Levels Of Water Regimes Research Articles

Growth-Promoting Bacteria and Salicylic Acid Improve Essential Oil, Flower Yield, And Compatible Osmolyte Content of Common Yarrow (Achillea millefolium L.) Under Drought Stress

Drought is one of the major constraints on agricultural productivity in arid and semiarid regions. Coping with drought stress involves several adaptations and mitigation strategies such as the use of plant-growth promoting bacteria and salicylic acid, which was examined in this study under two levels of water regimes (well-watered as control and drought stress) in southwest Iran in 2018 and 2020 on common yarrow (Achillea millefolium). Catalase levels significantly increased in response to drought stress and salicylic acid application. Salicylic acid and combined application treatment of both bacteria also resulted in a significant increase in proline compared with the control. Different bacteria strains also resulted in a significant increase in peroxidase and superoxide dismutase when compared with the control. Drought stress, salicylic acid application, and different bacteria strains significantly reduced total protein. The use of salicylic acid and the combined application of both bacteria significantly increased the percentage of essential oil compared with the control. Moreover, 41 compounds were isolated, accounting for 92.08% of the essential oil, with more than 90.00% being volatile terpenes. The main components of yarrow essential oil were borneol (16.79%), flanderin (15.92%), cineole (14.32%), camphor (9.77%), and alpha-pinene (3.44%). In general, growth-promoting bacteria and salicylic acid application constitute an advantageous management practice for the commercial production of Achillea millefolium, increasing the nutraceutical and medicinal values of this species.

Handheld NDVI sensor-based rice productivity assessment under combinations of fertilizer soil amendment and irrigation water management in lower Moshi irrigation scheme, North Tanzania

Handheld optical sensor was used to measure canopy reflectance at red region (656 nm) and near-infrared region (774 nm) to generate NDVI data for monitoring rice productivity under soil amendment with combinations of fertilizers at two levels of water regime in smallholder Irrigation Scheme, in Lower Moshi, North Tanzania. The study was carried out in an experimental design which consisted of two irrigation water levels (flooding and system of rice intensification) with multi-nutrients (NPK) and single nutrient (urea) application replicated three times in a randomized complete block design. Flood irrigation water was applied at 7 cm height throughout the growing season, while SRI treatment irrigation water was applied at 4 cm height under alternate wetting and drying conditions. The annual rates of fertilizers applied was 120 kg N/ha, 20 kg P/ha, and 25 kg K/ha. The variety SARO-5 was used in this experiment. Simple correlation coefficient (r) was used to measure the degree of association between field crop performance parameters (plant height, number of tillers, biomass, yield) and NDVI across growth stages and three positions of the sensor above the canopy in the tested fertilizer combinations and water regimes. Results show that at any given fertiliser combinations and water levels, there was no significant correlation between plant height and NDVI except for the plant height at a vegetative stage for 0.6 m above the crop canopy and booting stage at 0.3 m and 0.6 m above the canopy, respectively (P < 0.05). A good correlation was also observed between NDVI at booting and full booting stage regardless of the position of the sensor above the canopy and the number of tillers at full booting growth stage (P < 0.05). A significant relationship was observed between rice grain yield and NDVI at the vegetative, booting, and full booting stage. The simple linear regression models explained only slightly < 30% of the yield predictions by NDVI at the early stage of the crop growth, decreasing gradually to 5% at the full booting growth stage. Results demonstrate a positive linear relationship between rice grain yield and NDVI for the tested soil fertiliser amendments and irrigation water regimes. Thus, we conclude that handheld NDVI-based sensor can be used in smallholder rice yield predictions for optimising soil fertiliser use and irrigation water management. This allows future multi-functional land management within the soil–water-food nexus.

