胀果甘草种子萌发对干旱胁迫的生理响应

为探讨胀果甘草种子萌发对干旱胁迫的生理生化适应机制,以聚乙二醇(PEG)-6000模拟干旱胁迫,分析了胀果甘草(Glycyrrhiza inflata)种子萌发过程中发芽率(GR)、丙二醛(MDA)及游离脯氨酸(Pro)、可溶性糖(SS)含量和超氧化物歧化酶(SOD)、过氧化物酶(POD)活性的动态变化规律。结果显示,水势为-0.1MPa时,GR达到100%,之后随着干旱胁迫增强而显著降低(P0.05);MDA、Pro含量及SOD、POD活性都表现出水势≥-0.2MPa时增加和-1.4MPa≤水势-0.2MPa时减少的明显趋势(P0.05),这4个指标两两之间的相关关系均达到显著水平(P0.05);而干旱胁迫增强使SS含量显著增加(P0.05)。     

Spd浸种对盐胁迫下番茄（Solanum lycopersicum)幼苗的保护效应

通过水培试验,研究了100 mmol/L NaCl盐浓度下,0.25 mmol/L Spd浸种处理对两个番茄品种白果强丰(耐盐基因型)和江蔬14号(盐敏感基因型)植株干重、根冠比(R/T)、幼苗叶片和根系抗氧化酶活性及活性氧含量的影响.具体试验处理如下:(a) 对照(蒸馏水浸种+ 0 mmol/L NaCl),(b) NaCl (蒸馏水浸种+ 100 mmol/L NaCl),(c) Spd(0.25 mmol/L Spd浸种 +100 mmol/L NaCl).结果表明,在盐胁迫下,两个番茄品种幼苗叶片和根系内超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性升高,H2O2含量和O·-2产生速率增高,幼苗生长受到抑制,幼苗地上部、地下部干重均明显低于对照,R/T增大,且江蔬14号的变化幅度大于白果强丰.Spd浸种处理降低了盐胁迫下番茄幼苗叶片和根系内O·-2产生速率和H2O2含量,进一步提高了SOD、POD和CAT活性,促进幼苗干重增加,缓解了盐胁迫对植株的伤害.与耐盐基因型番茄品种白果强丰相比,Spd浸种处理对盐敏感基因型番茄品种江蔬14号的作用效果更为明显.总之,Spd浸种处理通过提高盐胁迫下植株体内抗氧化酶活性,降低ROS水平来缓解盐胁迫对番茄幼苗的伤害,提高幼苗耐盐能力.     

Plant sugars are crucial players in the oxidative challenge during abiotic stress: extending the traditional concept

Plants suffering from abiotic stress are commonly facing an enhanced accumulation of reactive oxygen species (ROS) with damaging as well as signalling effects at organellar and cellular levels. The outcome of an environmental challenge highly depends on the delicate balance between ROS production and scavenging by both enzymatic and metabolic antioxidants. However, this traditional classification is in need of renewal and reform, as it is becoming increasingly clear that soluble sugars such as disaccharides, raffinose family oligosaccharides and fructans – next to their associated metabolic enzymes – are strongly related to stress‐induced ROS accumulation in plants. Therefore, this review aims at extending the current concept of antioxidants functioning during abiotic stress, with special focus on the emanate role of sugars as true ROS scavengers. Examples are given based on their cellular location, as different organelles seem to exploit distinct mechanisms. Moreover, the vacuole comes into the picture as important player in the ROS signalling network of plants. Elucidating the interplay between the mechanisms controlling ROS signalling during abiotic stress will facilitate the development of strategies to enhance crop tolerance to stressful environmental conditions.     

