Dehydration tolerance of leaf tissues of six woody angiosperm species

Electrolyte leakage from leaf discs (measured as an index of dehydration tolerance) increased as water potentials of excised leaves declined for field-grown saplings of six woody species. Until late in the growing season (mid-August), leaves of Cornus florida L. exhibited greater leakage than those of other species; however, in August and September leakage in this species was much reduced, indicating apparent hardening in response to mid-season drought. Leaves of Quercus alba L., Q. rubra L. and Q. velutina Lam. generally exhibited less electrolyte leakage than did those of Acer saccharum Marsh, and Juglans nigra L. over the season. Moreover, leaves of Quercus species showed a reduction in electrolyte leakage late in the season similar to (but less accentuated than) that of C. florida . Saplings of A. saccharum and J. nigra showed little and no drought-hardening response, respectively. The responses shown by the studied species suggest that dehydration tolerance plays a role in plant distribution and that environmentally induced shifts in this tolerance are a significant phenomenon in natural plant communities.     

小麦耐盐细胞系耐盐性分析

通过一步筛选获得了耐盐（１．０％,ＮａＣｌ）的小麦（Ｔｒｉｔｉｃｕｍ ａｅｓｔｉｖｕｍ）细胞系（Ｓｒ１）,当ＳＲ１在含１．０％,ＮａＣｌ的培养基上继代半年后,钭其中的一部分移入无盐培养基代１０次,得到细胞系ＳＲ２。无论是在正常还是办迫条件下,ＳＲ１的鲜重增量／克鲜重、脯氨酸及可溶性蛋白含量均高于原始型（ＳＮ）,而含水量均高于原始型（ＳＮ）,而含水量、Ｋ＾＋及可溶性糖含量却低于ＳＮ。Ｎａ＾＋和Ｃｌ＾     

Direct heat injury of roots of woody swamp species

1. 1.Three month-old seedlings of Taxodium distichum, Nyssa aquatica, Cephalanthus occidentalis and cuttings of Salix nigra were acclimated to simulated natural swamp conditions (ambient temperature, saturated soil) and then used to assess direct high temperature injury of root tissue.

2. 2.Electrolyte leakage from excised root tissue exposed for 30 min to temperatures ranging from 30 to 66°C was used to assess cellular injury.

3. 3.The relationship between leakage and temperature was sigmoidal for each species.

4. 4.Inflection point temperatures on the response curves, ranged from 45.4 to 51.0°C, were species-specific, and indicated differences in thermal tolerance of root membranes.

5. 5.Root of C. occidentalis and N. aquatica were more heat tolerant than roots of T. distichum and S. nigra.

盐胁迫对4树种叶片中K^＋和Na^＋的影响及其耐盐能力的评价

通过盆栽试验,对我国南方银杏（Ginkgo biloba L.)、侧柏[Patycladus orentalis(L.)Franco]、火炬松（Pinus taeda L.)和剌槐(Robinia Pseudoacacia L.)4造林树种苗木叶片中K^ 、N^ 浓度浓度和N^ ／K^ 比进行测定,盐处理水平为0.0％（CK）、0.1%、0.3%和0.5％。随着盐浓度的提高,各树种叶片中Na^ 浓度和N^ ／K^ 有逐渐升高的趋势,但K^ 浓度变化较小;随着盐胁迫时间的推移,各树种叶片中Na^ 、K^ 浓度和Na^ /K^ 比都没有明显的变化规律。方差分析和多层比较表明,侧柏、火炬松和剌槐叶片中Na^ 、K^ 浓度和N^ ／K^ 比在4组处理间的差异均达显著或极显著水平。4树种中剌槐和侧柏的耐盐能力最强,银杏次之,火炬松最弱。     

盐胁迫下树种幼苗生长及其耐盐性

采用盆栽方法,以11个树种实生幼苗为材料,用不同浓度(0、3、5、8 g·kg-1和10 g·kg-1)NaCl溶液进行1次性浇灌处理,对盐胁迫下各树种的形态表现、生长及耐盐性进行了研究,结果表明:(1)当盐含量达到8 g·kg-1时,欧洲荚蒾、甜桦和光叶漆植株死亡,当含量增加到10 g·kg-1时,沃氏金链花植株死亡,其它各存活树种也均出现不同程度的盐害症状;(2)盐胁迫后,各树种的苗高生长量下降、生物量累积减少,且随着处理浓度的增加均呈下降趋势,其中榆桔、甜桦和光叶漆的降幅最大;(3)盐处理后,各树种的根冠比值增大,其中盐胁迫对光叶漆、银水牛果和沃氏金链花有显著影响(p<0.05);(4)综合分析各树种的生长和形态表现,认为日本丁香、银水牛果、三裂叶漆和豆梨具有高度耐盐性,沃氏金链花、金雀儿、鹰爪豆和榆桔具有中高度耐盐性,而欧洲荚蒾、甜桦和光叶漆具有中度耐盐性.     

