive main effects and multiplicative interaction (AMMI), genotype main effect and genotype × environment interaction (GGE) were used to evaluate genotypes. The AMMI analyses indicated significant GGE for fruit weight. The AMMI stability value indicated genotypes 33, 11, 23 and 28 are stable. The GGE-biplot models indicated irrigation regimes belonged to 1 mega-environment. The GGE indicated genotypes 11 and 28 as the most stable and can be used in creation of hybrids. Based on 75% water depletion, genotype 28 was identified as best due to its stability and yield and would be suitable for crossing and breeding. This methodology uses a biplot to indicate factors genotype main effect and genotype × environment interactions important in genotype evaluation and the interaction of genotypes under different irrigation depletion can be monitored. This method can be used to identify stable genotypes that can be used in arid zones to increase production.

Effects of water deficit on shoot, root and some physiological characteristics in some greenhouse grown potato cultivars

A greenhouse experiment was conducted to evaluate the response of ten potato cultivars to two levels of soil water in terms of contents of total chlorophyll (Chltot), chlorophyll florescence (Fv/Fm), shoot fresh weight (SFW), shoot dry weight (SDW), root fresh weight (RFW), root dry weight (RDW), mean root length (MRL), root length density (RLD), special root length (SRL), root volume (RV), ascorbate peroxidase (APX), peroxidase (POX) and proline content. Plants were grown under two irrigation levels (30 and 80% depletion of available soil water). Greenhouse test plots were arranged in a randomized complete block design with four replications. Under control level of irrigation, the maximum and the minimum shoot dry weight were achieved for cultivars Satina (12.7 g/plant) and Sante (4.7 g/plant) and root dry weight for Marfona (2.95 g/plant) and Milva (1.17 g/plant), respectively. SDW and RDW were decreased in all cultivars under 80% depletion of available soil water. Based on the biplot analysis cultivars Agria, Satina and Marfona were hence identified as preferable cultivars for 80% depletion of available soil water conditions. However, this investigate has been able to gather evidence that water deficit increased the activities of antioxidant enzymes and proline content in all tested potato cultivars. Also, our results revealed the pivotal role of proline in response of potato plants to water deficit and biomass production.

To what extent arbuscular mycorrhiza can protect chicory (Cichorium intybus L.) against drought stress

Water deficiency is one of the most significant limiting factors resulting in severe crop yield reduction. This study hypothesizes that the inoculation of arbuscular mycorrhiza (AM) minimize the detrimental effects of drought in chicory (Cichorium intybus L.). The objective was to evaluate how AM inoculation affects agro-biochemical traits of chicory under different irrigation rates. Field experiments were conducted in 2017 and 2018 in north of Iran and designed as a factorial combination of three irrigation rates [40, 65 and 90 % of maximum allowable depletion of available soil water (IR1, IR2 and IR3, respectively)], two AM inoculations [inoculated and not inoculated (AM+ and AM−, respectively)] and two chicory ecotypes [Sefid Isfahan and Siyah Shiraz (E1 and E2, respectively)]. Crop growth, pigments and minerals content, carbon exchange rate, transpiration rate and stomatal conductance were evaluated. The data showed that the mycorrhizal colonization increased chicory growth performance by 12.4 %, 16.1 % and 21.0 %, under I1, I2, and I3 water regime, respectively. The mineral content and photosynthesis parameters decreased as irrigation water decreased, irrespective of whether plants were inoculated or not. Similarly, AM+ plants had higher inulin percentage and the mean inulin degree of polymerisation than AM− plant under all of irrigation levels. Furthermore, inoculated chicory plants under drought stress showed an enhanced activity of the antioxidant system, such as superoxide dismutase, peroxidase, ascorbic acid and glutathione, while the accumulation of hydrogen peroxide and the oxidative damage were reduced. The two ecotypes tended to respond similarly to irrigation and AM treatments for all growth and quality parameters measured in the experiment, even if ecotype Siyah Shiraz performed better than ecotype Sefid Isfahan. The improved plant performance and inulin content in the inoculated plants demonstrate that AM has the potential to minimize the detrimental effects of drought stress on chicory under semi-arid conditions.

