Severe Water Stress Conditions Research Articles

Effect of shading and water stress on light interception, physiology and yield of apple trees

Net shading was explored as a corrective tool for mitigating the effect of a single year drought event on apple (‘Imperial Gala’) yield in Bologna (Italy). In 2013, trees were grown under three nets with different shading levels (red-50%, white-50%, and black-20%) and without nets. Those treatments received three irrigation doses from 60 days after full bloom until harvest: 260 (control), 115 (moderate water stress, WS) and 50 (severe WS) mm of water. Control trees had midday stem water potential (Ψstem) values around -1.0 MPa when they were shaded, but values were more negative when they were grown without nets. Ψstem ranged between -1.0 and -1.5 MPa under moderate WS and was about -1.5 MPa for severe WS although this value was reached sooner in trees grown without nets. Leaf photosynthesis decreased with more negative Ψstem values but was not affected by shading. Yield was very low (3–4 kg per tree) for trees grown without nets with no differences between irrigation treatments. Yield was also very low for shaded trees grown under severe WS (5–7 kg per tree). Under control and moderate WS, shaded trees had higher yields (9–13 kg per tree) than trees grown without nets, but no differences were found between shading. The benefits of net shading on yield were explained by several additive factors: i) improved water status, ii) delay in fruit maturity giving more time to the fruit to grow, and iii) reduction of photo-inhibition. These results may encourage fruit growers to install nets in their orchards when water is limited. Under severe water stress conditions net shading was not effective and low yields are expected. No effect of net colour was observed but its effect may be observed in a longer term. Further research is necessary to determine the sustainability of shading over multiple years.

Performance of potato (Solanum tuberosum) advanced hybrid MS/6-1947 under high temperature stress and water deficit conditions

In present investigation, potato (Solanum tuberosum L.) advanced stage hybrid MS/6-1947 was evaluated along with controls under high temperature and water stress regimes for three successive winter crop seasons. Under high temperature at Modipuram, MS/6-1947 (13.3 t/ha) showed yield enhancement of 20, 9 and 11% over the controls Kufri Bahar, Kufri Pukhraj and Kufri Surya. It also exhibited at par tolerance to hopper with Kufri Surya and damages due to mite burn were lower than Kufri Bahar and Kufri Pukhraj. The hybrid possessed 18% tuber dry matter. Results ondrought toleranceat Modipuram revealed superior performance of MS/6-1947 under normal irrigation, mild water and severe water stress conditions as compared to best control Kufri Pukhraj as yield reduction was comparatively lower under mild and severe water stress treatments. Drought tolerance index (DTI) values were maximum in MS/6-1947 (1.02 and 0.79) followed by Kufri Pukhraj (0.86 and 0.51) and Kufri Bahar (0.72 and 0.58) under mild and severe water deficit treatments, respectively. Drought tolerance studies at Jodhpur revealed better performance of MS/6-1947 under normal and mild water stress conditions as compared to the controls Kufri Pukhraj and Kufri Surya as yield reduction was comparatively lower under mild water stress conditions. DTI values were maximum in MS/6-1947 (1.08) followed by Kufri Puhkraj (1.01) and Kufri Surya (0.41) under mild water deficit treatment. Tuber dry matter content increased under water stress over normal irrigation at both the locations. MS/6-1947 is suitable for table potatoes. MS/6-1947 may be a better option for integrating in cereal based crop sequences, for exploiting its yield potential in early season and for attaining sustainable productivity in areas where high temperature and lower water availability are constraint for raising the successful potato crop.

Projected impact of future climate on water-stress patterns across the Australian wheatbelt.

