盐渍化土壤中盐胁迫是作物种子萌发和生长发育的主要限制因子, 探究盐分胁迫下提高种子萌发率的技术及机制对开发利用盐碱地有重要意义。本文以不同耐盐能力的高粱品种国甜2011和国甜106为材料, 研究了盐分对甜高粱种子萌发期生长过程的影响, 并比较了耐盐性差异。以耐盐性弱的国甜106为试材, 探究盐分胁迫下不同生长调节物质[γ-氨基丁酸(GABA)、赤霉素(GA₃)、激动素(KT)和水杨酸(SA)]对甜高粱种子吸水萌发过程中生长特性的调节效应。表明, 盐分胁迫显著抑制种子的吸水萌发, 降低种子的吸水速率、发芽势、发芽率、发芽指数, 增加种子的相对盐害率和丙二醛(MDA)含量。外源生长调节物质可有效缓解盐害, 显著增加种子的吸水率、发芽率、可溶性糖含量、可溶性蛋白含量, 提高SOD (超氧化物岐化酶)、POD (过氧化物酶)、CAT (过氧化氢酶)的活性, 促进K ⁺、Ca ²⁺、Mg ²⁺离子的吸收, 降低Na ⁺和MDA含量。外源生长调节物质主要是通过提高保护酶活性、渗透调剂物质含量和维持体内离子平衡来提高耐盐性。GA₃和GABA对盐害的缓解效应较好, 而KT促进种子对Mg ²⁺的吸收效果较好。本研究表明外源生长调节物质(尤其是 GA₃和 GABA)可用于盐碱地高粱生产, 为减轻盐碱地对高粱的盐碱胁迫提供了理论依据。

Impact of long-term salinity and subsequent oxidative stress was studied on cellular antioxidants, proline accumulation and lipid profile of Artemisia annua L. (Sweet Annie or Qinghao) which yields artemisinin (Qinghaosu), effective against cerebral malaria-causing strains of Plasmodium falciparum. Under salinity (0.0-160 mM NaCl), in A. annua, proline accumulation, contents of ascorbate and glutathione and activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR) and catalase (CAT) increased, but the contents of reduced forms of glutathione (GSH) and ascorbate declined. The fatty-acid profiling revealed a major salinity-induced shift towards long-chain and mono-saturated fatty acids. Myristic acid (14:0), palmitoleic acid (16:1), linoleic acid (18:2) and erucic acid (22:1) increased by 141%, 186%, 34% and 908%, respectively, in comparison with the control. Contents of oleic acid (18:1), linolenic acid (18:3), arachidonic acid (22:0) and lignoceric acid (24:0) decreased by 50%, 17%, 44% and 78%, respectively. Thus, in A. annua, salinity declines ascorbate and GSH contents. However, increased levels of proline and total glutathione (GSH+GSSG), and activities of antioxidant enzymes might provide a certain level of tolerance. Modification in fatty-acid composition might be a membrane adaptation to long-term salinity and oxidative stress.

Salinity is one of the major abiotic factors threatening food security worldwide. Recently, our understanding of early processes underlying salinity tolerance has expanded. In this review, early signaling events, such as phospholipid signaling, calcium ion (Ca(2+)) responses, and reactive oxygen species (ROS) production, together with salt stress-induced abscisic acid (ABA) accumulation, are brought into the context of long-term salt stress-specific responses and alteration of plant growth. Salt-induced quiescent and recovery growth phases rely on modification of cell cycle activity, cell expansion, and cell wall extensibility. The period of initial growth arrest varies among different organs, leading to altered plant morphology. Studying stress-induced changes in growth dynamics can be used for screening to discover novel genes contributing to salt stress tolerance in model species and crops.

Melatonin (N-acetyl-5-methoxytryptamine), a well-known animal hormone, was discovered in plants in 1995 but very little research into it has been carried out since. It is present in different parts of all the plant species studied, including leaves, stems, roots, fruits and seeds. This brief review will attempt to provide an overview of melatonin (its discovery, presence and functions in different organisms, biosynthetic route, etc.) and to compile a practically complete bibliography on this compound in plants. The common biosynthetic pathways shared by the auxin, indole-3-acetic, and melatonin suggest a possible coordinated regulation in plants. More specifically, our knowledge to date of the role of melatonin in the vegetative and reproductive physiology of plants is presented in detail. The most interesting aspects for future physiological studies are presented.

Brassinosteroids (BRs) induce plant tolerance to a wide spectrum of stresses. To study how BR induces stress tolerance, we manipulated the BR levels in cucumber (Cucumis sativus) through a chemical genetics approach and found that BR levels were positively correlated with the tolerance to photo-oxidative and cold stresses and resistance to Cucumber mosaic virus. We also showed that BR treatment enhanced NADPH oxidase activity and elevated H(2)O(2) levels in apoplast. H(2)O(2) levels were elevated as early as 3 h and returned to basal levels 3 d after BR treatment. BR-induced H(2)O(2) accumulation was accompanied by increased tolerance to oxidative stress. Inhibition of NADPH oxidase and chemical scavenging of H(2)O(2) reduced BR-induced oxidative and cold tolerance and defense gene expression. BR treatment induced expression of both regulatory genes, such as RBOH, MAPK1, and MAPK3, and genes involved in defense and antioxidant responses. These results strongly suggest that elevated H(2)O(2) levels resulting from enhanced NADPH oxidase activity are involved in the BR-induced stress tolerance.

