Water relations and yield of wheat (Triticum aestivum L.) exposed to interactions of drought and fungal root diseases (Rhizoctonia and Pythium)

A pot experiment investigated the effects of root diseases (Pythium and Rhizoctonia) under drought conditions at either tillering or anthesis stages on the water-use efficiency (WUE), water relations, and yield components of wheat cultivars Janz and Mulgara. The pathogens reduced transpiration in Janz during drought at tillering and in both cultivars during the period of recovery after drought at anthesis. However, the pathogens did not affect WUE. WUE did not differ between well-watered plants and those droughted at tillering but it was reduced by 80% by drought at anthesis. Un-infected plants of cultivar Janz subjected to drought at tillering had a higher total water potential (Ψ_w) and osmotic potential (Ψ_s) than diseased plants. However, Ψ_s of un-inoculated plants that were droughted at anthesis was lower than diseased plants in the period following anthesis. Yield components were significantly higher in well-watered than droughted plants and higher in cv. Mulgara than cv. Janz. The pathogens affected transpiration during tillering, but not at later stages, when roots developed beyond the inoculation point. Although the pathogens caused damage to the roots, the effects on water relations parameters were minor. This suggests that wheat can tolerate moderate levels of these root diseases under drought.     

Foliar application of silicon at different growth stages alters growth and yield of selected wheat cultivars

To evaluate the response of some selected wheat cultivars to silicon application at different growth stages under drought stress, an experiment was carried out in the greenhouse of College of Agriculture, Shiraz University, Iran, during 2012 using a completely randomized factorial design with four replications. Experimental treatments included drought stress (100% F.C. as control and 40% F.C. as drought) and foliar application of 6 mM sodium silicate (control, application at mid tillering stage, at anthesis stage, and application at tillering + anthesis stages) and wheat cultivars (Sirvan and Chamran, relatively drought-tolerant, and Shiraz and Marvdasht, drought-sensitive cultivars). Drought stress significantly reduced chlorophyll content, leaf area, relative water content, grains per spike, 1000-grain weight, grain yield and biomass of all wheat cultivars. Furthermore, drought stress increased electrolyte leakage of the flag leaves of all cultivars. In contrast, foliar-applied silicon significantly increased these parameters and reduced electrolyte leakage. Furthermore, highest positive influence of silicon application was observed at combined use of silicon both at the tillering + anthesis stages in wheat plants under both stress and non-stress conditions. Significant differences were found in physiological responses among wheat cultivars. The drought tolerant cultivars (Sirvan and Chamran) had significantly higher growth and yield than those of drought sensitive cvs. Shiraz and Marvdasht under drought stress. In conclusion, foliar application of silicon especially at the tillering + anthesis stages was very effective in promoting resistance in wheat plants to drought conditions by maintaining cellular membrane integrity and relative water content, and increasing chlorophyll content.     

Growth,morphological and yield responses of irrigated wheat (Triticum aestivum L.) genotypes to water stress

Water shortages is a major constraint in wheat production in South Africa. It is important therefore to assist irrigated wheat farmers to identify water stress tolerant growth stages in irrigated wheat genotypes. This study evaluated new wheat genotypes for water stress at different growth stages. An 8 (genotypes) × 2 (water treatments) × 3 (growth stages) factorial experiment was laid out in a randomised complete block design with three replicates. The results indicated that plant height was not affected (p > .05) by water stress at tillering and grain filling. Water stress imposed at the tillering stage reduced the number of fertile tillers (p < .05) in susceptible genotypes while at the flowering and grain filling stages all genotypes were tolerant (p > .05). Aboveground biomass was only affected (p < .05) by water stress imposed at the tillering stage. Water stress reduced grain yield on the genotypes where stress was imposed at the tillering stage (p < .05); whereas when stress was imposed at flowering and grain filling the grain yield was not reduced (p > .05). This study provided evidence to suggest that most genotypes were tolerant to water stress at the flowering and grain filling stages.     