大豆出苗期和苗期对盐胁迫的响应及耐盐指标评价

比较了4个大豆品种出苗期和苗期的耐盐性,测定150 mmol/L NaCl胁迫下的株高、下胚轴长、侧根数、地上干/鲜重、根干/鲜重、MDA含量、SOD活性、游离Pro含量,并将幼苗移栽到田间生长至成熟。结果表明:出苗期和苗期盐胁迫下4个品种的株高都显著降低、地上干/鲜重和根干/鲜重降低;出苗期胁迫侧根数减少,下胚轴长降低;而苗期胁迫侧根数增加,下胚轴长升高。未胁迫条件下,出苗期和苗期耐盐性强的品种22021-1的MDA含量和SOD活性高于耐盐性弱的品种22293-1。胁迫后,22021-1的MDA含量降低、SOD活性升高,其MDA含量分别比对照低51.03%和21.45%,SOD活性比对照高5.85%和45.77%;22293-1的MDA含量出苗期比对照高58.97%,苗期基本无变化,SOD活性出苗期和苗期升高都不显著。MDA和SOD可以作为大豆耐盐性筛选指标。早期的短时胁迫对不同耐盐性大豆品种的经济产量影响不同。     

Differential salt tolerance of two Artemisia species growing in contrasting coastal habitats

To investigate factors determining the differences in their salt tolerance, growth and germination, experiments were conducted on two plant species belonging to genus Artemisia: Artemisia fukudo Makino, a biennial salt marsh plant and Artemisia stelleriana Bess, a perennial coastal hind dune plant. Growth experiments revealed that salinity (100 and 300 m m NaCl) inhibited the relative growth rate (RGR) in A. stelleriana significantly but not in A. fukudo. These specific differences in salt tolerance were mainly attributed to differential responses of net assimilation rate (NAR). That is, the reduction in RGR in A. stelleriana was mainly due to the reduction in NAR, whereas no significant reduction in NAR was observed in A. fukudo. The reduction in RGR in A. stelleriana in the salt treatment was also attributable to a reduced leaf area ratio (LAR). Specific leaf area (SLA) in the two species decreased in the 300 m m treatment. The decrease in SLA in A. fukudo was, however, compensated for partly by an increase in leaf weight ratio (LWR). Germination experiments also showed that A. fukudo has a higher salt tolerance than does A. stelleriana. These results are consistent with the differences in the salinity conditions between the native habitats of the two species.     

The microfilament cytoskeleton plays a vital role in salt and osmotic stress tolerance in Arabidopsis

Although recent studies have suggested that the microfilament (MF) cytoskeleton of plant cells participates in the response to salt stress, it remains unclear as to whether the MF cytoskeleton actually plays an active role in a plant's ability to withstand salt stress. In the present study, we report for the first time the role of MFs in salt tolerance of Arabidopsis thaliana . Our experiments revealed that Arabidopsis seedlings treated with 150 m m NaCl maintained MF assembly and bundle formation, whereas treatment with 250 m m NaCl initially induced MF assembly but subsequently caused MF disassembly. A corresponding change in the fluorescence intensity of MFs was also observed; that is, a sustained rise in fluorescence intensity in seedlings exposed to 150 m m NaCl and an initial rise and subsequent fall in seedlings exposed to 250 m m NaCl. These results suggest that MF assembly and bundles are induced early after salt stress treatment, while MF polymerization disappears after high salt stress. Facilitation of MF assembly with phalloidin rescued wild-type seedlings from death, whereas blocking MFs assembly with latrunculin A and cytochalasin D resulted in few survivors under salt stress. Pre-treatment of seedlings with phalloidin also clearly increased plant ability to withstand salt stress. MF assembly increased survival of Arabidopsis salt-sensitive sos2 mutants under salt stress and rescued defective sos2 mutants. Polymerization of MFs and its role in promoting survival was also found in plants exposed to osmotic stress. These findings suggest that the MF cytoskeleton participates and plays a vital role in responses to salt and osmotic stress in Arabidopsis .     

