盐胁迫对桑树幼苗生长、叶片水分状况和离子分布的影响

以黑龙江省两个桑树品种（秋雨桑和泰来桑）为试验材料,研究了不同盐浓度下桑树幼苗生长、叶片水分关系和不同器官中离子的分布.结果表明：盐胁迫明显降低了桑树幼苗的植株高度和每株干物质量,且对新生叶片干质量的影响大于老叶片.随着盐胁迫的加重,两个品种桑树的叶片水势、渗透势、压力势和相对含水量明显下降,根、茎中Na⁺浓度明显增加,当外界NaCl浓度达到或超过150 mmol·L^-1时,各器官中Na⁺浓度达到饱和.盐胁迫明显降低了两个品种桑树根、茎和叶片中K⁺ 和 Ca²⁺浓度,以及茎和叶片中Mg²⁺浓度,而对根中Mg²⁺浓度影响不大.Na⁺在根、茎和老叶中的区域化分布是两个品种桑树生长过程中表现出耐盐性的机理之一,而盐胁迫使叶片中的Ca²⁺、K⁺和Mg²⁺浓度降低,导致植株体内的离子亏缺,从而限制了植株的生长.     

Growth Adaptability and Salt Tolerance Osmoregulation of Aneurolepidium chinense Grown on Saline Grassland

The growth of Aneurolepidium chinense Kitag. grown on different saline soil of a Northeast grassland of China was studied and the K+,Na+proline and citric acid accumulated in plants or their organs were determined . The results showed that A. chinense had a strong adaptability to saline habitat and could grow on soil with a salt content of 0. 088%--1.63%,and pH ranging from 8.3 to 9.8. Sodium,proline and citric acid were accumulated by plants for osmotic adjustment when the salinity and Na+content of the soil increased. A. chinense absorbed Na+ rapidly from the soil and excluded K+ when the soil Na+ concentration was less than 20 μmol/g. Sodium was adsorbed slowly and K+ remained constant in plants when Na+ concentrations of soil were 20–80 μmol/g,and proline and citric acid contents were markedly increased. Sodium and K+ decreased slightly in plant tissue and organic solutes increased when Na+ concentrations exceeded 80 μmol/g in soil. Most K+ was distributed in young leaves which were metabolically active. The major sites of Na+ accumulation were in the roots and older mature leaves;whereas proline and citric acid accumulation occurred primarily in young leaves,mature leaves and stems. Tillering buds had strong ability to absord and accumulate K+,Na+ and Proline.     

Evaluation of the stress-inducible production of proline in transgenic sugarcane (Saccharum spp.): osmotic adjustment, chlorophyll fluorescence and oxidative stress

Proline accumulates in a variety of plant species in response to stresses such as drought, salinity and extreme temperatures. Although its role in plant osmotolerance remains controversial, proline is thought to contribute to osmotic adjustment, detoxification of reactive oxygen species and protection of membrane integrity. In the present study, we evaluated the effects of stress-inducible proline production on osmotic adjustment, chlorophyll fluorescence and oxidative stress protection in transgenic sugarcane transformed with a heterologous P5CS gene. In well-watered conditions, free proline, malondialdehyde (MDA) levels, Fv/Fm ratios and chlorophyll contents (Chls) in transgenic sugarcane were not statistically different from non-transformed control plants. After 9 days without irrigation, proline content in transgenic events was on the average 2.5-fold higher than in controls. However, no osmotic adjustment was observed in plants overproducing proline during the water-deficit period. The photochemical efficiency of PSII observed was higher (65%) in the transgenic events at the end of the water-deficit experiment. The effects of proline on lipid peroxidation as MDA levels and on the decline of Chl in paraquat-treated leaf discs along the drought period suggest that proline protected the plants against the oxidative stress caused by the water deficit. The overall capacity of transgenic plants to tolerate water-deficit stress could be assessed by the significantly higher biomass yields 12 days after withholding water. These results suggest that stress-inducible proline accumulation in transgenic sugarcane plants under water-deficit stress acts as a component of antioxidative defense system rather than as an osmotic adjustment mediator.     