Exudation of an allelopathic substance lepidimoide from seeds during germination

Lepidimoide promotes growth of the cockscomb hypocotyl. It is exuded from germinating seeds of various plant species into their culture environment. The mode of exudation of lepidimoide from seeds into the culture solution, using sunflower and buckwheat seeds, was studied in relation to seed germination. In the dry seeds, about 75% of the lepidimoide was found in the seed coat and about 25% in the kernel. Upon water imbibition it was released into the culture solution. However, the quantity of lepidimoide detected in the seed exudate was more than three times the total amount in dry and imbibed seeds, suggesting that lepidimoide was also produced de novo in the seeds and subsequently released. When seed coats or kernels were imbibed separately, the quantity of lepidimoide released from the seed coats into the culture solution was much the same as that in the dry seeds, but the amount of lepidimoide detected in the exudate of kernels was about 16 times that in the dry kernels. These results suggest that lepidimoide, already present in dry seeds, as well as that newly produced in the kernels following imbibition, was released into the environment.     

红砂和霸王种子萌发对干旱与播深条件的响应

红砂(Reaumuria soongorica)和霸王(Zygophyllum xantho xylum)分别是我国西北干旱荒漠区重要的超旱生小灌木和灌木.试验室条件下,研究了两种灌木种子萌发对干旱胁迫(以PEG模拟干旱条件)和播深的响应.干旱胁迫设0、 -0.3、 -0.6、-0.9、-1.2、-1.5、-1.8、-2.1、-2.4、-2.7MPa共10个处理,播深设0、0 .3,0.5,1.0,1.5,2.0,3.0,4.0cm共8个处理.结果显示模拟干旱条件下,供试种的发芽势(3d发芽率)皆从-0.3MPa起即开始显著下降(P<0.05) .发芽率红砂从-0 .9MPa渗透势、霸王从-0.6MPa开始显著降低;种子萌发的最低渗透势阈值红砂和霸王分别为-1.8MPa和-1.5MPa.干旱胁迫对种子胚芽生长有抑制作用,但轻度干旱可促进初生根生长,重度干旱胁迫抑制初生根生长.播深实验表明,红砂和霸王种子均为子叶出土发芽类型 .一般情况下,供试种随播深增加胚芽长度呈增加而初生根呈下降趋势,但霸王在播于土表时初生根生长受到抑制.实验室条件下,达到最大出苗率的播深红砂为0～0.5cm,霸王为0 ～2cm.在适宜条件下,红砂和霸王种子萌发的最低需水量分别为110%和90%,初始萌发时间分别为40h和48h.红砂种子发芽势低(28%)、萌发持续而分散;霸王种子发芽势高(87%) 、萌发整齐.讨论了两种种子发芽对干旱和播深的响应特征及其生态生物学意义.     

水分胁迫对蔓性千斤拔种子萌发和生理指标的响应

利用不同浓度的聚乙二醇(PEG)模拟水分胁迫条件,测定蔓性千斤拔种子发芽率、发芽指数、平均发芽速度、苗长等萌发特性及渗透调节物质、保护酶活性等生理指标。结果显示,随着PEG浓度的增加,苗长受到明显抑制,发芽率影响不大,降低了平均发芽速度,在4%浓度范围内提高了发芽指数;可溶性糖、脯氨酸、可溶性蛋白含量呈上升趋势,超氧化物歧化酶(SOD)、过氧化物酶(POD)活性呈逐渐上升的趋势。这些结果表明,在一定的PEG胁迫浓度范围内,蔓性千斤拔种子萌发有较高的膜保护酶系统及渗透调节能力,并能不同程度的提高其萌发的整齐度。     

Antagonism between abscisic acid and gibberellins is partially mediated by ascorbic acid during seed germination in rice

The antagonism between abscisic acid (ABA) and gibberellin (GA) plays a key role in controlling seed germination,^1,2 but the mechanism of antagonism during this process is not known. In the associated study,³ we investigated the relationship among ABA, reactive oxygen species (ROS), ascorbic acid (ASC) and GA during rice seed germination. ROS production is reduced by ABA, which hence results in decreasing ASC accumulation during imbibition. GA accumulation was also suppressed by a reduced ROS and ASC level, whereas application of exogenous ASC can partially rescue seed germination from ABA treatment. Further results show that production of ASC, which acts as a substrate in GA biosynthesis, was significantly inhibited by lycorine which thus suppressed the accumulation of GA. Consequently, expression of GA biosynthesis genes was suppressed by the low levels of ROS and ASC in ABA-treated seeds. These studies reveal a new role for ASC in mediating the antagonism between ABA and GA during seed germination in rice.     