Drought frequently limits Australian wheat production, and the expected future increase in temperatures and rainfall variability will further challenge productivity. A modelling approach captured plant×environment×management interactions to simulate water-stress patterns experienced by wheat crops at representative locations across the Australian wheatbelt for 33 climate model projections, considering the 'business as usual' emission scenario RCP8.5. The results indicate that projections of future water-stress patterns are region specific. Significant variations in projected impacts were found across climate models, providing local ranges of uncertainty to consider in planning efforts. Most climate models projected an increase in the frequency of severe water-stress conditions in the Western area, the largest producing region, and fewer severe water stresses in other regions. Where found, reductions in water-stress conditions were largely due to shorter crop cycles (a result of warmer temperatures), increased water use efficiency (resulting from increased CO2 levels), and, in some cases, increased local rainfall. Overall, simulations indicate that all areas of the Australian wheatbelt will continue to experience severe water-stress conditions (43.9, 42.6, and 40.2% for 2030, 2050, and 2070 compared with 42.8% for 1990). Given projected frequencies of severe water stress and warmer conditions, efforts towards maintaining or improving yields are essential.

Seed priming improves seedling emergence and reduces oxidative stress in Nigella sativa under soil moisture stress

ABSTRACTNigella sativa seeds have multiple industrial and pharmaceutical uses for the diseases treatment such as bronchitis, rheumatism, high blood pressure, cough, eczema, inflammation, and influenza. Although semi-arid areas are suitable for production of annual medicinal plants because they receive favorable amounts of solar radiations, the establishment of these plants' seedling requires frequent irrigations because their seeds are small and the climate is hot at the time of planting. When the irrigation sources are limited, poor establishment and inadequate production will result. Therefore, in order to improve nitrogen (N) in N. sativa seedling establishment, different effects of seed priming treatments were evaluated under drought stress. Different levels of soil moisture (irrigation after 11, 22, 33, and 44 mm of evaporation as no water stress, mild water stress, moderate water stress, and severe water stress, respectively) and seed priming treatments [no priming, potassium nitrate (KNO3), zinc sulfate (ZnSO4), polyethylene glycol 6000, and gibberellic acid (GA)] were evaluated as the main plot and subplot factors, respectively. The results showed that under mild water stress condition, seed priming significantly increased proline content and the highest percentage of emergence was obtained with ZnSO4. Furthermore, the highest amount of soluble protein was observed in the KNO3 treatment and the catalase enzyme content increased in all priming treatments, except polyethylene glycol treatment. Under moderate water stress condition, the KNO3 treatment raised the rate and percentage of emergence and the seedling length. However, under severe water stress condition, the highest percentage of emergence was achieved by GA and ZnSO4 treatments. Moreover, hydropriming and GA produced the highest proline content and seedling dry weight. Under moderate and severe water stress conditions, the hydropriming and ZnSO4 treatments showed a significant increase in catalase activity. It can be concluded that priming of N. sativa seeds with ZnSO4 and GA can alleviate drought stress in the early stages of seedling growth by increasing the antioxidants in the seedlings. Farmers in semi-arid regions can prime N. sativa seeds with these compounds before planting to increase production of this valuable medicinal plant and reduce water consumption.

Nutrition and biochemical responses of chickpea (Cicer Arietinum L.) to vermicompost fertilizer and water deficit stress

ABSTRACTVermicompost can have an effective role in plant growth and nutrition. It can also reduce the harmful effects of stress caused by environmental factors. This study was a factorial experiment with a completely randomized plot design and three replications. The results showed that the calcium concentration (+40% +39%) of root and calcium (+71% +67%) and potassium contents (+49% +59%) of leaf under conditions of moderate and severe water stress increased under vermicompost treatments at the ratio of 30%. Sodium absorption (−37% −21%) in moderate and severe conditions was significantly reduced by vermicompost treatment. In moderate and severe water stress, the growth medium of 30% vermicompost significantly enhanced proline (+39%) and soluble protein content (+28%) compared to the control. In conclusion, our results proved vermicompost fertilizer due to its structural properties and components, served to reduce the negative effects of water stress by increasing the absorption of calcium (Ca) and potassium (K), and decreasing sodium (Na) absorption that resulted in increased evaluations for proline and protein content.

