Future drought is projected to occur under warmer temperature conditions as climate change progresses, referred to here as globalchange-type drought yet quantitative assessments of the triggers and potential extent of drought-induced vegetation die-off remain pivotal uncertainties in assessing climate-change impacts. Of particular concern is regional-scale mortality of overstory trees, which rapidly alters ecosystem type, associated ecosystem properties, and land surface conditions for decades. Here, we quantify regional-scale vegetation die-off across southwestern North American woodlands in 2002-2003 in response to drought and associated bark beetle infestations. At an intensively studied site within the region, we quantified that after 15 months of depleted soil water content, >90% of the dominant, overstory tree species (Pinus edulis, a$pi\tilde{n}on$) died. The die-off was reflected in changes in a remotely sensed index of vegetation greenness (Normalized Difference Vegetation Index), not only at the intensively studied site but also across the region, extending over 12,000 km2or more; aerial and field surveys confirmed the general extent of the die-off. Notably, the recent drought was warmer than the previous subcontinental drought of the 1950s. The limited, available observations suggest that die-off from the recent drought was more extensive than that from the previous drought, extending into wetter sites within the tree species' distribution. Our results quantify a trigger leading to rapid, drought-induced die-off of overstory woody plants at subcontinental scale and highlight the potential for such die-off to be more severe and extensive for future global-change-type drought under warmer conditions.

In response to drought bdelloid and monogonont rotifers undergo anhydrobiosis and are assumed to synthesize protective chemicals, which are commonly sugars. In contrast to most anhydrobionts, bdelloids have earlier been shown to lack trehalose as protective chemical, and more importantly to lack trehalose synthase (tps) genes. It remains to be assessed if the absence of trehalose is a characteristic common to the entire taxon Rotifera, or if it is limited to bdelloids, or is peculiar to the two bdelloid species investigated so far. In this study, anhydrobiotic adults of a bdelloid species ( Macrotrachela quadricornifera) and resting eggs of a monogonont species ( Brachionus plicatilis) were analysed by thin layer chromatography and gas chromatography to detect the presence of trehalose. No trehalose was detected in the bdelloid, while the anhydrobiotic resting egg of the monogonont rotifer contained about 0.35% trehalose of its dry weight. Although very little, the presence of trehalose in B. plicatilis suggests that the trehalose synthase genes, absent in bdelloid rotifers, are present in non-bdelloid rotifers.

采用盆栽控水法,研究了珍稀濒危植物堇叶紫金牛(Ardisia violacea)在持续干旱条件下的生理响应.随着持续干旱时间的延长,堇叶紫金牛应对持续干旱的阶段可分为适应期、轻度干旱期、中度干旱期和重度干旱 期.在适应期和轻度干旱期,堇叶紫金牛叶片游离脯氨酸和可溶性糖含量稳定在一个较低水平,可溶性蛋白质含量先下降后快速上升,细胞膜系统和抗氧化酶系统能 主动进行生理调节;中度干旱期,丙二醛(MDA)含量和质膜相对透性迅速升高,细胞膜系统受损加剧,游离脯氨酸、可溶性糖含量均急剧增加,对抵御干旱起到 重要的渗透调节作用.在轻度干旱期和中度干旱期,光合色素中叶绿素a和叶绿素b含量显著提高,以抵抗干旱胁迫.重度干旱期,细胞膜系统、抗氧化酶SOD、 游离脯氨酸和可溶性糖含量上升,但MDA略微下降,这时可能达到植物耐受干旱的极限,不再发生膜脂过氧化作用.综上表明,堇叶紫金牛具有较强的耐旱 性,RWC为49.94％是细胞膜系统、抗氧化酶系统和渗透调节物质含量变化的拐点,渗透调节和抗氧化酶系统的主动适应是其耐旱的主要机制.

采用盆栽控水法,研究了珍稀濒危植物堇叶紫金牛(Ardisia violacea)在持续干旱条件下的生理响应.随着持续干旱时间的延长,堇叶紫金牛应对持续干旱的阶段可分为适应期、轻度干旱期、中度干旱期和重度干旱 期.在适应期和轻度干旱期,堇叶紫金牛叶片游离脯氨酸和可溶性糖含量稳定在一个较低水平,可溶性蛋白质含量先下降后快速上升,细胞膜系统和抗氧化酶系统能 主动进行生理调节;中度干旱期,丙二醛(MDA)含量和质膜相对透性迅速升高,细胞膜系统受损加剧,游离脯氨酸、可溶性糖含量均急剧增加,对抵御干旱起到 重要的渗透调节作用.在轻度干旱期和中度干旱期,光合色素中叶绿素a和叶绿素b含量显著提高,以抵抗干旱胁迫.重度干旱期,细胞膜系统、抗氧化酶SOD、 游离脯氨酸和可溶性糖含量上升,但MDA略微下降,这时可能达到植物耐受干旱的极限,不再发生膜脂过氧化作用.综上表明,堇叶紫金牛具有较强的耐旱 性,RWC为49.94％是细胞膜系统、抗氧化酶系统和渗透调节物质含量变化的拐点,渗透调节和抗氧化酶系统的主动适应是其耐旱的主要机制.