Effect of Different Nano-NPK Fertilizers on Vegetative Growth Parameter and Soil Microbial Activity of Fig Crop under Different Irrigation Regims

World face several challenges the most decisive climatic changes , freshwater poverty and poor usage efficiency for natural resources (soil &amp; water) particularly in developing countries.&#x0D; Applying Nanotechnology may represent a smart mechanism toward sustainable agricultural. Much efforts have been exerted to utilizing nano-technology and producing agro-chemicals in nano-form i.e, nano-fertilizers and nano-pesticides.&#x0D; Current work that carried out in greenhouse belong pomology department , National Research Centre, Cairo, Egypt during 2020/2021, aims to assessing impact of nano-fertilizers on growth performance and soil microbial activity under different drought stress levels. NPK-nano-fetrilizer was applied on uniform one-year old fig seedlings, as foliar application at two levels (200 and 400ppm) compared with traditional NPK fertilizer, under three levels of water regimes (once, twice and three times irrigation weekly. Obtained results indicated that under drought stress nano-fertilizers enhanced fig seedlings growth performance and nutrient content. Moreover, nano-fertilizer raised antioxidant enzyme activity that work on scavenging active oxygen species and thereby reinforce drought stress tolerance in plants. Besides, nano-fertilizer had a positive impact on soil microbial under low soil moisture. This study came in chain of studies which proved the efficiency of nano-fertilizer under drought stress with no negative impact on environments under this study conditions. This study concluded that nano-fertilizer has a bright future particularly under challenges that face the world (climatic changes, poverty of water resources, soil degradation and global food famine risk with fast growing of population) toward sustainable agriculture with low risk on environment.

Osmolyte-induced water deficit stress mitigation during panicle initiation stage in transplanted rice (Oryza sativa L.)

A field experiment was conducted to observe the osmolyte-induced water deficit stress mitigation during the panicle initiation stage in transplanted rice (Oryza sativa L. cv. BRRI dhan72). At the panicle initiation stage, plants were simulated with four levels of water regimes viz., well-irrigated (D0), water deficit for 5 d (D1), 10 d (D2) and 15 d (D3). Plants were treated with or without 10 mM of proline (Pro) and trehalose (Tre) as foliar spray started at mid-vegetative stage and continued till the end of stress period. Results revealed that water deficit stress drastically reduced most of the plant morpho-physiological attributes while other yield contributing characters were also affected due to prolonged water deficit stress. However, exogenous application of osmolytes like Pro and Tre significantly increased all those morphological, physiological and yield contributing parameters. Foliar addition of osmolytes concomitantly decreased the number of non-effective tillers hill-1 and the number of unfilled grain panicle-1 under water stress condition. Although both the osmolytes performed well under multiple duration of drought stress, the application of 10 mM Pro markedly improved all growth and yield contributing parameters under D1 water deficit stress compared to other stress durations. Hence, it may be concluded that the use of osmolytes would be a prospective remedy against moderate water deficit stress in transplanted rice production.

Foliar application of zinc improves morpho-physiological and antioxidant defense mechanisms, and agronomic grain biofortification of wheat (Triticum aestivum L.) under water stress

Agronomic biofortification with zinc (Zn) may be engaged to improve the nutritious value of food crops along-with tolerance to water deficit conditions. The Zn may increase plant resistance to water stress by boosting physiological and enzymatic antioxidants defense mechanisms. Major objective of this study was to investigate the effect of foliar applied Zn on grain zin biofortification and drought tolerance in wheat. Treatments include application of Zinc at terminal growth phases (BBCH growth stage 49 and BBCH growth stage 65) with five levels: 0 (control-ck), water spray, 5, 10 and 15 mM under two levels of water regimes; well-watered (where 80% water holding capacity (WHC) was maintained in the soil) and water stress, (where 40% WHC was maintained in the soil). Results revealed that water stress significantly reduced relative water contents, gas exchange attributes, plant height, yield and yield related attributes of wheat. In contrast, hydrogen peroxide, free proline levels, activities of malondialdehyde, and concentration of soluble protein were markedly increased under water stress condition. Application of various levels of Zn significantly improved the CAT, SOD, POD and ASP activities at 40% WHC compared with control treatment. Foliarly applied 10 and 15 mM Zn predominantly reduced the damaging impact of water stress by improving the plant status in the form of plant height, RWC and gas exchange attributes. Likewise, wheat plant treated with 10 mM Zn under water stress condition increased the grain yield by improving number of grains per spike, 100 grain weight and biological yield compared with control. Moreover, increasing Zn levels also increased Zn concentration in grains and leaves. Overall, this study suggests that optimum level of Zn (10 mM) might be promising for alleviating the adverse impacts of water stress and enhance the grain biofortification in wheat.