Metabolic responses of endophytic Nicotiana benthamiana plants experiencing water stress

Endophytic fungal colonization may influence how plants respond to environmental stress. Two promising fungal isolates, one resembling Cladosporium cladosporioides and another unidentified ascomycetous fungus, isolated from wild N. benthamiana plants in northern Australia were inoculated to plants of the research accession of N. benthamiana (RA-4). Inoculated seedlings were grown under adequate or water deficit conditions. We examined leaf metabolites using gas chromatography-mass spectrometry (GC–MS) to compare levels of sugars, sugar alcohols, amino acids and other metabolites at various stages of plant growth and stress application. Ninety-three metabolites were detected in leaves, including 20 sugars, 13 sugar alcohols, 21 amino acids, 29 organic and fatty acids and ten other compounds. Endophyte colonization caused significantly differential accumulation of 17–21 metabolites when the plants were grown under well-watered condition. The presence of endophytes under water stress conditions caused differential accumulation of cytosine, diethylene glycol, galactinol, glycerol, heptadecanoate, mannose, oleic acid, proline, rhamnose, succinate, and urea. Accumulation of these metabolites suggests that fungal endophytes influence plants to accumulate certain metabolites under water-stress. Further, plants colonised by the two different endophytes tested, showed some differences in the metabolites they accumulated. Colonization with endophytic fungi significantly increased root dry mass and relative water content in plants under severe water stress condition, suggestive of a symbiotic relationship between these fungi and N. benthamiana plants, a species adapted to the hot and unpredictable soil moisture conditions of northern Australia. We reveal that endophyte colonization triggers reprogramming of host metabolism and indices changes in host development. This study sheds lights on the mechanisms underlying increased tolerance to water stress in plants conferred by fungal endophytes. Fungal endophytes have the potentials for application to increase the inherent water stress tolerance of crops.

The coupling effects of water deficit and nitrogen supply on photosynthesis, WUE, and stable isotope composition in Picea asperata

Water stress and nitrogen (N) availability are the two main factors limiting plant growth, and the two constrains can interact in intricate ways. Moreover, atmospheric N depositions are altering the availability of these limiting factors in many terrestrial ecosystems. Here, we studied the combined effects of different soil water availability and N supply on photosynthesis and water-use efficiency (WUE) in Picea asperata seedlings cultured in pots, using gas exchange, and stable carbon and nitrogen isotope composition (δ 13C and δ 15N). Photosynthesis under light saturation (A sat) and stomatal conductance (g s) of P. asperata decreased as the soil moisture gradually diminished. Under severe water-stress condition, N addition decreased the A sat and g s, whereas the positive effects were observed in moderate water-stress and well-watered conditions. The effect of N addition on the intrinsic WUE (WUEi) deduced from gas exchange was associated with soil water availability, whereas long-term WUE evaluated by leaf δ 13C only affected by soil water availability, and it would be elevated with soil moisture gradually diminished. Water deficit would restrict the uptake and further transport of N to the aboveground parts of P. asperata, and then increasing δ 15N. Therefore, δ 15N in plant tissues may reflect changes in N allocation within plants. These results indicate that the effect of N enrichment on photosynthesis in P. asperata is largely, if not entirely, dependent on the severity of water stress, and P. asperata would be more sensitive to increasing N enrichment under low soil water availability than under high soil moisture.

Using climate model simulations to assess the current climate risk to maize production

The relationship between the climate and agricultural production is of considerable importance to global food security. However, there has been relatively little exploration of climate-variability related yield shocks. The short observational yield record does not adequately sample natural inter-annual variability thereby limiting the accuracy of probability assessments. Focusing on the United States and China, we present an innovative use of initialised ensemble climate simulations and a new agro-climatic indicator, to calculate the risk of severe water stress. Combined, these regions provide 60% of the world’s maize, and therefore, are crucial to global food security. To probe a greater range of inter-annual variability, the indicator is applied to 1400 simulations of the present day climate. The probability of severe water stress in the major maize producing regions is quantified, and in many regions an increased risk is found compared to calculations from observed historical data. Analysis suggests that the present day climate is also capable of producing unprecedented severe water stress conditions. Therefore, adaptation plans and policies based solely on observed events from the recent past may considerably under-estimate the true risk of climate-related maize shocks. The probability of a major impact event occurring simultaneously across both regions—a multi-breadbasket failure—is estimated to be up to 6% per decade and arises from a physically plausible climate state. This novel approach highlights the significance of climate impacts on crop production shocks and provides a platform for considerably improving food security assessments, in the present day or under a changing climate, as well as development of new risk based climate services.

