盐分和水分胁迫对芦荟幼苗渗透调节和渗调物质积累的影响

用不同浓度NaCl和等渗聚乙二醇(PEG 6000)处理芦荟(Aloe vera L.)幼苗,10 d后测定叶片相对生长速率和厚度、叶片中主要有机溶质、无机离子含量及渗透调节能力.结果表明,-0.44、-0.88 MPa NaCl和PEG处理使芦荟叶片的相对生长速率和叶片厚度明显下降,且盐胁迫对幼苗生长的抑制和叶片含水量降低的效应明显高于等渗的水分胁迫,其叶片渗透调节能力随处理渗透势的降低而增加, -0.88 MPa PEG胁迫的芦荟幼苗的渗透调节能力高于等渗盐分胁迫.在主要渗透调节物质可溶性糖、有机酸、K 、Ca2 和Cl-中,-0.88 MPa PEG处理下含量比相同渗透势的NaCl处理下显著增加的是有机溶质,因此推断有机溶质含量高是PEG胁迫下渗透调节能力较强的主要因素.     

Effects of NaCl and iso-osmotic PEG stress on growth,osmolytes accumulation and antioxidant defense in cultured sugarcane cells

In order to discriminate between the ionic and osmotic components of salt stress, sugarcane (Saccharum officinarum L. cv. Co 86032) calli were cultured on media containing NaCl or polyethylene glycol (PEG) 8000 that exerted the same osmotic pressure (−0.7 MPa). PEG stress exposure for 15 days led to significant growth reduction and loss in water content than salt stressed and control tissues. Osmotic adjustment (OA) was observed in callus tissues grown on salt, but was not evident in callus grown on PEG. Oxidative damage to membranes, estimated in terms of accumulation of thiobarbituric acid reactive substances-TBARS and electrolytic leakage was significantly higher in both the stressed calli than the control however, the extent of damage was more in the PEG stressed calli. The stressed callus tissues showed inhibition of ascorbate peroxidase activity, while catalase activity was increased. These results indicate sensitivity of cells to PEG-mediated stress than salt stress and differences in their OA to these two stress conditions. The sensitivity to the osmotic stress indicate that expression of the stress tolerance response requires the coordinated action of different tissues in a plant and hence was not expressed at the cellular level.     

Response of French bean cultivars to water deficits: Changes in endogenous hormones, proline and chlorophyll

Effects of water stress at different stages of plant growth on leaf relative water content (RWC), osmotic potential (Ψos) and changes in contents of chlorophyll, abscisic acid (ABA), zeatin riboside (t-ZR), ethylene and proline in six cultivars of French bean (Phaseolus vulgaris L.) were studied. Under water stress, Ψos and RWC were highest in cv. Contender and lowest in cvs. IIHR-909 and Sel-2. The increase in contents of ABA and proline was marked in cv. Contender followed by cv. UPF-626. Decrease in t-ZR and chlorophyll contents was prominent in cv. IIHR-909. Ethylene production surged in all the cultivars under 4- and 8-d stress and declined under 12-d stress. This revised version was published online in August 2006 with corrections to the Cover Date.     

等渗的盐分和水分胁迫对杠柳种子萌发的影响

通过等渗的NaCl和PEG溶液模拟盐分和水分胁迫,设置渗透梯度,在控制条件下对杠柳种子的萌发过程中总萌发率、幼苗鲜重、胚根生长、种子活力、发芽值等指标系统研究,对种子萌发率与渗透势之间关系进行回归分析,主要结果包括：（1）杠柳种子萌发过程中总萌发率、幼苗鲜重、活力指数和发芽值四项指标均随NaCl和PEG溶液的渗透势降低逐渐下降,综合研究活力指数和发芽值表明渗透势≥-0.5 MPa和≤-1.4 MPa时,PEG对种子萌发抑制作用大于NaCl,其他情况相反;（2）杠柳种子逐日萌发率和胚根日变化研究表明,与NaCl相比,PEG推迟杠柳种子萌发,并且对胚根增长抑制作用较大;（3）建立盐分和水分胁迫条件下种子萌发率与渗透势回归方程,发现杠柳种子在PEG胁迫下的萌发临界值和极限值为-1.0和-1.4 MPa,在NaCl胁迫下是-0.9和-1.3 MPa,解除胁迫条件,不同处理的杠柳种子复水萌发率均达到100%。说明杠柳具有良好的耐盐抗旱的特性。     

