Induction of Drought Tolerance in Maize (Zea mays L.) due to Exogenous Application of Trehalose: Growth,Photosynthesis, Water Relations and Oxidative Defence Mechanism

The present investigation was conducted to assess the ameliorative effects of foliar‐applied trehalose on growth, photosynthetic attributes, water relation parameters and oxidative defence mechanism in two maize cultivars under field water deficit conditions. Various components of the experiment comprised two maize cultivars (EV‐1098 and Agaiti‐2002), two water‐stress levels (irrigation after 2 weeks and irrigation after 3 weeks during the entire period of growth), and two levels of trehalose (0 and 30 mm ) and four replicates of each treatment. Water stress significantly reduced the plant biomass production, photosynthetic attributes and water relation parameters in both maize cultivars. In contrast, water stress considerably increased the leaf malondialdehyde (MDA) contents, the activities of antioxidant enzymes such as peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT), and the levels of non‐enzymatic compounds such as ascorbic acid and tocopherols. In contrast, water stress caused a marked reduction in leaf phenolic contents. Foliar‐applied trehalose significantly increased plant biomass production, and improved some key photosynthetic attributes and plant–water relation parameters. The ameliorative effect of exogenously applied trehalose was also observed on the activities of some key antioxidant enzymes (POD and CAT) and non‐enzymatic compounds (tocopherols and phenolics). Overall, exogenously applied trehalose considerably improved drought tolerance of maize plants by up‐regulating photosynthetic and water relation attributes as well as antioxidant defence mechanism.     

DROUGHT STRESS: Comparative Time Course Action of the Foliar Applied Glycinebetaine,Salicylic Acid,Nitrous Oxide,Brassinosteroids and Spermine in Improving Drought Resistance of Rice

Worldwide rice productivity is being threatened by increased endeavours of drought stress. Among the visible symptoms of drought stress, hampered water relations and disrupted cellular membrane functions are the most important. Exogenous use of polyamines (PAs), salicylic acid (SA), brassinosteroids (BRs), glycinebetaine (GB) and nitrous oxide (NO) can induce abiotic stresses tolerance in many crops. In this time course study, we appraised the comparative role of all these substances to improve the drought tolerance in rice (Oryza sativa L.) cultivar Super‐Basmati. Plants were subjected to drought stress at four leaf stage (4 weeks after emergence) by maintaining soil moisture at 50 % of field capacity. Pre‐optimized concentrations of GB (150 mg l^?1), SA (100 mg l^?1), NO (100 μmol l^?1 sodium nitroprusside as NO donor), BR (0.01 μm 24‐epibrassinolide) and spermine (Spm; 10 μm ) were foliar sprayed at five‐leaf stage (5 weeks after emergence). There were two controls both receiving no foliar spray, viz. well watered (CK1) and drought stressed (CK2). There was substantial reduction in allometric response of rice, gas exchange and water relation attributes by drought stress. While drought stress enhanced the H₂O₂, malondialdehyde (MDA) and relative membrane permeability, foliar spray of all the chemicals improved growth possibly because of the improved carbon assimilation, enhanced synthesis of metabolites and maintenance of tissue water status. Simultaneous reduction in H₂O₂ and MDA production was also noted in the plants treated with these substances. Drought tolerance was sturdily associated with the greater tissue water potential, increased synthesis of metabolites and enhanced capacity of antioxidant system. Of all the chemicals, foliar spray with Spm was the most effective followed by BR.     

Fulvic Acid Application Improves the Maize Performance under Well‐watered and Drought Conditions

Water deficit is perhaps the most severe threat to sustainable crop production in the conditions of changing climate. Researchers are striving hard to develop resistance against water deficit in crop plants to ensure food security for the coming generations. This study was conducted to establish the role of fulvic acid (FA) application in improving the performance of hybrid maize (Zea mays L.) under drought. Maize plants were grown under normal conditions till tasselling and were then subjected to drought by cessation of water followed by foliar application of FA (1.5 mg l^?1). Drought stress disrupted the photosynthetic pigments and reduced the gas exchange leading to reduction in plant growth and productivity. Nonetheless, exogenous FA application substantially ameliorated the adversities of drought by sustaining the chlorophyll contents and gas exchange possibly by enhanced levels of antioxidant enzyme (superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)) activities and proline. These beneficial effects yielded in terms of plant growth and allometry, and grain yield. It is interesting to note that FA application also improved the crop performance under well‐watered conditions. Hence, FA may be applied to improve the crop performance under drought and well‐watered conditions.     