Responses of pomegranate cultivars to severe water stress and recovery: changes on antioxidant enzyme activities, gene expression patterns and water stress responsive metabolites.

The biochemical and molecular responses of five commercially well-known pomegranate cultivars to severe water stress were studied. The cultivars were subjected to 14-day water stress by withholding irrigation, followed by re-watering for 7days. Results showed clear differences in metabolites contents and activities of antioxidant enzymes among various pomegranate cultivars during severe water stress and recovery. According to our results, increased accumulation of proline in pomegranate was not related to osmotic adjustment during severe water stress. Except for 'Ghojagh', leaves grown under severe water stress conditions showed symptoms of oxidative stress such as reduced chlorophyll concentration. The improved performance of 'Ghojagh' under drought stress may be associated with an efficient osmotic adjustment. The up- or down regulated expression of cytosolic glutathione reductase (cytosolic GR) and glutathione peroxidase were observed under drought conditions. Moreover, the suppressed expression of cytosolic GR was also noted. Comparatively, 'Rabab' exhibited higher antioxidant capacity and an efficient ROS-scavenging mechanism under drought stress. Lower levels of membrane lipid peroxidation in 'Ghojagh' and 'Rabab' under drought stress and the marked reduction of malondialdehyde concentration after re-watering represents that these cultivars have a good tolerance to drought stress. As a first step towards the study of the biochemical and molecular responses of pomegranate plants to water stress, this research provides new information into the mechanisms of drought tolerance in the plants.

Modulation of Brassica napus source–sink physiology through film antitranspirant induced drought tolerance amelioration that is dependent on the stress magnitude

AbstractIncrease in drought conditions during the oilseed rape (OSR) reproductive phase is predicted to occur more often in the temperate zone, leading to significant yield losses. Crop management solutions such as film antitranspirant (AT) applied at key drought‐sensitive growth stages on both wheat and oilseed rape have recently been shown to alleviate drought‐induced yield losses. However, there is a lack of information regarding potential AT effectiveness to reduce drought damage on OSR plants at different soil moisture regimes. Therefore, two similar experiments were performed in a computer‐controlled glasshouse/phenotyping centre to investigate the physiological responses of OSR to well‐watered (WW), moderate water stress (MWS), water stress (WS) and severe water stress (SWS) conditions. Stress treatments were imposed at the initiation of flowering and treated with an AT or water onto the leaf canopy. Stress limited the gas‐exchange and increased leaf temperature, leaf‐to‐air temperature, bud‐to‐air temperature and ABA concentrations which increased with stress intensity in all tissues analysed. Yield components were significantly reduced by WS and SWS treatments when compared to the WW plants. Application of AT counteracted the detrimental effect of WS and SWS by decreasing water use over the first few days of stress application thus improving relative water content and leaf water‐use efficiency, decreasing ABA accumulation in leaf and all the reproductive organs analysed (buds, flowers and pods) and avoiding bud‐to‐air temperature increases. AT application sustained pod formation and seed production under WS but only seed production under SWS conditions. These data suggest that leaf‐canopy application of AT at key phenological stages under particular magnitudes of soil moisture deficit may sustain OSR reproduction and reduce yield losses.