Relationship between Salt Tolerance and Resistance to Polyethylene Glycol-Induced Water Stress in Cultured Citrus Cells

Salt-tolerant selected cells of Shamouti orange (Citrus sinensis) and Sour orange (Citrus aurantium) grew considerably better than nonselected cells at any NaCl concentration tested up to 200 millimolar. Also, the growth response of each treatment was identical in the two species. However, the performance of cells of the two species under osmotic stress induced by polyethylene glycol (PEG), which is presumably a nonabsorbed osmoticum, was significantly different. The nonselected Shamouti cell lines were significantly more sensitive to osmotic stress than the selected cells. The salt adapted Shamouti cells were apparently also adapted to osmotic stress induced by PEG. In Sour orange, however, the selected lines had no advantage over the nonselected line in response to osmotic stress induced by PEG. This response was also similar quantitatively to the response of the selected salt-tolerant Shamouti cell line. It seems that the tolerance to salt in Shamouti, a partial salt excluder, involves an osmotic adaptation, whereas in Sour orange, a salt accumulator, such an adaptation apparently does not occur. PEG-induced osmotic stress causes an increase in the percent dry weight of salt-sensitive and salt-tolerant cells of both species. No such increase was found under salt stress. The size of control and stressed cells is not significantly different.     

不同基因型小麦幼苗抗旱抗盐性比较研究

利用等渗的NaCl和PEG处理8种不同基因型小麦进化材料,在处理的3d,6d,9d分别采样测定叶片相对含水量,胁迫敏感指数,游离脯氨酸,可溶性糖,无机离子Na^ ,K^ 含量及荧光参数Fv/m生理指标等。结果表明;在相同渗透势胁迫下,NaCl胁迫引起的小麦叶片荧光参数Fv/m的下降;胁迫敏感指数,脯氨酸,可溶性糖,Na^ 含量的增加均大于PEG胁迫引起的变化,而叶片相对含水量的K^ 含量的下降却小于PEG胁迫下的变化,含有DD染色体组的2n小麦较含有BB和AA的2n小麦有较强的抗旱抗盐性,且由它与4n小麦（AABB）杂交合成的6n小麦（AABBDD）较2n和4n小麦有较强的抗旱抗盐性,且由它与4n小麦（AABB）杂交合成的6n小麦（AABBDD）较2n和4n小麦有较强的抗旱抗盐性,说明DD染色体组上具有控制小麦抗旱和抗盐的有效基因。     

Osmotic adjustment in Lycopersicon esculentum and L. Pennellii under NaCl and polyethylene glycol 6000 iso–osmotic stresses

Changes in leaf solute contents in response to saline (NaCl) and osmotic (polyethylene glycol, PEG, 6000) stresses were measured in three different salt tolerant cultivars of Lycopersicon esculentum (L.) Mill. (Pera, P-73 and Volgogradskij), and its wild relative L. pennellii (Correll) D'Arcy accession PE-47. Iso-osmotic stresses (–0. 5 MPa) of NaCl (140 mM) and PEG 6000 (150 g l^-1) were applied to one-month old plants for 3 weeks. Decreasing leaf dry weight was similar in L. pennellii or L. esculentum cv. P-73 and Volgogradskij under both stresses, while leaf dry weight of L. esculentum cv. Pera decreased more under PEG stress than under NaCl stress. Water contents decreased in all the PEG treated populations, while their calculated solute potential (Ψ_s increased. Under osmotic stress, the total ion contents decreased in relation to control, whereas organic solutes (sugars, amino acids and organic acids) markedly increased in both tomato species, specially in the tomato cultivars, where these solutes represented 50% of the Ψ₅ calculated. Soluble sugar increase was three times higher in leaves of L. esculentum than in the leaves of L. pennellii. Free proline increased under both stresses and its content was highest in L. esculentum and in L. pennellii, respectively, under NaCl and PEG stresses. Nevertheless, the contribution of this metabolite to Ψ_s did not exceed 5%, irrespective of treatment and species. The greater organic solute accumulation in L. esculentum than in L. pennellii– which was not reflected in their Ψ₅ values – was not correlated with the tolerances of the two species to osmotic stress. Therefore, osmotic adjustment may not be the only process influencing salt and drought tolerances in tomato; the ability of plants to regulate their metabolic and physiological functions could also play an important role under these harmful conditions. The possible roles of inorganic solutes and metabolites in osmotic adjustment, energetic metabolism and redox regulation are discussed     