Proline accumulation by tomato leaf tissue in response to salinity

The capacity of tomato leaf tissues to accumulate proline in response to a salt shock (150 mM NaCl) applied to excised shoots, leaves, leaflets or leaf discs was determined and compared to that of whole plants grown at the same salinity. The associated changes in free amino acids, Na+, K+ and Cl- contents were also investigated. In excised organs treated for 80 h, up to 200 mumol g-1 DW of proline were accumulated, whereas the amount of proline in leaf discs did not exceed a value ten-fold lower. In the whole plants subjected to salinity the Na+, Cl- and K+ contents remained low in comparison to that observed in excised organs. Proline and other amino acids increased more slowly in whole plants than in excised shoots. The contribution of roots and vascular tissues to the control of Na+ and Cl- accumulation and to the regulation of proline metabolism are discussed.     

盐胁迫下构树幼苗各器官中K+、Ca2+、Na+和Cl-含量分布及吸收特征

将当年生构树幼苗置于含有不同浓度（04、1、2、3、4 g·kg^-1）NaCl的土壤中,研究其生物量积累、叶片细胞质膜透性和K⁺、Ca²⁺、Na⁺、Cl^-等离子的吸收、分布及运输,并观察盐害症状.结果表明：构树幼苗的叶片质膜透性随着NaCl浓度的增加和胁迫时间的延长而升高,根冠比随NaCl浓度的升高而增加,大于3 g·kg^-1的土壤盐胁迫对构树叶片的质膜透性及植株的生物量积累影响显著.构树幼苗各器官中Na⁺和Cl^-含量随土壤NaCl浓度升高而显著增加,K⁺和Ca²⁺则随之降低,叶片各离子含量均明显高于根和茎.说明盐胁迫影响根系对K⁺和Ca²⁺的吸收,并抑制了它们向地上部分的选择性运输,使叶和茎的K⁺和Ca²⁺含量下降.构树通过吸收积累Na⁺和Cl^-抵御土壤盐分带来的渗透胁迫,但过量的Na⁺和Cl^-积累会造成单盐毒害.作为抗盐性较高的非盐生植物,构树地上部分的拒盐作用不显著.     

Abscisic acid, indole-3-acetic acid and mineral–nutrient changes induced by drought and salinity in longan (Dimocarpus longan Lour.) plants

Longan species (Dimocarpus longan Lour.) exhibit a high agronomic potential in many subtropical regions worldwide; however, little is known about its responses to abiotic stress conditions. Drought and salinity are the most environmental factors inducing negative effects on plant growth and development. In order to elucidate the responses of longan to drought and salinity, seedlings were grown under conditions of drought and salt stresses. Drought was imposed by suspending water supply leading to progressive soil dehydration, and salinity was induced using two concentrations of NaCl, 100 and 150 mM in water solution, for 64 days. Data showed that salt concentrations increased foliar abscisic acid (ABA) and only 150 mM NaCl reduced indole-3-acetic acid (IAA) and increased proline levels. NaCl treatments also increased Na⁺ and Cl^? content in plant organs proportionally to salt concentration. Drought increased leaf ABA but did not change IAA concentrations, and also increased proline synthesis. In addition, drought and salt stresses reduced the photosynthesis performance; however, only drought decreased leaf growth and relative leaf water content. Overall, data indicate that under severe salt stress, high ABA accumulation was accompanied by a reduction of IAA levels; however, drought strongly increased ABA but did not change IAA concentrations. Moreover, drought and high salinity similarly increased (or maintained) ion levels and proline synthesis. Data also suggest that ABA accumulation may mitigate the impact of salt stress through inducing stomatal closure and delaying water loss, but did not mediate the effects of long-term drought conditions probably because leaves reached a strong dehydration and the role of ABA at this stage was not effective to detain leaf injuries.     

盐胁迫下构树幼苗各器官中K+、Ca2+、Na+和Cl-含量分布及吸收特征

将当年生构树幼苗置于含有不同浓度（04、1、2、3、4 g·kg^-1）NaCl的土壤中,研究其生物量积累、叶片细胞质膜透性和K⁺、Ca²⁺、Na⁺、Cl^-等离子的吸收、分布及运输,并观察盐害症状.结果表明：构树幼苗的叶片质膜透性随着NaCl浓度的增加和胁迫时间的延长而升高,根冠比随NaCl浓度的升高而增加,大于3 g·kg^-1的土壤盐胁迫对构树叶片的质膜透性及植株的生物量积累影响显著.构树幼苗各器官中Na⁺和Cl^-含量随土壤NaCl浓度升高而显著增加,K⁺和Ca²⁺则随之降低,叶片各离子含量均明显高于根和茎.说明盐胁迫影响根系对K⁺和Ca²⁺的吸收,并抑制了它们向地上部分的选择性运输,使叶和茎的K⁺和Ca²⁺含量下降.构树通过吸收积累Na⁺和Cl^-抵御土壤盐分带来的渗透胁迫,但过量的Na⁺和Cl^-积累会造成单盐毒害.作为抗盐性较高的非盐生植物,构树地上部分的拒盐作用不显著.     