Influence of Vermicompost Fertilizer and Water Deficit Stress on Morpho-Physiological Features of Chickpea (Cicer arietinum L. cv. karaj)

ABSTRACTOne goal in the face of deficit water conditions is to increase growth and yield. Agro-industrial production frequently causes environmental pollution by using chemical fertilizers. In recent decades, bio-fertilizers such as vermicompost have been used as a safe alternative to chemical fertilizer. The present study considered the response of the chickpea to different combinations of vermicompost and water deficit stress in a greenhouse environment. Plant response was determined by measuring a range of morpho-physiologic parameters. The treatments were addition of 0%, 10%, 20%, and 30% of vermicompost to soil, and water deficit stress at the following levels: non-stress (100% of field capacity), moderate water stress (75% of field capacity), and severe water stress (25% of field capacity). The results showed that vermicompost had a significant effect on all traits under stress and non-stress conditions. The vermicompost treatments under non-stress conditions significantly increased plant height, number of pods, leaf area, stem and leaf dry weight, pod dry weight, chlorophyll a, carotenoid, total chlorophyll content, CO2 assimilation rate, internal CO2 concentration, and water-use efficiency over that of the control condition. The addition of 30% vermicompost under moderate and severe water stress conditions significantly increased plant height, number of pods, leaf area, leaf dry weight, carotenoids, and water-use efficiency over that of the control level. This study confirmed that vermicompost improved the morphological features, soil biological activity, and quality of the chickpea, but did not positively influence the physiological features under moderate and severe water deficit stress.

Grape Ripening Is Regulated by Deficit Irrigation/Elevated Temperatures According to Cluster Position in the Canopy.

The impact of water deficit on berry quality has been extensively investigated during the last decades. Nonetheless, there is a scarcity of knowledge on the performance of varieties exposed to a combination of high temperatures/water stress during the growing season and under vineyard conditions. The objective of this research was to investigate the effects of two irrigation regimes, sustained deficit irrigation (SDI, 30% ETc) and regulated deficit irrigation (RDI, 15% ETc) and of two cluster positions within the canopy (east- and west-exposed sides) on berry ripening in red Aragonez (Tempranillo) grapevines. The study was undertaken for two successive years in a commercial vineyard in South Portugal, monitoring the following parameters: pre-dawn leaf water potential, berry temperature, sugars, polyphenols, abscisic acid (ABA) and related metabolites. Additionally, expression patterns for different transcripts encoding for enzymes responsible for anthocyanin and ABA biosynthesis (VviUFGT, VvNCED1, VvβG1, VviHyd1, VviHyd2) were analyzed. In both years anthocyanin concentration was lower in RDI at the west side (RDIW- the hottest one) from véraison onwards, suggesting that the most severe water stress conditions exacerbated the negative impact of high temperature on anthocyanin. The down-regulation of VviUFGT expression revealed a repression of the anthocyanin synthesis in berries of RDIW, at early stages of berry ripening. At full-maturation, anthocyanin degradation products were detected, being highest at RDIW. This suggests that the negative impact of water stress and high temperature on anthocyanins results from the repression of biosynthesis at the onset of ripening and from degradation at later stages. On the other hand, berries grown under SDI displayed a higher content in phenolics than those under RDI, pointing out for the attenuation of the negative temperature effects under SDI. Irrigation regime and berry position had small effect on free-ABA concentration. However, ABA catabolism/conjugation process and ABA biosynthetic pathway were affected by water and heat stresses. This indicates the role of ABA-GE and catabolites in berry ABA homeostasis under abiotic stresses. Principal component analysis (PCA) showed that the strongest influence in berry ripening is the deficit irrigation regime, while temperature is an important variable determining the improvement or impairment of berry quality by the deficit irrigation regime. In summary, this work shows the interaction between irrigation regime and high temperature on the control of berry ripening.

People and Fresh Water Ecosystems: Pressures, Responses and Resilience

Freshwater ecosystems are central to the global water cycle, in local generation of freshwater flows, and the healthy functioning and resilience of other ecosystems. Freshwater security depends on healthy ecosystems. Current human threats to freshwater ecosystems include rapid infrastructure development and land-use change, inefficient water use and over-abstraction, and pollutants. These threats, combined with increasing demand for water resources, exacerbate the sustainable development challenge. By 2025, two-thirds of the world's population may be living in conditions of severe water stress. It is essential to find solutions that provide for the maintenance of freshwater ecosystems while meeting human needs. This paper examines responses to three pressures to freshwater ecosystems: declining ecosystem services, hydropower and urban development. It explores opportunities for improved decision-making and enhanced resilience including: better evaluation of trade-offs and interlinkages; improved monitoring; decision-making that incorporates long-term perspectives and risks; and the leveraging of crises to advance change.