水分胁迫下植物活性氧代谢研究进展(综述Ⅰ)

本文概述植物活性氧代谢的研究及水分胁迫下活性氧与植物抗旱性(抗水分胁迫)之间的关系;着重叙述水分胁迫响应中植物脱毒酶和抗氧化物的功能和机制;并对植物抗氧化基因的研究进展作了讨论。     

桔梗种子萌发对低温、干旱及互作胁迫的响应

以药用植物桔梗种子为材料,研究了低温、干旱及其互作对种子萌发和幼苗生长的影响,旨在探索在春寒干旱条件下其种子萌发对策及生态适应性,为桔梗野生种群恢复及人工栽培群体构建提供依据.结果表明,温度、干旱及其互作对桔梗种子萌发和幼苗生长均有显著影响.0-10％ PEG水分条件下,在变温10/20℃及恒温15-25℃下桔梗种子能够良好萌发(10％ PEG、20℃除外),而15％ PEG可显著抑制萌发.低温(10℃)下种子萌发始时间延迟,发芽率降低.随干旱胁迫程度的增加,10℃发芽率呈先升后降趋势,而其它温度下,发芽率和发芽指数均呈下降趋势.随温度的降低,幼苗根长、茎长及鲜重均呈下降趋势,且幼根生长对温度变化更为敏感.     

野牛草叶片活性氧及其清除系统对水分胁迫的响应

逆境条件下活性氧产生及其清除效率是衡量植物抗性的重要指标,而活性氧对植物组织的氧化伤害和抗氧化酶活性常因材料的遗传或生理差异性而发生变化。以同一基因型的野牛草(Buchloe dactyloides(Nutt.)Engelm'texoka')克隆分株叶片为材料,采用Hoagland营养液培养,研究了10%、20%和30%PEG-6000模拟干旱胁迫下,野牛草叶片活性氧的产生、脂质过氧化和抗氧化酶活性变化规律。结果表明:随着PEG-6000浓度的增加及胁迫时间的延长,超氧阴离子(O2-.)的产生速率、过氧化氢(H2O2)和丙二醛(MDA)含量均显著增加;超氧化物歧化酶(SOD EC1.15.1.1)、愈创木酚过氧化物酶(G-POD EC1.11.1.7)和过氧化氢酶(CATEC1.11.1.6)活性呈先上升后下降的变化趋势;SOD、G-POD与CAT活性达到峰值的时间随PEG-6000浓度的增加而提前。认为水分胁迫下,抗氧化酶可有效清除活性氧自由基,但随胁迫时间的延长,抗氧化酶活性受到抑制。     