During germination in distilled water (dH(2)O) on a horizontally positioned Petri dish, emerging primary roots of grass pea (Lathyrus sativus L) grew perpendicular to the bottom of the Petri dish, due to grayitropism. However, when germinated in exogenous hydrogen peroxide (H2O2), the primary roots grew parallel to the bottom of the Petri dish and asymmetrically, forming a horizontal curvature. Time-course experiments showed that the effect was strongest when H2O2 was applied prior to the emergence of the primary root. H2O2 failed to induce root curvature when applied post-germination. Dosage studies revealed that the frequency of primary root curvature was significantly enhanced with increased H2O2 concentrations. This curvature could be directly counteracted by dimethylthiourea (DMTU), a scavenger of H2O2, but not by diphenylene iodonium (DPI) and pyridine, inhibitors of H2O2 production. Exogenous H2O2 treatment caused both an increase in the activities of H2O2-scavenging enzymes [including ascorbate peroxidase (APX: EC 1.11.1.11), catalase (CAT: EC 1.11.1.6) and peroxidase (POD: EC 1.11.1.7)] and a reduction in endogenous H2O2 levels and root vitality. Although grass pea seeds absorbed exogenous H2O2 during seed germination, DAB staining of paraffin sections revealed that exogenous H2O2 only entered the root epidermis and not inner tissues. These data indicated that exogenously applied H2O2 could lead to a reversible loss of the root gravitropic response and a horizontal curvature in primary roots during radicle emergence of the seedling. (C) 2012 Elsevier Masson SAS.

为了阐明栓皮栎种子萌发期对盐碱胁迫的耐受性,研究了不同浓度(0、50、100、200和400 mmol/L) NaCl和Na₂CO₃胁迫对其种子萌发、生长、保护酶活性和有机渗透调节物质等的影响,结果表明:(1)盐碱胁迫对栓皮栎种子的萌发率和发芽指数均没有显著影响;随着Na⁺浓度的升高,NaCl和Na₂CO₃处理下的胚根长度、胚根生长速率、胚根鲜重均受到抑制,呈现下降趋势;活力指数和耐盐指数在NaCl胁迫下表现为较低浓度(50 mmol/L)促进,较高浓度(100, 200, 400 mmol/L)抑制,而在Na₂CO₃处理下则不断下降;相对盐害率在两种处理下均表现波动趋势。(2)通过建立活力指数、胚根长度等与Na⁺浓度的回归方程,发现在NaCl胁迫下栓皮栎种子活力指数、胚根鲜重、胚根长度和胚根生长速率的临界值分别为300.0、300.0、333.6、369.6 mmol/L。(3)在NaCl和Na₂CO₃胁迫下,随Na⁺浓度的增加,丙二醛含量增幅显著;NaCl处理下的SOD(superoxide dismutase)活性呈现先升高后降低的趋势,而Na₂CO₃处理下则均低于对照;POD(peroxidase)活性变化不显著;CAT(catalase)活性均表现为先降低后升高;脯氨酸、可溶性蛋白和可溶性糖含量均随着Na⁺浓度的升高而呈现不同程度上升趋势。(4)等Na⁺浓度时,NaCl处理下的各项生长指标均高于Na₂CO₃处理,丙二醛、保护酶活性及渗透调节物质含量均低于Na₂CO₃处理,说明Na₂CO₃对栓皮栎种子的影响比NaCl更为显著。

本试验以蒺藜苜蓿种子为材料,预先用0.1,0.3和1.0 mmol/L 硝普钠(SNP, NO 供体)浸种,通过计算相关萌发指标,测定种子萌发过程中各项生理指标及抗氧化系统酶活性,研究外源NO对2.0% NaCl胁迫下蒺藜苜蓿种子萌发生理特性及活性氧代谢的影响。结果表明,0.1 mmol/L SNP能显著缓解盐胁迫对蒺藜苜蓿种子造成的伤害,使蒺藜苜蓿种子的发芽率、发芽势、发芽指数和活力指数分别提高了333.40%,79.64%,171.93%和100.00%;种子可溶性糖、可溶性蛋白和脯氨酸含量分别提高了21.1%,42.3%和123.1%,淀粉含量降低了17.7%,淀粉酶活性提高了29.7%,丙二醛(MDA)和超氧阴离子(\begin{array}{c}{O_2}^{-·}\end{array})含量分别降低了21.8%和27.2%,超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性和抗坏血酸过氧化物酶(APX)活性分别增加了28.6%,43.1%,56.2%和60.3%;与0.1 mmol/L SNP处理相比,0.3 mmol/L SNP处理对盐胁迫下蒺藜苜蓿种子萌发的促进、氧化损伤的缓解和抗氧化系统酶活性的提高显著降低;1.0 mmol/L SNP处理对盐胁迫下蒺藜苜蓿种子的萌发起到抑制作用。说明低浓度的NO可通过降低种子MDA和\begin{array}{c}{O_2}^{-·}\end{array}含量,提高种子脯氨酸含量以及激活抗氧化系统酶活性,减轻盐胁迫对蒺藜苜蓿种子的伤害,促进淀粉、可溶性蛋白的水解,从而加速种子萌发。