Biochemical and physiological responses of Brassica napus plants to humic acid under water stress

This study examines the effects of humic acid (HA, control, 3 and 6 mg/L) on some biochemical and physiological parameters of rapeseed (Brassica napus L.) plants under different water supply conditions (60, 100, and 140 mm evaporation from class A pan). Water stress decreased chlorophyll a (Chl a) and total chlorophyll (ChlT) content in plants but proline content partly increased with increasing water stress severity. Plants treated by HA had more Chl a and ChlT content under both well and limited water conditions. Application of HA improved the PSII and peroxidase activity of rapeseed plants under all irrigation treatments. Ascorbate peroxidase activity under severe water stress condition increased by 70 and 95%, compared with that under moderate and well watering conditions, respectively. Catalase activity was 51 and 69% less under well watering than that of moderate and severe water stress conditions, respectively. The highest activity of ascorbate peroxidase was recorded in plants treated by 6 mg/L HA. HA-treated plants had 42, 8.5, and 15% more soluble protein content under well watering, moderate and severe water stress conditions, respectively, compared with control plants. Malondialdehyde increased with increasing the severity of water stress, in contrast, application of HA significantly reduced the amount of this trait under water stress conditions. It was shown that application of HA increased the activity of antioxidant enzymes, improved PSII activity and consequently decreased lipid peroxidation in rapeseed plants.

DEVELOPING A PHYSIOLOGICAL BASIS FOR MODELING PEACH CANOPY PHOTOSYNTHESIS UNDER WATER STRESS CONDITIONS

Daily leaf photosynthesis was reported to be linearly related with daily leaf PAR (photosynthetic active radiation) interception, in peach trees. This relationship was considered as a fundamental step for modeling whole peach canopy photosynthesis. However, data reporting linear relationships was obtained under non-water-stressed trees. Although commercial peach orchards are usually managed under full irrigation, reduced irrigation might become inevitable in water limited areas. Water shortage is becoming increasingly frequent in peach producing areas with Mediterranean climates. Modeling the effect of water stress, on whole canopy photosynthesis, requires studies on the effect of water stress on the relationship between daily leaf photosynthesis and daily leaf light interception. We, therefore, studied the effects of water stress on the linear relationship between daily photosynthesis and light interception in a commercial ‘Ryan’s Sun’ peach orchard. Water stress was imposed during the final stage of fruit development (50 days before harvest), because irrigation restrictions usually occur mid-summer. Under full irrigation conditions, there was a linear relationship between daily intercepted PAR and daily photosynthetic CO2 assimilation. This relationship had approximately a zero y-intercept. Under water stress conditions, the y-intercept was maintained, but there was a significant decrease in daily photosynthetic CO2 assimilation rates, at high levels of daily intercepted PAR. The higher the level of water stress, the higher the reduction in CO2 assimilation. The main consequence is that linearity between daily intercepted PAR and daily photosynthetic CO2 assimilation was not maintained under severe water stress conditions. Photosynthetic radiation use efficiency (PhRUE), for all leaves of the canopy, was similar under full irrigation conditions. However, under water stress conditions, the leaves that intercepted high values of PAR had significantly reduced PhRUE. These results can facilitate modeling the effect of water stress on whole canopy photosynthesis, in peach trees.