油菜素内酯浸种对盐胁迫番茄种子萌发的影响及其生理机制

为揭示油菜素甾醇类化合物提高作物耐盐的效应和机理,研究了10^-11、10^-10、10^-9、10^-8、10^-7、10^-6、10^-5 mol/L 2,4-表油菜素内酯（EBL）浸种处理对0、50、100、150、175 mmol/L NaCl胁迫7 d的番茄种子萌发、生长、溶质积累、抗氧化代谢的影响。结果显示：NaCl浓度越高的盐胁迫下,10^-9 mol/L EBL浸种可体现出越显著的促进番茄种子萌发的效应;在所有处理下,EBL浸种浓度过高,即10^-6、10^-5 mol/L EBL,均表现出对种子萌发的抑制效应。盐胁迫下种子萌发后,一定浓度的EBL浸种可表现出明显的增加种子胚根和下胚轴长,提高萌发种子鲜重和种子活力指数,其中10^-9 mol/L EBL浸种处理促进效果最适;EBL浸种浓度过高,则表现出抑制效应。150 mmol/L NaCl胁迫或非盐胁迫下,10^-9 mol/L EBL浸种均可降低萌发种子体内的O₂^·-、H₂O₂、丙二醛（MDA）和脯氨酸（Pro）含量;盐胁迫下,10^-9 mol/L EBL浸种可显著提高萌发种子可溶性糖（SS）和可溶性蛋白（SP）的含量。150 mmol/L NaCl胁迫或非盐胁迫下,10^-9 mol/L EBL处理可不同程度促进番茄种苗超氧化物歧化酶（SOD）和过氧化物酶（POD）活性的上升。综上所述,盐胁迫下,一定浓度范围内的EBL浸种可明显促进番茄种子萌发或成苗,其中以10^-9 mol/L EBL浸种的效果最好,主要是因为EBL施用可积极促进番茄种子萌发中物质转化,SS和SP等溶质积累增多,增强其渗透调节能力;同时SOD和POD酶活增强,缓解盐胁迫导致番茄种子萌发中的次生氧化胁迫。     

Redox regulatory mechanisms in cellular stress responses

BACKGROUND: Reactive oxygen species are produced in a highly localized and specific pattern in biological stress responses. The present review examines the redox regulatory aspects of a number of molecular stress response mechanisms in both prokaryotes and eukaryotes. SCOPE: The present review provides examples representing both the cytoplasmic stress response, often studied as the heat shock response, as well as the stress response of the endoplasmic reticulum, known as the unfolded protein response. The examples have been selected to illustrate the variety of ways that redox signals mediate and affect stress responses. CONCLUSIONS: Redox regulatory mechanisms are intricately embedded in both the cytoplasmic and endoplasmic reticulum stress responses at multiple levels. Many different stimuli, both internal and external, activate endogenous production of reactive oxygen species as a necessary part of the intracellular communication system that activates stress responses.     

盐分和水分胁迫对盐生植物灰绿藜种子萌发的影响

研究了不同浓度的NaCl和复合盐及等渗溶液(PEG-6000)处理下盐生植物灰绿藜(Chenopodium glaucum L.)种子的萌发状况.结果表明:灰绿藜种子的萌发率与处理溶液的浓度或渗透势之间有显著的负相关关系;在低浓度盐溶液(2.9 g*L-1)中灰绿藜种子的萌发率高于对照(蒸馏水);NaCl溶液对灰绿藜种子萌发的抑制作用大于复合盐溶液.渗透势为-0.2和-0.5 mPa 时,PEG-6000溶液对灰绿藜种子萌发的抑制作用小于等渗NaCl溶液,而在较高渗透势溶液中则正好相反.用渗透势≤-1.8 mPa 的PEG-6000溶液及所有浓度的NaCl和复合盐溶液处理的种子复水后相对萌发率都达到了90%以上,说明一定程度的盐分和水分胁迫对灰绿藜种子萌发潜力并没有很大的影响,并且萌发恢复率随处理盐浓度或PEG-6000溶液渗透势(≤-1.4 mPa)的增加而增加.     