The amino acid L-proline has been the subject of intensive research during the past ten to fifteen years. This stems from the observations that it incorporates into peptide linkage thereby serving as a precursor to peptidyl-bound L-hydroxyproline, a constituent of "extensin," and that it accumulates when some plants are exposed to diverse biological and environmental stresses. The contents of selected papers which have been published during the last quarter of a century regarding the isolation, assay, biosynthesis, metabolism, transport and function of L-proline within various plant tissues and their cells are both interpreted and summarized in this review. Occasionally, relevant information from animal and bacterial systems concerning these topics is included. Hydroxyproline-containing proteins are not considered. L-proline was reported to be a constituent of leaves as early as the 1950's. Since then, it and its analogues have been extracted from the organs of a variety of plants. The analogues include: methyl-hydroxylproline; 4-methylene-DL-proline; L-azetidine-2-carboxylic acid; 2,3,cis-3,4-trans-dihydroxy-L-proline; L-pipecolic acid and 4-trans-hydroxyproline. L-proline can be both detected and quantified by colorimetric, combined fluorometric-amino acid analyzer and gas chromatographic procedures. L-proline may be synthesized from L-glutamic acid via the following biosynthetic pathway: L-glutamic acid $@>\gamma \text{-glutamic acid kinase}>>$ γ-glutamyl phosphate $@>\gamma \text{-glutamyl phosphate reductase}>>$ γ-glutamyl semialdehyde $@>\text{spontaneous cyclization}>>$ Δ′-pyrroline-5-carboxylate (P5C) $@>{\rm P}5{\rm C}\ \text{reductase}>>$ L-proline. Proline can also originate from L-arginine and L-ornithine. Biosynthesis from the latter compound proceeds either through the γ-glutamyl semialdehyde and pyrroline-5-carboxylate pathway or alternatively a α-keto-δ-aminovaleric and pyrroline-2-carboxylate pathway. The metabolism of L-proline most likely involves the reverse of the biosynthetic pathway with an initial prolyl dehydrogenase- or prolyl oxidase-mediated conversion of L-proline to Δ′-pyrroline-5-carboxylate. The metabolism of L-proline has been demonstrated to occur in excised tissues and cell free extracts, cell suspension cultures and reproductive structures. Little is known about the mechanism by which L-proline is taken up by cultured plant cells and excised tissues. Once within the plant L-proline can be translocated through the phloem at velocities similar to those for carbon dioxide assimilates. In addition to serving as a substrate for peptidyl-bound hydroxyproline, L-proline may function as an adaptation to diverse biological and environmental stresses, a cryoprotectant, a nitrogen pool, a precursor for chlorophyll synthesis upon relief of stress, a regulator together with L-histidine of fertility and sterility and/or a substrate for respiration. /// Depuis ces quinze dernières années, l'amino-acide L-proline a été l'objet de recherches très intensives parce que l'on a observé que L-proline s'incorpores dans les liaisons peptidiques, et par ce moyen se sers de précurseur à la fraction peptidique L-hydroxyproline, un des constituants de "l'extensine," et s'accumule lorsque les plantes sont soumise à des contraintes environmentales et biologique diverses. Le contenu d'un certain nombre d'articles qui furent publiés ce dernier quart de siècle traite de l'isolement, les essais en laboratoire, la biosynthèse, le métabolisme, le transport et les fonctions de la L-proline dans les cellules et les tissus variés de plante sont interprétés et résumé dans cette revue. Occasionnellement, des informations complémentaires relevant des systèmes animaux et bactériens jugés utiles ont été introduites. Les protéines contenant de l'hydroxyproline n'est pas envisagé ici. Depuis le début des années mille neuf cent cinquante, la L-proline fut reconnue d'être un des constituants dans les feuilles. Depuis lors, L-proline ont été extraite, ainsi que ses analogues, d'organes de diverses sortes de plantes. Ses analogues comportent: la methyle-hydroxyle-proline; la 4-methylene DL-proline; l'acide L-azetidine-2-carboxylique; la 2,3, cis-3, 4-trans-dihydroxy-L-proline; l'acide L-pipécolique et l'hydroxyproline 4-trans. La L-proline peut être détectée et quantifié par la colorimétrie à l'analyse fluorométrique des acides aminés et par la chromatographie en phase gazeuse. La L-proline peut être synthétisée de l'acide L-glutamique par les étapes biosynthétiques suivantes: acide L-glutamique $@>\text{acide}\ \gamma \text{-glutamique kinase}>>$ γ glutamyl phosphate $@>\gamma \text{-glutamyl phosphate r}\acute{{\rm e}}\text{ductase}>>$ γ glutamyl semialdéhyde $@>\text{clyclisation spontan}\acute{{\rm e}}\text{e}>>$ Δ′-pyrroline-5-carboxylate (P5C) $@>{\rm P}5{\rm C}\ \text{r}\acute{{\rm e}}\text{ductase}>>$ L-proline. La proline peut aussi avoir son origine de L-arginine ou de L-ornithine. La biosynthèse de cette dernière a lieu soit par voie du γ glutamyl semi-aldehyde et P5C, soit par celui des réaction biosynthétiques de l'acide γ-keto δ amino valérique et du pyrroline-2-carboxylate. Le métabolisme de la L-proline probablement inclut les étapes inverses de la biosynthèse avec une conversion initiale de la L-proline dans Δ′-pyrroline-5-carboxylate gr09ce à la prolyl déhydrogenase ou la prolyl oxidase. Le métabolisme de la L-proline a été démontré de survenir dans des tissus excisés, des extraits sans cellules, des cultures de suspension cellulaires et des structures reproductives. On ne sait que très peu du mécanisme par lequel la L-proline est incorporée dans les cultures cellulaires des plantes et des tissus excisés. Une fois dans la plante la L-proline peut être transportée dans le phloème à des vélocités semblable de cells des assimilats d'oxyde de carbone. Outre son utilité comme substrat pour la hydroxyproline, bondé avec la peptidyle la L-proline peut fonctionner comme une adaptation à des contraintes biologique et environmentales diverses, un cryoprotecteur, une reserve d'azote, un précurseur de la synthèse chlorophyllienne lorsque la contrainte est levée; un régulateur, avec la L-histidine, de la fertilité et de la sterilité et/ou un substrat respiratoire.

ABSTRACT Aluminum (Al) is the most abundant metal in the earths crust, comprising about 7% of its mass. Since many plant species are sensitive to micromolar concentrations of Al, the potential for soils to be A1 toxic is considerable. Fortu- nately, most of the A1 is bound by ligands or occurs in other nonphytotoxic forms such as aluminosilicates and precip- itates. However, solubilization of this A1 is enhanced by low pH and A1 toxicity is a major factor limiting plant production on acid soils. Soil acidification can develop naturally when basic cations are leached from soils, but it can be accelerated by some farming practices and by acid rain (Kennedy, 1986). Strategies to maintain production on these soils include the application of lime to raise the soil pH and the use of plants that are tolerant of acid soils. Although A1 toxicity has been identified as a problem of acid soils for over 70 years, our knowledge about the primary sites of toxicity and the chain of events that finally affects plant growth remains largely speculative. In this paper we review recent progress that has been made in our understanding of A1 toxicity and the mechanisms of A1 tolerance in plants.

Shoots, roots, and seeds of corn (Zea mays L., cv. Michigan 500), oats (Avena sativa L., cv. Au Sable), and peas (Pisum sativum L., cv. Wando) were analyzed for their superoxide dismutase content using a photochemical assay system consisting of methionine, riboflavin, and p-nitro blue tetrazolium. The enzyme is present in the shoots, roots, and seeds of the three species. On a dry weight basis, shoots contain more enzyme than roots. In seeds, the enzyme is present in both the embryo and the storage tissue. Electrophoresis indicated a total of 10 distinct forms of the enzyme. Corn contained seven of these forms and oats three. Peas contained one of the corn and two of the oat enzymes. Nine of the enzyme activities were eliminated with cyanide treatment suggesting that they may be cupro-zinc enzymes, whereas one was cyanide-resistant and may be a manganese enzyme. Some of the leaf superoxide dismutases were found primarily in mitochondria or chloroplasts. Peroxidases at high concentrations interfere with the assay. In test tube assays of crude extracts from seedlings, the interference was negligible. On gels, however, peroxidases may account for two of the 10 superoxide dismutase forms.