Effect of Arbuscular Mycorrhizal Fungi on Water Relations and Growth of Young Plum Trees under Severe Water Stress Conditions

Aims: Arbuscular mycorrhizal fungi (AMF) can mitigate plant response to severe water stress. On this basis, an experiment was carried out under field conditions to evaluate the effect of arbuscular mycorrhization, realized by a mixture of two AMF species, Rhizophagus intraradices and Funneliformis mosseae, on drought tolerance of young plum trees. Study Design: The experimental design was a criss cross with three variable factors: water regime, mycorrhization and plum variety. Place and Duration of Study: the trial was conducted during one year (2013) under field condition in experimental station Ain Taoujdate of the Regional Agricultural Research Center of Meknes, in northern Morocco. Methodology: The experiment was performed on four one year old mycorrhizal and nonmycorrhizal plum varieties submitted to two water regimes, 50% and 100% of crop evapotranspiration (ETc). Measurements have concerned vegetative growth parameters (shoot elongation, trunk growth and leaf area), water status (predawn and midday leaf water potential, Original Research Article Razouk and Kajji; IJPSS, 5(5): 300-312, 2015; Article no.IJPSS.2015.083 301 stomatal conductance and leaf relative water content) and leaf phosphorus content). Results: the young plum trees, even mycorrhized, did not tolerate water stress applied. However, plants were dependent on AMF under water stress, highly compensating its effects even at 50% of ETc. The compensatory effect of AMF was related to an increase of water potential and stomatal conductance without changing relative water content of plants. AMF also induced a significant increase of phosphorus uptake under water stress. Conclusion: it was demonstrated that AMF significantly improve water and nutrient use efficiency of young plum trees submitted to water stress amounting to 50% of ETc. The observed improvements due to AMF were considerable, suggesting possibility of adoption of this water restriction to optimize deficit irrigation of mycorrhizal plants of this rosacea under low water availability conditions.

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Currently, the use of herbicides is essential in a practical and common in agricultural areas, but efficiency of these herbicides can be compromised when applied on plants that thrive in water deficit conditions, due to low uptake and translocation of the product. Therefore, t he aim of this study was to compare the efficiency of control ACCase inhibiting herbicides applied post-emergence in plants of Eleusine indica under different soil water contents. The experiment was conducted in a greenhouse and the experimental design was completely randomized design with four replications, consisting of a 9x4 factorial, with the combination of three soil water potentials (-0.03, -0.07 and -1.5 MPa) three herbicides (fluazifop-p -butyl, haloxyfop-methyl and sethoxydim + oil) and four doses (0, 25, 50, and 100 % of the recommended dose). Herbicide application was made in plants in vegetative stage 2-3 tillers. The soil water potential was initiated in the development stage of two leaves, and the water was supplemented until the soil reaches the potential of -0.01 MPa, when it came to minimum pre-determined for each water management. The physiological parameters evaluated were: photosynthetic rate, stomatal conductance, transpiration leaf temperature and plant dry mass. The visual assessments of phytotoxicity were performed at 7 and 14 days after application. The herbicides behaved in different ways according to the used water management. In severe water stress conditions (soil moisture at 8%) only fluazifop-p-butyl herbicide achieved satisfactory control (>90%) in E. indica plants.

Yield and Water Productivity of Chickpea (<i>Cicer arietinum</i> L.) as Influenced by Different Irrigation Regimes and Varieties under Semi Desert Climatic Conditions of Sudan

A field experiment was conducted at Hudeiba Research Station Farm, located at Ed-Damer, Sudan during 2011/2012 and 2012/2013 winter seasons to investigate the effect of different irrigation regimes and varieties on chickpea (Cicer arietinum L.) yield, yield components and water productivity. The treatments include three irrigation regimes; irrigation every 10 days (I1 = full irrigation), irrigation every 15 days (I2 = moderate stress) and irrigation every 20 days (I3 = severe stress) and two varieties (Borgieg and Wad Hamid). The treatments were arranged in factorial randomized complete block design (RCBD) with 3 replications. Irrigation water being applied, grain yield, yield components (number of pods per plant, number of seeds per pod and the 100 seeds weight) and crop water productivity (CWP) and irrigation water productivity (IWP) were recorded. Results showed that the number of pods per plant, number of seeds per pod, 100-seeds weight, grain yield and irrigation water applied were significantly (p ≤ 0.001) affected by irrigation regimes. The highest values of these traits obtained with full irrigation, whereas the lowest values were recorded under severe water stress conditions. Results also indicated that, moderate and severe water stress regimes saved irrigation water by 24% and 32%, respectively compared with full irrigation. This study indicated that treatment I1 which was irrigated every 10-days did not produce the highest IWP, while treatment I2 which irrigated every 15-days gave the highest IWP. The lowest IWP occurred at severe water stress regime (I3). It could be concluded that moderate water stress might be adopted. Contrarily, the adoption of severe water stressed that produce high water savings would lead to yield losses that might be economically not acceptable. The late maturing chickpea variety of Borgieg significantly (p ≤ 0.05) out-yielded the early maturing variety Wad Hamid by 11%. Borgieg displayed the highest values of CWP and IWP.

