Relationship between water use efficiency (WUE) and production of different wheat genotypes at soil water deficit

Through 2-year field experiments, 7 wheat genotypes were better in their field yield. These 7 wheat genotypes and other 3 wheat species, which are being popularized on a large scale in different locations of China, were selected as experimental materials for the sake of measuring their difference in WUE and production and comparing their relationship at soil water deficits, future more, providing better drought resistance lines and theoretical guide for wheat production and practices and exploring anti-drought physiological mechanisms of different wheat genotypes. Under the condition of 3 soil–water–stress treatments (75% field capacity (FC), 55% FC, 45% FC, named level 1, level 2 and level 3, respectively), pot experiments for them were conducted and the related data were collected from their life circle. The main results were as followed: (1) according to the selected soil stress levels, water use efficiency (WUE) of 10 different wheat genotypes was divided into two groups (A and B); group A included genotypes 2, 3, 4, 5, 6, 7, 8, whose WUE decreased basically from level 1 to level 3 and reached individual peak of WUE at level 1; Group 2 included genotypes 1, 9, 10, whose WUE reached their individual peak at level 2; (2) based on total water consumption through all life circle, genotypes 1, 4, 8, 9 had lower water consumption (TWC) at level 1, genotypes 2, 3, 5, 6, 7 lower TWC at level 2, genotype 10 lower TWC at level 3; (3) at level 1, genotypes 2, 3, 4, 5, 6, 7, 8 had higher grain weight of single spike (GWSS), genotypes 1, 9, 10 better GWSS at level 2, which was in good line with individual WUE of different wheat genotypes; (4) by analyzing the indexes related to examining cultivars, it was found that genotypes 1, 2, 3, 4, 5, 6, 9, 10 had longer plant length (PL), spike length (SL), bigger grain number (GN) except genotypes 7 and 8 at level 1, RL was in better line with genotypes 1, 2, 3, 8, 9, 10, but not in the other genotypes at level 1.     

Osmotic regulation of 10 wheat (Triticum aestivum L.) genotypes at soil water deficits

Drought is a worldwide problem, seriously influencing plant (crop) productivity. Wheat is a stable food for 35% of the world population, moreover about 60% of land area on the globe belongs to arid and semi-arid zone. Wheat drought resistance is a multi-gene-controlling quantitative character and wheat final production in field is realized mainly by physiological regulation under the condition of multi-environmental factor interaction. Exploring drought resistance physiological mechanisms for different wheat genotypes is of importance to finding new drought resistance gene resources and conventional breeding and the basis for wheat drought resistance biotechnological breeding and platform. Osmotic adjustment regulation is the main component for physiological machinery of wheat drought resistance. By pot-cultivating experiments, investigation of osmotic adjustment comparison for 10 wheat genotypes at soil water deficits (75% FC, 55% FC, 45% FC, respectively), was conducted. The main results were as followed: (1) K⁺ content in 10 wheat genotypes at three levels of soil water stress and at the same soil water deficit was very different. Five of these 10 wheat genotypes had higher K K⁺ content under the condition of 75% FC. (2) Five of these 10 wheat genotypes possessed greater soluble sugar content at 55% FC soil water level. (3) Proline (Pro) content in five wheat genotypes was higher at 75% FC. (4) Five of these 10 wheat genotypes had lower malondialdehyde (MDA) content at 45% FC at seedling stage. Osmotic adjustment of wheat different genotypes was discussed in terms of different content of osmotic solutes.     

Regulation of photosynthesis, fluorescence, stomatal conductance and water-use efficiency of cowpea (Vigna unguiculata [L.] Walp.) under drought

Drought is the major abiotic stress factor that causes extensive losses to agriculture production worldwide. The objective of this study was to evaluate the dynamics of photosynthesis and water-use efficiency parameters in 15 cowpea genotypes under well-watered and drought condition. Photosynthesis (A) and chlorophyll fluorescence (Fv'/Fm') declined linearly with decreasing soil water content whereas intrinsic water-use efficiency (WUE) increased under drought stress, suggesting stomatal regulation was a major limitation to photosynthesis. However, under increasing drought conditions, increase in ratio of intercellular CO(2) to ambient CO(2) concentrations along with reduced WUE showed the role of non-stomatal limitation of photosynthesis. The resistant nature of Fv'/Fm' and electron transport rate under drought appeared to be important mechanisms for photoinhibition protection under drought stress. Oxidative stress was apparent due to drought-induced reduction in total chlorophyll and carotenoid which was accompanied with increased leaf wax contents. The accumulation of proline appeared to be in response of drought injury rather than a drought tolerance mechanism. A clear separation based on the genotypes site of origin among the genotypes for drought tolerance could not be established when analyzed using principal component analysis. The identified genotypes and physiological traits from this study may be useful for genetic engineering and breeding programs integrating drought adaptation in cowpea.     