Azospirillum strains isolated from roots and rhizosphere soil of wheat (Triticum aestivum L.) grown under different soil moisture conditions

The present study deals with the isolation and characterization of Azospirillum strains isolated from roots and rhizosphere soil of wheat (at tillering and anthesis stages) plants grown under different moisture regimes in the field and in pots. The survival of Azospirillum isolates from plants of irrigated field and those from well-watered pots was higher than that of Azospirillum strains isolated from roots and rhizosphere soils of plants grown under arid and semiarid (14–8% soil moisture) field conditions and under water-stressed (8% soil moisture) conditions in pots. On the basis of carbon/nitrogen source utilization, the Azospirillum strains isolated from wheat under field and pot conditions were grouped in three groups. The unweighted pair group method with arithmetic means cluster analysis based on random amplification of polymorphic DNA showed that two groups of Azospirillum were similar. The strains isolated from plants (at tillering stage) grown under low moisture conditions either in pots or in field were genetically similar to strains isolated from plants grown under well-watered conditions in both pots and field. Inoculation of wheat with isolates from water-stressed plants induced tolerance to water stress in inoculated plants. Isolates from water-stressed conditions exhibited lower production of indole acetic acid, gibberellic acid, and trans zeatin riboside but a higher production of abscisic acid.     

Physiological responses of irrigated wheat (Triticum aestivum L.) genotypes to water stress

The recent drought in South Africa has reduced the production of both dryland and irrigated wheat. This study evaluated physiological traits of irrigated wheat genotypes in response to water stress (WS) imposed at different growth stages. A 8?×?2?×?3 [(genotypes)?×?(water treatmets; stresses and non-stressed)?×?(growth stages; tillering, flowering and grain filling)] factorial experiment based on a randomised complete block design with three replicates was conducetd. In general, the rate of photosynthesis was unaffected by WS except for genotypes LM43 at tillering and LM98 at grain filling. Stomatal conductance (SC) and transpiration rate (Tr) followed the same treand except for genotype LM35 which reduced its SC and Tr significantly at grain filling. Instantaneous waster use efficiency (IWUE) of genotype LM35 and LM57 was unaffected (p?>?0.05) by WS at tillering but at flowering stage it was affected. However, at grain filling IWUE was affected (p?<?0.05) in genotypes LM35, ML57, LM79 and LM 98. The relative water content was unaffected at tillering except for LM35 and LM47 genotypes whereas at flowering LM57, ML79, LM83 and LM98 were affected. These results indicate some degree of drought tolerance of these genotypes at different growth stages.     

Alleviation of drought stress in winter wheat by late foliar application of zinc,boron, and manganese

In many regions, drought during flowering and grain‐filling inhibits micronutrient acquisition by roots resulting in yield losses and low micronutrient concentrations in cereal grains. A field and a greenhouse experiment were conducted to study the effect of foliar applications of zinc (Zn), boron (B), and manganese (Mn) at late growth stages of winter wheat (Triticum aestivum L.) grown with or without drought stress from booting to maturity. Foliar applications of Zn, B, and Mn did not affect grain yield in the absence of drought. However, under drought, foliar application of Zn and B in the field increased grain yield (15% and 19%, respectively) as well as raising grain Zn and B concentration, while Zn and Mn sprays in the greenhouse increased grain yield (13% and 10%, respectively), and also increased grain Zn and Mn concentrations. Furthermore, under drought stress both in the field and greenhouse experiment the rate of photosynthesis, pollen viability, number of fertile spikes, number of grains per spike, and particularly water‐use efficiency (WUE) were increased by late foliar application of micronutrients. These results indicate that by increasing WUE foliar application of Zn, B, and Mn at booting to anthesis can reduce the harmful effects of drought stress that often occur during the late stages of winter wheat production. These findings therefore are of high relevance for farmers' practice, the extension service, and fertilizer industry.     