Physiological and Yield Responses of Faba bean (Vicia faba L.) to Drought Stress in Managed and Open Field Environments

Water scarcity is threatening the sustainability of global food grain production systems. Devising management strategies and identification of crop species and genotypes are direly required to meet the global food demands with limited supply. This study, consisted of two independent experiments, was conducted to compare faba bean (Vicia faba L.) genotypes Giza Blanka, Goff‐1, Hassawi‐1, Hassawi‐2 and Gazira‐2 in terms of physiological attributes and yield under water‐limited environments. In first experiment, conducted in a growth chamber, osmotic stress of ?0.78, ?0.96, ?1.19 and ?1.65 MPa was induced using polyethylene glycol for 4 weeks. In second experiment, conducted in open field for two consecutive growing seasons, water deficit treatments were applied 3 weeks after sowing. In this experiment, irrigation was applied when an amount of evaporated water from the ‘class A pan’ evaporation reached 50 mm (well watered), 100 mm (moderate drought) and 150 mm (severe drought). Water deficit, applied in terms of osmotic stress or drought, reduced the root and shoot length, related leaf water contents, total chlorophyll contents and efficiency of photosystem‐II, plant height, grain yield and related attributes in faba bean; increased the leaf free proline, leaf soluble proteins and malondialdehyde contents, and triggered the maturity in tested faba bean genotypes. However, substantial genetic variation was observed in the tested genotypes in this regard. For instance, root length of genotypes Giza Blanka and Hassawi‐2 decreased gradually, whereas it was increased in genotypes Goff‐1, Hassawi‐1 and Gazira‐2 with increase in the level of osmotic stress. Genotypes Gazira‐2 and Hassawi‐2 had better relative leaf water contents, leaf free proline and soluble proteins under water deficit conditions; however, these were minimum in genotype Giza Blanka. Better accumulation of leaf free proline, soluble proteins, and maintenance of chlorophyll contents, tissue water, efficiency of photosystem‐II and grain weight in water‐limited conditions helped some genotypes like Hassawi‐2 to yield better. Future breeding programs for developing new faba bean genotypes for water‐limited environments may consider these traits.     

辽宁苗期玉米根叶对水分胁迫的响应

为了提炼辽宁春玉米苗期干旱胁迫影响的定量化评价指标,以‘丹玉39’为试验材料,采用盆栽称重控水法,对不同水平土壤含水量对春玉米苗期根叶生长的影响进行研究。结果表明：正常（75%）和偏湿（85%）水分条件下玉米具有较高的株高,茎粗和叶面积。干旱胁迫下,玉米生长发育受到抑制,株高降低、茎粗变细、根系和地上部的生物量降低,叶片光合面积减小,根冠比增大。但一定程度的干旱（55%）有利于根系下扎,增大根冠比。干旱胁迫对玉米的株高和根系的生长发育有较大的影响,地上生物量受干旱胁迫影响大于根系。     

Interactive Effects of Sudden and Gradual Drought Stress and Foliar‐applied Glycinebetaine on Growth,Water Relations,Osmolyte Accumulation and Antioxidant Defence System in Two Maize Cultivars Differing in Drought Tolerance

Influence of sudden and gradual drought stress (DS) and foliar‐applied glycinebetaine (GB) on growth, water relations, osmolyte accumulation and antioxidant defence system were investigated in the plants of two maize (Zea mays L.) cultivars, that is, drought‐tolerant Shaandan 9 (S₉) and drought‐sensitive Shaandan 911 (S₉₁₁). Sudden DS caused less accumulation of GB and free proline, but a more accumulation of malondialdehyde (MDA), which resulted in a greater reduction in leaf relative water content (RWC) and dry matter (DM) in both cultivars compared with the gradual DS. Exogenous GB application caused a rise in DM, RWC, contents of GB and free proline as well as the activities of SOD, CAT and POD along with a decline in MDA content to various extent in both cultivars under both types of DS. A more pronounced effectiveness of GB application was observed in S₉₁₁ than that in S₉ under the same type of DS. It seemed that the more serious damage of DS was on maize plants, and the better positive role of GB was observed in terms of mitigating the adverse effects of DS. From this study, it was possible to propose that hardening for drought resistance by gradual DS treatment and GB application are effective to make plants robust to thrive under water‐deficit conditions.     