On evolution and perspectives of bio-watersaving

As shortage in water resources is a fact, bio-watersaving becomes one hot topic at present. The concept of bio-watersaving has been developed from agronomic watersaving to physiological watersaving then to gene watersaving. The definition of bio-watersaving is yielding more agricultural productions under the same water condition by exploiting the physiological and genetic potential of organisms themselves. There are two aspects in bio-watersaving: one is managing crop system and watersaving irrigation according to the drought characteristics and physiological water need of plants; the second is breeding new varieties with good drought resistance and high water use efficiency (WUE) and high yield and good quality traits, through exploiting new drought resistance genes and high WUE genes with the aid of biotechnology. Gene watersaving is the base for physiological watersaving, so gene watersaving has the biggest potential to be exploited in future, and will play an important role in high use efficiency of water and soil resources, and agricultural sustainable development in China and the globe.     

Investigation on dynamic changes of photosynthetic characteristics of 10 wheat (Triticum aestivum L.) genotypes during two vegetative-growth stages at water deficits

Drought is a worldwide problem, seriously influencing plant (crop) productivity. Wheat is a stable food for 35% of the world population, and moreover, about 60% of land area on the globe belongs to arid and semiarid zone. Wheat drought resistance is a multi-gene controlling quantitative character and wheat final production in field is realized mainly by physiological regulation under the condition of multi-environmental factor interaction. Exploring drought resistance physiological mechanisms for different wheat genotypes is of importance to finding new drought resistance gene resources and conventional breeding, and the basis for wheat drought resistance biotechnological breeding and platform. Photosynthesis is the main component for physiological machinery of wheat assimilates conversion and wheat production. Investigation on photosynthetic characteristics of different wheat genotypes at soil water deficits also has other implications for refine physiological regulation of photosynthesis in fields and field management of crops in arid and semiarid areas. By pot-cultivating experiments, investigation of photosynthesis for 10 wheat genotypes at seedling stage and tillering stage at soil water deficits (75%FC, 55%FC and 45%FC, respectively) was conducted. The main results were as followed: developmental stages influenced wheat photosynthesis greatly and tillering stage played more roles; there were significant difference in the main photosynthetic parameters, photosynthesis rate (Photo), stomatal conductance (Cond) and transpiration rate (Tr), among 10 wheat genotypes; general photosynthesis and drought resistance in different wheat genotypes was related much to their domesticated origin soil water environment and selected generations and there was a photosynthetic threshold effect in terms of different wheat genotypes at soil water deficits.     

Potential effects of biochar application on mitigating the drought stress implications on wheat (Triticum aestivum L.) under various growth stages

Drought is the main abiotic stress that severely reduces wheat yield across the globe. To cope up this situation, use of organic amendments is the best option. Biochar is an organic soil amendment that is used to improve soil carbon, organic contents, improve water holding capacity of soil, enhance soil fertility and maintain desired soil. Present study was carried out under semi-arid climatic conditions to mitigate the adverse effects of drought at critical wheat growth stages i.e., tillering (DTS), flowering (DFS) and grain filling stage (DGFS) by using three biochar treatments viz. B₀ = Control, B₁ = 27.88 g kg⁻¹ and B₂ = 37.18 g kg⁻¹. Results revealed that drought stress negatively affected the growth and yield attributes of wheat at all critical growth stages, while, grain filling stage was found the most sensitive stage resulted severe yield reduction. However, biochar application significantly mitigated the detrimental effects of drought by improving number of fertile tillers (19.50%), spike length (6.52%), number of grains per spike (3.07%), thousand grain weight (6.42%), biological (9.43%) and economic yield (13.92%) as compared to control treatment. Moreover, biochar significantly improved water use efficiency and physiological attributes of drought stressed wheat. Principal component analysis linked different scales of study and demonstrated the potential of physio-biochemical traits to explain the wheat yield variations under drought condition with response to biochar application. In crux, biochar application (37.18 g kg⁻¹) can be used as an effective stratagem to achieve improved wheat grain yield through mitigating the adverse effects of drought stress.     