Osmoregulation, growth and sucrose accumulation in germinated Trigonella foenum-graecum (fenugreek) seeds treated with polyethylene glycol

Germinated seeds of Trigonella foenum-graecum L. (fenugreek) were grown in water or in polyethylene glycol (PEG) solutions. After endosperm removal, the water relations, growth, dry weight, sucrose and reducing sugar content of the embryo were determined. Under water sstress conditions, water content and osmotic potential (π₀) at saturation, growth and dry weight were lower than in non-stressed controls. The reduction in dry weight indicated a lower uptake of solutes from the endosperm and the decrease in π₀ was not accompanied by an increase in the amount of the accumulated solutes. It is suggested that embryos of stressed fenugreek seeds control osmotic potential by reduction of water uptake and that this results in reduction of growth. Embryos isolated from germinated seeds ("naked" embryos) were grown in water or in PEG solutions, with or without galactose (as an external solute source substituting for the endosperm). The results indicate that a decrease in the external solute did not account for growth reduction under conditions of water stress, and that decreased solute transport to the embryo may be important. The sucrose contents of "naked" embryos and of embryos from whole seeds were higher after PEG treatment, while reducing sugar contents were lower compared to non-stressed controls. The increased sucrose accumulation may be due to decreased sucrose hydrolysis.     

In vitro water stress bioassays with the nematophagous fungus Pochonia chlamydosporia: Effects on growth and parasitism

The biocontrol potential of Pochonia chlamydosporia, a fungus with parasitic activity against economically important plant-parasitic nematodes, can be influenced by abiotic factors such as water availability. The objective of this study was to evaluate the effects of different water stress regimes on in vitro growth, sporulation, germination and parasitism of P. chlamydosporia isolates. The osmotic water potential of 1.7% corn meal agar (CMA) was modified by addition of potassium chloride (KCl) or glycerol, and the matric water potential was modified using polyethylene glycol (PEG 8000). The fungus was able to grow over a range of potentials but radial growth rates decreased with the increase of osmotic and matric stress. No growth was observed at −10 MPa on 1.7% CMA amended with glycerol and at −7.1 MPa on medium with PEG 8000 but all isolates were able to resume growth when transferred onto unmodified 1.7% CMA. The production of chlamydospores was repressed in both osmotic and matric modified media. Although the production of conidia increased in medium modified with KCl, the germination rate was lower. Spores/hyphal fragments remained viable in all isolates that were previously inoculated onto media with growth-limiting water potential (−10 MPa on 1.7% CMA amended with glycerol and −10 MPa on medium with PEG 8000). The percentage of viable conidia produced on 1.7% CMA, after inoculation under osmotic or matric stress conditions for 25 days, was over 74.5% in all isolates (osmotic stress) and ranged from 1% (Pc1) to 65.8% (Pc280) (matric stress). The in vitro infection of potato cyst nematodes, Globodera rostochiensis eggs by P. chlamydosporia isolates, grown under these limiting conditions, was studied using a standard bioassay. The percentage of parasitized eggs was significantly higher under osmotic stress except for isolates Pc2 and Pc3. P. chlamydosporia spores/hyphal fragments can remain viable at water potentials limiting for growth, for prolonged periods of time, suggesting that the osmoregulation mechanisms, used to compensate water stress, affect in vitro sporulation and increased pathogenicity. Knowledge on water requirements of P. chlamydosporia enables a better understanding of its survival and growth strategies in the soil environment and could aid the development of effective strategies to increase the production and quality of inoculum, thus contributing to the implementation of biosafe, sustainable management strategies against plant-parasitic nematodes.     