Seed quality, water use efficiency and eco physiological characteristics of Lallemantia (Lallemantia sp.) species as effected by soil moisture content

This study investigated the effect of drought stress on the yield, water use efficiency (WUE), physiology, and seed quality of two species Lallemantia sp. Field experiments with three irrigation regimes were carried out in a split plot factorial in a randomized complete block design with three replications. Treatments included irrigation after 40 %, 60 %, and 100 % depletion of available soil water (ASW) (I40, I60, and I100, respectively) as main plots and Lallemantia species L. iberica (M. Bieb.) Fisch. &amp; C. A. Mey. (S1) and L. royleana Benth. in Wall (S2) as subplots. Increment in depletion of ASW (I40 to I100) resulted in progressively less chlorophyll a content (Chl­ a), open stomata percentage (OS), and leaf area index (LAI). The highest Chl­ a and LAI were found to be 0.0087­ mg g−1, and 2.68 mg g−1 leaf mass in I40 treatment, respectively, while closed stomata percentage (CS) increased significantly as drought stress increased. The results of this experiment indicated that the appropriate yield of production was obtained in plots which were fully irrigated (I40) for all species of Lallemantia; however, the WUE increased as drought stress increased. The interaction of drought stress, Lallemantia species with grain yield and WUE was significant.

Interactive effects of CO2 and nitrogen supply on growth and physiological traits of millet cultivars under drought stress

ABSTRACTAn experiment was conducted to evaluate the effects of irrigation regimes (irrigation after 40 and 75% depletion of available soil water) and nitrogen levels (0 and 85 mg N kg−1 soil) on millet cultivars (Bastan and Pishahang) under two atmospheric CO2 concentrations (390 ± 50 and 700 ± 50 µmol mol−1). Evaluation of different biochemical traits at 50% flowering stage and measurement of dry matter weight at milk stage revealed that water shortage reduced shoot dry weight as the consequence of decreasing chlorophyll and carotenoid contents, leaf area, membrane stability index, and root dry weight but it increased not only the production of H2O2 but also MDA and antioxidant enzyme activities. Drought conditions with elevated levels of CO2 and nitrogen supply, however, partly relaxed limitations observed under water shortage conditions so that H2O2 and MDA production decreased but chlorophyll content and leaf area increased, leading to reduced loss of shoot dry weight. Increased CO2 had a greater effect on the reduction of ascorbate peroxidase and catalase in Bastan, while in Pishahang it had more effect on the reduction of malondialdehyde. Results showed that elevated CO2 and nitrogen supply depended for their effects on both irrigation regime and the genotype grown.

Application of zeolite and bacterial fertilizers modulates physiological performance and essential oil production in dragonhead under different irrigation regimes

Organic farming and low-input production agroecosystems are the major components of sustainable agriculture; therefore, application of biofertilizers containing beneficial soil microorganisms to reduce environmental difficulties related to the use of chemical and manufactured fertilizers is the first step towards sustainability. Considering the importance of the production of medicinal and aromatic plant materials in sustainable ways, a 2-year field research was done as a split factorial experiment based on a randomized complete block design with three replicates. Three factors were investigated: (1) water-deficit stress in three levels comprising irrigation after 30%, 60%, and 90% depletion of available soil water (ASW) as main factor, (2) zeolite application (0 and 8 t ha− 1), and (3) seed inoculation with biofertilizers including nitroxin, phosphate barvar-2, and mixture of nitroxin × phosphate barvar-2, and the control (non-inoculation) as subplots. Results showed that the examined traits such as leaf relative water content, chlorophyll a and b, and total chlorophyll contents, leaf soluble sugars and proline contents, flower yield, essential oil percentage and yield, and irrigation water use efficiencies for flower yield (IWUEFY) and for essential oil yield (IWUEEOY) were significantly (p < 0.05) influenced by experimental treatments in dragonhead for both years. According to second-order interaction among treatment groups, the highest IWUEEOY (3.117 ml m− 3) was obtained in nitroxin × phosphate barvar-2 and zeolite treatments under 60% depletion of ASW. A positive and highly significant (r0.01 = 0.85 and 0.98) correlation was observed between essential oil content and essential oil yield and IWUEEOY, respectively. Regarding significant interaction between biofertilizers and zeolite, the treatment combinations of zeolite and nitroxin × phosphate barvar-2 could improve physiological functions and essential oil yield of dragonhead plants following irrigation after 60% depletion of ASW.