Kernel Water Relations and Kernel Filling Traits in Maize (Zea mays L.) Are Influenced by Water-Deficit Condition in a Tropical Environment.

Water deficit is a major limiting condition for adaptation of maize in tropical environments. The aims of the current observations were to evaluate the kernel water relations for determining kernel developmental progress, rate, and duration of kernel filling, stem reserve mobilization in maize. In addition, canopy temperature, cell membrane stability, and anatomical adaptation under prolonged periods of pre- and post-anthesis water deficit in different hybrids was quantified to support observations related to kernel filling dynamics. In this context, two field experiments in two consecutive years were conducted with five levels of water regimes: control (D1), and four water deficit treatments [V10 to V13 (D2); V13 to V17 (D3); V17 to blister stage (D4); blisters to physiological maturity (D5)], on three maize hybrids (Pioneer 30B80, NK 40, and Suwan 4452) in Expt. 1. Expt. 2 had four water regimes: control (D1), three water deficit treatments [V10 to anthesis (D2); anthesis to milk stage (D3); milk to physiological maturity (D4)], and two maize hybrids (NK 40 and Suwan 4452). Water deficit imposed at different stages significantly reduced maximum kernel water content (MKWC), kernel filling duration (KFD), final kernel weight (FKW), and kernel weight ear–1 while it increased kernel water loss rate (KWLR), kernel filling rate (KFR), and stem weight depletion (SWD) across maize hybrids in both experiments. The lowest MKWC under water deficit was at D3 in both experiments, indicating that lower KFR results in lowest FKW in maize. Findings indicate that the MKWC (R2 = 0.85 and 0.41) and KFR (R2 = 0.62 and 0.37) were positively related to FKW in Expt. 1 and 2, respectively. The KFD was reduced by 5, 7, 7, and 11 days under water deficit at D3, D4 in Expt. 2 and D4, D5 in Expt. 1 as compared to control, respectively. Water deficit at D5 in Expt. 1 and D4 in Expt. 2 increased KWLR, KFR, and SWD. In Expt. 2, lower canopy temperature and electrical conductivity indicated cell membrane stability across water regimes in NK 40. Hybrid NK 40 under water deficit had significantly higher cellular adaptation by increasing the number of xylem vessel while reducing vessel diameter in leaf mid-rib and attached leaf blade. These physiological adjustments improved efficient transport of water from root to the shoot, which in addition to higher kernel water content, MKWC, KFD, KFR, and stem reserve mobilization capacity, rendered NK 40 to be better adapted to water-deficit conditions under tropical environments.

Screening for drought tolerance and molecular variability among some sugar beet cultivars

Drought is one of the significant abiotic stress factors that affect plant development and productivity. Screening and producing of more tolerant genotypes with higher yield capacity is the breeders' principal purpose. Therefore, this work was carried out to evaluate the performance of four sugar beet cultivars (Top, Hossam, Hercules and Kawamera) under water limitation. The drought stress experiment was applied based on three water regimes, 25%, 50% and 75% (severe, moderate and non-stress conditions, respectively) of relative water capacity (RWC). The study incorporated some productivity and quality traits. The results showed that drought stress has a significant effect on all studied traits. Whereas, increasing of water deficiency led to decrease of the productivity traits and increasing of quality parameters. Kawamera cultivar has superior performance in all the studied traits under all three different levels of water regime. Besides, the four cultivars were assessed by both SSR and ISSR molecular markers. SSR marker exhibited a higher polymorphism percentage (71.43%) than ISSR marker (44.26%). In addition, the mean polymorphism information content (PIC) value was higher for the SSR marker (0.25) than the ISSR marker (0.18) too. Moreover, the constructed dendrograms revealed that the SSR marker was able to separate the cultivars according to their drought-tolerance, where the highest drought-tolerant cultivar (Kawamera) was classified alone in the main cluster. However, the superiority of Kawamera cultivar under drought stress indicated that it could be utilized in breeding programs for developing more drought-tolerant sugar beet cultivars.