不同时期干旱对玉米生长发育及产量的影响

为探明不同时期的干旱对玉米生长发育及产量的影响,以‘浚单20’为试验材料,分别在拔节—抽穗期和抽穗—乳熟期进行水分控制处理,令土壤水分分别控制在田间持水量的40%（重旱）和60%（轻旱）,以自然生长(CK1)为对照,分析了不同发育阶段不同程度的干旱对玉米生长发育及产量的影响。结果表明：不同时期的干旱对玉米的生长发育有抑制作用,具体表现为株高变矮,叶面积降低,干物重减少,玉米各个产量构成因素（穗长、穗粒数、百粒重等）在受旱时都呈下降趋势。与自然生长(CK1)相比,拔节—抽穗期遭受重旱(G1)的玉米,生长至乳熟期,株高偏低26.1%,叶面积下降30.9%,果穗长、穗粒数、百粒重分别下降27.6%、46.5%和8.7%;抽穗—乳熟期遭受重旱(G3)的玉米,生长至乳熟期,株高偏低21.7%,叶面积下降23.6%,果穗长、穗粒数、百粒重分别下降36.1%、60.5%和30.2%。说明干旱是制约玉米高产的一个关键因子,特别是抽穗—乳熟期遭受重旱,玉米产量降幅更大。     

Drought Tolerance and Water‐Use Efficiency of Biogas Crops: A Comparison of Cup Plant,Maize and Lucerne‐Grass

The cup plant (Silphium perfoliatum L.) is discussed as an alternative energy crop for biogas production in Germany due to its ecological benefits over continuously grown maize. Moreover, a certain drought tolerance is assumed because of its intensive root growth and the dew water collection by the leaf cups, formed by fused leaf pairs. Therefore, the aim of this study was to estimate evapotranspiration (ET ), water‐use efficiency (WUE ) and the relevance of the leaf cups for the cup plant's water balance in a 2‐year field experiment. Parallel investigations were conducted for the two reference crops maize (high WUE ) and lucerne‐grass (deep and intensive rooting) under rainfed and irrigated conditions. Root system performance was assessed by measuring water depletion at various soil depths. Transpiration‐use efficiency (TUE ) was estimated using a model approach. Averaged over the 2 years, drought‐related above‐ground dry matter reduction was higher for the cup plant (33 %) than for the maize (18 %) and lucerne‐grass (14 %). The WUE of the cup plant (33 kg ha^?1 mm^?1) was significantly lower than for maize (50 kg ha^?1 mm^?1). The cup plant had a lower water uptake capacity than lucerne‐grass. Cup plant dry matter yields as high as those of maize will only be attainable at sites that are well supplied with water, be it through a large soil water reserve, groundwater connection, high rainfall or supplemental irrigation.     

Wheat Rht‐B1 Dwarfs Exhibit Better Photosynthetic Response to Water Deficit at Seedling Stage Compared to the Wild Type

Wheat reduced height (Rht) genes encode modified DELLA proteins, which are gibberellin insensitive, accumulate under stress, restrain growth and affect plant stress response. The seedling reaction to soil water deficit regarding leaf gas exchange and chlorophyll fluorescence was compared in near‐isogenic lines carrying the alleles Rht‐B1a (tall), Rht‐B1b (semi‐dwarfing) and Rht‐B1c (dwarfing) and was related to leaf water content and anatomy. Under drought, Rht‐B1c line was characterized by less decreased CO₂ assimilation, delayed non‐stomatal limitation of photosynthesis and higher instantaneous water use efficiency. The functional state of its photosynthetic apparatus was better preserved as evidenced by the less decreased actual quantum yield (Φ_PSII) and potential maximum quantum yield (F_v/F_m) of PSII, and the less increased quantum yield of non‐regulated energy dissipation (Φ_NO). Rht‐B1b line also tended to perform better than Rht‐B1a, but differences were less pronounced. Although the leaves of both dwarf lines were smaller, thicker and more pubescent, their water content was not higher in comparison with the tall line. Nevertheless, in Rht‐B1c, leaf thickness was less decreased and mesophyll cells were less shrunk under drought. The more effective performance of the photosynthetic machinery of dwarf lines under water deficit could be explained by a combination of morpho‐anatomical and metabolic characteristics.     