Exogenous Application of Salicylic Acid and Glycine Betaine as Tools to Enhance Biomass and Tolerance of Potato Cultivars

This pot experiment was aimed at characterization of agro-physiological responses of potato to water deficit and exogenously application of salicylic acid (SA) and glycine betaine (GB). Four potato cultivars, Spirit, Born, Arinda and Banba, were exposed to two irrigation regimes (30 and 60% depletion of available soil water) and two levels of both SA (0.5 and 1.0 mM) and GB application (1.0 and 2.0 mM) in addition to the control (0.0 mM SA and GB). Activities of ascorbate peroxidase (APX), superoxide dismutase (SOD), total antioxidant capacity (TAC), ion leakage (IL), fluorescence chlorophyll (Fv/Fm), chlorophyll pigments, root dry mass (RDM) and plant dry mass (PDM) were measured. Water deficiency resulted in significant effects on all characteristics. Antioxidant enzymes and IL increased, but the other characteristics decreased significantly with water deficit. Tolerant cultivars (Spirit and Born) revealed higher activity of SOD enzyme, chlorophyll content, PDM and lower IL than non-tolerant cultivars (Arinda and Banba). This investigation has been able to provide evidence that SA and GB affected antioxidant enzymes and increased chlorophyll pigments and PDM. The range of the increases seemed greater when potato cultivars were grown under water deficit circumstances. PDM increased by increasing SA and GB levels. This led to the supposition that injurious effects on potato cultivars due to water deficit could be relieved by SA and GB.

Physiological traits determining tolerance to intermittent drought in the Capsicum annuum complex

The use of physiological traits directly-linked to mechanisms of drought tolerance (DT) as selection criteria could accelerate the development of tolerant varieties. To identify such physiological traits in chilli pepper (Capsicum annuum L.), we screened a range of diverse genotypes, a series of parental breeding lines produced from C. annuum and C. frutescens/C. chinense crosses, under well-watered and water-stressed (65% depletion of available soil water) conditions in the field with a movable rainshelter. Water regime x genotype interaction was significant (p < 0.05) in the majority of measured traits, which showed significant genotypic variation under the two water regimes. Stomatal conductance (gs) showed strong positive correlations with yield under both water regimes. Furthermore, relative reduction of gs in response to drought positively correlated with relative yield reduction. Canopy temperature (Tc) showed significant negative correlations with yield in both water regimes. Lower yield reductions due to drought were associated with lower increases of Tc across the genotypes. Similarly, lower reductions in shoot relative water content were strongly correlated to lower yield reductions. Yield under drought (Yd) showed significant positive correlation to maximum rooting depth and dry root weight. Greater flower numbers and conversion of flowers to pods, traits indicating the DT of reproductive processes positively correlated with Yd. Factor Analysis showed that the above physiological, growth and reproductive traits constituted composite traits which underpin DT in chilli. As such, they can be used as screening tools in identifying drought tolerant germplasm in breeding programmes of Capsicum annuum.