不同生育期玉米叶片光合特性及水分利用效率对水分胁迫的响应

The field experiments of water stress and rewatering for maize were carried out using the large moving water-proof shed. The effects of water stress on the photosynthetic characteristics and water use efficiency of maize in different growth stages were revealed by the photosynthetic data of leaves. The results showed as followed: water stress led to the decrease of the values of photosynthesis rate,transpiration rate and stomatal conductance and the earlier emergence of peak value of the daily variation of photosynthesis. Compared with the control,the transpiration rate,photosynthesis rate and stomatal conductance of maize leaves were decreased significantly,in order to adapt to the drought under the water stress condition so that the water use efficiency was improved and the difference of water use efficiency between the water stress and normal condition was shrunk. Under moderate or severe water stress condition,the decrease of water use efficiency was less than that of the photosynthesis,transpiration rate and stomatal conductance of maize leaves and the water use efficiency was sometimes even higher than that of the normal environment. The water use efficiency of maize leaves was improved under moderate water stress so that the ability of leaf using water was enhanced and maize better resisted drought environment; the subsequent effects of water stress on photosynthesis and transpiration and water use efficiency was obvious. After waterstress and rewater treatments,the inhibition of photosynthesis of maize leaves was still continued. Longer time and more severe the water stress was,the more nonreversible the photosynthesis of maize leaves might be. The inhibition of water stress on photosynthesis of maize leaves was more difficult to recovery from the jointing to silk stage than from three leaf to jointing stage.

Changes in Protein Expression in Peanut Leaves in the Response to Progressive Water Stress.

This investigation was carried out at the Department of Plant Science and Agricultural Resources, Khon Kaen University in the rainy season of 2011. The objective of this study was to identify proteins in leaves of drought-susceptible peanut plants when regulated by progressive water stresses. The drought-susceptible peanut plants of Khon Kaen 4 cultivar were grown in pots under controlled environment. At day 30 after seed emergence, the plants were subjected to stress conditions for 5 and 6 days. The results showed that withheld water supply for 5 and 6 days gave moderately and severely water stresses, respectively. Under moderate water stress conditions, two up-regulated and eight down-regulated proteins were attained. The up-regulated proteins were striated fibre assembling and flap endonuclease 1. The down-regulated proteins were peptidyl-prolyl cis-trans isomerase FKBP4, tRNA(Ile)-lysidine synthase, chloroplastic, chloroplastic thioredoxin F-type, cytidinedeaminase 7, ALF domain class transcription factor, nudix hydrolase 8, pentatricopeptide repeat super-family protein, putative and ribulose-1,5-bisphosphate carboxylase/oxygenase, a large sub-unit. Under severe water stress conditions, two proteins, i.e., tRNA(Ile) lysidine synthase, chloroplastic and ALF domain class transcription factor did not change their relative abundance significantly where it indicated drought acclimation. The remaining proteins displayed significant changes and the changes were the same as those found in the peanut leaves when deprived water for 5 days. Up-regulated proteins are responsible for alleviating oxidative damages to plant genome and mediating plants responsive to the environmental factors in providing mechanical support, barriers and a rapid transport route. Down-regulated proteins were associated with drought susceptibility of the Khon Kaen 4 peanut plants.