Effect of water deficits on the activity of anti-oxidative enzymes and osmoregulation among three different genotypes of Radix Astragali at seeding stage

Water is a key factor influencing the yield and quality of crops. Plants mainly adapt to water deficits by biochemical changes and osmotic adjustment (OA). Research on drought tolerance of field crops has been done intensively, but there is little work to be done in medical plants. Traditional Chinese medicine (TCM) has a long history of several thousand years. TCM is playing an important role in daily life in China and applied widely in clinical experience on the globe. More and more wild medical plants are cultivated and introduced. It is known that ecological and environmental conditions are vital to cultivation and efficient component accumulation of medical plants. This study is concerned about biochemical changes of three genotypes of Radix Astragali during water deficient periods and we evaluated the relative ability of their drought tolerance on the above basis. We analyzed the effect of soil water deficits on antioxidant enzymes activity and osmoregulation substances in R. Astragali leaves of three genotypes collected on day 0, 5, 10, 15, 20 and 25 after onset of water deprivation. Under water deficient conditions, biochemical changes include protecting enzyme system, for instance superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD). Osmoregulation matters include proline (Pro) and soluble sugar. Antioxidant enzyme activities and Pro, and soluble sugar content correlated between water deficient degree and time course. Antioxidant enzyme activities increased before 20 days, then decreased at the end of experiment. Proline content increased gradually, and soluble sugar content reached the highest on day 20. The order of the ability of drought tolerance in three genotypes of R. Astragali is Mongolia>Wild>Hebei by using index of drought tolerance. The research results are instructive for cultivation and introduction of R. Astragali under different conditions of water status.     

Investigation on the relationship between leaf water use efficiency and physio-biochemical traits of winter wheat under rained condition

Different statistical methods and path analysis were used to study the relationship between leaf water use efficiency (WUE) and physio-biochemical traits for 19 wheat genotypes, including photosynthesis rate (P_n), stomatal conductance (g_s), transpiration rate (T_r), intercellular concentration of carbon oxide (C_i), leaf water potential (Ψ_w), leaf temperature, wax content, leaf relative water content (RWC), rate of water loss from excised-leaf (RWL), peroxidase (POD) and superoxide dismutase (SOD) activities. The results showed that photosynthesis rate, stomatal conductance and transpiration rate were the most important leaf WUE variables under rainfed conditions. Based on the results of five statistical analyses, it is reasonable to assume that high leaf WUE wheat under the rained could be obtained by selecting breeding materials with high photosynthesis rate, low transpiration rate and stomatal conductance.     

Effect of paclobutrazol on water stress amelioration through antioxidants and free radical scavenging enzymes in Arachis hypogaea L

An investigation was carried out to find out the extent of changes occurred in groundnut (Arachis hypogaea L.) cultivars in response to paclobutrazol (PBZ) treatment under water deficit stress. Two groundnut cultivars namely ICG 221 and ICG 476 were used for the study. Individual treatment with PBZ and drought stress showed an increase in ascorbic acid, -tocopherol and reduced glutathione, superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) activities. PBZ with drought stressed plants maintained higher levels of antioxidant and scavenging enzymes. Significant differences were observed between cultivars and treatments. These results suggests that the adverse effects of water stress can be minimized by the application of PBZ by increasing the antioxidant levels and activities of scavenging enzymes such as SOD, APX and CAT. The Cv. ICG 221 appears to be more tolerant to water stress than the ICG 476.     