持续高温干旱胁迫对春玉米生长的影响

为了探究高温和干旱对春玉米生长的影响,本研究以春玉米‘科河28号’为材料,设置正常灌溉、持续干旱和持续高温3种处理,探求干旱区高温干旱发生发展过程对春玉米生长的影响。结果表明：（1）持续高温处理下,春玉米苗期缩短9~13天,穗期生育间隔延长6~12天,花粒期不完整;而持续干旱处理,春玉米营养生长与生殖生长并进期延长3~8天,无法正常灌浆成熟。（2）持续高温处理,春玉米前期生长快,抽雄后高度不再增加;而持续干旱处理,春玉米生长缓慢,拔节期之后植株高度显著偏小;持续高温和干旱处理,单株总叶面积和比叶面积拔节期之后均较对照偏小。（3）干物质分配率在持续高温处理中呈现茎>叶片>叶鞘,在持续干旱处理中呈现叶片>茎>叶鞘,穗很小,造成经济产出少,而在对照处理中呈现穗>茎>叶片>叶鞘。（4）持续高温和干旱处理下含水率呈现叶鞘>茎>叶片。受高温和干旱胁迫,产量不保时,抽雄期进行粮转饲较合适。本研究可以为科学抗旱减灾工作提供理论依据。     

Maize harvest index and water use efficiency can be improved by inhibition of gibberellin biosynthesis

Possibilities to improve maize harvest index and nutrient utilization efficiency by application of plant growth regulators were investigated. In container experiments, the effects of different growth regulators on the development of the maize (Zea mays L.) cultivars Pioneer 3906 and Fabregas were tested. Paclobutrazol (PAC) and chlorocholine chloride (CCC), two inhibitors of gibberellin biosynthesis, as well as gibberellic acid (GA₃) were applied at growth stage V5. Three weeks after application of PAC, shoot growth of both maize cultivars was strongly affected with a significant decrease in plant height in the PAC treatment by 44% and 36% for Pioneer 3906 and Fabregas, respectively. The growth‐retarded plants had higher leaf areas and reduced transpiration rates. The higher shoot growth after GA₃ application was accompanied by a reduction in leaf area and an increase in transpiration rate during 1 week before anthesis. CCC treatment showed no significant effects on plant height, leaf area and transpiration rate. The PAC‐treated cultivar Pioneer 3906 produced several cobs per plant, which were mainly barren at maturity. However, PAC application to Fabregas resulted in just one cob per plant with good kernel development and a grain yield, which was not significantly reduced in comparison with the control. With this similar grain yield in combination with a straw yield decrease of 32%, the harvest index was significantly improved by 12%. In addition, with PAC‐treated Fabregas plants, a 19% increased water use efficiency of the grain (WUE_grain) during the critical period of kernel setting was achieved. In this maize cultivar, CCC application also improved harvest index by 5%, but no effect on WUE_grain occurred. GA₃ treatment decreased harvest index of both maize cultivars, and it either reduced WUE_grain (Pioneer 3906) or showed no effect (Fabregas). Utilization efficiencies of N, P and K were not increased with growth regulator application, even in the PAC‐treated Fabregas plants with a significantly improved allocation of assimilates to the grain, mirrored by the higher harvest index. The results indicate that fertilizer applications must be adjusted to the reduced demand of growth‐retarded plants, most likely leading to higher nutrient utilization efficiencies.     

Salt‐Induced Regulation of Some Key Antioxidant Enzymes and Physio‐Biochemical Phenomena in Five Diverse Cultivars of Turnip (Brassica rapa L.)

A greenhouse experiment was carried out to examine the differential morpho‐physiological responses of five cultivars of turnip (Brassica rapa L.) to salt stress. Five diverse cultivars of turnip (shaljum desi surakh, shaljum purple top, shaljum golden bal, neela shaljum, and peela shaljum) were subjected for 6 weeks to varying levels of NaCl, i.e. 0, 80 and 160 mm in Hoagland’s nutrient solution in sand culture. Imposition of varying levels of salt substantially decreased shoot and root fresh and dry weights, chlorophyll contents, leaf osmotic potential, relative water contents, different gas exchange attributes, total phenolics, malondialdehyde, activities of superoxide dismutase, peroxidase catalase, and leaf and root K⁺ levels while enhanced the proline contents, membrane permeability, level of H₂O₂, leaf and root Na⁺ and Cl^? and leaf Ca²⁺ in all turnip cultivars under study. Of all cultivars, peela shaljum and neela shaljum were consistently higher in their growth than the other turnip cultivars at all salt concentrations of the growth medium. Photosynthetic capacity (A) and stomatal conductance (g_s) were higher in high biomass‐producing cultivars, i.e. peela shaljum and neela shaljum, which provide to be potential selection criteria of salt tolerance in turnip. However, the regulation of antioxidant system was cultivar‐specific under saline conditions.     