Iso-osmotic effect of NaCl and PEG on growth, cations and free proline accumulation in callus tissue of two indica rice (Oryza sativa L.) genotypes

One-month old calli of two indica rice genotypes, i.e., Basmati-370 and Basmati-Kashmir were subjected to two iso-osmotic concentrations (−0.57 MPa and −0.74 MPa) created with 50 and 100 mol m⁻³ NaCl or 10 and 18% solutions of PEG-8000. Both genotypes tolerated only low levels of stress and showed severe growth suppression at −0.74 MPa. The degree of stress tolerance of both genotypes was greater for PEG induced stress than for NaCl induced stress. The relative growth rate of callus was reduced under both stresses, however, the reverse was true for callus dry weight. Sodium (Na⁺) content of the callus tissue was increased only under NaCl induced stress. Salt induced stress reduced K⁺ and Ca²⁺ contents, but the PEG induced stress increased them. Higher levels of stress increased the proline content many folds with more increase being under PEG stress than that under NaCl. Water and osmotic potentials of the callus tissue decreased, whereas turgor potential increased under both abiotic stresses. Overall, Basmati-370 was more tolerant to both NaCl and PEG induced stresses than Basmati-Kashmir, because of less reduction in growth and more dry weight. Moreover, Basmati-370 accumulated higher amounts of cations, free proline, and maintained maximum turgor as compared to Basmati-Kashmir. In conclusion, at cellular level, mechanism of NaCl induced osmotic stress tolerance was found to be associated with more ionic accumulation of inorganic solutes and that of PEG induced osmotic stress tolerance with the accumulation of free proline, as an important osmolyte in the cytosol.     

Screening for drought tolerance in Sorghum using cell culture

Summary Callus growth from 10 cultivars ofSorghum bicolor (L.) Moench was measured with increasing levels of polyethylene glycol (PEG) as an osmoticum in the medium to determine whether differences among these cultivars at the cellular level in response to osmotic stress existed. These cellular ratings were compared to field ratings from the 10 tolerant-to-susceptible cultivars when grown under drought conditions to determine whether cellular ratings corresponded to differences in drought tolerance at the plant level. Callus cultures were grown on Murashige and Skoog inorganic salt formulation plus vitamins, 2,4-dichlorophenoxyacetic acid (2,4-D), kinetin and sucrose, supplemented with 0 to 25% (wt/vol) PEG corresponding to −0.2 to −1.62 MPa osmotic potential. Results suggest that PEG-induced osmotic stress on callus cultures can be used to screen sorghum cultivars for potential early field (preflowering) drought tolerance. This implies that at least a component of the early field drought tolerance in sorghum may have a cellular basis. This study was supported by U.S. Agency for International Development Grant AID/DSAN/XII/G-0149, and USDA Competitive Grants Program.     

Transgenic tomato plants overexpressing chloroplastic monodehydroascorbate reductase are resistant to salt- and PEG-induced osmotic stress

RNA gel hybridization showed that the expression of monodehydroascorbate reductase (MDHAR) in the wild type (WT) tomato was decreased firstly and then increased under salt- and polyethylene glycol (PEG)-induced osmotic stress, and the maximum level was observed after treatment for 12 h. WT, sense transgenic and antisense transgenic tomato plants were used to analyze the antioxidative ability to cope with osmotic stresses. After salt stress, the fresh mass (FM) and height of sense transgenic lines were greater than those of antisense lines and WT plants. Under salt and PEG treatments, sense transgenic plants showed a lower level of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA), a higher net photosynthetic rate (P _N), and the maximal photochemical efficiency of PSII (F_v/F_m) compared with WT and antisense transgenic plants. Moreover, sense lines maintained higher ascorbate peroxidase (APX) activity than WT and antisense plants under salt- and PEG-induced osmotic stress. These results indicate that chloroplastic MDHAR plays an important role in alleviating photoinhibition of PSII by elevating ascorbate (AsA) level under salt- and PEG-induced osmotic stress.     