The water use dynamics of canola cultivars grown under elevated CO2 are linked to their leaf area development

The ‘CO2 fertilisation effect’ is often predicted to be greater under drier than wetter conditions, mainly due to hypothesised early season water savings under elevated [CO2] (e[CO2]). However, water savings largely depend on the balance between CO2-induced improvement of leaf-level water use efficiency and CO2-stimulation of transpiring leaf area. The dynamics of water use during the growing season can therefore vary depending on leaf area development.Two canola (Brassica napus L.) cultivars of contrasting growth and vigour (vigorous hybrid cv. Hyola 50 and non-hybrid cv. Thumper) were grown under ambient [CO2] (a[CO2], ∼400 μmol mol−1) or e[CO2] (∼700 μmol mol−1) with two water treatments (well-watered and mild drought) in a glasshouse to investigate the interdependence of leaf area development and water use.Dynamics of water use during the growing season varied depending on [CO2] and cultivars. Early stimulation of leaf growth under e[CO2], which also depended on cultivar, overcompensated for the effect of increased leaf-level water use efficiency, so that weekly water use was greater and water depletion from soil greater under e[CO2] than a[CO2]. This result shows that the balance between leaf area and water use efficiency stimulation by e[CO2] can tip towards early depletion of available soil water, so that e[CO2] does not lead to water savings, and the ‘CO2 fertilisation effect’ is not greater under drier conditions.

Comparative photosynthetic attributes of emmer and modern wheats in response to water and nitrogen supply

A field study was conducted with the aim to elucidate photosynthetic responses of five emmer hulled wheat (Triticum turgidum ssp. dicoccum) accessions to 30 (N-limited) and 100 kg(N) ha–1 (N-sufficient) conditions at control and drought stress (irrigation after 30–40% and 60–70% depletion of available soil water, respectively). Chlorophyll (Chl) a and Chl b concentrations of the emmer wheats remained unchanged but net photosynthetic rate and dry mass increased and decreased, respectively, when received a sufficient amount of N. Smaller drought-induced decreases in Chl concentration, membrane stability index, and dry mass were concomitant to a greater decrease in intercellular CO2 concentration of emmer compared to the durum (Triticum turgidum) and bread wheats (Triticum aestivum). The lack of negative effect of insufficient N on Chl concentration and dry mass of emmer wheat suggests that this type of wheat possesses an obvious potential for organic farming.

Effect of salt and water stress on gas exchange, dry matter production and K+/NA+ ions selectivity in soybean

The experiment was conducted in a vinylhouse at the Banghabandhu Sheikh Mujibur Rahman Agricultural University, Bangladesh during January to May, 2012 to evaluate the effect of salt and water stress on gas exchange characters, dry matter production and K+/Na+ ions selectivity in three selected soybean genotypes, namely Galarsum, BD 2331 and BARI Soybean-6. The genotypes were exposed to six treatments viz. (i) control (tap water), (ii) water shortage (irrigation with 70% depletion of available soil water when leaf began to wilt at 10:00 am), (iii) 50 mM NaCl irrigation, (iv) 50 mM NaCl irrigation + water shortage, (v) 75 mM NaCl irrigation, and (vi) 75 mM NaCl irrigation + water shortage conditions. The results revealed that 75 mM NaCl salt + water stress treatment drastically reduced stomatal conductance, photosynthesis and transpiration rate irrespective of soybean genotypes. However, the genotype Galarsum showed minimum transpiritional water loss (1.45 mmol H2O m-2 s-1) and maximum photosynthesis (20.45 μmol CO2 m-2 s-1) as compared to BD 2331 and BARI Soybean-6 under 75 mM NaCl salt + water stress condition. Combined salt and water stress caused greater inhibition of shoot growth than either of the two in soybean. The shoot dry weights were decreased to 24.58, 23.00 and 21.57% of the control in Galarsum, BD 2331 and BARI Soybean-6, respectively at 75 mM NaCl salt + water stress. The genotype Galarsum accumulated higher amount of K+ (1.19%) and lower amount of Na+ ( 0.11%) in leaf tissue under 75 mM NaCl salt + water stress. Results indicated that the genotype Galarsum was more capable to cope with the high levels of salt under water stress condition than the other two genotypes.Bangladesh J. Agril. Res. 42(3): 487-501, September 2017