During controlled water stress applied at the three-leaf stage, the barley (Hordeum vulgare L.) cultivars 'Proctor' and 'Excelsior' showed different rates of free proline accumulation and leaf-firing. Both processes were faster in Proctor (a drought-susceptible cultivar) than in Excelsior (a drought-resistant cultivar). The different rates of proline accumulation during stress in Proctor, in Excelsior, and in a wild barley (H. spontaneum C. Koch) could be attributed to differences in the rate of decline of leaf water potential ( psi leaf); at the same psi leaf value, all three genotypes contained similar amounts of free proline. After non-destructive screening of the F2 generation from a Proctor X Excelsior cross for proline-accumulating capacity under controlled water stress conditions, F3 seed from plants selected for high and low proline accumulation was obtained. When F3 palnts were tested for proline accumulation during controlled stress, the selection for proline accumulation was found to have been effective. Reselection among F3 plants and subsequent testing of the F4 generation confirmed this result. Among individual plants of the F3 generation (which was segregating for the proline accumulation trait) there was a positive association between the amount of free proline accumulated during stress and the severity of leaf-firing. Massive proline accumulation is a symptom of severe internal water stress in barley and apparently has no survival value during drought. Although there is heritable variation in the amount of proline accumulated during stress, it is not of practical value in breeding for drought resistance.ADDITIONAL ABSTRACT:During controlled water stress, rates of proline accumulation and leaf firing were greater in Proctor (drought-susceptible) than in Excelsior (drought-resistant) seedlings. The different rates of proline accumulation among the above varieties and Hordeum spontaneum (intermediate resistance) were attributable to differences in the rate of decline of leaf water potential. At a given value of the latter, similar concentrations of free proline were present in the leaves of the three genotypes. F2 plants derived from a Proctor X Excelsior cross were selected for high or low proline accumulation. F3 and subsequent F4 progenies (obtained by F3 reselection) retained the proline accumulation characteristics of the F2 selections. Both high proline concentration and intensity of leaf firing are symptomatic rather than causative of drought susceptibility. Leaf firing would be a more readily measurable selection criterion.ADDITIONAL ABSTRACT:Studies were carried out determine if high proline accumulation was associated with susceptibility or with resistance to water stress. During controlled water stress applied at the 3-leaf stage the drought-susceptible barley cv. Proctor showed higher rates of free proline accumulation and leaf firing [scorch] than did the drought-resistant cv. Excelsior. The different rates of proline accumulation during stress in Proctor, Excelsior and a wild barley were attributed to differences in the rate of decline of leaf water potential; at the same leaf water potential, all 3 genotypes contained similar amounts of free proline. Progeny from a Proctor X Excelsior cross selected for high and low proline accumulation showed a positive association between the amount of free proline accumulated during stress and the severity of leaf firing. Massive proline accumulation is a symptom of severe internal water stress in barley but has apparently no survival value during drought

Biological adaptation by-plants to drying (dessication) or drought-prone environments is analyzed. The metabolic components of adaptation and the metabolic symptoms of stress injury are reviewed. Breeding programs for selection of drought-resistance in plants are suggested.

Exposure of the excised growing region of the mesocotyl of young corn seedlings to heat shock stimulated the production of specific heat shock proteins and the intensification of synthesis of two proteins with a molecular weight of approximately 70,000. Water stress and abscisic acid also stimulated synthesis of these 70,000-dalton proteins, and other unique proteins distinct from those induced by heat shock. Growing tissues of intact corn mesocotyls exposed to heat shock, water stress, or abscisic acid accumulated mRNA species homologous to a cloned genomic probe of the 5鈥 end of the 70,000-dalton Drosophila heat shock protein gene. Since cut segments of the mesocotyl under unstressed conditions produced a similar mRNA, we suggest that the hsp 70 gene is activated in corn by a variety of diverse stresses. Production of the mRNA is rapid, but transient, being induced within 3 hours of the imposition of the stress, but declining after reaching a maximum at 9 hours.

Abstract The relationship between mannitol-induced water stress and protein synthesis was investigated in hypocotyl slices of loblolly pine (Pinus taeda L.). Mannitol-induced water stress inhibited the incorporation of l-[35S]methionine into protein. As the water potential decreased, incorporation of label into protein decreased in both the soluble- and membrane-protein fractions. There were no significant differences in response to water stress among seed sources from four different geographical regions.

The article discusses an improvement of a previously developed method for assessment of ion leakage from plant tissues as a gauge of membrane and cell wall performance under stressful environment. It employs conductometric measurements of the ion efflux from leaves and their quantitative interpretation by a theoretical model based on the laws of diffusion. Experimental data are readily fit with the model and results are in accordance with relative water content of dehydrated barley (Hordeum vulgare) seedlings of two distinct cultivars. Some new parameters obtained from fitting are proposed as reliable indicators of the leaf status. They appear to be helpful in further distinguishing the behavior of two separate cellular structures with respect to their electrolyte permeability. It is concluded that the established method based on the kinetics of ion leakage is adequate for evaluation of contrasting genotypes under normal and stress conditions. Furthermore, it could be used as a simple and powerful tool for routine analysis and screening for drought tolerance in crops.

Summary Experimental studies on CO 2 assimilation of mesophytic C3 plants in relation to relative water content (RWC) are discussed. Decreasing RWC slows the actual rate of photosynthetic CO 2 assimilation (A) and decreases the potential rate (A pot ). Generally, as RWC falls from c . 100 to c. 75%, the stomatal conductance (g s ) decreases, and with it A. However, there are two general types of relation of A pot to RWC, which are called Type 1 and Type 2. Type 1 has two main phases. As RWC decreases from 100 to c. 75%, A pot is unaffected, but decreasing stomatal conductance (g s ) results in smaller A, and lower CO 2 concentration inside the leaf (C i ) and in the chloroplast (C c ), the latter falling possibly to the compensation point. Down-regulation of electron transport occurs by energy quenching mechanisms, and changes in carbohydrate and nitrogen metabolism are considered acclimatory, caused by low C i and reversible by elevated CO 2 . Below 75% RWC, there is metabolic inhibition of A pot , inhibition of A then being partly (but progressively less) reversible by elevated CO 2 ; g s regulates A progressively less, and C i and CO 2 compensation point, 螕 rise. It is suggested that this is the true stress phase, where the decrease in A pot is caused by decreased ATP synthesis and a consequent decreased synthesis of RuBP. In the Type 2 response, A pot decreases progressively at RWC 100 to 75%, with A being progressively less restored to the unstressed value by elevated CO 2 . Decreased g s leads to a lower C i and C c but they probably do not reach compensation point: g s becomes progressively less important and metabolic limitations more important as RWC falls. The primary effect of low RWC on A pot is most probably caused by limited RuBP synthesis, as a result of decreased ATP synthesis, either through inhibition of Coupling Factor activity or amount due to increased ion concentration. Carbohydrate synthesis and accumulation decrease. Type 2 response is considered equivalent to Type 1 at RWC below c. 75%, with A pot inhibited by limited ATP and RuBP synthesis, respiratory metabolism dominates and C i and 螕 rise. The importance of inhibited ATP synthesis as a primary cause of decreasing A pot is discussed. Factors determining the Type 1 and Type 2 responses are unknown. Electron transport is maintained (but down-regulated) in Types 1 and 2 over a wide range of RWC, and a large reduced/oxidized adenylate ratio results. Metabolic imbalance results in amino acid accumulation and decreased and altered protein synthesis. These conditions profoundly affect cell functions and ultimately cause cell death. Type 1 and 2 responses may reflect differences in g s and in sensitivity of metabolism to decreasing RWC.