土壤盐度对加拿利海枣幼苗生长与生理指标的影响

将加拿利海枣(Phoenix canariensis Hort. ex Chab.)幼苗培养在不同盐度(1.2~14.5)的土壤中,探讨土壤含盐量对其生长及生理指标的影响。结果表明:随基质盐度的提高,幼苗新生叶片数降低且叶片死亡数增加。随基质盐度的提高,叶绿素含量增加,叶绿素a/b在低盐度时增加而当盐度超过5.1时下降。土壤盐度在1.2~5.1时,MDA含量约为4.30 μmol g^-1,以后随土壤盐度的升高而升高。SOD活性在低盐时升高,土壤盐度超过10.8时,SOD活性迅速下降。盐胁迫下叶片Na⁺和Cl^-含量升高,K⁺、Ca²⁺、Mg²⁺含量及K⁺/Na⁺下降。盐胁迫导致加拿利海枣生长下降的主要原因是叶片有效光合面积减少,离子平衡破坏。这些表明加拿利海枣具有很高的耐盐能力,其幼苗在土壤盐度5.1时生长正常,当土壤盐度为10.8时才开始出现受害症状,适宜在滨海地区推广应用。     

Oxygation Enhances Growth, Gas Exchange and Salt Tolerance of Vegetable Soybean and Cotton in a Saline Vertisol

Impacts of salinity become severe when the soil is deficient in oxygen. Oxygation (using aerated water for subsurface drip irrigation of crop) could minimize the impact of salinity on plants under oxygen-limiting soil environments. Pot experiments were conducted to evaluate the effects of oxygation (12% air volume/volume of water) on vegetable soybean (moderately salt tolerant) and cotton (salt tolerant) in a salinized vertisol at 2, 8, 14, 20 dS/m ECe. In vegetable soybean, oxygation increased above ground biomass yield and water use efficiency (WUE) by 13% and 22%, respectively, compared with the control. Higher yield with oxygation was accompanied by greater plant height and stem diameter and reduced specific leaf area and leaf Na+ and Cl-concentrations. In cotton, oxygation increased lint yield and WUE by 18% and 16%, respectively, compared with the control, and was accompanied by greater canopy light interception, plant height and stem diameter. Oxygation also led to a greater rate of photosynthesis, higher relative water content in the leaf, reduced crop water stress index and lower leaf water potential. It did not, however, affect leaf Na+ or Cl- concentration. Oxygation invariably increased, whereas salinity reduced the K+ : Na+ ratio in the leaves of both species. Oxygation improved yield and WUE performance of salt tolerant and moderately tolerant crops under saline soil environments, and this may have a significant impact for irrigated agriculture where saline soils pose constraints to crop production.     

Effects of kinetin on growth, grain yield and some mineral elements in wheat plants growing under excess salinity and oxygen deficiency

