Effect of Foliar Salicylic Acid Applications on Growth,Chlorophyll, and Mineral Content of Cucumber Grown Under Salt Stress

The objective of this study was to determine the effect of foliar salicylic acid (SA) applications on growth, chlorophyll, and mineral content of cucumber grown under salt stress. The study was conducted in pot experiments under greenhouse conditions. Cucumber seedlings were treated with foliar SA applications at different concentrations (0.0, 0.25, 0.50, and 1.00 mM). Salinity treatments were established by adding 0, 60, and 120 mM of sodium chloride (NaCl) to a base complete nutrient solution. The SA was applied with spraying two times as before and after transplanting. Salt stress negatively affected the growth, chlorophyll content and mineral uptake of cucumber plants. However, foliar applications of SA resulted in greater shoot fresh weight, shoot dry weight, root fresh weight, and root dry weight as well as higher plants under salt stress. Shoot diameter and leaf number per plant increased with SA treatments under salt stress. The greatest chlorophyll content was obtained with 1.00 mM SA treatment in both saline and non-saline conditions. Leaf water relative content (LWRC) reduced in response to salt stress while SA raised LWRC of salt stressed cucumber plants. Salinity treatments induced significant increases in electrolyte leakage. Plants treated with foliar SA had lower values of electrolyte leakage than non-treated ones. In regard to nutrient content, it can be interfered that foliar SA applications increased almost all nutrient content in leaves and roots of cucumber plants under salt stress. Generally, the greatest values were obtained from 1.00 mM SA application. Based on these findings, the SA treatments may help alleviate the negative effect of salinity on the growth of cucumber.     

RESPONSE OF FRIJOLILLO RHYNCHOSIA MINIMA (L) DC. TO SUPPLEMENTARY PHOSPHORUS WITH THREE SOIL MOISTURE CONDITIONS: II. SOLUTE ACCUMULATION

The objective of this study was to evaluate the effects of induced drought conditions and phosphorous (P) application on osmotic adjustment as reflected in the accumulation of organic solutes in the leaves of frijolillo. The experiment took place under greenhouse conditions without climate control. Plastic containers were used measuring 20 cm high × 15 cm in diameter. In each container, five plants were evaluated from emergence to vegetative growth phase. Three soil moisture regimes were evaluated (25%, 50%, and 100% of field capacity) combined with four concentrations of phosphorous (0, 50,100 and 150 mg kg^?1 of soil). A completely randomized block design with a factorial arrangement of 3×4 with four replications was used. The cellular osmotic adjustment as a response to drought stress in frijolillo was associated with the accumulation of sugars, amino acids and proline in that higher concentrations than the control were measured with moisture at 25%. Concentrations of chlorophyll and carotene increased as soil moisture levels decreased.     

Aloe vera long-term saline irrigation increases contents of hydrogen peroxide,lipid peroxidation and phenolic compounds

Salt stress is more and more becoming a serious problem in the world especially if we consider its damaging effect on the plant growth and yield. The cultivation of medicinal plants, such as Aloe vera, might be an alternative for the saline water use and salt-affected soils occupation. Aloe vera, commonly known as aloe, is one of the primary medicinal plants with multipurpose applications going from pharmaceutical to cosmetic aspects with a promising economic return. Aloe plants were cultivated and irrigated, for 14 months, with drinking water (C0) and with two levels of salt (C1 and C2). Changes in growth, hydrogen peroxide (H₂O₂), lipid peroxidation and phenolic compounds were examined in leaves at harvest. Depressive effects of salt irrigation on the plant growth parameters and a perturbation in inorganic ion contents were found especially with a high level of salt in the irrigation water. The intracellular oxidative stress was evaluated with the H₂O₂ production. Our results showed that the H₂O₂ content increased with the accumulation of the toxic ion (Na) in the leaf tissues. In addition, lipid peroxidation, measured by the malondialdehyde (MDA) level, increased as well with salt augmentation in the irrigation water. In response to salt stress, Aloe leaves showed a significant increase in the levels of phenolic compounds too. These results suggest that Aloe can be planted in soils affected by salinity and irrigated with salt water at least at a moderate concentration used in the present study.     