采用液体培养法,研究了不同浓度聚乙二醇(PEG)模拟干旱处理对青稞幼苗叶片可溶性蛋白含量的影响,并利用SDS-PAGE电泳检测干旱对供试青稞品种叶片可溶性蛋白的变化及其与干旱胁迫的关系.结果表明:在短时间干旱胁迫下,旱地紫青稞、大麻青稞叶片可溶性蛋白含量均随着干旱胁迫增强呈先降低、后升高的趋势;但在长时间干旱胁迫下,2份材料的可溶性蛋白含量随着干旱胁迫增强逐渐降低;对干旱胁迫4d的可溶性蛋白进行SDS-PAGE分析,发现在55 ku处有1个蛋白或1组蛋白为干旱诱导蛋白.

采用液体培养法,研究了不同浓度聚乙二醇(PEG)模拟干旱处理对青稞幼苗叶片可溶性蛋白含量的影响,并利用SDS-PAGE电泳检测干旱对供试青稞品种叶片可溶性蛋白的变化及其与干旱胁迫的关系.结果表明:在短时间干旱胁迫下,旱地紫青稞、大麻青稞叶片可溶性蛋白含量均随着干旱胁迫增强呈先降低、后升高的趋势;但在长时间干旱胁迫下,2份材料的可溶性蛋白含量随着干旱胁迫增强逐渐降低;对干旱胁迫4d的可溶性蛋白进行SDS-PAGE分析,发现在55 ku处有1个蛋白或1组蛋白为干旱诱导蛋白.

为提高杜鹃的抗旱性,通过对西鹃和毛鹃干旱胁迫过程中叶片含水量、细胞膜透性、叶绿素含量、过氧化物酶(POD)、过氧化氢酶(CAT)活性等生理指标的测定,研究土壤干旱胁迫下杜鹃的生理响应机制并利用隶属函数法综合评价杜鹃的抗旱性。结果表明:西鹃和毛鹃的叶片含水量随着干旱胁迫时间的延长而逐渐降低,细胞膜透性逐渐上升,叶绿素、脯氨酸、可溶性蛋白质随着干旱胁迫时间的增加呈先增加后减小的趋势,过氧化物酶(POD)活性呈上升趋势,过氧化氢酶(CAT)活性呈先增加后减小的趋势;西鹃丙二醛含量上升,而毛鹃丙二醛含量先上升后下降。利用隶属函数法综合评价得出西鹃的抗旱性大于毛鹃。

为提高杜鹃的抗旱性,通过对西鹃和毛鹃干旱胁迫过程中叶片含水量、细胞膜透性、叶绿素含量、过氧化物酶(POD)、过氧化氢酶(CAT)活性等生理指标的测定,研究土壤干旱胁迫下杜鹃的生理响应机制并利用隶属函数法综合评价杜鹃的抗旱性。结果表明:西鹃和毛鹃的叶片含水量随着干旱胁迫时间的延长而逐渐降低,细胞膜透性逐渐上升,叶绿素、脯氨酸、可溶性蛋白质随着干旱胁迫时间的增加呈先增加后减小的趋势,过氧化物酶(POD)活性呈上升趋势,过氧化氢酶(CAT)活性呈先增加后减小的趋势;西鹃丙二醛含量上升,而毛鹃丙二醛含量先上升后下降。利用隶属函数法综合评价得出西鹃的抗旱性大于毛鹃。

随着全球气候与环境变化的加剧,地球表面平均温度升高、水资源日趋短缺、土壤有效含水量逐年减少以及大气氮沉降已成为重要的全球性环境问题。土壤氮素和水分是许多陆地生态系统中植物生长的主要限制因子,显著影响植物的分布和生长发育。全球气候导致的干旱导致我国落叶松林北移,加之我国大气氮沉降持续增加,导致森林土壤中可利用氮的含量不断增加。因此,探究干旱与氮素综合作用下落叶松幼苗的生长特性、生理特性以及适应性机制,对改善干旱系统植被条件、了解北方森林生态系统功能及格局的改变具有重要意义,也为落叶松人工林繁育过程中合理调节水肥管理、优化培育措施提供理论参考。本研究以1年生落叶松(Larix)为研究对象,采用大棚盆栽方法人为控制土壤水分和施N控制试验,设置三个水分梯度：CK(正常供水,土壤水分含量占田间持水量的80%-70%,下同)、MS(中度干旱胁迫,60%-50%)、HS(严重干旱胁迫,40%-30%)；四种施氮水平：NO(不施氮,Og NH4NO3-N·m-2·a-1)、LN(低氮,5g NH4NO3-N·m-2·a-1、MN(中氮,10g NH4NO3-N·m-2·a-1)、HN(高氮,15gNH4NO3-NN·m-2·a-1),从植株生长、生理指标入手,系统的研究了落叶松幼苗对干旱胁迫和施N的生理生态响应,并揭示了落叶松幼苗的耐旱性机制。研究结果表明： (1)随着干旱胁迫程度的增加,不同氮处理下的落叶松幼苗株高、基径生长量呈下降趋势,并对对落叶松幼苗的生物量积累和生物量分配格局具有明显的影响,干旱胁迫越严重,幼苗叶面积、总生物量的积累越少,地上生物量越来越小,地下生物量积累越来越多,R/S升高,SLA和LAR增逐渐加,并产生极显著影响(P0.001)。在干旱胁迫与施氮的交互作用下,施氮处理可在一定程度上改善落叶松幼苗株高、基径、RGR、叶面积、总生物量,促进生长,但是不同水分条件下的氮素效应不同。正常水分供应条件下,施氮水平的提高增加了幼苗生长指标和生物量的积累。而干旱胁迫条件下,施加了过量的氮后幼苗生长量、生物量积累反而降下降,植株通过降低叶面积、降低叶片分配比例来降低自身的水分消耗状况,并增加茎和根的分配比例,将有限的资源较多的生物量分配给地下部分和茎生物量。 (2)不同干旱胁迫处理下,落叶松幼苗光合作用明显受到抑制,随干旱程度增加在同一光强时幼苗Pn逐渐降低,光饱和点逐渐降低。而不同干旱胁迫条件下适量的施氮能在一定程度上提高落叶松幼苗的光合能力。低氮处理下在严重干旱时对植株光合能力有明显的促进作用,而高氮处理下的促进作用减弱并转向抑制。严重干旱情况下,幼苗Pmax在HN水平下表现出最低值,在LN水平下表现出最大值。此时氮处理水平下的Pn和Ci都表现出相同的变化趋势,Pn的下降是非气孔因素引起的。 不同干旱胁迫处理下,落叶松幼苗茎的呼吸作用也明显受到抑制。严重干旱情况下的高氮处理下幼苗的呼吸值最小,说明过量增加氮肥抑制了植物的生长,幼苗的光合作用低的同时,所能固定的光合产物也随之减少,用以为幼苗提供生命活动所需的能量就少。而正常水分供应条件下的高氮浓度下的幼苗呼吸值,和中度干旱情况下的中氮处理下幼苗的呼吸值明显高于同一供水条件下的其他施氮水平,说明在适当的氮处理水平下,落叶松幼苗的生长代谢速度最快,需要通过呼吸作用为其生命活动提供能量。 干旱胁迫使得落叶松幼苗叶片中的叶绿素a、叶绿素b、总叶绿素以及叶绿素a/b上升。但是同一水分处理下各个氮处理水平之间的变化趋势不同,适量的氮素水平能显著提高落叶松幼苗的叶绿素a、叶绿素b、总叶绿素含量,且变化趋势一致。MS和HS条件下下,HN水平都抑制了光合色素的积累,以HN处理下幼苗的Chla、Chlb和Ch1含量最低。但在MS条件下,MN水平下表现出较高的光合色素水平。而在HS条件下,LN水平下表现出较高的光合色素水平。 (3)落叶松幼苗叶片相对含水量(LRWC)随干旱胁迫程度的增加而降低,同一水分处理下不同氮处理水平下的LRWC表现出来的变化也各不相同。中度干旱胁迫下,LRWC随施氮水平的增高表现出先升高后降低的趋势,在MN水平下幼苗LRWC最高,显著高于其他施氮水平(P0.05)。严重干旱胁迫下,LRWC表现出与中度干旱胁迫下相同的变化趋势,但LRWC在LN水平下表现出最高值,且HN水平下表现出最低值。 (4)幼苗总SS含量均随干旱胁迫程度的增加而降低,且同一水分处理下不同氮处理水平之间的变化趋势也显示为一致的趋势,只是变化幅度不同。在HS条件下,叶片、茎、根SS含量随施氮量的增加表现出先增加后降低的趋势,且LN处理表现出SS含量最高,HN处理表现出叶片含量最低。而随着干旱胁迫的加剧,各个施氮水平的幼苗Pro、MDA含量同对照相比整体呈上升趋势。其中,中度干旱胁迫下,各个施氮水平的幼苗Pro含量、MDA含量同对照相比整体呈小幅度上升趋势,但在MN水平下升上幅度最小；而严重干旱胁迫下,各个施氮水平的幼苗Pro含量、MDA含量同正常水分条件下相比上升幅度较大,并以HN水平下的含量最高,LN水平下的含量最低。