Perturbation of nutrient source–sink relationships by post‐anthesis stresses results in differential accumulation of nutrients in wheat grain

Mineral nutrients in grains act as a source of nutrients in human diets, in which deficiencies of key minerals including calcium, magnesium, copper, iron, and zinc have prompted efforts to increase their concentrations in the edible portions of staple grain crops. Wheat (Triticum aestivum L.) crops in many regions often suffer abiotic stresses such as drought, extreme heat or frost during grain filling, which affect mineral source–sink relationships. We hypothesized that these stresses would have nutrient‐specific impacts on grain nutrient concentrations due to differences among nutrients in phloem mobility, post‐anthesis uptake and grain loading patterns. Nutrient loading patterns into wheat grains were investigated in two wheat cultivars in the field by sequentially harvesting tagged ears and analyzing tissues for key nutrients. In addition, the impact of perturbed source–sink relations during grain filling on nutrient loading was investigated by inducing post‐anthesis drought /floret abortion in a glasshouse study. Over 90% of Ca and around 70% of Na, K, and Mg accumulated in both wheat cultivars in the field during the first 14 d of grain development. The concentrations of micronutrients (Mn, Fe, Cu and Zn), Mg and P in grains generally increased when florets were aborted, and were unchanged under drought stress, while concentrations of Ca and K were highest under drought stress and lowest under the 66% floret abortion treatment. The observed changes in grain nutrient concentrations from post‐anthesis drought/floret abortion could not be fully explained by nutrient‐specific differences in phloem mobility, post‐anthesis uptake and grain loading patterns. This study will inform future research to define the precise roles of individual nutrients within developing grains and to fully understand the observed variations in grain nutrient concentrations due to source/sink modifications.     

Evaluation of assimilate remobilization and yield of wheat cultivars under different irrigation regimes in an arid climate

To investigate the effects of irrigation regimes on assimilate remobilization, water use efficiency (WUE), relative water content (RWC), photosynthesis and yield of five wheat cultivars, a field experiment was conducted at Shiraz University during the 2008 and 2009 growing seasons. The experimental design was a randomized complete block and treatments were arranged as split-plot in three replicates. There were four levels of water regime including well-watered [irrigation based on 100% field capacity (FC)], excess watered (125% FC), mild drought (75% FC) and severe drought (50% FC) stress, and four bread wheat cultivars (Shiraz, Bahar, Pishtaz and Sistan) and a durum wheat (Yavaros). In all cultivars, progressed leaf senescence at 30 days after anthesis (DAA), was associated with a reduction in chlorophyll content. The reduction was more pronounced in Shiraz and Yavaros than Pishtaz and Sistan. With increasing temperature and remobilization of assimilate to grain, net photosynthesis and stomatal conductance were decreased significantly at 18 DAA compared with 8 DAA. Sistan and Pishtaz cultivars maintained higher RWC than sensitive cultivars of Shiraz and Yavaros under drought stress. The higher WUE in Pishtaz and Sistan was attributed to the effectiveness of a small amount of water in alleviating severe stress during the sensitive stages of growth. Under mild drought stress, controlled soil drying could enhance remobilization efficiency of assimilates in Pishtaz and Sistan and under severe drought, these cultivars had the highest grain yield compared with the other cultivars. Reduction of assimilates remobilization to the grain and 1000-grain weight, caused lower grain yield in Shiraz under severe drought. Overall, controlled soil drying in Sistan and Pishtaz might result in better mobilization of pre-stored assimilates to the grain in arid areas, where a rapid depletion of water resources is threatening crop production.     