外源NO对Ca(NO3)2胁迫下黄瓜幼苗生长和抗氧化系统的影响

本研究以黄瓜为试材,采用营养液水培,研究了外源NO对Ca(NO3)2胁迫下黄瓜幼苗生长和抗氧化酶系的影响.结果显示,在70mmol·L-1的Ca(NO3)2胁迫下,植株生长受到抑制,干重和叶绿素含量显著下降,叶片和根系抗氧化酶SOD、POD、CAT和APX活性均升高,膜脂过氧化产物MDA及可溶性 蛋白含量增加.而叶面喷施NO供体SNP显著缓解了Ca(NO3)2胁迫对黄瓜幼苗生长的抑制,植株干重显著增加.同时,抗氧化酶活性、可溶性蛋白和叶绿素含量也有不同程度的上升,MDA含量显著下降.以上表明,NO能够增强黄瓜幼苗对Ca(NO3)2胁迫的耐性.喷施SNP对正常营养液培养的黄瓜幼苗无显著影响.     

羊草对盐碱胁迫的生理生化响应特征

研究羊草对盐碱胁迫生理响应特征,旨在找出羊草耐盐碱范围及其对盐碱地改良的应用潜力。通过模拟5组不同盐碱梯度土壤胁迫试验(p H值为7.61、8.05、8.33、8.73、9.37,电导率为0.109、0.301、0.437、0.486、0.591 m S/cm),研究了羊草体内离子含量和运输能力、有机小分子渗透调节和保护酶活性变化。结果表明,盐碱胁迫由低到高,超氧化物歧化酶和甜菜碱在中度盐碱胁迫(p H值8.33,电导率0.437 m S/cm)积累最多,其他测定的耐盐碱物质,钠离子、脯氨酸、丙二醛、有机酸(草酸、柠檬酸、酒石酸)、过氧化物酶、过氧化氢酶、可溶性总糖、可溶性蛋白均呈直线增加。在盐碱胁迫条件下,羊草叶片中积累的钾离子、甜菜碱、有机酸、可溶性蛋白高于根茎,而脯氨酸、丙二醛、保护酶(超氧化物歧化酶、过氧化物酶、过氧化氢酶)、可溶性总糖叶片中含量低于根茎。根茎大量积累保护酶、脯氨酸及丙二醛有助于防止盐碱环境下根茎中膜过氧化,并保持根茎正常的渗透调节能力,从而有利于将K+等养分运送到叶片。在盐碱胁迫下,羊草叶片主要积累甜菜碱和有机酸进行渗透调节。该试验结果表明,羊草根茎和叶片在不同盐碱胁迫条件下各耐盐碱生理指标均产生一系列适应性反应,使其在盐碱环境正常生长,进而降低土壤盐碱性。该研究可为耐盐碱饲草选育及根茎型禾草改良盐碱化草地提供理论和实践依据。     

硒缓解植物重金属胁迫和累积的机制

硒(Se)在提高植物抗逆性、缓解重金属胁迫以及降低植物对重金属吸收方面有着重要的作用。本文综述了Se参与缓解植物重金属胁迫和累积的机制,Se能够缓解重金属的胁迫,主要是因为在植物体内由Se转化而来的相关产物的生理生化作用产生的综合效果。Se是谷胱甘肽过氧化物酶(GSH-Px)的必需组分,GSH-Px利用谷胱甘肽(GSH)将有毒的过氧化物还原成无毒的物质,清除由重金属引起的自由基。Se可以激活植物螯合肽(PC)合成酶及增加PC合成的前体,使植物产生更多的PC,形成更多的重金属-PC配合物。Se还可以与重金属形成大分子的复合物,降低重金属的毒害。Se能够与多种重金属元素产生拮抗效应,降低植物对重金属的吸收。     