Substrate Dependency and Effect of Xylanase Supplementation on Enzymatic Hydrolysis of Ammonia-Treated Biomass

Pretreatment based on aqueous ammonia was investigated under two different modes of operation: soaking in aqueous ammonia and ammonia recycle percolation. These processes were applied to three different feedstocks with varied composition: corn stover, high lignin (HL), and low lignin (LL) hybrid poplars. One of the important features of ammonia-based pretreatment is that most of the hemicellulose is retained after treatment, which simplifies the overall bioconversion process and enhances the conversion efficiency. The pretreatment processes were optimized for these feedstocks, taking carbohydrate retention as well as sugar yield in consideration. The data indicate that hybrid poplar is more difficult to treat than corn stover, thus, requires more severe conditions. On the other hand, hybrid poplar has a beneficial property that it retains most of the hemicellulose after pretreatment. To enhance the digestibility of ammonia-treated poplars, xylanase was supplemented during enzymatic hydrolysis. Because of high retention of hemicellulose in treated hybrid poplar, xylanase supplementation significantly improved xylan as well as glucan digestibility. Of the three feedstocks, best results and highest improvement by xylanase addition was observed with LL hybrid poplar, showing 90% of overall sugar yield.     

Pseudomonas fluorescens enhances biomass yield and ajmalicine production in Catharanthus roseus under water deficit stress

The effect of plant growth promoting rhizobacteria (PGPR) like Pseudomonas fluorescens on growth parameters and the production of ajmalicine were investigated in Catharanthus roseus under drought stress. The plants under pot culture were subjected to 10, 15 and 20 days interval drought (DID) stress and drought stress with Pseudomonas fluorescens at 1mgl(-1) and 1mgl(-1)Pseudomonas fluorescens alone from 30 days after planting (DAP) and regular irrigation was kept as control. The plants were uprooted on 41 DAS (10 DID), 46 DAS (15 DID) and 51 DAS (20 DID). Drought stress decreased the growth parameters and increased the ajmalicine content. But the treatment with Pseudomonas fluorescens enhanced the growth parameters under drought stress and partially ameliorated the drought induced growth inhibition by increasing the fresh and dry weights significantly. The ajmalicine content was again increased due to Pseudomonas fluorescens treatment to the drought stressed plants. From the results of this investigation, it can be concluded that, the seedling treatments of native PGPRs can be used as a good tool in the enhancement of biomass yield and alkaloid contents in medicinal plants, as it provides an eco-friendly approach and can be used as an agent in water deficit stress amelioration.     

Intrinsic bioremediation of gas condensate hydrocarbons

Condensate liquids have been found to contaminate soil and ground water at two gas production sites in the Denver Basin operated by Amoco Production Co. These sites have been closely monitored since July 1993 to determine whether intrinsic aerobic or anaerobic bioremediation of hydrocarbons occurs at a sufficient rate and to an adequate end point to support a no-intervention decision. Ground water monitoring, soil gas analysis, and analysis of soil cores suggest that bioremediation is occurring at these sites by multiple pathways, including aerobic oxidation, sulfate reduction, and methanogenesis. Results of over two years of monitoring of ground water and soil chemistry at these sites are presented to support this conclusion.

     

Alleviation of adverse effects of drought stress on growth and some potential physiological attributes in maize (Zea mays L.) by seed electromagnetic treatment

Effects of varying preseed magnetic treatments on growth, chlorophyll pigments, photosynthesis, water relation attributes, fluorescence and levels of osmoprotectants in maize plants were tested under normal and drought stress conditions. Seeds of two maize cultivars were treated with different (T0 [0 mT], T1 [100 mT for 5 min], T2 [100 mT for 10 min], T3 [150 mT for 5 min] and T4 [150 mT for 10 min]) electromagnetic treatments. Drought stress considerably suppressed growth, chlorophyll a and b pigments, leaf water potential, photosynthetic rate (A), stomatal conductance (g(s)) and substomatal CO(2) concentration (C(i)), while it increased leaf glycinebetaine and proline accumulation in both maize cultivars. However, pretreated seeds with different magnetic treatments significantly alleviated the drought-induced adverse effects on growth by improving chlorophyll a, A, E, g(s), C(i) and photochemical quenching and nonphotochemical quenching, while it had no significant effect on other attributes. However, different magnetic treatments negatively affected the g(s) and C(i) particularly in cv. Agaiti-2002 under drought stress conditions. Of all magnetic treatments, 100 and 150 mT for 10 min were most effective in alleviating the drought-induced adverse effects. Overall, preseed electromagnetic treatments could be used to minimize the drought-induced adverse effects on different crop plants.     