花后渍水对不同耐渍型冬小麦籽粒灌浆特性的影响

江汉平原冬小麦中后期常遭受涝渍灾害,为明确花后渍水对冬小麦籽粒灌浆进程的影响,以郑麦9023（耐渍型）和扬麦20（敏感型）2个小麦品种为研究对象,利用灌排可控的测坑模拟冬小麦花后不同天数（5、9、13和17 d）的渍水胁迫,应用Richards模型对冬小麦籽粒灌浆进程进行了模拟,在此基础上分析各籽粒灌浆参数与渍水天数的关系。结果表明：花后渍水5、9、13和17 d,郑麦9023（耐渍型）分别减产10.84%、19.51%、25.93%和36.52%,扬麦20（敏感型）分别减产14.25%、25.84%、37.26%和47.84%。导致冬小麦减产的主要原因是千粒质量降低,花后渍水天数每增加1 d,冬小麦郑麦9023和扬麦20千粒质量分别降低0.961和0.996 g。Richards方程能极显著模拟花后渍水冬小麦籽粒灌浆过程,拟合方程决定系数均在0.99以上。对耐渍型冬小麦,花后渍水主要显著缩短活跃灌浆期,且主要是显著缩短籽粒灌浆快增期和缓增期的持续天数;对敏感型冬小麦,花后渍水主要显著降低籽粒灌浆三阶段的灌浆速率。花后渍水增加1 d,郑麦9023籽粒活跃灌浆期缩短0.827 d,籽粒灌浆快增期、缓增期灌浆持续天数分别缩短0.492、0.963 d,扬麦20单粒最大灌浆速率降低0.046 mg/d、单粒平均灌浆速率降低0.032 mg/d,籽粒灌浆渐增期、快增期和缓增期单粒灌浆速率分别降低0.011、0.040和0.010 mg/d。研究可揭示花后渍水致使冬小麦减产的影响过程,为冬小麦涝渍灾害防控提供理论支撑。     

硅对干旱胁迫下小麦幼苗生长及光合参数的影响

采用溶液培养试验,以两个抗旱性不同的小麦品种:低抗的扬麦9号(Yangmai.9)和高抗的豫麦18(Yumai.18)为材料,用PEG6000(聚乙二醇6000,渗透势约为-0.589MPa)模拟干旱胁迫条件,研究了硅对干旱胁迫下小麦幼苗生长、光合作用及可溶性糖含量的影响。结果表明,干旱胁迫条件下,小麦幼苗的生长和光合作用显著受到抑制,加硅处理能有效地提高干旱胁迫条件下小麦幼苗的生长状况及光合作用,且1.0.mmol/L.Si处理的效果优于0.1mmol/L.Si处理。与不加硅处理相比,干旱胁迫条件下加硅处理后,小麦幼苗的鲜干重、叶片可溶性蛋白含量、净光合速率(Pn)、蒸腾速率(Tr)、水分利用率(WUE)和气孔限制值(Ls)均显著升高,叶绿素含量也有一定程度的升高;而气孔导度(Gs)和细胞间隙CO2浓度(Ci)显著下降,可溶性糖积累量也降低。因此,硅可显著提高小麦对干旱胁迫的抗性。     

Selection and characterization of wheat genotypes for saline soils prone to water‐logging

Wheat (Tritcum aestivum L.) genotypes were screened and characterized for performance under salt stress and/or water‐logging. In a solution‐culture study, ten wheat genotypes were tested under control, 200 mM–NaCl salt stress and 4‐week water‐logging (nonaerated solution stagnated with 0.1% agar), alone or in combination. Shoot and root growth of the wheat genotypes was reduced by salinity and salinity × water‐logging, which was associated with increased leaf Na⁺ and Cl^– concentrations as well as decreased leaf K⁺ concentration and K⁺ : Na⁺ ratio. The genotypes differed significantly for their growth and leaf ionic composition. The genotypes Aqaab and MH‐97 were selected as salinity×water‐logging‐resistant and sensitive wheat genotypes, respectively, on the basis of their shoot fresh weights in the salinity × water‐logging treatment relative to control. In a soil experiment, the effect of water‐logging was tested for these two genotypes under nonsaline (EC = 2.6 dS m^–1) and saline (EC = 15 dS m^–1) soil conditions. The water‐logging was imposed for a period of 21 d at various growth stages, i.e., tillering, stem elongation, booting, and grain filling alone or in combinations. The maximum reduction in grain yield was observed after water‐logging at stem‐elongation + grain‐filling stages followed by water‐logging at grain‐filling stage, booting stage, and stem‐elongation stage, respectively. Salinity intensified the effect of water‐logging at all the growth stages. It is concluded that the existing genetic variation in wheat for salinity × water‐logging resistance can be successfully explored using relative shoot fresh weight as a selection criterion in nonaerated 0.1% agar–containing nutrient solution and that irrigation in the field should be scheduled to avoid temporary water‐logging at the sensitive stages of wheat growth.     

