Responses of growth and germination to water stress induced by PEG 6000 and NaCl in two maize (Zea mays L.) cultivars 704 and 301 were studied. Water stress was generated by additions of PEG 6000 or sodium chloride to the root medium. Water potentials were: zero as control and -0.15, -0.49, -1.03 and -1.76 MPa as treatments. After 24 h treatment, the roots and shoots length and dry weight were of plants determined. In water stress, roots and shoots length and dry weight decreased at both treatments in both varieties. The germination is inversely proportional to the NaCl and PEG concentrations, it means that 704 and 301 cultivars of maize showed a reduction in germination with an increasing in NaCl or PEG concentrations induced water deficit, but this reduction in NaCl treatment were higher than PEG treatment. At treatment by PEG, the germination was severely decreased at -1.03 MPa. At treatment by NaCl no germination occurred at -1.03 in 301 var. and germination was very low at -1.03 MPa in 704 var., no germination occurred at -1.76 MPa in both varieties at both treatments. Decrease of germination in 704 variety was higher than 301 variety.

No abstract

Drought is one of most important environmental factors inhibiting photosynthesis and decreasing growth and productivity of plants. The sensitivity of crop plants such as wheat to soil drought is particularly serious during reproductive phase is extremely sensitive to plant water status. The aim of this work was to study the effects of drought stress on photosynthesis, photosynthetic pigments, soluble proteins, α-tocopherol and abscisic acid content in six wheat genotypes, two tolerant (Daric and 92 Zhong), two moderately tolerant (Sabalan and DH-2049-3) and two sensitive (Shark and Tevee's'). Total chlorophyll content, relative water content and chlorophyll a/b ratio decreased after long-time drought stress, that decrease in sensitive genotypes was higher than others. Net photosynthesis and stomatal conductance decreased significantly (P < 0.05) in flag leaves of our genotypes under drought stress after pollination, that decrease in sensitive genotypes was higher, too. Abscisic acid content, soluble protein content and α-tocopherol increased under drought stress, that increase in tolerant genotypes was higher. There was a significant negative correlation (P < 0.05) between photosynthesis factors and abscisic acid content in flag leaves of all genotypes. It can be concluded that Daric and 92 Zhong had a better photosynthesis factors compared to other genotypes and showed a higher capacity to tolerate drought stress.

Recent studies have shown that application of salt stress induced massive changes in grapevine gene expression (Vincent et al., 2007;Jellouli et al., 2008). Comparative gene expression analysis could be a useful approach for understanding the mechanisms of tolerance and susceptibility (Kozian and Kirschbaum, 1999).

No abstract

No abstract

Salinity is a major environmental stress and grape is classified as a moderately sensitive plant to salinity. Plants have anti-oxidative systems involving antioxidant enzymes and secondary metabolites like phenolic compounds. The aim of this study was to examine the salinity induced alterations, PAL enzyme activity and total phenolics contents in four grape genotypes. In this study two tolerant (Gharashani and H6) and two sensitive (Shirazi and GhezelUzum) grapes-according to screening experiments under salinity-were selected. 50 mM NaCl was used for salinity treatment. Total phenolics content and phenylalanine ammonia-lyase (PAL) activity increased in all the genotypes under salinity. A positive significant correlation (P<0.01, r>0.8) was observed between total phenolics and PAL activity in leaves and roots of grapes. Ten phenolic acids including hydroxybenzoic acid and hydroxycinnamic acid derivatives were analyzed. Our tolerant and sensitive genotypes showed main differences in phenolic compounds accumulation under salinity. Some compounds like gallic, syringic and p-coumaric acids accumulated higher in tolerant genotypes and others like vanillic, caffeic and sinapic acids accumulated in sensitive genotypes. Considering our results it seems that syringic and p-coumaric acids-that was higher in leaves and roots of tolerant genotypeshad a key role in salinity tolerance.

<p style="text-align: justify;"><strong>Aim</strong>: To study the salinity tolerance of own rooted grape cuttings taken from nine table grape (<em>Vitis vinifera</em> L.) genotypes growing in the Urmia Salt Lake region (Iran): LaaleBidaneh, Gharashani, Sachagh, Shahroodi, LaaleSefid, Khalili, Chawga, GhezelUzum and Gharagandomeh.</p><p style="text-align: justify;"><strong>Methods and results</strong>: Plants were treated with nutrient solutions containing 0, 25, 50 and 100 mM NaCl for two weeks. Shoot and root growth and dry weights (DW) were significantly (<em>P</em>&lt;0.05) reduced in all treatments. Chloride (Cl^-) and sodium (Na⁺) ions highly accumulated in the various parts of the vines with increasing external NaCl concentration. Na⁺ accumulation exceeded that of Cl^- in all treatments and all genotypes. However, Gharashani showed a higher ability to restrict Cl^- and Na⁺ accumulation in lamina (1.08% of DW and 2.56% of DW, respectively) in comparison to the other genotypes, particularly to GhezelUzum (4.1% of DW and 9.10% of DW, respectively), which showed intensive leaf burn symptoms. Lamina soluble sugar, proline and glycine betaine contents increased with increasing salinity. Correlation analysis (<em>P</em>&lt;0.01) indicated that there was a high positive correlation between Cl^- and Na⁺ contents and osmolyte accumulation in lamina.</p><p style="text-align: justify;"><strong>Conclusion</strong>: Taken together, it seems that Gharashani and GhezelUzum, respectively, had a higher and a lower capacity to alleviate salt stress symptoms when compared to the other genotypes.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: Salinity is a serious environmental stress in the regions around Urmia Salt Lake and grapevine is one of the most economically important fruit crops in Urmia. Therefore, screening the native grape genotypes for salt tolerance and using the tolerant genotypes directly as rootstocks or producing hybrids with desirable traits could be one of the improvement programs for viticulture in this area.</p>