Salt and drought tolerance of sugarcane under iso-osmotic salt and water stress: growth,osmolytes accumulation,and antioxidant defense

In order to discriminate between the ionic and osmotic components of salt stress, sugarcane (Saccharum officinarum L. cv. Co 86032) plants were treated with salt-NaCl or polyethylene glycol-PEG 8000 solutions (?0.7 MPa) for 15 days. Both the salt and PEG treatments significantly reduced leaf width, number of green leaves, and chlorophyll stability index. Osmotic adjustment (OA) indicated that both the stresses led to significant accumulation of osmolytes and sugars. Salt stressed plants appeared to use salt as an osmoticum while the PEG stressed plants showed an accumulation of sugars. Oxidative damage to membranes was not severe in plants subjected to salt or PEG stress. The salt stressed plants showed an increase in the activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX), while PEG stress led to an increase in SOD but not APX activity as compared to the control. Thus, results indicate that the iso-osmotic salt or PEG stress led to differential responses in plants especially with respect to growth, OA, and antioxidant enzyme activities.     

Osmotic Stress and Ion-Specific Effects on Xylem Abscisic Acid and the Relevance to Salinity Tolerance in Poplar

We designed two experiments to investigate the osmotic stress and ion-specific effects on xylem abscisic acid (ABA) and the relevance to salinity tolerance in one-year-old seedlings of Populus euphratica Oliv. (a salt-resistant genotype) and one-year-old rooted cuttings of P. 'popularis 35-44' (P. popularis) (a salt-sensitive genotype). Net photosynthetic rates (Pn) and unit transpiration rates (TRN) of the two genotypes were significantly decreased upon osmotic shock caused by PEG 6000 (osmotic potential = -0.24 MPa) or iso-NaCl (50 mM). Shoot xylem ABA concentrations in both genotypes increased rapidly after the onset of PEG stress, resulting from a decreased water flow. NaCl-treated trees of P. euphratica maintained considerably greater concentrations of ABA than PEG-treated plants in a longer term, whereas salinized P. popularis exhibited a transient accumulation of ABA in the shoot. TRN was greatly enhanced in both genotypes when pressure (0.24 MPa) was applied to counteract the osmotic suction of 50 mM NaCl. Pressurizing of root systems diluted solutes in the root xylem, but the dilution effect was more pronounced in P. popularis. Root xylem ABA concentrations in P. euphratica steadily increased with salt stress although pressurization lowered its levels. In contrast, there were no observed changes in ABA response to salinity in pressured P. popularis. Therefore, we concluded that the salt-tolerant P. euphratica had a greater capacity to synthesize ABA under saline conditions, which may partially result from specific salt effects. In addition, P. euphratica exhibited a higher capacity for salt (Na+ and Cl-) transport control under salt stress, compared with P. popularis. The possible association between ABA and salt transport limitation, and the relevance to salinity tolerance were discussed.     

Osmotic Stress and Ion-Specific Effects on Xylem Abscisic Acid and the Relevance to Salinity Tolerance in Poplar