Nitrogen nutrition effects on triticale photosynthesis and assimilate translocation under late-season water stress conditions

In this study, photosynthesis and assimilate translocation and their contribution to improving grain yield and harvest index (HI) of triticale under different N sources and irrigation regimes in an arid climate were evaluated. There were two levels of water regimes: normal irrigation (IRN) and deficit irrigation (cutting irrigation after anthesis stage - IRD). Four N sources: Azospirillum brasilense (Bio), Azospirillum brasilense + 75 kg N ha−1 as urea (Bio + N75), 150 kg N ha−1 as urea (N150) and control unfertilized (N0) plots were used. Results showed the highest net photosynthesis rate (Pn ) was observed in Bio + N75 (24 and 20 µmol CO2 m−2 s−1 at the milking and soft dough stages, respectively) under IRN. The IRD decreased Pn in all N sources, however, the highest reduction was observed in N150 and the lowest in Bio and Bio + N75 treatments. Similar trends were observed in other photosynthetic traits and assimilate remobilization, except for the instantaneous water use efficiency (IWUE), which increased by IRD when bio-fertilizer was applied. The highest grain yield was found by N150 under IRN, which was not significantly different from Bio + N75 treatment. In contrast, application of Bio + N75 resulted in the highest grain yield compared to the other N sources under IRD. Overall, since the lowest reduction in photosynthetic traits, assimilate remobilization, and grain yield of triticale under IRD conditions occurred when bio-fertilizer was applied, this N fertilizer regime could be recommended for the arid areas where water shortage occurs frequently.

Effect of Vermicompost and Municipal Solid Waste Compost on Growth and Yield of Canola under Drought Stress Conditions

ABSTRACT In order to study the effect of municipal solid waste (MSW) compost and vermicompost on morpho-physiological properties and yield of canola under drought stress conditions, an experiment was conducted as factorial arrangement based on randomized complete block design with four replications. Treatments consisted of three levels of water regimes, including: 75% of the field capacity for well-watered and 55% and 35% for moderate and severe stress, respectively, and biofertilizer in five levels, including: nonapplication of biofertilizer (control), application of MSW compost, and vermicompost at 2% and 4% levels. Results showed that interaction of irrigation and biofertilizer had significantly affected on all traits except leaf area ratio and nitrogen percent. The moderate and severe stress significantly reduced all traits compared to normal irrigation. Application of 4% vermicompost was resulted in increased growth, biomass and yield of canola under normal irrigation, moderate and severe drought stress compared to other biofertilizer treatments.

Combined Effects of Water Deficit, Exogenous Ethylene Application and Root Symbioses on Trigonelline and ABA Accumulation in Fenugreek

Secondary metabolites (SMs) have high economic impact thanks to their exploitability in chemical, pharmaceutical and cosmetic industries. Trigonella foenum-graecum has an importance due to the production of bioactive compounds with pharmaceutical values. Among them, the alkaloid trigonelline is known for its role in the treatment of different human diseases. SM accumulation is influenced by environmental factors but is modulated by the application of exogenous compounds. Ethephon, a precursor of the phytohormone ethylene, was already used to influence SM accumulation. Our work is aimed at evaluating the accumulation of trigonelline and the phytohormone abscisic acid (ABA) when three factors were combined: i) two levels of water regimes (well-watered and water deficit), ii) ethephon treatments and iii) inoculation with an arbuscular mycorrhizal (AM)-based inoculum also leading to nodulation. The content of trigonelline and ABA was significantly affected by symbioses, showing high accumulation in AM-colonized plants irrespective of the water regimes applied. In terms of trigonelline accumulation with respect to ethephon treatments, while symbiotic plants showed a dose-dependent trend, non-symbiotic plants showed a significantly difference only when 550 ppm of ethephon was applied. In conclusion, our work provides new information on the effects of both ethephon and symbioses on plant growth and accumulation of valuable compounds, such as trigonelline, in fenugreek.