Wheat plants, 22d. old, were exposed to wide range of soil water osmotic potential (s = 0 to –1.2 MPa) induced by NaCl and CaCl2 treatments in combination with roots maintained under aerobic (drained at field capacity) or nonaerobic (flooded) conditions in the soil, and sprayed with 10 mg L–1 kinetin solution. In drained plants, not receiving kinetin, increased soil salinity resulted in appreciable inhibition of shoot growth and reduction in chlorophyll (Ch1.), soluble sugars (SS) contents and grain yield. Shoot growth, Ch1. content, soluble sugars and grain yield were significantly lower for flooded plants than unflooded analogues over the entire s range. Both salinity and waterlogging synergize to increase Na+, Ca+ and Cl– accumulation in shoot tissues and to decrease the stability of leaf membranes to either dehydration (40% polyethylene glycol 6000) or heat (51 °C) stress. The ratio of K+/Na+ transported to shoots under aerobic and anaerobic conditions decreased progressively on salinization. The association between the internal mineral element concentrations was largely affected by kinetin treatment. Kinetin application ameliorated the deleterious effects of salinity and oxygen deficiency. It reduced Na+, Ca2+ and Cl– accumulation and improved K+ uptake under salinity and waterlogging stresses. Increased K+/Na+ ratio helped the plants to avoid Na+ toxicity and enhanced shoot growth and grain yield. Kinetin also reduced membrane injury by dehydration and heat stresses and improved the water status of plants under both aerobic and anaerobic conditions. The effects of single factors (Soil salinity s, soil waterlogging WL and Kinetin Kin) and their interactions (s × WL, s × Kin, WL × Kin and s × WL × Kin) were shown by analysis of variance to be statistically significant for most parameters tested. Calculation of the coefficient of determination (+) led to three important findings. (1) Salinity (s) was dominant in affecting leaf relative water content (RWC), shoot dry mass, grain yield, stability of leaf membranes to dehydration stress and the contents of Na+, Ca2+, Mg2+ and Cl–. (2) Kinetin (Kin) had a dominant effect on the stability of leaf membranes to heat stress as well as on chlorophyll and soluble sugars contents. (3) The share of waterlogging (WL) was dominant for K+ content. It can be concluded that kinetin application helped wheat plants to grow successfully in the areas subjected to combined effects of salinity and oxygen deficiency, such as in salt marshes.     

Photosynthetic capacity is related to the cellular and subcellular partitioning of Na+, K+ and Cl- in salt-affected barley and durum wheat

The capacity of plants to tolerate high levels of salinity depends on the ability to exclude salt from the shoot, or to tolerate high concentrations of salt in the leaf (tissue tolerance). It is widely held that a major component of tissue tolerance is the capacity to compartmentalize salt into safe storage places such as vacuoles. This mechanism would avoid toxic effects of salt on photosynthesis and other key metabolic processes. To test this, the relationship between photosynthetic capacity and the cellular and subcellular distribution of Na+, K+ and Cl- was studied in salt-sensitive durum wheat (cv. Wollaroi) and salt-tolerant barley (cv. Franklin) seedlings grown in a range of salinity treatments. Photosynthetic capacity parameters (Vcmax, Jmax) of salt-stressed Wollaroi decreased at a lower leaf Na+ concentration than in Franklin. Vacuolar concentrations of Na+, K+ and Cl- in mesophyll and epidermal cells were measured using cryo-scanning electron microscopy (SEM) X-ray microanalysis. In both species, the vacuolar Na+ concentration was similar in mesophyll and epidermal cells, whereas K+ was at higher concentrations in the mesophyll, and Cl- higher in the epidermis. The calculated cytoplasmic Na+ concentration increased to higher concentrations with increasing bulk leaf Na+ concentration in Wollaroi compared to Franklin. Vacuolar K+ concentration was lower in the epidermal cells of Franklin than Wollaroi, resulting in higher cytoplasmic K+ concentrations and a higher K+ : Na+ ratio. This study indicated that the maintenance of photosynthetic capacity (and the resulting greater salt tolerance) at higher leaf Na+ levels of barley compared to durum wheat was associated with the maintenance of higher K+, lower Na+ and the resulting higher K+ : Na+ in the cytoplasm of mesophyll cells of barley.     

Leaf water relations and net gas exchange responses of salinized Carrizo citrange seedlings during drought stress and recovery