Relationships Between Carbon Isotope Discrimination and Yield of Spring Wheat Under Different Water and Nitrogen Levels

ABSTRACT

A greenhouse experiment was conducted to investigate the relationships between foliar carbon isotope discrimination (Δ) and above ground dry matter (ADM) at different stages during a plant's life cycle, and grain carbon isotope discrimination and grain yield (GY) at maturity of spring wheat (Triticum aestivum L.) under different nitrogen (N) and water levels. Results showed that ADM and GY both increased significantly with decreasing water stress, while the effects of nitrogen on ADM and GY varied with the water conditions. Foliar and grain carbon isotope discrimination decreased with increasing water stress and increasing nitrogen levels. For all water conditions, relationships between carbon isotope discrimination (foliar and grain) and yields (ADM and GY) were significantly positive (P < 0.001) at various growth stages. However, at the same water level, the correlations were complex, and under well-watered conditions, ADM and GY were strongly and negatively correlated with foliar and grain carbon isotope discrimination at all growth stages (P < 0.001). The correlations were inconsistent and not significant at moderate water level, but were positive under drought. Our results showed that water and nitrogen both significantly affected the relationships between yield and carbon isotope discrimination of spring wheat, that there are interactions between these two parameters, and that environmental conditions such as water and fertilizer must thus be considered in future research on the relationship between yield and carbon isotope discrimination of spring wheat.     

Screening different crested wheatgrass (Agropyron cristatum (L.) Gaertner.) accessions for drought stress tolerance

A pot experiment was conducted in a greenhouse to evaluate the effect of drought stress on growth and turf quality of 24 accessions of crested wheatgrass (Agropyron cristatum (L.) Gaertner.) and ‘Rembrandt’ tall fescue, and to find the most drought-tolerant accession(s) of crested wheatgrass. The grasses were treated in well-watered or exposed to drought stress by withholding water for 20 days. Visual turf quality of drought-stressed plants had no significant differences with well-watered plants until day 8 of drought and 1727 P10 had the highest turf quality at day 20 of drought. Cluster analysis classified the accessions and Rembrandt into five clusters comprised of drought tolerant (I), intermediate (II, IV and V) and susceptible (III) in response to soil drying. Turf quality, green tissue, relative water content and electrolyte leakage of cluster I (1727 M, 208 M, 4056, 2854 and 1727 P1) were 1.8-, 2.0-, 1.6- and 0.6-fold of cluster III (Rembrandt) under drought stress conditions, respectively. Genetic diversity of cluster I could be used for plant breeding programmes and introduction of the drought-tolerant accessions to turfgrass breeders for drought tolerance varietal development programme.     

Nutrient Uptake,Water Relations,and Yield Performance lf Different Wheat Cultivars (Triticum aestivum L.) under Salinity Stress

A pot experiment was conducted in the wire house of Department of Crop Physiology, University of Agriculture, Faisalabad to evaluate the effect of salinity stress on water relations, nutrient uptake and yield of six local spring wheat cultivars. The seeds were sown in plastic pots (25 × 15 cm) and experiment was laid out in a randomized complete block design in factorial arrangement with three repeats. De-ionized water was used as control treatment while salinity stress was imposed by irrigating plants with sodium chloride (NaCl) solution of 10 mM at tillering, stem elongation, anthesis, and grain development stages. Results of the study demonstrated that salinity stress decreased water potential by 32%, osmotic potential by 12%, and relative water contents by 20% as compared to control treatment. The nitrogen (N) uptake was decreased by 36% under salinity stress, while phosphorous (P) and potassium (K) uptake were decreased by 56% and 42%, respectively. The yield of wheat plants was also significantly reduced under salinity stress. It reduced grain yield by 25% and grain weight by 7%. The response of different cultivars was also different to salinity stress as cultivars ‘Lasani-08’ and ‘FSD-08’ were found to be more tolerant as compared to other cultivars.     