Eco-physiological responses of desert and riverain legume plant species to extreme environmental stress

Abstract Drought and heat events frequency and severity are expected to increase in the near future as responses to global warming, influencing crops productivity and human diet as result in the increasing soil aridity and area affected by drought. It is becoming increasingly important to find new crop plants or genotypes of crops that have adaptation strategies to water loss at extreme arid conditions. It was hypothesized that growth and development of plants are affected differently by drought stress, depending on their nature habitats whether desert or riverain. In this current research, we compared the changes in physiological behavior between desert and riverain legume plants, as response to drought stress at two levels of water regimes. Rates of transpiration were highly correlated to radiation. Transpiration increases with the increase in photosynthetic active radiation (PAR) at both levels of water regimes. Highest photosynthesis (pn) and transpiration (E) were achieved in R. minima at both low water regime and high PAR (1250). The super oxide dismutase (SOD), catalase (CAT), phenyl ammonia lyase (PAL) and peroxidase activities were higher in Rhynchosia minima. Drought stress induced significant accumulation of total sugars, flavonoids, saponins, proteins and phenolics. The higher photosynthesis rate, higher flavonoids and phenolics content and stronger activity of protective enzymes were the important physiological reasons for the drought resistance of Rhynchosia minima.

Cultivation of soybeans for seeds in different levels of water regime

Cultivation of soybeans for seeds in different levels of water regime

Proline accumulation induces the production of total phenolics in transgenic tobacco plants under water deficit without increasing the G6PDH activity

Proline metabolism has been proposed to play an important role in activating the shikimic acid pathway for increased secondary metabolites production in plants. Here we evaluated the role of proline per se and in combination with water deficit on the production of phenolic compounds in leaves of transgenic tobacco plants (Nicotiana tabacum) with increased proline content. For this, an experiment was carried out under greenhouse conditions using three genotypes (transgenic events E1 and E2 constitutively expressing the mutant gene VaP5CSF129A and an untransformed control) and two levels of water regimes (100% and 30% of soil field capacity). Total phenolics, proline, activities of glucose-6-phosphate dehydrogenase (G6PDH) and phenylalanine ammonia-lyase (PAL), and lignin were measured in the leaves. As expected, a reduction in biomass was observed in all genotypes under drought conditions and the maximum accumulation of proline occurred in transgenic plants in both water regimes. Under irrigated conditions, phenolics were only slightly superior in leaves of the transgenic event E2, while both events presented a noticeable increment in total phenolics and PAL activity under water deficit. Lignin biosynthesis also increased in all genotypes in response to drought stress, but it was more noticeable in the transgenic plants. On the other hand, the activity of the G6PDH enzyme was consistently lower in the transgenic plants in both irrigated and water-deficit condition. Our results do not confirm the association between de novo proline synthesis and the stimulation of G6PDH to produce phenolics.

Effects of Biotic and Abiotic Environmental Stimuli on the Morphology and Biomass Allocation of Mimosa pigra L.

The main focus of this study was to examine the morphology of Mimosa pigra, an invasive weed in response to artificial biotic and abiotic stressors. Seedlings of M. pigra were subjected to stressors such as seed sowing density, leaf defoliation and water regime. Comparatively, morphological performance related to different sowing practices differed significantly (p 0.05) in morphological performance under different levels of water regime. However, seedlings that received low water (LW) treatment showed better growth performance than seedlings that received high water (HW) treatment, which had the lowest morphological traits and biomass allocation.