BACKGROUND AND AIMS: Since salinity and drought stress can occur together, an assessment was made of their interacting effects on leaf water relations, osmotic adjustment and net gas exchange in seedlings of the relatively chloride-sensitive Carrizo citrange, Citrus sinensis x Poncirus trifoliata. METHODS: Plants were fertilized with nutrient solution with or without additional 100 mm NaCl (salt and no-salt treatments). After 7 d, half of the plants were drought stressed by withholding irrigation water for 10 d. Thus, there were four treatments: salinized and non-salinized plants under drought-stress or well-watered conditions. After the drought period, plants from all stressed treatments were re-watered with nutrient solution without salt for 8 d to study recovery. Leaf water relations, gas exchange parameters, chlorophyll fluorescence, proline, quaternary ammonium compounds and leaf and root concentrations of Cl(-) and Na(+) were measured. KEY RESULTS: Salinity increased leaf Cl(-) and Na(+) concentrations and decreased osmotic potential (Psi(pi)) such that leaf relative water content (RWC) was maintained during drought stress. However, in non-salinized drought-stressed plants, osmotic adjustment did not occur and RWC decreased. The salinity-induced osmotic adjustment was not related to any accumulation of proline, quaternary ammonium compounds or soluble sugars. Net CO(2) assimilation rate (A(CO2)) was reduced in leaves from all stressed treatments but the mechanisms were different. In non-salinized drought-stressed plants, lower A(CO2) was related to low RWC, whereas in salinized plants decreased A(CO2) was related to high levels of leaf Cl(-) and Na(+). A(CO2) recovered after irrigation in all the treatments except in previously salinized drought-stressed leaves which had lower RWC and less chlorophyll but maintained high levels of Cl(-), Na(+) and quaternary ammonium compounds after recovery. High leaf levels of Cl(-) and Na(+) after recovery apparently came from the roots. CONCLUSIONS: Plants preconditioned by salinity stress maintained a better leaf water status during drought stress due to osmotic adjustment and the accumulation of Cl(-) and Na(+). However, high levels of salt ions impeded recovery of leaf water status and photosynthesis after re-irrigation with non-saline water.     

Interactive effects of salinity and phosphorus availability on growth, water relations, nutritional status and photosynthetic activity of barley (Hordeum vulgare L.)

The interactive effects of salinity and phosphorus availability on growth, water relations, nutritional status and photosynthetic activity were investigated in barley (Hordeum vulgare L. cv. Manel). Seedlings were grown hydroponically under low or sufficient phosphorus (P) supply (5 or 180 μmol KH(2) PO(4) plant(-1) week(-1) , respectively), with or without 100 mm NaCl. Phosphorus deficiency or salinity significantly decreased whole plant growth, leaf water content, leaf osmotic potential and gas exchange parameters, with a more marked impact of P stress. The effect of both stresses was not additive since the response of plants to combined salinity and P deficiency was similar to that of plants grown under P deficiency alone. In addition, salt-treated plants exposed to P deficiency showed higher salt tolerance compared to plants grown with sufficient P supply. This was related to plant ability to significantly increase root:shoot DW ratio, root length, K(+)/Na(+) ratio, leaf proline and soluble sugar concentrations and total non-enzymatic antioxidant capacity, together with restricting Na(+) accumulation in the upper leaves. As a whole, our results indicate that under concomitant exposure to both salt and P deficiency, the impact of the latter constraint is pre-dominant.     

Effects of some salts and sodicity on the growth of a Rhizobium leguminosarum bv. viceae strain isolated from a salt-affected soil.

The effects of sodium (Na+), calcium (Ca2+), magnesium (Mg2+), and boron (B) concentrations and sodicity, as measured by the sodium adsorption ratio (SAR), on the growth of a Rhizobium leguminosarum bv. viceae strain isolated from a salt-affected soil were studied. The rate of growth was measured in a yeast extract-mannitol broth, amended with salts having electrical conductivity (EC) of 4, 8, and 16 dS x m(-1). Each salinity level was prepared to achieve SAR values of 10, 20, and 30 with or without graded B concentrations of 0.5, 1, 3, and 5 mg x L(-1). We found that salinity levels equal to or more than 8 dS x m(-1) had negative effects on Rhizobium growth during the first days of incubation, but the effects became less pronounced after 1 week. Na+ concentrations of more than 1.1 g x L(-1) retarded growth, especially at high SAR values (i.e., at low Ca2+ concentrations). The retardation of growth increased with increases in EC up to 16 dS x m(-1), at all sodicity levels. Mg2+ added together with Na+ or with Ca2+ + Na+ affected growth more negatively than Ca2+ + Na+ alone. The effect of Mg2+ became more pronounced with increased salinities and sodicities. It was concluded that EC of more than 4 dS x m(-1) retarded growth of Rhizobium, but only at high sodicity levels. The relative specific ion effect on growth was in the order Na+ < Ca2+ < Mg2+. The harmful effect of Mg2+ on this strain was accentuated by adding Ca2+ to the cultural medium. When SAR increased from 10 to 30, Na+ had no clear effect on growth, irrespective of the accompanied cations, i.e, Ca2+, Mg2+, or Ca2+ + Mg2+. Growth was reduced by B concentrations as low as 0.5 mg x L(-1), and the B effect was enhanced by increased salinity.     