度胁迫对罂粟种子萌发影响及其活力变化规律的研究

为妥善保存罂粟种质资源及防止种子老化,研究了温度对罂粟种子萌发及种子活力的影响。结果表明:罂粟为高温敏感低温萌发型种子,发芽的适宜温度为10～20℃,最适温度为18℃左右,低于5℃和高于20℃的温度,种子萌发受到抑制;在对其进行丸化包衣时,加热温度应控制在60℃以内,时间应控制在60min以内;在常温库存条件下,罂粟种子活力随贮藏年限的增加而下降,贮藏时间超过五年后,发芽率低于50%,不宜作种用,在作为种质资源保存时,须每隔五年繁殖一次。     

Changes in the antigenic properties of proteins of laboratory mice during oxidative stress

Changes in the level of oxidative damage to proteins in CD1 outbred mice γ irradiated with a dose of 3 Gy have been studied. The changes were estimated from the amount of carbonyl groups (CG) in the proteins. It was found that two hours after exposure to γ radiation, the amount of CG in the cytoplasmic and nuclear fractions of the liver, heart, brain, and spleen sharply increased. Two months after irradiation, the level of CG in the cytoplasmic and nuclear subcellular fractions of the liver and brain decreased to the level of CG in the control animals, which were not exposed to radiation. In the subcellular fractions of the heart and spleen, the increase in the degree of damage was more significant and a high level of damage was observed even two months after irradiation. An enhancement of the antigenic properties of proteins from the liver, heart, and spleen in the postirradiation period was found. Spleen proteins were most immunogenic. A comparison of the antigenic properties of proteins isolated from the tissues 60 days after irradiation revealed a correlation between the level of oxidative damage and the immunogenicity of the total protein fraction.     

Variation in temperature and light but not salinity invokes antioxidant enzyme activities in germinating seeds of Salsola drummondii

Seeds with efficient antioxidant defence system show higher germination under stress conditions; however, such information is limited for the halophyte seeds. We therefore studied lipid peroxidation and antioxidant responses of a leaf-succulent halophyte Salsola drummondii during seed germination under different salinity levels (0, 200 and 800 mM NaCl), temperature (10/20, 20/30 and 25/35°C) and light regimes. Seeds absorbed water and germinated in less than 1 h in non-saline control while increases in salinity decreased the rate of water uptake as well as seed germination. Non-optimal temperatures (10/20 and 25/35°C) and complete dark condition reduced seed germination in comparison to those seeds germinated under optimal temperature (20/30°C) and 12-h photoperiod, respectively. Generally, higher lipid peroxidation and antioxidant enzyme activities were observed in seeds at non-optimal temperature and in those seeds germinated in dark. Decrease in reduced ascorbic acid content was found in highest salinity and temperature treatments, while reduced glutathione content did not change significantly with changes in salinity, temperature and light regimes. These results indicate variation in temperature and light but not salinity enhances antioxidant enzyme activities in germinating seeds of Salsola drummondii.     

Regulation of growth response to water stress in the soybean primary root. I. Proteomic analysis reveals region‐specific regulation of phenylpropanoid metabolism and control of free iron in the elongation zone

In water‐stressed soybean primary roots, elongation was maintained at well‐watered rates in the apical 4 mm (region 1), but was progressively inhibited in the 4–8 mm region (region 2), which exhibits maximum elongation in well‐watered roots. These responses are similar to previous results for the maize primary root. To understand these responses in soybean, spatial profiles of soluble protein composition were analysed. Among the changes, the results indicate that region‐specific regulation of phenylpropanoid metabolism may contribute to the distinct growth responses in the different regions. Several enzymes related to isoflavonoid biosynthesis increased in abundance in region 1, correlating with a substantial increase of isoflavonoid content in this region which could contribute to growth maintenance via various potential mechanisms. In contrast, caffeoyl‐CoA O‐methyltransferase, which is involved in lignin synthesis, was highly up‐regulated in region 2. This response was associated with enhanced accumulation of lignin, which may be related to the inhibition of growth in this region. Several proteins that increased in abundance in both regions of water‐stressed roots were related to protection from oxidative damage. In particular, an increase in the abundance of ferritin proteins effectively sequestered more iron and prevented excess free iron in the elongation zone under water stress.     