Assimilate and nitrogen remobilization of six-rowed and two-rowed winter barley under drought stress at different nitrogen fertilization

ABSTRACTField experiments were conducted to investigate the effects of irrigation regimes and N levels on assimilate remobilization of two barley cultivars (Yousefsix-rowed and Nimrouztwo-rowed) in 2011 and 2012. There were three levels of water regimes (full irrigation (I100), 75% and 50% of I100: I75 and I50, respectively) in 2011. Rain-fed treatment (I0) was included in 2012. Three N levels (0, 60, and 120 kg ha−1) were used. Grain yield and assimilate remobilization decreased by severe water stress (I0), however, the reduction of them were intensified by N fertilizer application. The N remobilization was negatively affected by N fertilization and water stress. The two-rowed showed higher N remobilization (10.7%) and contribution of N remobilized to N content of grain (5.8%) than the six-rowed. The two-rowed cultivar showed significantly higher assimilate remobilization and grain yield than the six-rowed under I50 (26.3% and 6.5%, respectively) and I0 (48.7% and 17.1%, respectively), while the six-rowed had similar or higher performances in terms of these traits under I100 and I75. This study showed that optimizing irrigation and N rates (decrease N level with increasing water stress) and selection of the suitable cultivars (Nimrouztwo-rowed) might increase assimilate remobilization and consequently grain yield under drought stress conditions.

ECONOMIC MAXIMIZATION OF ALFALFA ANTIMICROBIAL EFFICACY USING STRESSFUL FACTORS

&lt;p&gt;&lt;strong&gt;Objective: &lt;/strong&gt;The present study addresses the effect of water deficit stress on the antimicrobial capacity of alfalfa (&lt;em&gt;Medicago sativa&lt;/em&gt;) plants. &lt;strong&gt;&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Methods: &lt;/strong&gt;Methanolic extracts of alfalfa plants grown in different soil types, varying in sand proportion, either alone or combined with various levels of water regimes were assessed for antibacterial and antifungal activities following cup plate method. The phytochemical profiles of plant extracts were also qualitatively screened using appropriate chemical reagents. Moreover, data were intensively processed &lt;em&gt;via&lt;/em&gt; two different statistical designs. &lt;strong&gt;&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Results: &lt;/strong&gt;Increasing sand amount induced the inhibitory effect of plant extracts on &lt;em&gt;Escherichia&lt;/em&gt;&lt;strong&gt;&lt;em&gt; &lt;/em&gt;&lt;/strong&gt;&lt;em&gt;coli&lt;/em&gt;, &lt;em&gt;Klebsiella pneumonia&lt;/em&gt;, &lt;em&gt;Proteus&lt;/em&gt;&lt;strong&gt;&lt;em&gt; &lt;/em&gt;&lt;/strong&gt;&lt;em&gt;vulgaris&lt;/em&gt;, &lt;em&gt;Salmonella typhi&lt;/em&gt;, &lt;em&gt;Mucor circinelloides&lt;/em&gt;, &lt;em&gt;Rhizopus azygosporus&lt;/em&gt; and &lt;em&gt;R. microsporus&lt;/em&gt; with less pronounced action on &lt;em&gt;Shigella flexneri&lt;/em&gt;,&lt;em&gt; Staphylococcus epidermidis&lt;/em&gt;,&lt;em&gt; Candida albicans&lt;/em&gt; and&lt;em&gt; Emericella quadrillineata&lt;/em&gt;;&lt;em&gt; &lt;/em&gt;as well as a reversed influence on &lt;em&gt;Pseudomonas aerugenosa&lt;/em&gt; and &lt;em&gt;Streptococcus pyrogenes&lt;/em&gt;. Furthermore, withholding irrigation water enhanced the plant suppressive action on &lt;em&gt;E. coli, &lt;/em&gt;&lt;em&gt;Salmonella typhi&lt;/em&gt;, &lt;em&gt;Staphylococcus epidermidis&lt;/em&gt;,&lt;em&gt; Candida albicans&lt;/em&gt; and &lt;em&gt;R. microsporus&lt;/em&gt; with less marked or reversed influence on the other tested microbes. However, &lt;em&gt;Pseudallescheria ellipsoidea&lt;/em&gt;, two species of &lt;em&gt;Penicillium&lt;/em&gt; and five of &lt;em&gt;Aspergillus&lt;/em&gt; could resist the studied plant extracts. The results also revealed that the extracts of water-unsatisfied plants generally contained higher amounts of alkaloids, amino acids, flavonoids, glycosides, phytosterols, saponins, steroids, tannins, terpenoids and reducing sugars.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Conclusion: &lt;/strong&gt;The employed biological evaluations point out to promising antimicrobial efficiency of alfalfa plants particularly when stressed.&lt;/p&gt;