Microsatellite signature of ecological selection for salt tolerance in a wild sunflower hybrid species, Helianthus paradoxus

The hybrid sunflower species Helianthus paradoxus inhabits sporadic salt marshes in New Mexico and southwest Texas, USA, whereas its parental species, Helianthus annuus and Helianthus petiolaris, are salt sensitive. Previous studies identified three genomic regions - survivorship quantitative trait loci (QTLs) - that were under strong selection in experimental hybrids transplanted into the natural habitat of H. paradoxus. Here we ask whether these same genomic regions experienced significant selection during the origin and evolution of the natural hybrid, H. paradoxus. This was accomplished by comparing the variability of microsatellites linked to the three survivorship QTLs with those from genomic regions that were neutral in the experimental hybrids. As predicted if one or more selective sweeps had occurred in these regions, microsatellites linked to the survivorship QTLs exhibited a significant reduction in diversity in populations of the natural hybrid species. In contrast, no difference in diversity levels was observed between the two microsatellite classes in parental populations.     

Expression of a calcineurin gene improves salt stress tolerance in transgenic rice

Calcineurin is a Ca²⁺- and calmodulin-dependent serine/threonine phosphatase and has multiple functions in animal cells including regulating ionic homeostasis. We generated transgenic rice plants that not only expressed a truncated form of the catalytic subunit of mouse calcineurin, but also were able to grow and fertilize normally in the field. Notably, the expression of the mouse calcineurin gene in rice resulted in its higher salt stress tolerance than the non-transgenic rice. Physiological studies have indicated that the root growth of transgenic plants was less inhibited than the shoot growth, and that less Na⁺ was accumulated in the roots of transgenic plants after a prolonged period of salt stress. These findings imply that the heterologous calcineurin plays a significant role in maintaining ionic homeostasis and the integrity of plant roots when exposed to salt. In addition, the calcineurin gene expression in the stems of transgenic plants correlated with the increased expression of the Rab16A gene that encodes a group 2-type late-embryogenesis-abundant (LEA) protein. Altogether our findings provide the first genetic and physiological evidence that expression of the mouse calcineurin protein functionally improves the salt stress tolerance of rice partly by limiting Na⁺ accumulation in the roots.     

三种泌盐红树植物对盐胁迫的耐受性比较

在盐度 0、5、15、2 5和 35 (% )下种植泌盐红树植物老鼠 (Acanthus ilicifolius)、桐花树 (Aegiceras corniculatum)和白骨壤(Avicennia marina)的繁殖体 ,以繁殖体萌发、幼苗生长、叶片泌盐量、叶片组织液盐含量和蒸腾蒸发量为指标 ,比较其对盐胁迫的耐受性。盐度提高对胎生种类桐花树和白骨壤的萌根速率无显著影响 ,但高盐度明显抑制非胎生种类老鼠的萌根。白骨壤的萌苗率不受盐度影响 ,但 2 5以上的盐度导致桐花树和老鼠的萌苗率下降。在盐度范围 5～ 35内 ,白骨壤幼苗的茎高生长随盐度的增加而减少 ,但减少量比桐花树小 ,而老鼠的减少量最大。老鼠因盐度提高而导致的叶片长度的减少量最大。在盐度提高的情况下 3种植物均具有泌盐量增加的效应 ,在任一盐度下泌盐能力的顺序均为白骨壤 >桐花树 >老鼠。淡水培养时 ,3种红树植物的叶片组织液盐含量 (约 2 % )均高于环境盐度 0。在盐度范围 5～ 35内 ,白骨壤的叶片组织液盐含量维持在较稳定的水平 (4 .3%～ 5 .0 % ) ,桐花树的变化范围为 2 .4 %～ 4 .5 % ,老鼠 2 .3%～ 5 .3%。淡水培养时 ,3种植物的蒸腾蒸发量类似 ,但盐性条件下白骨壤的蒸腾蒸发量显著高于桐花树和老鼠。随着盐度的增加 ,老鼠的蒸腾蒸发量下降最多。这些结果均表     

Arabidopsis sos1 mutant in a salt-tolerant accession revealed an importance of salt acclimation ability in plant salt tolerance