We designed two experiments to investigate the osmotic stress and ion-specific effects on xylem abscisic acid (ABA) and the relevance to salinity tolerance in one-year-old seedlings of Populus euphratica Oliv. (a salt-resistant genotype) and one-year-old rooted cuttings of P. 'popularis 35-44' (P. popularis) (a salt-sensitive genotype). Net photosynthetic rates (Pn) and unit transpiration rates (TRN) of the two genotypes were significantly decreased upon osmotic shock caused by PEG 6000 (osmotic potential = -0.24 MPa) or iso-NaCl (50 mM). Shoot xylem ABA concentrations in both genotypes increased rapidly after the onset of PEG stress, resulting from a decreased water flow. NaCl-treated trees of P. euphratica maintained considerably greater concentrations of ABA than PEG-treated plants in a longer term, whereas salinized P. popularis exhibited a transient accumulation of ABA in the shoot. TRN was greatly enhanced in both genotypes when pressure (0.24 MPa) was applied to counteract the osmotic suction of 50 mM NaCl. Pressurizing of root systems diluted solutes in the root xylem, but the dilution effect was more pronounced in P. popularis. Root xylem ABA concentrations in P. euphratica steadily increased with salt stress although pressurization lowered its levels. In contrast, there were no observed changes in ABA response to salinity in pressured P. popularis. Therefore, we concluded that the salt-tolerant P. euphratica had a greater capacity to synthesize ABA under saline conditions, which may partially result from specific salt effects. In addition, P. euphratica exhibited a higher capacity for salt (Na+ and Cl-) transport control under salt stress, compared with P. popularis. The possible association between ABA and salt transport limitation, and the relevance to salinity tolerance were discussed.     

Overexpression of wheat dehydrin DHN-5 enhances tolerance to salt and osmotic stress in <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

Late Embryogenesis Abundant (LEA) proteins are associated with tolerance to water-related stress. A wheat (Triticum durum) group 2 LEA proteins, known also as dehydrin (DHN-5), has been previously shown to be induced by salt and abscisic acid (ABA). In this report, we analyze the effect of ectopic expression of Dhn-5 cDNA in Arabidopsis thaliana plants and their response to salt and osmotic stress. When compared to wild type plants, the Dhn-5 transgenic plants exhibited stronger growth under high concentrations of NaCl or under water deprivation, and showed a faster recovery from mannitol treatment. Leaf area and seed germination rate decreased much more in wild type than in transgenic plants subjected to salt stress. Moreover, the water potential was more negative in transgenic than in wild type plants. In addition, the transgenic plants have higher proline contents and lower water loss rate under water stress. Also, Na⁺ and K⁺ accumulate to higher contents in the leaves of the transgenic plants. Our data strongly support the hypothesis that Dhn-5, by its protective role, contributes to an improved tolerance to salt and drought stress through osmotic adjustment.     

WATER RELATIONS OF WATER-STRESSED,SPLIT-ROOT C4 (SORGHUM BICOLOR; POACEAE) AND C3 (HELIANTHUS ANNUUS; ASTERACEAE) PLANTS

Sorghum [Sorghum bicolor (L.) Moench] and sunflower (Helianthus annuus L.) were grown in a greenhouse with roots divided between sand irrigated with nutrient solution (–0.097 MPa) or nutrient solution containing polyethylene glycol (PEG) (–0.570 MPa) to compare the effect of unequal root zone stress on plant water relations of a C₄ (sorghum) and a C₃ (sunflower) plant. Roots also were divided between two pots of sand irrigated only with nutrient solution (controls) or only with PEG in nutrient solution. In addition to plant water-status measurements, photosynthetic rate, growth (height, root, and shoot dry weights), and evolution of ethylene (a gaseous hormone indicative of stress) were measured. Under all three split-root treatments, sunflower had a lower leaf water potential and produced more ethylene than sorghum. Sunflower was able to survive the PEG stress if half of its root system was under nonstressed conditions. Sunflower with half its root system irrigated with PEG usually had values of leaf water potential, osmotic potential, stomatal resistance, transpiration rate, photosynthetic rate, ethylene evolution, height, and dry weights that were close to those of the control plants. Sunflower with all roots exposed to PEG was wilted severely. Sorghum was little affected by PEG stress applied either to half or all the root system. Growth of sorghum was the same under all treatments. Apparently because stomata of sorghum were more closed in the partial stress test than those of sunflower, sorghum conserved water and had a higher leaf water potential, which might have permitted growth with stress.     