Greenhouse and in vitro screening of sweetpotato genotypes for drought tolerance

Breeding sweetpotato [Ipomoea babatas (L.) Lam] for drought tolerance requires inexpensive, reproducible and high throughput screening systems. The objective of this study was to apply greenhouse and in vitro techniques to select drought tolerant sweetpotato genotypes. Greenhouse and in vitro experiments were established at Rubona Research Station of the Rwandan Agricultural Board using 54 sweetpotato genotypes. Genotypes were evaluated in the greenhouse using four levels of water regime [control, drought stress imposed by withholding water for one, two or three month(s)], while in vitro tests were carried out using four treatment solutions [control or basic culture medium (0 M), control supplemented with 0.2, 0.4 or 0.6 M sorbitol]. In the greenhouse study, data collected included: soil water potential (ψ w), weights of storage root, biggest storage root and vines, dry matter content (DMC) of storage root and vine and water content (WC) of vines. Whereas ψ w of culture media, fresh weight gain (FWG), DMC and WC were recorded during the in vitro experiment. In the greenhouse test, ψ w of drought stressed treatments varied from-1.94 to-0.05 MPa and showed an increased trend with prolonged drought stress. The control treatment showed ψ w ranging between-0.02 to 0 MPa. During the in vitro experiment, the mean ψ w were-0.07, -0.81, -1.35 and-1.73 MPa for control, 0.2, 0.4 and 0.6 M sorbitol treatments, respectively. Under greenhouse condition, genotype by water regime, genotype and water regime had significant effects (P≤0.01) on yield and yield related traits. Genotypes showed significant differences between the control and drought stress imposed for one month. Under in vitro test, the control and 0.2 M sorbitol treatments were not significantly different in the FWG. However, the control treatment was significantly different from 0.4 and 0.6 M sorbitol concentrations. Positive correlations were observed between vine yield and FWG; and between total biomass and FWG, during greenhouse and in vitro studies, respectively. Overall, genotypes 2005-146, 4–160, 8–1038, Kemb 37, Kwezikumwe, Purple 4419, NASPOT 9, Nsasagatebo, Karebe, 440037, Mwanakumi, 97–062 and Matembere were selected with comparatively high drought tolerance using the two screening procedures. The selected genotypes are useful genetic resources to breed sweetpotatoes for drought tolerance.