随着全球气候与环境变化的加剧,地球表面平均温度升高、水资源日趋短缺、土壤有效含水量逐年减少以及大气氮沉降已成为重要的全球性环境问题。土壤氮素和水分是许多陆地生态系统中植物生长的主要限制因子,显著影响植物的分布和生长发育。全球气候导致的干旱导致我国落叶松林北移,加之我国大气氮沉降持续增加,导致森林土壤中可利用氮的含量不断增加。因此,探究干旱与氮素综合作用下落叶松幼苗的生长特性、生理特性以及适应性机制,对改善干旱系统植被条件、了解北方森林生态系统功能及格局的改变具有重要意义,也为落叶松人工林繁育过程中合理调节水肥管理、优化培育措施提供理论参考。本研究以1年生落叶松(Larix)为研究对象,采用大棚盆栽方法人为控制土壤水分和施N控制试验,设置三个水分梯度：CK(正常供水,土壤水分含量占田间持水量的80%-70%,下同)、MS(中度干旱胁迫,60%-50%)、HS(严重干旱胁迫,40%-30%)；四种施氮水平：NO(不施氮,Og NH4NO3-N·m-2·a-1)、LN(低氮,5g NH4NO3-N·m-2·a-1、MN(中氮,10g NH4NO3-N·m-2·a-1)、HN(高氮,15gNH4NO3-NN·m-2·a-1),从植株生长、生理指标入手,系统的研究了落叶松幼苗对干旱胁迫和施N的生理生态响应,并揭示了落叶松幼苗的耐旱性机制。研究结果表明： (1)随着干旱胁迫程度的增加,不同氮处理下的落叶松幼苗株高、基径生长量呈下降趋势,并对对落叶松幼苗的生物量积累和生物量分配格局具有明显的影响,干旱胁迫越严重,幼苗叶面积、总生物量的积累越少,地上生物量越来越小,地下生物量积累越来越多,R/S升高,SLA和LAR增逐渐加,并产生极显著影响(P0.001)。在干旱胁迫与施氮的交互作用下,施氮处理可在一定程度上改善落叶松幼苗株高、基径、RGR、叶面积、总生物量,促进生长,但是不同水分条件下的氮素效应不同。正常水分供应条件下,施氮水平的提高增加了幼苗生长指标和生物量的积累。而干旱胁迫条件下,施加了过量的氮后幼苗生长量、生物量积累反而降下降,植株通过降低叶面积、降低叶片分配比例来降低自身的水分消耗状况,并增加茎和根的分配比例,将有限的资源较多的生物量分配给地下部分和茎生物量。 (2)不同干旱胁迫处理下,落叶松幼苗光合作用明显受到抑制,随干旱程度增加在同一光强时幼苗Pn逐渐降低,光饱和点逐渐降低。而不同干旱胁迫条件下适量的施氮能在一定程度上提高落叶松幼苗的光合能力。低氮处理下在严重干旱时对植株光合能力有明显的促进作用,而高氮处理下的促进作用减弱并转向抑制。严重干旱情况下,幼苗Pmax在HN水平下表现出最低值,在LN水平下表现出最大值。此时氮处理水平下的Pn和Ci都表现出相同的变化趋势,Pn的下降是非气孔因素引起的。 不同干旱胁迫处理下,落叶松幼苗茎的呼吸作用也明显受到抑制。严重干旱情况下的高氮处理下幼苗的呼吸值最小,说明过量增加氮肥抑制了植物的生长,幼苗的光合作用低的同时,所能固定的光合产物也随之减少,用以为幼苗提供生命活动所需的能量就少。而正常水分供应条件下的高氮浓度下的幼苗呼吸值,和中度干旱情况下的中氮处理下幼苗的呼吸值明显高于同一供水条件下的其他施氮水平,说明在适当的氮处理水平下,落叶松幼苗的生长代谢速度最快,需要通过呼吸作用为其生命活动提供能量。 干旱胁迫使得落叶松幼苗叶片中的叶绿素a、叶绿素b、总叶绿素以及叶绿素a/b上升。但是同一水分处理下各个氮处理水平之间的变化趋势不同,适量的氮素水平能显著提高落叶松幼苗的叶绿素a、叶绿素b、总叶绿素含量,且变化趋势一致。MS和HS条件下下,HN水平都抑制了光合色素的积累,以HN处理下幼苗的Chla、Chlb和Ch1含量最低。但在MS条件下,MN水平下表现出较高的光合色素水平。而在HS条件下,LN水平下表现出较高的光合色素水平。 (3)落叶松幼苗叶片相对含水量(LRWC)随干旱胁迫程度的增加而降低,同一水分处理下不同氮处理水平下的LRWC表现出来的变化也各不相同。中度干旱胁迫下,LRWC随施氮水平的增高表现出先升高后降低的趋势,在MN水平下幼苗LRWC最高,显著高于其他施氮水平(P0.05)。严重干旱胁迫下,LRWC表现出与中度干旱胁迫下相同的变化趋势,但LRWC在LN水平下表现出最高值,且HN水平下表现出最低值。 (4)幼苗总SS含量均随干旱胁迫程度的增加而降低,且同一水分处理下不同氮处理水平之间的变化趋势也显示为一致的趋势,只是变化幅度不同。在HS条件下,叶片、茎、根SS含量随施氮量的增加表现出先增加后降低的趋势,且LN处理表现出SS含量最高,HN处理表现出叶片含量最低。而随着干旱胁迫的加剧,各个施氮水平的幼苗Pro、MDA含量同对照相比整体呈上升趋势。其中,中度干旱胁迫下,各个施氮水平的幼苗Pro含量、MDA含量同对照相比整体呈小幅度上升趋势,但在MN水平下升上幅度最小；而严重干旱胁迫下,各个施氮水平的幼苗Pro含量、MDA含量同正常水分条件下相比上升幅度较大,并以HN水平下的含量最高,LN水平下的含量最低。