Evaluating the role of seed priming in improving drought tolerance of pigmented and non‐pigmented rice

This study was conducted to evaluate the influence of seed priming on drought tolerance of pigmented and non‐pigmented rice. Seeds of pigmented (cv. Heug Jinju Byeo) and non‐pigmented (cv. Anjoong) rice were soaked in water (hydropriming) or solution of CaCl₂ (osmopriming). Seeds were sown in soil‐filled pots retained at 70 (well‐watered) and 35% (drought) water‐holding capacity. Drought stress caused erratic and poor stand establishment and decreased the growth of both rice types. More decrease in plant height and leaf area under drought stress was noted in pigmented rice, whereas decrease in root length and seedling dry weight, under drought, was more obvious in non‐pigmented rice. Pigmented rice maintained more tissue water and photosynthesis and had more polyphenols, flavonoids and antioxidant activity than non‐pigmented rice. Seed priming was effective in improving stand establishment, growth, polyphenols, flavonoids and antioxidant activity; however, extent of improvement was more in pigmented rice under drought. In conclusion, drought caused erratic germination and suppressed plant growth in both rice types. However, pigmented rice had better drought tolerance owing to uniform emergence, and better physiological and morphological plasticity. Seed priming was quite helpful in improving the performance of both rice types under drought and well‐watered conditions.     

Alleviation of drought stress in maize by exogenous application of gibberellic acid and cytokinin

The study was conducted to investigate the ameliorative roles of GA₃ and CK on adverse effects of drought in maize. Drought stressed maize plants were applied with GA₃ and CK at 50, 100, and 150 mg L^?l as foliar spray at the vegetative and the reproductive stages. Plant height, internode length, stem diameter, leaf chlorophyll index, and dry matter production were significantly affected by drought. In most cases, GA₃ and CK significantly improved the depressed plant traits, but in varying degrees depending on the growth stage encountering hormones, and their types and concentrations. Both GA₃ and CK were found to be very effective in alleviating drought-imposed adverse effects on maize at the vegetative phase. Such alleviating effects varied depending on the concentration of the hormones. Application of CK at 150 mg L^?l was excellent resulting in a 106% yield advantage compared to drought stress and 79.9% increase relative to well-watered controls. Conversely, GA₃ at 50 mg L^?l performed well showing 78.8% increase in grain yield. However, both GA₃ and CK had very little effect on improving the depressed growth and yield attributes in maize at the reproductive phase. The relative yield advantages for the hormones were mainly attributed to improving the cob and seed-bearing capacity of drought-stressed maize plants.     

Seed Priming with Ascorbic Acid Improves Drought Resistance of Wheat

The study, consisting of two independent experiments, was conducted to evaluate the role of seed priming with ascorbic acid (AsA) in drought resistance of wheat. In the first experiment, seeds of wheat cultivars Mairaj‐2008 and Lasani‐2008 were either soaked in aerated water (hydropriming) for 10 h or not soaked (control). In the second experiment, seeds of same wheat cultivars were soaked in aerated (2 mm ) AsA solution (osmopriming) or water (hydropriming) for 10 h. In both experiments, seeds were sown in plastic pots (10 kg) maintained at 70 % and 35 % of water‐holding capacity designated as well watered and drought stressed, respectively. Both experiments were laid out in a completely randomized design with six replications. Drought caused delayed and erratic emergence and disturbed the plant water relations, chlorophyll contents and membranes because of oxidative damage; however, root length in cultivar Lasani‐2008 was increased under drought. Hydropriming significantly improved the seedling emergence and early growth under drought and well‐watered conditions; however, improvement was substantially higher from osmopriming with AsA. Similarly, osmopriming with AsA significantly improved the leaf emergence and elongation, leaf area, specific leaf area, chlorophyll contents, root length and seedling dry weight. Owing to increase in proline accumulation, phenolics and AsA, by seed priming with AsA, plant water status was improved with simultaneous decrease in oxidative damages. These improved the leaf emergence and elongation, and shoot and root growth under drought. However, there was no difference between the cultivars in this regard. In conclusion, osmopriming with AsA improved the drought resistance of wheat owing to proline accumulation and antioxidant action of AsA and phenolics, leading to tissue water maintenance, membrane stability, and better and uniform seedling stand and growth.     