Canola seed germination and seedling emergence from pre-hydrated and re-dried seeds subjected to salt and water stresses at low temperatures

Low soil temperatures and low water potentials reduce and delay the seed germination of canola (Brassica rapa L., B. napus L.) in western Canada. Germination is also very sensitive to the salinity effects of nitrogen fertiliser placed with the seed, especially when the seed bed is relatively dry. The effects of pre-hydration and re-drying treatment on canola (Brassica rapa L. cv. Tobin) seed germination and seedling emergence at 10°C subjected to either a water or salt stress were determined. Low water potentials, induced by polyethylene glycol (PEG 8000), low soil moisture, or high concentrations of salts, reduced both germination and seedling emergence, and increased the time to 50% germination and emergence of seeds at 10°C. At equal osmotic potentials, Na₂SO₄ was less inhibitory on low temperature germination than either NaCl or PEG, suggesting that the sulphate ion partially alleviated the inhibitory effects of low water potential. Solutions of NaCI produced more abnormal seedlings compared to Na₂SO₄, suggesting that NaCl was more toxic than Na₂SO₄ during seedling development. Pre-hydration and re-drying partially overcame the inhibitory effects of both low water potential and salts on seed germination and seedling emergence at 10°C. The seed treatment increased the germination rate in Petri dishes and seedling emergence from a sandy loam soil. Water potentials or soil water contents required to inhibit 50% germination or emergence at 10°C were lower for treated seeds compared to control seeds. Salt concentrations inhibiting 50% emergence were higher for treated seeds than control seeds. Neither treated nor control seeds produced seedlings which emerged if the soil water content was lower than 9% or when the soil was continuously irrigated with salt solutions of 100 mmol kg^-1 of NaCl or 50 mmol kg^-1 of Na₂SO₄. These results suggest that the pre-hydration and re-drying treatment did not lower the base water potentials at which seedling emergence could occur. Abnormal seedlings were observed in both treated and control seeds, particularly if the soil was watered with NaCl solutions; however, the seed treatment reduced the number of abnormal seedlings.     

Role of plant respiratory burst oxidase homologs in stress responses

Plant respiratory burst oxidase homologs (Rbohs), which are also named nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOXs), are the homologs of mammalian phagocyte gp91^phox. As a unique among other reactive oxygen species (ROS) production mechanisms in plants, NADPH oxidases can integrate different signal transduction pathways, such as calcium, protein phosphorylation catalysed by protein kinases, nitric oxide, and lipid messengers. Coupling with genetic studies, the ability of plant NADPH oxidases to integrate different signal transduction pathways with ROS production demonstrates their involvement in many important biological processes in cells, such as morphogenesis and development, and stress responses. Here, we focus on several current studies concerning the role of plant NADPH oxidases in stress responses.     

水分胁迫下紫花苜蓿和高粱种子萌发特性及幼苗耐旱性

利用PEG溶液(水势梯度:-0.1～-0.5MPa)模拟水分胁迫,研究了紫花苜蓿(品种:阿尔冈金和陇东)和高粱(品种:抗四)种子的萌发能力的变化及对萌发环境的最低水分需求,并进行种间差异比较.结果显示:PEG水分胁迫通过限制种子有效水分的吸收而抑制了其萌发,且随着胁迫强度的增加,萌发能力减弱,主要表现在:萌发率、吸水速率、萌发活力、萌发胁迫指数等随胁迫强度的增加而下降,根芽比则随之增加.另一方面,种子群体萌动、萌发和出苗达50%概率时间随胁迫强度的增加而越发延迟,且各阶段对环境临界水势的需求不同,出苗阶段最为严格,说明种子出苗过程对环境水分胁迫最为敏感,耐旱能力最弱.相比之下,在同等胁迫条件下,高粱种子的萌发能力较苜蓿种子受到影响较小,各个阶段对环境水势的需求也相对较为宽松.因此,苜蓿苗期对干旱胁迫的忍耐能力不及高粱,且出苗过程中对环境水分条件的需求存在品种间差异.