水分是影响植物生长的主要环境因子之一。近年来,随着全球气候变暖,我国水资源的匮乏日益严重,尤其是东北的广大地区,这一问题尤为突出。干旱胁迫已经成为制约东北地区植物生长发育和城市绿化的重要生态问题。荻和芒是理想的第二代能源植物,具有广泛的应用价值,但东北地区水资源匮乏的状况制约了荻和芒在该地区的推广和应用。因此研究干旱胁迫下荻和芒的生长、光合特性和生理特性的变化规律,对提高它的水分管理水平,促进荻和芒在东北地区的可持续发展具有重要意义。 本研究选用芒属植物荻(Miscanthus sacchariflorus)和芒(Misconstrues sinensis)为实验材料,采用聚乙二醇(PEG)模拟干旱法对其种子进行4个PEG浓度水平的胁迫处理(5%、10%、15%、20%),研究荻和芒种子在PEG干旱胁迫下的萌发特性；采用盆栽控水的方法分别对荻和芒的实生苗进行4种土壤水分处理即：正常供水(土壤含水量为最大田间持水量80%,下同)、轻度土壤干旱胁迫(65%)、中度土壤干旱胁迫(50%)和重度土壤干旱胁迫(35%),分别测定了不同土壤干旱胁迫下荻和芒光合、生理和生长指标,研究荻和芒对土壤干旱胁迫的适应性；同时调查了东北地区荻和芒的分布和生境特征,主要研究结果如下： (1)东北野生荻芒分布和生境特征 荻和芒在东北地区属点状分布,喜低海拔、土壤湿润,光照充足的生境；不同生境下荻和芒的生长性状存在差异,随着生境内土壤含水量的上升和光照条件的改善,荻和芒的生长性状和生物量提高,各生境间部分性状差异显著；荻和芒的叶形指数(叶长／叶宽),株高、地下茎粗、分布深度等表型性状受环境因素影响小,相对稳定；荻和芒的株高、茎粗等茎部性状与生物量显著相关。 (2)PEG胁迫对荻和芒种子萌发特性的影响 低浓度的PEG(5-20%)对芒和荻种子的发芽率没有明显的影响,但对芒种子的发芽指数、活力指数、胚根长度、胚根鲜重以及荻种子胚芽的长度有一定的促进作用；高浓度的PEG(15～20%),对芒和荻种子的发芽率、发芽指数、活力指数、胚根胚芽长度以及鲜重都有明显的抑制作用；荻种子的半致死浓度为15%,致死浓度为20%,而芒种子的半致死浓度为20%；随着PEG浓度的升高,芒和荻的萌发抗旱指数逐渐下降,芒在20%PEG处理时表现为中间型,而荻在15%PEG处理时就表现为不抗旱。 (3)土壤干旱胁迫对荻和芒光合特性的影响 土壤干旱胁迫下,荻和芒叶片的相对含水量(RWC)、叶绿素含量(Chl)、净光合速率(Pn)、最大净光合速率(Pmax)、表观量子效率(AQE)、暗呼吸速率(Rd)、光饱和点(LSP)、蒸腾速率(Tr)、最大羧化速率(Vcmax)和电子传递速(Jmax)均随着土壤干旱胁迫程度的加剧而下降；光补偿点(LCP)和水分利用效率(WUE)随土壤干旱胁迫程度的加剧而上升。荻和芒的气孔导度(Gs)随着土壤干旱胁迫程度的加剧而下降;胞间C02浓度(Ci)随着土壤干旱胁迫程度的加剧呈先下降后上升的趋势；气孔阻力值(Ls)随着土壤干旱胁迫程度的加剧呈先上升后下降的趋势。 荻在轻度土壤干旱胁迫下、芒在轻度和中度土壤干旱胁迫下,对光合作用的抑制由气孔限制所引起；而荻在中度、重度土壤干旱胁迫下,芒在重度土壤干旱胁迫下对光合作用的抑制由非气孔限制所引起。 (4)土壤干旱胁迫对荻和芒的生理特性的影响 在土壤干旱胁迫下荻和芒的细胞膜相对透性,丙二醛(MDA)和过氧化氢(H202)含量随着土壤干旱胁迫程度的加剧而显著增加。 在轻度干旱胁迫下,荻的超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD)活性随着干旱胁迫时间的延长而逐渐上升；而在中度和重度干旱胁迫下SOD、CAT和POD活性随着干旱胁迫时间的延长呈先上升后下降趋势。在不同程度土壤干旱胁迫下,芒的SOD和CAT活性随着干旱胁迫时间的延长而逐渐上升；而POD活性则在不同干旱胁迫处理下无明显变化。 在不同程度干旱胁迫下芒叶片的抗坏血酸过氧化物酶(APX)、甘肽还原酶(GR)活性和还原型抗坏血酸(AsA)、还原型谷胱甘肽(GSH)含量始终保持上升趋势；而荻在轻度干旱胁迫下也可以保持较高的抗坏血酸合成和代谢活性,但在中度和重度干旱胁迫下,随着干旱胁迫的加剧和胁迫时间的延长荻的APX、GR活性和AsA、GSH含量开始下降。 (5)土壤干旱胁迫对荻和芒的生长和生物量的影响 荻和芒的株高、地径、茎节间长度、叶面积和比叶重随着土壤干旱胁迫程度的加剧而下降。轻度干旱胁迫下,芒的地下茎粗和长度均高于正常供水处理,表明适宜的土壤干旱胁迫对芒地下茎的生长有一定的促进作用；而在荻和芒在中、重度干旱胁迫下,地下茎粗、长度和分蘖数量均随着土壤干旱胁迫程度的加剧而显著下降。 土壤干旱胁迫下,除芒在轻度干旱胁迫下地下部分生物量增加外,其余胁迫处理中荻和芒的单株总生物量、地上部分生物量、地下部分生物量和冠根比均随土壤干旱胁迫程度的加剧而下降,胁迫越重,生长速度越慢,生长量越小,生物量越低。