Melatonin may exert a protective role against drought stress in maize

Melatonin (N‐acetyl‐5methoxytryptamine) is an amphiphilic low‐molecular‐weight compound found in evolutionary distant living organisms, from bacteria to mammals. It can be synthesized by plants and acts as a potent antioxidant and/or a regulator of plant growth and development. Here, we investigated the role of melatonin in plant response to drought stress and recovery in maize (Zea mays L.) plants, with an emphasis on its possible photoprotective and antioxidant role and/or signalling function in relation to the stress‐related phytohormones, abscisic acid, salicylic acid and jasmonic acid. Results show a positive correlation between endogenous contents of melatonin and photoprotection, as indicated by the maximum efficiency of photosystem II photochemistry (F_v/F_m ratio), which was confirmed further by exogenous application of melatonin during recovery from drought stress. Melatonin applications during drought recovery improved the F_v/F_m ratio in maize plants exposed to a subsequent drought stress. Furthermore, endogenous contents of melatonin positively correlated with those of stress‐related phytohormones, particularly with those of salicylic acid, although exogenous application of melatonin did not alter the contents of these defence compounds. It is concluded that melatonin can exert a defensive role in maize plants exposed to drought stress, particularly improving the efficiency of photosystem II photochemistry.     

玉米沟塘覆膜模式间作马铃薯产量效益研究

针对云南省农业生产中玉米马铃薯间作面临的突发干旱危害和低产低效问题,在云南省宣威市农业技术示范基地,进行了玉米打塘开沟地膜覆盖间作马铃薯抗旱增产增效试验研究。结果表明：玉米开沟或打塘+地膜覆盖间作马铃薯复合技术可以提高土壤水分积蓄量,玉米开沟间作和打塘间作土壤含水量分别比玉米平垄和马铃薯单作最多增加28.32%和25.16%;在玉米生育前期,玉米开沟或打塘地膜覆盖间作马铃薯措施有利于促进玉米和马铃薯的生长发育,开沟和打塘模式玉米株高比平垄分别增加31.94%和26.33%,叶面积指数（LAI）分别增加49.56%和25.29%;开沟和打塘措施的玉米理论产量和经济系数均高于玉米平垄间作和单作,玉米产量、复合产量和土地当量比（LER）均显著增加,打塘种植的土地当量比最大（LER=1.20）,比平地处理增加10.52%,增产效益显著。所以,该措施能有效提高作物间作系统抗旱能力,增产增效,对稳定农业收益和保障粮食安全具有重要意义。     

Exogenous 6‐benzyladenine improves antioxidative system and carbon metabolism of summer maize waterlogged in the field

A field experiment was performed to study the effects of spraying exogenous 6‐benzyladenine (6‐BA) after waterlogging for 6 days at the third leaf stage and the sixth leaf stage on the activities of key enzymes in carbon metabolism, leaf gas exchange parameters, fluorescent characteristic, antioxidant enzymes activities and MDA content of summer maize hybrids Denghai605 (DH605) and Zhengdan958 (ZD958), in order to illuminate the regulations of exogenous spraying 6‐BA to antioxidative system and carbon metabolism of waterlogged summer maize. Results showed that exogenous application of 6‐BA effectively alleviated the adverse effects of waterlogging on carbon metabolism by improving photosynthetic characteristics and the activities of RuBPCase (in the range of 48%–81%) and PEPCase (in the range of 14%–46%). Treatments with spraying exogenous 6‐BA resulted in significant and substantial increases in net photosynthetic rate (around 49%) and Φ_PSII (around 16%) compared to those of waterlogging treatments. In addition, spraying 6‐BA effectively alleviated waterlogging damages on antioxidative enzyme activity and decreased MDA content, delaying leaf senescence, resulted in significant and substantial (around 19%) increases in grain yield. Visibly, spraying exogenous 6‐BA effectively alleviated waterlogging damages on antioxidative system and carbon metabolism of summer maize, resulting in yield increase in waterlogged maize.     