盐胁迫对药用蒲公英生长特性及有效成分积累与离子吸收分配效应的影响

以药用蒲公英(Taraxacum officinale)为试材,研究不同浓度盐胁迫对其生长特性、有效成分积累和离子吸收分配的影响。结果表明,低盐胁迫(0.1%NaCl)对药用蒲公英生长和菊苣酸含量无显著影响,叶中Na⁺含量与对照无显著差异,K⁺含量及K⁺/Na⁺显著升高;高盐胁迫(≥0.2%NaCl)下其生长受到显著抑制,菊苣酸含量显著降低,类囊体膜结构随着盐胁迫加剧趋于紊乱,光合能力减弱,叶片Na⁺含量显著上升,而K⁺、Ca²⁺和Mg²⁺含量下降,K⁺/Na⁺、Ca²⁺/Na⁺和Mg²⁺/Na⁺显著降低。离子运输选择性系数(S_Ca,Na、S_Mg,Na、S_K,Na)随着盐胁迫加剧呈先升后降趋势。相关性分析表明,盐胁迫下...     

Water relations and leaf expansion: importance of time scale

The role of leaf water relations in controlling cell expansion in leaves of water-stressed maize and barley depends on time scale. Sudden changes in leaf water status, induced by sudden changes in humidity, light and soil salinity, greatly affect leaf elongation rate, but often only transiently. With sufficiently large changes in salinity, leaf elongation rates are persistently reduced. When plants are kept fully turgid throughout such sudden environmental changes, by placing their roots in a pressure chamber and raising the pressure so that the leaf xylem sap is maintained at atmospheric pressure, both the transient and persistent changes in leaf elongation rate disappear. All these responses show that water relations are responsible for the sudden changes in leaf elongation rate resulting from sudden changes in water stress and putative root signals play no part. However, at a time scale of days, pressurization fails to maintain high rates of leaf elongation of plants in either saline or drying soil, indicating that root signals are overriding water relations effects. In both saline and drying soil, pressurization does raise the growth rate during the light period, but a subsequent decrease during the dark results in no net effect on leaf growth over a 24 h period. When transpirational demand is very high, however, growth-promoting effects of pressurization during the light period outweigh any reductions in the dark, resulting in a net increase in growth of pressurized plants over 24 h. Thus leaf water status can limit leaf expansion rates during periods of high transpiration despite the control exercised by hormonal effects on a 24 h basis.     

Salinity tolerance of 'Valencia' orange trees on rootstocks with contrasting salt tolerance is not improved by moderate shade

The effects of shading in combination with salinity treatments were studied in citrus trees on two rootstocks with contrasting salt tolerance to determine if shading could reduce the negative effects of salinity stress. Well-nourished 2-year-old 'Valencia' orange trees grafted on Cleopatra mandarin (Cleo, relatively salt tolerant) or Carrizo citrange (Carr, relatively salt sensitive), were grown either under a 50% shade cloth or left unshaded in full sunlight. Half the trees received no salinity treatment and half were salinized with 50 mM Cl- during two 9 week salinity periods in the spring and autumn interrupted by an 11 week rainy period. The shade treatment reduced midday leaf temperature and leaf-to-air vapour pressure deficit regardless of salinity treatments. In non-salinized trees, shade increased midday CO2 assimilation rate (A(CO2)) and stomatal conductance, but had no effect on leaf transpiration (E(lf)). Shade also increased leaf chlorophyll and photosynthetic water use efficiency (A(CO2)/E(lf)) in leaves on both rootstocks and increased total plant dry weight in Cleo. The salinity treatment reduced leaf growth and leaf gas exchange parameters. Shade decreased Cl- concentrations in leaves of salinized Carr trees, but had no effect on leaf or root Cl- of trees on Cleo. There were no significant differences in leaf gas exchange parameters of shaded and unshaded salinized plants but the growth reduction from salinity stress was actually greater for shaded than for unshaded trees. Shaded trees on both rootstocks had higher leaf Na+ than unshaded trees after the first salinity period, and this shade-induced elevated leaf Na+ persisted after the second salinity period in trees on Carr. Thus, shading did not alleviate the negative effects of salinity on growth and Na+ accumulation.     