水分是影响植物生长的主要环境因子之一。近年来,随着全球气候变暖,我国水资源的匮乏日益严重,尤其是东北的广大地区,这一问题尤为突出。干旱胁迫已经成为制约东北地区植物生长发育和城市绿化的重要生态问题。荻和芒是理想的第二代能源植物,具有广泛的应用价值,但东北地区水资源匮乏的状况制约了荻和芒在该地区的推广和应用。因此研究干旱胁迫下荻和芒的生长、光合特性和生理特性的变化规律,对提高它的水分管理水平,促进荻和芒在东北地区的可持续发展具有重要意义。 本研究选用芒属植物荻(Miscanthus sacchariflorus)和芒(Misconstrues sinensis)为实验材料,采用聚乙二醇(PEG)模拟干旱法对其种子进行4个PEG浓度水平的胁迫处理(5%、10%、15%、20%),研究荻和芒种子在PEG干旱胁迫下的萌发特性；采用盆栽控水的方法分别对荻和芒的实生苗进行4种土壤水分处理即：正常供水(土壤含水量为最大田间持水量80%,下同)、轻度土壤干旱胁迫(65%)、中度土壤干旱胁迫(50%)和重度土壤干旱胁迫(35%),分别测定了不同土壤干旱胁迫下荻和芒光合、生理和生长指标,研究荻和芒对土壤干旱胁迫的适应性；同时调查了东北地区荻和芒的分布和生境特征,主要研究结果如下： (1)东北野生荻芒分布和生境特征 荻和芒在东北地区属点状分布,喜低海拔、土壤湿润,光照充足的生境；不同生境下荻和芒的生长性状存在差异,随着生境内土壤含水量的上升和光照条件的改善,荻和芒的生长性状和生物量提高,各生境间部分性状差异显著；荻和芒的叶形指数(叶长／叶宽),株高、地下茎粗、分布深度等表型性状受环境因素影响小,相对稳定；荻和芒的株高、茎粗等茎部性状与生物量显著相关。 (2)PEG胁迫对荻和芒种子萌发特性的影响 低浓度的PEG(5-20%)对芒和荻种子的发芽率没有明显的影响,但对芒种子的发芽指数、活力指数、胚根长度、胚根鲜重以及荻种子胚芽的长度有一定的促进作用；高浓度的PEG(15～20%),对芒和荻种子的发芽率、发芽指数、活力指数、胚根胚芽长度以及鲜重都有明显的抑制作用；荻种子的半致死浓度为15%,致死浓度为20%,而芒种子的半致死浓度为20%；随着PEG浓度的升高,芒和荻的萌发抗旱指数逐渐下降,芒在20%PEG处理时表现为中间型,而荻在15%PEG处理时就表现为不抗旱。 (3)土壤干旱胁迫对荻和芒光合特性的影响 土壤干旱胁迫下,荻和芒叶片的相对含水量(RWC)、叶绿素含量(Chl)、净光合速率(Pn)、最大净光合速率(Pmax)、表观量子效率(AQE)、暗呼吸速率(Rd)、光饱和点(LSP)、蒸腾速率(Tr)、最大羧化速率(Vcmax)和电子传递速(Jmax)均随着土壤干旱胁迫程度的加剧而下降；光补偿点(LCP)和水分利用效率(WUE)随土壤干旱胁迫程度的加剧而上升。荻和芒的气孔导度(Gs)随着土壤干旱胁迫程度的加剧而下降;胞间C02浓度(Ci)随着土壤干旱胁迫程度的加剧呈先下降后上升的趋势；气孔阻力值(Ls)随着土壤干旱胁迫程度的加剧呈先上升后下降的趋势。 荻在轻度土壤干旱胁迫下、芒在轻度和中度土壤干旱胁迫下,对光合作用的抑制由气孔限制所引起；而荻在中度、重度土壤干旱胁迫下,芒在重度土壤干旱胁迫下对光合作用的抑制由非气孔限制所引起。 (4)土壤干旱胁迫对荻和芒的生理特性的影响 在土壤干旱胁迫下荻和芒的细胞膜相对透性,丙二醛(MDA)和过氧化氢(H202)含量随着土壤干旱胁迫程度的加剧而显著增加。 在轻度干旱胁迫下,荻的超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD)活性随着干旱胁迫时间的延长而逐渐上升；而在中度和重度干旱胁迫下SOD、CAT和POD活性随着干旱胁迫时间的延长呈先上升后下降趋势。在不同程度土壤干旱胁迫下,芒的SOD和CAT活性随着干旱胁迫时间的延长而逐渐上升；而POD活性则在不同干旱胁迫处理下无明显变化。 在不同程度干旱胁迫下芒叶片的抗坏血酸过氧化物酶(APX)、甘肽还原酶(GR)活性和还原型抗坏血酸(AsA)、还原型谷胱甘肽(GSH)含量始终保持上升趋势；而荻在轻度干旱胁迫下也可以保持较高的抗坏血酸合成和代谢活性,但在中度和重度干旱胁迫下,随着干旱胁迫的加剧和胁迫时间的延长荻的APX、GR活性和AsA、GSH含量开始下降。 (5)土壤干旱胁迫对荻和芒的生长和生物量的影响 荻和芒的株高、地径、茎节间长度、叶面积和比叶重随着土壤干旱胁迫程度的加剧而下降。轻度干旱胁迫下,芒的地下茎粗和长度均高于正常供水处理,表明适宜的土壤干旱胁迫对芒地下茎的生长有一定的促进作用；而在荻和芒在中、重度干旱胁迫下,地下茎粗、长度和分蘖数量均随着土壤干旱胁迫程度的加剧而显著下降。 土壤干旱胁迫下,除芒在轻度干旱胁迫下地下部分生物量增加外,其余胁迫处理中荻和芒的单株总生物量、地上部分生物量、地下部分生物量和冠根比均随土壤干旱胁迫程度的加剧而下降,胁迫越重,生长速度越慢,生长量越小,生物量越低。

Ｔｉ（Ⅳ）－Ｈ２Ｏ２比色法因背景物质干扰而测得的植物叶片内Ｈ２Ｏ２含量偏高，５％三氯乙酸抽提，活性炭脱色，Ｔｉ（Ⅳ）－４－（２－吡啶偶氮）间苯二酚（ＰＡＲ）比色法测得的Ｈ２Ｏ２含量偏低。萃取法有效地脱去丙酮提液中的色素，且Ｈ２Ｏ２的回收率在９５％以上。用过氧化氢酶（ＣＡＴ）处理作空白对照，利用Ｈ２Ｏ２与Ｔｉ（Ⅳ）－ＰＡＲ的显色反应，建立了一种简便、快速、准确的植物叶片内的Ｈ２Ｏ２含量测定方法，Ｈ２

Ｔｉ（Ⅳ）－Ｈ２Ｏ２比色法因背景物质干扰而测得的植物叶片内Ｈ２Ｏ２含量偏高，５％三氯乙酸抽提，活性炭脱色，Ｔｉ（Ⅳ）－４－（２－吡啶偶氮）间苯二酚（ＰＡＲ）比色法测得的Ｈ２Ｏ２含量偏低。萃取法有效地脱去丙酮提液中的色素，且Ｈ２Ｏ２的回收率在９５％以上。用过氧化氢酶（ＣＡＴ）处理作空白对照，利用Ｈ２Ｏ２与Ｔｉ（Ⅳ）－ＰＡＲ的显色反应，建立了一种简便、快速、准确的植物叶片内的Ｈ２Ｏ２含量测定方法，Ｈ２