丙环唑对玉米幼苗生长的调控及其相关机制

丙环唑(propiconazole,简称Pcz)作为一种杀菌剂被广泛应用于作物生产,它同时具有调节作物生长发育的作用,但关于丙环唑在玉米上的应用研究较少。本研究以玉米品种郑单958为材料,研究丙环唑(Pcz)对玉米苗期植株生长、细胞形态和激素信号的影响。结果表明,Pcz处理显著抑制玉米中胚轴与胚芽鞘的生长,降低株高,缩短叶片和叶鞘长度,减小叶夹角,同时显著抑制叶片和叶鞘细胞的纵向伸长,促使叶枕细胞排列由疏松变为紧密;Pcz处理显著降低玉米中赤霉素(GA1和GA3)的含量,下调GA合成酶基因GA3ox1基因的表达,上调GA钝化酶基因GA2ox5和GA2ox8表达,而GA合成酶基因GA20ox1的表达呈现先上调后下调模式;Pcz处理显著降低油菜素内酯(BR)含量,但BR合成基因CPD和DWF4的表达上调,可能是由于反馈调节。此外,Pcz处理下调扩张蛋白基因EXPA4、EXPA5和木葡聚糖内糖基转移酶/水解酶基因XTH1、XET1的表达。综上所述,Pcz处理调节GA和BR信号转导途径,抑制GA和BR在植株内积累,调控扩张蛋白、木葡聚糖内糖基转移酶/水解酶基因表达,操纵细胞生长,有效调控株型。     

Effect of Water Stress on Physiological Attributes and their Relationship with Growth and Yield of Wheat Cultivars at Different Stages

The effects of water stress on physiological attributes of drought‐sensitive (Kalyansona) and drought‐tolerant (C‐306) wheat cultivars were studied in a pot experiment. Water stress was imposed by withholding irrigation at boot and anthesis stages. Leaf water potential, leaf osmotic potential and leaf turgor potential (measured with pressure chamber and osmometer), as well as leaf diffusive resistance, leaf transpiration rate and leaf‐to‐air transpiration gradient (measured with a steady‐state porometer) were measured diurnally. Growth and yield parameters were recorded after harvesting of the crop. Triplicate data were analysed using a completely randomized design and correlations amongst these parameters were computed. Water stress was found to reduce diurnal leaf water potential and leaf osmotic potential in both the genotypes but leaf osmotic potential was significantly higher in the drought‐tolerant cultivar C‐306 than in the drought‐sensitive cultivar Kalyansona. Positive turgor was recorded in both the genotypes under water stress and non‐stress conditions. Water‐stressed plants showed significantly lower turgor potential than control plants. In diurnal observations, water‐stressed plants exhibited significantly higher leaf diffusive resistance in both genotypes at both stages. The diffusive resistance of C‐306 was predominantly higher than that of Kalyansona. Water stress decreased leaf transpiration rate at both stages but the reduction was higher at the anthesis stage. The leaf‐to‐air temperature gradient was much higher in C‐306 than in Kalyansona at the boot stage but at the anthesis stage genotypic variation was non‐significant. The capacity to maintain cooler foliage was lower at the anthesis stage than at the boot stage in both the cultivars. Shoot dry weight, number of grains, test weight, grain yield, biological yield and harvest index decreased to a greater extent when water stress was imposed at the anthesis stage, while imposition of water stress at the boot stage caused a greater reduction in plant height and number of tillers. Similarly, water stress caused a smaller reduction in growth, yield and yield attributes in C‐306 than in Kalyansona. In general, the correlation coefficient of grain and biological yield with water potential and its components was positive and highly significant. Similarly, turgor potential was also correlated positively and significantly with grain yield at both the stages, but with biological yield it was significant only at the anthesis stage. A negative and significant correlation was obtained for diffusive resistance and leaf‐to‐air temperature gradient with grain yield at the boot and anthesis stages. The rate of transpiration was also positively and significantly correlated to grain and biological yields at both the stages. Amongst the yield attributes, number of leaves and number of tillers were positively correlated at the anthesis stage, whereas leaf area and shoot dry weight were significantly correlated with grain and biological yields at both the stages.