Inducing drought tolerance in wheat by applying natural and synthetic plant growth promoters

Crop productivity in future may be limited due to water scarcity. However, foliar spray of plant growth promoters may boost crop production even in adverse environments. In the present study, foliar application of one natural (moringa leaf extract, 3% MLE) and four synthetic (Polydol, Multisol, Classic, and Asahi Star) were applied at tillering, jointing, booting, and heading growth stages of wheat (Triticum aestivum L.) during severe, moderate, and light drought and well‐watered condition. No spray and water spray were taken as controls. Results showed significant reduction in growth parameters such as total dry matter production, mean crop growth rate, net assimilation rate, leaf area index, and duration due to drought employed at various phenophases of wheat. However, improvement in these parameters was observed after foliar application of growth promoters, whereas interactive effects between factors were found non‐significant. The activities of catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) were more accelerated under drought treatments from exogenously supplied growth promoters. Foliar application of promoters significantly alleviated drought‐induced reduction of yield and related traits. Grain weight (15%) and grain yield (27%) were improved due to exogenously applied MLE under moderate drought stress treatments relative to controls. Furthermore, 16% higher grain yield and 17% saving of irrigation water over fully irrigated and without promoter treatment (farmers' practice) was recorded from foliar‐applied MLE under skipped irrigation at jointing. In conclusion, foliar‐applied MLE may ameliorate drought‐induced deleterious effects by enhancing antioxidant activities under drought stress.     

Effects of Urea Foliar Application on Grain Yield and Quality of Winter Wheat

The effects of urea foliar application rates at different growth stages of wheat on protein and yield of winter wheat were evaluated in a factorial experiment. Time of application and amounts of urea foliar application rates were the treatments. Urea was applied at four stages including tillering, jointing, anthesis, and grain filling, and urea foliar application rates were 22.5, 45, 67.5, and 90 kg ha^?1 (12.5, 25, 37.5, and 50% of total urea application). Our data demonstrated that urea application time had significant effects on grain weight, number of seeds per spike, plant height, and protein content. Furthermore, total dry weight, grain weight, harvest index, 1000-seed weight, plant height, and protein content were significantly affected by amounts of urea foliar application. The effects of time?×?rate of urea foliar application on grain yield, 1000-seed weight, and plant height were significant.     

The diagnosis of nitrogen deficiency in wheat by means of a critical nitrate concentration in stem bases

Abstract

Stem bases from wheat plants in a glasshouse pot experiment conducted under varying nitrogen and two water regimes, were analysed for nitrate (NO₃) concentration. The concentration of NO₃ at three stages of growth i.e. tillering, jointing and anthesis were related both to rates of applied nitrogen and to shoot dry matter yield at time of sampling. Plotted against rate of increasing nitrogen application, the response curve of NO₃ concentration in wheat stem bases was sigmoidal. The level of nitrogen application at which NO₃ began to accumulate in the plants was the supply at which plants reached maximum dry matter yield. The concentration of NO₃ at which plant yield was 90% of maximum dry matter was taken as the critical level. This concentration was around 1000 ppm NO₃‐N at all stages. Compared with plants supplied with unlimited water, plants under moderate water stress accumulated relatively more NO₃ but had a similar critical NO₃ concentration.

Maximum grain yield was obtained from plants which stayed above the critical level throughout the growing season.     