采用盆栽实验,研究了不同程度干旱胁迫(重度、中度、轻度、对照,分别为15%、30%、50%、70%田间最大持水量)对荒漠灌木蒙古岩黄芪幼苗光合特性、抗氧化特性和渗透调节物质的影响。结果显示,在中度和重度干旱胁迫下,除胞间CO₂ 浓度外,其余各光合指标均显著下降;在轻度干旱胁迫下,蒙古岩黄芪幼苗净光合速率、PSⅡ的潜在活性与对照相比上升了20.7%和5.7%。中度和重度胁迫下蒙古岩黄芪叶片的丙二醛(MDA)含量、细胞相对质膜透性、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)以及过氧化物酶(POD)活性显著高于对照,而在轻度干旱胁迫下无明显变化。叶片中游离脯氨酸含量和可溶性糖含量以及K⁺含量随干旱胁迫的加剧而显著增加;根、茎、叶中的Na⁺含量在干旱胁迫处理中均显著下降。蒙古岩黄芪在干旱胁迫下采取协同升高叶片中SOD、 CAT、POD活性,提高脯氨酸和可溶性糖含量,同时选择性吸收K⁺的策略来减小干旱对植株所造成的伤害。实验结果可为蒙古岩黄芪适应干旱胁迫的策略提供理论依据,为其保护利用以及干旱与半干旱区的植被恢复提供参考。

采用盆栽实验,研究了不同程度干旱胁迫(重度、中度、轻度、对照,分别为15%、30%、50%、70%田间最大持水量)对荒漠灌木蒙古岩黄芪幼苗光合特性、抗氧化特性和渗透调节物质的影响。结果显示,在中度和重度干旱胁迫下,除胞间CO₂ 浓度外,其余各光合指标均显著下降;在轻度干旱胁迫下,蒙古岩黄芪幼苗净光合速率、PSⅡ的潜在活性与对照相比上升了20.7%和5.7%。中度和重度胁迫下蒙古岩黄芪叶片的丙二醛(MDA)含量、细胞相对质膜透性、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)以及过氧化物酶(POD)活性显著高于对照,而在轻度干旱胁迫下无明显变化。叶片中游离脯氨酸含量和可溶性糖含量以及K⁺含量随干旱胁迫的加剧而显著增加;根、茎、叶中的Na⁺含量在干旱胁迫处理中均显著下降。蒙古岩黄芪在干旱胁迫下采取协同升高叶片中SOD、 CAT、POD活性,提高脯氨酸和可溶性糖含量,同时选择性吸收K⁺的策略来减小干旱对植株所造成的伤害。实验结果可为蒙古岩黄芪适应干旱胁迫的策略提供理论依据,为其保护利用以及干旱与半干旱区的植被恢复提供参考。

Water relations, gas exchange as well as organic solute and ion accumulation were studied in the leaves of 2-year-old grapevines ( Vitis vinifera L, cv. Savatiano) grown under well watered (control) and water stress conditions. Both osmotic potential at full turgor ( 螤 100) and at turgor loss point ( 螤 0) decreased significantly in stressed plants compared with the control. Photosynthetic rate, and stomatal conductance were also significantly lower in stressed plants. Starch concentration decreased almost threefold in stressed plants, while there were no significant differences in sugar accumulation between the two treatments. Total inorganic ion concentration increased rapidly in stressed plants and seems to be the major component of osmotic adjustment in stressed grapevines. Thus, the energetic cost of osmotic adjustment in grapevines using inorganic ions would be expected to be much lower than for those species using organic solutes.

分析了氮、水分与上海结缕草(Zoysia japonica cv. Shanghai)生长之间的相互关系,为上海结缕草草坪科学施肥和灌溉提供依据。试验选择干旱胁迫和施氮2个因素,各设置3个水平,结果表明:轻度干旱胁迫+中氮组合处理的草坪品质非常好,草坪密度和地上生物量高于或接近无干旱胁迫+中氮组合处理,且显著好于轻度干旱胁迫的其他处理和重度干旱胁迫的全部处理(P0.05);高氮处理的结缕草株高在同一干旱水平中均明显高于其他处理(P0.05)。在相同干旱胁迫下,施氮后第19天,结缕草叶片的相对电导率、游离脯氨酸含量和可溶性糖含量均随施氮量的增加而呈现升高的趋势;与此相反,施氮后第41天时,则呈现出随施氮量的增加而降低的趋势;随着干旱胁迫程度的增加,叶片丙二醛含量呈现增加的趋势。研究结果表明,适度的干旱胁迫和适量的氮肥有助于维持上海结缕草较好的坪用品质。

分析了氮、水分与上海结缕草(Zoysia japonica cv. Shanghai)生长之间的相互关系,为上海结缕草草坪科学施肥和灌溉提供依据。试验选择干旱胁迫和施氮2个因素,各设置3个水平,结果表明:轻度干旱胁迫+中氮组合处理的草坪品质非常好,草坪密度和地上生物量高于或接近无干旱胁迫+中氮组合处理,且显著好于轻度干旱胁迫的其他处理和重度干旱胁迫的全部处理(P0.05);高氮处理的结缕草株高在同一干旱水平中均明显高于其他处理(P0.05)。在相同干旱胁迫下,施氮后第19天,结缕草叶片的相对电导率、游离脯氨酸含量和可溶性糖含量均随施氮量的增加而呈现升高的趋势;与此相反,施氮后第41天时,则呈现出随施氮量的增加而降低的趋势;随着干旱胁迫程度的增加,叶片丙二醛含量呈现增加的趋势。研究结果表明,适度的干旱胁迫和适量的氮肥有助于维持上海结缕草较好的坪用品质。

主要介绍了植物水分胁迫诱导蛋白的表达模式、特征、分类、功能及其诱导过程中的信号转导及诱导机制。认为胁迫诱导蛋白的产生是植物对逆境胁迫的一种适应性反应 ,诱导蛋白从多方面保护植物避免或减少胁迫所造成的伤害。植物通过多种途径感受并转导干旱胁迫信号 ,诱导出多种基因表达产物 ,从而尽可能地增强对逆境的抗性

主要介绍了植物水分胁迫诱导蛋白的表达模式、特征、分类、功能及其诱导过程中的信号转导及诱导机制。认为胁迫诱导蛋白的产生是植物对逆境胁迫的一种适应性反应 ,诱导蛋白从多方面保护植物避免或减少胁迫所造成的伤害。植物通过多种途径感受并转导干旱胁迫信号 ,诱导出多种基因表达产物 ,从而尽可能地增强对逆境的抗性

ABSTRACT Activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), as well as malondialdehyde (MDA) contents and solute potentials, were studied in seedlings of seven wheat ( Triticum ) species (nine genotypes representing three ploidy levels: hexaploid, tetraploid, diploid) subjected to water stress for 4, 8, and 12 days by withholding water. Solute potentials of all genotypes were lowered by water stress. In most species, SOD and CAT activities showed an increase or maintenance in the early phase of drought and then a decrease with further increase in magnitude of water stress. On the contrary, POD activities and MDA contents greatly increased in response to water stress. Enzymatic activities partly recovered and MDA contents decreased with rewatering. Under drought, hexaploid wheats had higher POD activities and MDA contents than tetraploid and diploid wheats; solute potentials and activities of SOD and CAT, however, were similar among the three groups. These results suggest that water stress alters the equilibrium between free radical production and enzymatic defense reactions in wheat species and that hexaploid wheats have less efficient antioxidant systems (e.g., the ascorbate-glutathione cycle and the nonenzymatic system) than tetraploid and diploid wheats.