水分和铅双重胁迫对紫穗槐苗木叶片抗氧化酶活性的影响

为了探讨在水分和铅双重胁迫条件下,紫穗槐(Amorpha fruticosa L.)苗木叶片抗氧化酶活性的变化,采用旱棚盆栽试验,研究了不同水分胁迫处理(土壤相对含水量分别为田间持水量的100%,80%,60%和40%)和铅胁迫处理(土壤中铅含量分别为0,1 000,2 000,4 000和6 000mg/kg)及其双重作用对紫穗槐苗木叶片的超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性的影响。结果表明,在单一的铅胁迫处理下,随着胁迫的加剧,紫穗槐苗木叶片的SOD和CAT活性呈先升高后降低的趋势,POD活性一直呈升高趋势;在单一的水分胁迫处理下,随着胁迫的加剧,SOD和POD活性呈先升高后降低的趋势,CAT活性呈先降低后升高的趋势;水分和铅双重胁迫对SOD和POD活性有显著的激活作用,对低铅含量(≤2 000mg/kg)处理的CAT活性有激活作用;适度的双重胁迫(铅含量≤2 000mg/kg,土壤相对含水量≥40%)有利于提高紫穗槐苗木对水分和铅双重胁迫的耐受性。     

干旱胁迫对2种速生树种叶绿素荧光特性的影响

【目的】对华南地区2个速生树种尾巨桉Eucalyptus urophylla×E.grandis和竹柳(bamboo willow)的抗旱性进行比较.【方法】采用干旱胁迫处理,利用脉冲调制式叶绿素荧光仪(OS5P-美国)对2树种叶绿素荧光参数进行测定.【结果和结论】在干旱胁迫条件下,实际光量子产量(Yield)、表观光合电子传递速率(ETR)、光化学淬灭系数(q P)、最大荧光(Fm)和PSⅡ最大光化学效率(Fv/Fm)均有不同程度的下降,在干旱处理第24天,尾巨桉ETR比对照下降48.02%,而竹柳仅下降25.12%;到重度干旱时期,尾巨桉和竹柳Fv/Fm分别下降31.55%和21.84%;供试树种的非光化学淬灭系数(q N)、初始荧光(F0)均呈上升趋势,与对照相比,竹柳q N上升幅度为217.59%,显著大于尾巨桉(146.40%,P0.05),F0上升幅度(49.11%)小于尾巨桉(92.03%);2种树种ETR与土壤含水量均呈极显著正相关(P0.01),尾巨桉F0与土壤含水量呈极显著负相关(P0.01),竹柳Fm和Fv/Fm与土壤含水量呈极显著正相关(P0.01).研究结果表明:在干旱胁迫下,竹柳与尾巨桉叶绿素荧光参数间均表现一定相关性,相比尾巨桉,竹柳在叶绿素荧光参数上表现出更强的抗旱性.     

外源水杨酸对毒死蜱胁迫下蔬菜上海青抗氧化防御反应的影响

在室内栽培条件下,观察毒死蜱(chlorpyrifos,CPF)对蔬菜上海青造成的胁迫和水杨酸(salicylic acid,SA)对上海青应对毒死蜱胁迫的影响。测定结果显示:喷施91.2、182.4、273.6mg/L的毒死蜱后,短期内(2~4d)上海青中超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性受到抑制,而过氧化物酶(POD)活性则有所升高,且伴随POD活性升高的还有丙二醛(MDA)、脯氨酸(Pro)和谷胱甘肽(GSH)含量的增加,表明毒死蜱在喷施后短期内对上海青具有一定的胁迫;高浓度外源水杨酸可缓解毒死蜱对上海青SOD和CAT的直接抑制,使SOD和CAT活性增强,但对POD活性和MDA、Pro含量无明显影响,表明在供试浓度范围内,外源水杨酸可部分缓解毒死蜱对上海青的胁迫。