Investigation on the relationship of proline with wheat anti-drought under soil water deficits

Proline (content) is closely with plant anti-drought, especially under soil water deficits. Many reports from crops and other plants have proved this. Wheat is the second important crop on the globe, whose research in this aspect of importance for food quality, safety, and yield in field. The related difference in physiological indicators and proline content for different soil water treatments among wheat with different genotypes is not clear, which has limited deep study of wheat anti-drought molecular biology and related anti-drought biotechnological breeding. Our current study was focused on the physiological relationship of proline and different genotype wheat anti-drought under soil water deficits. Main results showed that different wheat genotype had different soil water stress threshold. Pro content had closed relationship with soil water stress threshold and wheat anti-drought. Developmental course also impacted Pro content for different wheat genotypes.     

Length-of-stain indicator tubes for the determination of metals in water and solutions

 Indicator tubes have been proposed for the determination of heavy metals in solutions. Preparation procedures for indicator powders based on noncovalent modifications of reversed-phased silica gel sorbents by analytical reagents have been developed. The effects of pH of the sample, the capacity of the sorbent on the reagent, the flow rate, and the diameter of an indicator tube on the length of the colored zone have been studied. Procedures for the determination of Co(II), Fe(II, III), Cu(II), Cd, and the total content of heavy metals in water and solutions have been elaborated. The procedures have been used to analyze natural and waste waters, soil extracts, and industrial solutions. Received: 11 October 1995 / Revised: 7 June 1996 / Accepted: 12 July 1996     

Growth and production of buckwheat (Fagopyrum esculentum) treated with reduced, ambient, and enhanced UV-B radiation

The effect of enhanced UV-B radiation on buckwheat (Fagopyrum esculentum Moench. variety 'Darja'), an important high elevation crop, was studied in order to estimate its vulnerability in changing UV-B environment. Plants were grown in outdoor experiments from July to October under reduced and ambient UV-B levels, and an UV-B level simulating 17% ozone depletion in Ljubljana. During the development the following parameters were monitored: light saturated photosynthetic activity, transpiration, potential and effective photochemical efficiencies of photosystem II, the contents of photosynthetic pigments and methanol soluble UV-B absorbing compounds. At the end of the experiment, growth rate and production of seeds were estimated. In the following growth season the seeds collected from plants exposed to different UV-B treatments were tested for germination capacity. Total UV-B absorbing compounds during plant development were increased by UV-B radiation, photosynthetic pigments (chlorophyll a and b and carotenoids) decreased. Photosynthetic rate was lowered in an early stage of development. UV-B treatment resulted in the increase in the transpiration rate and consequently the decrease in water use efficiency (WUE). The disturbances in water economy and in photosynthesis affected the reproduction potential negatively; the production of seeds in plants cultivated under ambient and enhanced UV-B was 57 and 39% of the production of specimens treated with reduced UV-B, respectively. The germination of seeds collected from treated plants revealed on average about 95% success, independently of the treatment, but the time needed for germination was the shortest for seeds developed under enhanced UV-B level treatment. Enhanced UV-B radiation affected water relations and production of buckwheat, but not the potential of seeds for germination.     

Deterioration of polyethylene pipes exposed to water containing chlorine dioxide

Chlorine species used as disinfectants in tap water have a deteriorating effect on many materials including polyethylene. There are only very few scientific reports on the effect on polyethylene pipes of water containing chlorine dioxide. Medium-density polyethylene pipes stabilized with hindered phenol and phosphite antioxidants were pressure tested with water containing 4 ppm chlorine dioxide at 90 °C and pH = 6.8 as internal medium. The stabilizers were rapidly consumed towards the inner pipe wall; the rate of consumption was four times greater than in chlorinated water (4 ppm, pH = 6.8) at the same temperature. The depletion of stabilizer occurred far into the pipe wall. A supplementary study on a polymer analogue (squalane) containing the same stabilizer package showed that the consumption of the phenolic antioxidant was 2.5 times faster when exposed water containing chlorine dioxide than on exposure to chlorinated water. The subsequent polymer degradation was an immediate surface reaction. It was confirmed by differential scanning calorimetry, infrared spectroscopy and size exclusion chromatography that in the surface layer which came into contact with the oxidising medium, the amorphous component of the polymer was heavily oxidized leaving a highly crystalline powder with many carboxylic acid chain ends in extended and once-folded chains. Scanning electron microscopy showed that propagation of cracks through the pipe wall was assisted by polymer degradation.