An analysis of the salinity tolerance of 354 Arabidopsis thaliana accessions showed that some accessions were more tolerant to salt shock than the reference accession, Col-0, when transferred from 0 to 225 mM NaCl. In addition, several accessions, including Zu-0, showed marked acquired salt tolerance after exposure to moderate salt stress. It is likely therefore that Arabidopsis plants have at least two types of tolerance, salt shock tolerance and acquired salt tolerance. To evaluate a role of well-known salt shock tolerant gene SOS1 in acquired salt tolerance, we isolated a sos1 mutant from ion-beam-mutagenized Zu-0 seedlings. The mutant showed severe growth inhibition under salt shock stress owing to a single base deletion in the SOS1 gene and was even more salt sensitive than Col-0. Nevertheless, it was able to survive after acclimation on 100 mM NaCl for 7 d followed by 750 mM sorbitol for 20 d, whereas Col-0 became chlorotic under the same conditions. We propose that genes for salt acclimation ability are different from genes for salt shock tolerance and play an important role in the acquisition of salt or osmotic tolerance.     

The inheritance of salt exclusion in woody perennial fruit species

Citrus and grapevines are salt-sensitive perennial crops. Damage caused by salinity is due mostly to accumulation of excessive concentrations of salt (Na- and Cl ions) in shoot tissues. In both crops, however, some rootstock varieties can restrict the accumulation of salt in scion leaves and stems. Salt-excluding rootstocks, however, are often deficient with regard to other desirable characteristics and as such their use is limited. As a consequence, we have conducted a range of crosses within both crops to select new salt-excluding hybrids which may have potential as new rootstocks and also to investigate the inheritance of salt exclusion in these woody perennials.In citrus, both Cl-ion and Na-ion exclusion has been observed as a continuous character and progenies segregate widely for their ability to restrict the accumulation of these ions in shoot tissues. The ability to exclude Cl ions appears to be independent of the ability to exclude Na ions. Thus a good Cl-ion excluder is not necessarily a good Na-ion excluder and vice versa. It has been possible, however, to select new salt-excluding citrus hybrids which perform as well as and sometimes better than parent varieties when grafted with a common scion and grown in artificially salinised field plots.In grapevines, the research has concentrated on the ability for Cl-ion exclusion and depending on the Cl-ion-excluding parent chosen this is inherited as either a polygenic or monogenic trait. In crosses between Vitis champini (Cl-ion excluder) and Vitis vinifera (Cl-ion accumulator), the ability to restrict Cl-ion accumulation in shoot tissues segregates widely with some offspring transgressing the performance of either parent. In crosses and backcrosses involving V. berlandieri and V. vinifera, however, hybrids segregate as either Cl-ion excluders or accumulators suggesting the effect of a major dominant gene for Cl-ion exclusion from V. berlandieri. This was evident from both field and glasshouse experiments although possible modifying genes from V. vinifera may affect the expression of this gene under glasshouse conditions in some crosses.     

Plant traits as predictors of woody species dominance in climax forest communities

Abstract. The dominance of a given tree or shrub species in a particular forest community may be determined by many ecological traits of the target species, as well as those of the surrounding species as its potential competitors. The present study was conducted to evaluate the possibility of predicting community status (species composition and dominance) on the basis of traits of local flora using statistical methods, and to visualize the mathematical function which determines species dominance. A general linear model and logistic regression were used for the statistical analysis. Dependent variables were designated as dominance and presence/absence of species in climax forest, with independent variables as vegetative and reproductive traits. Subalpine, cool‐temperate, warm‐temperate and subtropical climax rain forests in East Asia were studied. Quantitative prediction of climax community status could readily be made based on easily measured traits of local flora. Species composition and 74.6% of the total variance of species dominance were predicted based on two traits; maximum height and shade tolerance. Through application of this method, the capacity of an alien species to invade a climax forest community could possibly be predicted prior to introduction of the alien species.     

Chlorophyll content and leaf elongation rate in wheat seedlings as a measure of manganese tolerance