INFLUENCE OF USING SOME SAFETY MATERIALS ON WATER REQUIREMENT AND WATER USE EFFICIENCY OF SNAP BEAN PLANT

Two field experiments were conducted during the two successive seasons of 2011/2012 at the Experimental Farm, Kaha station, Qulubia Governorate to study the effect of using four levels of water regime ,i.e. 60%, 80%, 100 and 120% from class A pan evaporation and five safety materials, i.e. water (as control),amino-z, lithovit (a natural intensified CO2 foliar fertilizer ) as foliar spray on snap bean plants as well as the biofertilize mycorrhizal as a seed treatment before sowing and sap material as a absorbent polymer to increase with holding water capacity before sowing and the effect of that on growth, green snap bean yield Poulista cv ., physical and chemical characters as well as water use efficiency. The results indicated that, mycorrhizal seed treatment, lithovit foliar spray and soil treatment with sap material gave the highest values of green pod characters as well as the vegetative growth, in addition all the safety material used led to significant increment on pod yield and the favorable treatments were obtained by using sap material and foliar spray with amino -z. Concerning to using safety materials with water regime levels, it was found that, spraying snap bean plants with amino- z and irrigation with 120% levels from class A pan evaporation was the superior treatment on green pod yield followed by soil treatment with sap material with 60% of water level. Regarding to the mean of green pod weight, the results showed that treating seed with mycorrhizal and 120% level of water regime gave the highest values during the two seasons, then the treatment of foliar spray with lithovite with 80% level of water regime and the treatment by sap soil treatments with supplied by 60% of water irrigation. Concerning to water use efficiency, the data showed that supplied the plants with the highest amount of water 120% and 100% from water irrigation decreased the values of water use efficiency, on the contrary , it can obtained the highest values of water use efficiency from water supplied with 60% then 80% calculated by class A pan evaporation method. Regarding to the effect of safety material on water use efficiency, it was found that, sap treatment or foliar spray with amino-z then, mycorrhizal treatments gave the highest value of water use efficiency. Generally, it can recommend by using sap material of soil addition before sowing and foliar spray by amino- z followed by treating the seeds with mycorrhizal with irrigation level 60% or 80%to obtained the favorable green pod yield and the favorable water use efficiency.

Nitrogen and water use efficiencies and yield response of barley cultivars under different irrigation and nitrogen regimes in a semi-arid Mediterranean climate

Experiments were conducted to determine barley cultivars (Yousefsix-rowed and Nimrouztwo-rowed) response to different water and nitrogen (N) regimes at Fars Agricultural Research Center using split-split-plot design. There were three levels of water regimes (full-irrigation (I100), 75% and 50% of I100: I75 and I50, respectively) in 2010. Rainfed treatment (I0) was included in 2011. Three N levels (0, 60 and 120 kg ha−1) were used. Grain and biomass water use efficiencies (WUEg and WUEb, respectively) were positively affected by N supply. The I75 improved WUEg and WUEb by 17% and 20% as compared to I100, respectively. Two-rowed cultivar showed higher WUEg and WUEb than six-rowed. Nitrogen use efficiency (NUE) was negatively affected by water stress and N fertilization. The highest grain yield was achieved by 120 and 60 kg N ha−1 under I100 and drought stress conditions, respectively. Two-rowed cultivar showed significantly higher NUE and grain yield than six-rowed cultivar under I50 and I0; by contrast, six-rowed cultivar had similar or higher performances in terms of these traits under I100 and I75. This study showed that optimizing irrigation and N rates and selection of suitable cultivars in semi-arid Mediterranean climate might increase NUE, WUE and produce economic grain yield.

Morphological Changes and Antioxidant Activity of &amp;lt;i&amp;gt;Stevia rebaudiana&amp;lt;/i&amp;gt; under Water Stress

Stevia rebaudiana, a herbaceous perennial shrub contains steviol glycosides, as an alternative source of sugar for diabetic patients. Water being an integral part plays a vital role in the maintenance of plant life. Availability of water is one of the limiting factors determining plant distribution and survival in natural ecosystem. The objective of this study was to investigate the ability of tolerance of Stevia plants to water stress. Potted plants of Stevia were subjected to different levels of water regimes (100 ml, 200 ml, 300 ml) per day, whereas control plants were watered daily with about 400 ml water. Plant height, leaf area, electrolyte leakage and antioxidant enzyme activity (peroxidase and catalase) were assayed during the experimental period. All these parameters were severely affected under water stress condition. Stress treatment caused an increase in electrolyte leakage compared to control. Plant height decreased under severe stress condition whereas a sharp increase in antioxidant enzyme activity was observed in stressed plants as compared to untreated control plants. Our experiment emphasizes the importance of proper watering schedule for the cultivation of Stevia as an agricultural crop to meet the challenges for sugar and energy crisis.