CO2浓度倍增、增温和轻度干旱对冬小麦根系生长和氮素吸收的影响

  【目的】  根系是作物氮素吸收的主要器官,研究CO₂浓度倍增和增温对根系生长和氮素吸收的影响,为应对气候变化提供科学的养分管理策略。  【方法】  以冬小麦(Triticum aestivum L.)为材料,在人工气候室内进行盆栽试验。设置对照(大气CO₂浓度400 μmol/mol+正常环境温度,CK)、CO₂浓度倍增(CO₂浓度800 μmol/mol+正常环境温度,ECO₂)、增温4℃ (CO₂浓度400 μmol/mol+增温4℃,ETem)和CO₂浓度倍增+增温4℃ (CO₂浓度800 μmol/mol+增温4℃,ECO₂+ETem) 4种气候情景,每种气候情景设置充分供水(80%田间持水量)和轻度干旱(60%田间持水量) 两个水分条件。调查了冬小麦根系生长(根生物量、根冠比、总根长、根总表面积和根总体积)和氮素吸收的情况,分析冬小麦氮素吸收与根系生长的关系。  【结果】  1) CO₂浓度倍增对冬小麦各生育期根系生长均无显著影响,而增温4℃和轻度干旱显著抑制了开花和灌浆期的根系生长。2) CO₂浓度倍增、增温、轻度干旱共同作用均显著抑制了冬小麦根系生长,其中增温和轻度干旱对根系生长具有协同抑制作用。3) CO₂浓度倍增显著降低了冬小麦灌浆期根氮含量,而对地上部氮含量无显著影响;增温4℃显著增加了冬小麦各生育期根氮含量和地上部氮含量;轻度干旱增加了根氮含量和地上部氮含量,且仅对地上部氮含量有显著影响;CO₂浓度倍增与增温交互作用仅对根氮含量增加有显著促进作用;增温与轻度干旱交互作用对根氮含量和地上部氮含量增加均有显著促进作用;CO₂浓度倍增与轻度干旱交互作用,以及CO₂浓度倍增、增温和轻度干旱三者交互作用对根氮含量和地上部氮含量增加均无显著影响。4)根氮积累量及地上部氮积累量均与根系形态指标对CO₂浓度倍增、增温、轻度干旱及其交互作用的响应具有相同变化特征,且根氮积累量和地上部氮积累量与各生育期根系形态指标有显著正相关关系。  【结论】  在本试验条件下增温和轻度干旱对冬小麦根系生长具有较强的抑制作用,且二者对根系生长具有协同抑制作用;CO₂浓度倍增对冬小麦各生育期根部和地上部氮素吸收的影响总体不显著,而增温和轻度干旱对根部和地上部氮含量增加均有一定的促进作用,对根部和地上部氮积累量增加均有抑制作用,增温是影响氮素吸收的主导因子。     

Evaluation of chitosan nanoparticles effects with two application methods on wheat under drought stress

Chitosan and its components have beneficial effects on a wide variety of plant species. Yet, their effects on wheat plants under drought stress are not well known. So, a field experiment was laid out in order to evaluate the effect of chitosan nanoparticles (NPs) on wheat. The wheat seeds were sown in plots. Then, the chitosan NPs were added to them through soil and foliar application at tillering, stem elongation, and heading stages. Results indicated that the drought stress significantly decreased majority of the studied traits compared to the normal irrigation. Application of the NPs especially 90?ppm increased leaf area (LA), relative water content (RWC), chlorophyll content, photosynthesis rate, catalase (CAT), and superoxide dismutase (SOD) activities, yield, and biomass compared to the control. Finally, our results highlight that usage of the chitosan NPs especially 90?ppm can mitigate adverse effects of drought in the wheat under drought stress.     

Nitrogen Availability Affects the Yield of Winter Wheat Subjected to Water Stress during Grain Filling

The effects of irrigation regimes (full irrigation and water-withholding at anthesis) and postanthesis nitrogen (N) supplies (LN, 0; MN 20; and HN, 40 kg N ha^?1) on grain yield and its components in winter wheat were studied, with attention to biomass gain by assimilation and its loss by respiration. Fully irrigated wheat responded to N fertilization with increased grain number (GN) and decreased grain weight (GW), whereas drought-stressed wheat responded with greater GN without significant changes in GW. Apparent whole-plant respiration (R_A) was not influenced by increased postanthesis N fertilizer. Thus, in drought-stressed wheat, the total biomass and stem reserves at maturity were increased by increasing N supply. These results suggest that high N supply at anthesis satisfied the grains’ increased demand for N by increasing postfloral assimilation, and the surplus assimilates not only compensated for the low-N-induced biomass loss by respiration but also may have increased the stem reserves.