Enhanced Maturation and Desiccation Tolerance of White Spruce [Picea glauca (Moench) Voss] Somatic Embryos: Effects of a Non-plasmolysing Water Stress and Abscisic Acid

A non-plasmolysing moisture stress effected by polyethyleneglycol (PEG) was beneficial when applied to maturing white spruce(Picea glauca) somatic embryos for the following reasons. Anosmotic treatment of 5.0–7.5% PEG stimulated a threefoldincrease in the maturation frequency. The osmotically treatedsomatic embryos displayed higher dry weights and lower moisturecontents than the controls, indicating a greater accumulationof storage reserves. Moisture contents of mature, osmotically-treated,hydrated somatic embryos were 40–45%, in contrast to 57%for the non-osmotically treated controls. Desiccation was achievedby placing the somatic embryos in a range of relative-humidityenvironments. No clear trend for the effect of PEG on survivalof desiccated somatic embryos was observed; mean survival valuesranged from 34 to 62% when somatic embryos from all osmotictreatments were desiccated for 14 d at 81% relative humidity.Following this desiccation treatment, somatic embryos from allosmotic concentrations had moisture contents of 26–31%,similar to the 32% recorded for unimbibed zygotic embryos. Afterimbibition, moisture contents for these zygotic and somaticembryos were in the order of 60%. Somatic embryos matured withPEG remained quiescent during desiccation due to their low initialmoisture contents, and gave rise to plantlets of normal appearance.Gradual desiccation of the somatic embryos directly followingmaturation with abscisic acid (ABA) was crucial to survivalduring desiccation. A plasmolysing water stress effected bysucrose at osmotic potentials similar to PEG was detrimentalto somatic embryo maturation, thereby emphasizing the importanceof the choice of osmoticum. Desiccation, maturation, osmotic potential, Picea glauca, polyethylene glycol, somatic embryo, water stress, white spruce     

Carbendazim alleviates effects of water stress on chickpea seedlings

Carbendazim (methyl-2-benzimidazole carbamate) promoted root growth of chickpea (Cicer arietinum L.) seedlings subjected to polyethylene glycol (PEG, osmotic potential −0.5 MPa) induced water stress. The relative water content, membrane stability index, 2,3,5-triphenyltetrazolium chloride reduction and contents of some osmolytes (proline, sucrose, glucose and fructose) enhanced significantly while the contents of lipid peroxides and hydrogen peroxide diminished effectively by addition of 0.05 % carbendazim into PEG solution. This revised version was published online in September 2005 with the corrected author information.     

Leaf Water Relations, Osmotic Adjustment, Cell Membrane Stability, Epicuticular Wax Load and Growth as Affected by Increasing Water Deficits in Sorghum

A field experiment was conducted with a non-irrigated waterstress treatment and an irrigated control using four sorghum(Sorghum bicolor L. Moench) cultivars. We investigated the effectsof water deficits on leaf water relations, osmotic adjustment,stomatal conductance, cuticular conductance, cell membrane stability(CMS) measured by the polyethylene glycol (PEG) test, epicuticularwax load (EWL), cytoplasmic lipid content, solute concentrationin cell sap, and growth. Osmotic adjustment was observed under water deficit conditions.Lower osmotic potential enabled plants to maintain turgor anddecreased the sensitivity of turgor-dependent processes. Sugarand K were identified as the major solutes contributing to osmoticpotential in sorghum. Sugar and K concentrations in cell sapincreased by 37·4% and 27%, respectively, under waterdeficit conditions in favour of decreasing osmotic potential.Stomatal conductance and cuticular conductance were lower inthe non-irrigated plants. A wide range in CMS among four cultivarswas observed. CMS increased with increasing water deficits.EWL increased on leaves of water deficient plants and was positivelycorrelated with cuticular conductance and CMS. Membrane phospholipidcontent increased in water-stressed plants. CMS as measured by the PEG test, was influenced by EWL, cuticularthickness, and osmotic concentration of leaf tissues. The cultivarswhich maintained higher CMS, higher EWL, lower cuticular conductance,higher turgor and higher osmotic adjustment under water deficitconditions were identified as drought tolerant. Key words: Sorghum bicolor, cell membrane stability, leaf water relationsosmotic adjustment, water stress