根茎在羊草响应短期NaCl胁迫过程中的作用

根茎是根状茎型克隆植物的特有结构,在养分储存、运输和分蘖茎的形成等方面起关键性作用。然而有关根茎生理学方面的研究却十分匮乏。为了探讨根茎在植物感应环境胁迫中的作用, 本文以羊草(Leymus chinensis)为实验材料,研究和比较了短期NaCl胁迫根、根茎、根和根茎3种处理方式下羊草对盐胁迫的响应。试验结果表明:200 mmol·L^-1 NaCl处理羊草根、根茎、根和根茎24 h,显著(p<0.05)降低羊草叶片净光合速率和蒸腾速率,增加叶片渗透浓度与脯氨酸含量;其中同时处理根和根茎叶片,蒸腾速率和净光合速率的降低程度显著高于分别处理根和根茎。在分别处理根与根茎的情况下,叶片含水量、脯氨酸含量、净光合速率、蒸腾速率均无显著性差异。不论单独胁迫根、根茎还是同时胁迫根和根茎,羊草根、根茎和叶片内Na⁺含量都显著高于对照,而羊草根、根茎和叶片内K⁺含量都显著低于对照。这些结果显示:1)根茎在羊草响应盐胁迫的生理过程中与根系具有类似的功能;2)羊草根茎在盐胁迫条件下能够有效地吸收Na⁺;3)鉴于根茎的生物量和表面积都明显地低于根系,在盐胁迫下羊草根茎吸收Na⁺的效率高于根系。     

Alleviation of phosphorus deficiency stress by moderate salinity in the halophyte <Emphasis Type="Italic">Hordeum maritimum</Emphasis> L.

Hordeum maritimum (Poacea) is a facultative halophyte potentially useful for forage production in saline zones. Here, we assessed whether moderate NaCl-salinity can modify the plant response to phosphorus (P) shortage. Plants were cultivated for 55 days under low or sufficient P supply (5 or 60 μmol plant⁻¹ week⁻¹ KH₂PO₄, respectively), with or without 100 mM NaCl. When individually applied, salinity and P deficiency significantly restricted whole-plant growth, with a more marked effect of the latter stress. Plants subjected to P deficiency showed a significant increase in root growth (as length and dry weight) and root/shoot DW ratio. Enhanced root growth and elongation presumably correspond to the well-known root adaptive response to mineral deficiency. However, leaf relative water content, leaf P concentration, and leaf gas exchange parameters were significantly restricted. The interactive effects of salinity and P deficiency were not added one to another neither on whole plant biomass nor on plant nutrient uptake. Indeed, 100 mM NaCl-addition to P-deficient plants significantly restored the plant growth and improved CO₂ assimilation rate, root growth, K⁺/Na⁺ ratio and leaf proline and soluble sugar concentrations. It also significantly enhanced leaf total antioxidant capacity and leaf anthocyanin concentration. This was associated with significantly lower leaf osmotic potential, leaf Na⁺ and malondialdehyde (MDA) concentration. Taken together, these results suggest that mild salinity may mitigate the adverse effects of phosphorus deficiency on H. maritimum by notably improving the plant photosynthetic activity, the osmotic adjustment capacity, the selective absorption of K⁺ over Na⁺ and antioxidant defence.     

Stress Effects of Mixed Salts with Various Salinities on the Seedlings of Aneurolepidium chinense

Seedlings of Aneurolepidium chinense (Trin.) Kitag. were subjected to stress with 30 kinds of 50 to 350 mmol/L of salt mixture which were composed of NaC1, NaHCO3, Na2SO4, and Na2CO3 in various proportion. The results showed that all the responded strains, such as changes in the relative growth rate (RGR), K+ and Na+ contents, content of proline accumulation, and leave electrolyte leakage rate, were aggravated with the increasing salt concentrations and the proportion of the basic salts. The strain reaction from high pH caused by the basic salt was closely related to salinity. The high pH reaction was weaker when the salinity was lower and became progressively stronger intensely with the increasing salinity. The results indicated that there were actually two stresses, the salt and the alkaline stress in the mixed salt stress. It was reasonable to consider the total salt concentration as the strength value of salt stress and the buffer capacity as the strength value of alkaline stress. When the alkaline stress was weak, the strain effect was mainly associated with the total salt concentration, but the buffer capacity became the dominant factor effecting strain with the increasing alkaline stress.