After aluminum toxicity, manganese (Mn) toxicity is probably the second most important growth limiting factor in acid soils. The purpose of this study was to determine the feasibility of using chlorophyll content and leaf elongation rate (LER) for regrowth of Mn stressed seedlings as a rapid seedling based screening bioassay for Mn tolerance in segregating populations of wheat (Triticum aestivum L.). In one experiment, chlorophyll was determined for the cultivars Norquay (Mn-tolerant) and Columbus (Mn-sensitive) subjected to twelve Mn levels (2 to 2000 μM) in nutrient solutions. As Mn concentration increased, chlorophyll ‘a’ and ‘b’ contents of the Mn-tolerant cultivar decreased up to 9%, while in the Mn-sensitive cultivar it was reduced by as much as 43%. The chlorophyll ‘a/b’ ratio did not differ among Mn concentrations for either cultivar. In a second experiment, chlorophyll content and LER for regrowth of Mn stressed seedlings (1000 μM) was determined for Columbus and Katepwa (Mn-sensitive), Oslo (Mn-intermediate), and Norquay and Laura (Mn-tolerant). Manganese tolerance as assayed by chlorophyll ‘a’ and ‘b’ and LER was significantly correlated with Mn tolerance as assayed by the relative root weight methodology (RRW). Thus, chlorophyll content of Mn-stressed seedlings and LER of seedling regrowth appear to be suitable techniques for screening unreplicated selections of segregating populations for tolerance to Mn.     

红豆草耐盐愈伤组织的筛选及植株再生

将红豆草种子在含１．２％ＮａＣｌ的ＭＳ培养基上萌发以消除盐敏感的幼苗,把存活的幼苗下胚轴切段在含１ｍｇ／Ｌ２,４－Ｄ、０．５ｍｇ／Ｌ６－ＢＡ及１．２％ＮａＣｌ的ＭＳ培养基上诱导愈伤组织,通过连续筛选得到可耐受１．８％ＮａＣｌ的愈伤组织,在有０．２ｍｇ／Ｌ ＮＡＡ和１ｍｇ／Ｌ ＩＡＡ存在下该愈伤组织分化出芽,待幼,待幼苗长至３ｃｍ左右时转至含２ｍｇ／ＬＮＡＡ和或ＩＢＡ的１／２ＭＳ培养基上生根。对对照     

Morphological changes and antioxidant defence systems in soybean genotypes as affected by salt stress

Abstract

The present investigation was conducted to evaluate salt tolerance in nine genotypes of soybean (Glycine max L.). Ten-day-old seedlings, grown hydroponically, were treated with 0, 25, 50, 75, 100, 125 and 150 mM NaCl for five days. Growth, lipid peroxidation and antioxidant enzyme activities were evaluated. Growth, measured in terms of length, fresh weight and dry weight of plants, was drastically reduced in PK-416, while there was little effect of NaCl treatment on Pusa-37 genotype of soybean. A high level of lipid peroxidation was observed in PK-416 as indicated by increased level of malondialdehyde. Activities of superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase were maximum in Pusa-37 where 9-fold, 1-fold, 5-fold and 6-fold increases over control were observed, respectively. The results suggested that PK-416 and Pusa-37 are salt-sensitive and salt-tolerant genotypes of soybean, respectively, and antioxidant defence systems involved in conferring the sensitiveness and tolerance in these genotypes.     

Relative growth rate of leaf biomass and leaf nitrogen content in several mediterranean woody species

In many plant species, herbivory is a major determinant of leaf mortality and it can cause a strong reduction in productive potential. Most predation occurs on young, expanding leaves. Thus, a rapid growth of the leaves can reduce the impact of predation. Furthermore, in cold Mediterranean climates the length of the growing season is constrained to a short period in spring and early summer owing both to low winter temperatures and drought stress in early summer. Therefore, a rapid deployment of leaf area and a high photosynthetic capacity during the spring and early summer might have important positive effects on the final carbon balance of the leaf population. Relative growth rates (RGR) of leaf biomass were measured in 19 woody species typical of Central Western Spain with deciduous and evergreen habits. Highly significant differences were detected in the leaf growth rate of the different species. The differences between species, however, did not correlate either with the mean leaf life-span of each of the species or with other leaf traits such as photosynthetic capacity, specific leaf area or nitrogen content. Leaf growth rate was positively correlated with time elapsed between leaf initiation and fruit maturation, so that species with fruit dispersal in spring and early summer in general had lower leaf growth rates than species with autumn fruit shedding. This relationship shows the effects of the concurrence between vegetative and reproductive organs for nutrients and other resources. Nitrogen concentration in the leaves was very high at the time of bud break, and declined during leaf expansion owing to the dilution associated with the increase in structural components. The rate of nitrogen dilution was, thus, positively related to the leaf growth rate. Relative growth rates calculated for nitrogen mass in leaves were very low compared to the growth in total mass. This suggests that most leaf nitrogen is translocated from the plant stores to the leaf biomass before the start of leaf expansion and that the contribution of root uptake during leaf expansion is comparatively low.