Dehydrins are proteins that play a role in the mechanism of drought tolerance. This study aimed at establishing dehydrin profile and accumulation in four local melon varieties of Iran: Mino, Dargazi, Saveii, and Semsori, as well as in a commercial variety Honeydew. Plants were treated with drought stress by adjusting the soil water content to 75, 50, 40, 30 and 20% of field capacity (FC) by withholding water. Water status of plants was monitored based on the seedling fresh weight (FW) and relative water content of leaves (RWC). Total protein content was extracted, then heat-stable protein (HSP) fraction was isolated for each variety and water stress treatment. After SDS-PAGE of HSP, Western blotting analysis was carried out with Anti-dehydrin rabbit (primary) and Goat anti rabbit (secondary) antibodies. ANOVA results showed that with decreasing FC below 75%, FW and RWC decreased, but these changes significantly varied among genotypes. On the basis of FW and RWC data under different drought stress treatments, the following drought-tolerant ranking was established: Mino > Dargazi > Saveii and Honeydew > Semsori, from tolerant to sensitive order. Results of Western blot analysis showed that expression of some proteins with molecular weights of 19– 52 kDa was induced in the studied varieties under drought stress (% FC). Expression level of the dehydrin proteins in different varieties was variable and also depending on the drought stress level applied. However, dehydrin proteins (45 and 50 kDa) showed strong expression levels in all varieties under severe drought stress (20% FC). The abundance of dehydrin proteins was higher in tolerant varieties (Mino and Dargazi) than in moderate and drought sensitive genotypes. Consequently, dehydrins represent a potential marker for selection of genotypes with enhanced drought tolerance.
The Salix variegata Franch. seedlings planted in the Three Gorges Reservoir (TGR) water level fluctuation zone (WLFZ) could survive after experiencing several seasons of winter submergence. We investigated the recovery mechanisms of S. variegata seedlings planted at the elevation of 168 m and 172 m in the TGR WLFZ after winter submergence. The results indicated that winter submergence caused some impacts on S. variegata seedlings with increases of hydrogen peroxide (H₂O₂), superoxide anions radical (O₂⁻˙), and malondialdehyde (MDA) levels, and decreases of antioxidant enzymatic systems during recovery stage after winter submergence. However, further analyses of relative water content (RWC), pigment content, proline content, carbohydrate content and several other antioxidant enzymatic activities (catalase (CAT), guaiacol peroxidase (G-POD), and glutathione peroxidase (GSH-POD)) showed that S. variegata seedlings were well recovered after winter submergence. These results indicate that S. variegata possesses strong winter submergence tolerance and adaptation to the specific hydrological environment in the TGR WLFZ. Therefore, S. variegata should be popularized as native tree species during the revegetation in the TGR WLFZ.
Common bean (Phaseolus vulgaris L.) is sensitive to drought and salinity, while an ancestral legume, tepary bean (P. acutifolius A. Gray) is cultivated successfully where high temperature and drought are common (Lazcano-Ferrat and Lovatt, 1999). Hence, P. acutifolius is a potential source of stress tolerant traits for P. vulgaris through interspecific hybrids. This study comparatively evaluated the effects of salt stress on leaf relative water content (RWC), soluble protein, the phytohormones indole acetic acid (IAA), gibberellic acid (GA3), zeatin, and abscisic acid (ABA) levels in P. vulgaris and P. acutifolius. With the exception of ABA, stress-induced changes in hormonal levels putatively related to stress tolerance have not been investigated previously in either species. Treatment with 50 mM, 100 mM and 150 mM NaCl reduced relative water and protein content in P. vulgaris, but did not affect relative water content and increased protein content in P. acutifolius. Varietal differences between P. vulgaris and P. acutifolius were also observed in hormonal content during the stress period. ABA levels in salt-treated plants of P. vulgaris increased but did not change in P. acutifolius versus the controls. Both IAA and gibberellin levels increased in leaves of P. acutifolius but decreased in P. vulgaris under salt stress. In salt-treated plants, zeatin concentrations in leaves of P. vulgaris decreased within 24-72 h after treatment. However, P. acutifolius responded to all tested NaCl levels by increasing zeatin concentrations after short-term NaCl treatment.
Pot experiments were carried out in years 2003-2005 the drought tolerance in 11 potato cultivars: Asterix, Danusia, Korona, Rosalind, Satina, Saturna, Syrena, Wiking, Zebra, Zeus in 2-or 3-year cycle. Main evaluation criterion of drought tolerance was decrease of yield and its quality. Plants were subjected to drought stress during the highest sensitivity of water deficit i.e. 3 weeks when on tuberization beginning. RWC - relative water content in leaf tissues was measured after drought period. The effects of cultivar and drought on yielding level were significant, what indicates very high differentiation of investigated potato cultivars. No influence of drought on the quantity of potato tubers was observed. Tested cultivars were ranked according to yield reduction degree by the water stress and increasing sensitivity to drought: Korona, Syrena, Zeus, Andromeda, Danusia, Asterix, Zebra, Wiking, Saturna, Satina, Rosalind.
The aim of the research conducted in 2010-2012 on one-year, two-year and three-year shoots of three verities of Salix viminalis: ‘Bjor’, ‘Jorr’ and ‘Tora’, grown from 14, 15 and 16 year old stumps, was to compare the shoots of different age in terms of selected physiological characteristics, that is the concentration of chloroplast pigments, water balance of leaves and water content and dry matter of shoots. The content of chloroplast pigments (chlorophyll a, chlorophyll b and carotenoids) and the water balance were determined on the basis of RWC-relative water content and WSD-water saturation deficit indicators. Moreover, the water and dry matter content of one-year, two-year and three-year old willow shoots were determined. It was found that the age of the shoots differentiated the physiological parameters of willow varieties. The highest concentration of chlorophylls was reported in the leaves of three-year old shoots of the Bjor variety, in turn the highest concentration of carotenoids was found in the leaves of one-year old shoots of Jorr. Regardless of the age of the shoots, the highest rate of hydration of leaves and stems was a characteristic trait of the Tora variety, and the lowest was found in Jorr. High levels of the measured physiological parameters, such as chlorophyll a and b, carotenoids and relative water content in leaves obtained in the 5th rotation, that is 14th, 15th and 16th year of running the plantation, indicate a high physiological activity and hence high productivity of the studied willow varieties.
Carrot production of valuable carotenes, carbohydrate and protein are hindered by elevated salinity levels in many parts of the world. To assess this problem, germination and growth of two carrot cultivars (Daucus carota cvs Jordan and Napoli) were studied in vivo and in vitro under different salt stress concentrations (0, 75, and 150 mM NaCl). Seeds were directly or gradually exposed to these salt concentrations. With elevated salinity levels, significant reductions in growth parameters (dry shoot weight, fresh shoot weight, shoot length, root length, and root number) were observed. Also, significant difference in germination percentage was observed at 150 mM NaCl in both cultivars when compared with control treatment (90% germination percentage in Napoli and 71% in Jordan cultivar). Growth rate, tolerant index, and relative water content (RWC) declined as salinity increased. The 150 mM NaCl salinity treatment significantly reduced the shoot chlorophyll and protein content, but increased carbohydrate content. Lesser impairment by the gradual exposure of seedling to salinity provides an opportunity to study the acquirement of salt tolerance.
Maize (Zea mays L.) hybrid with the Bt transgene from the bacterium Bacillus thuringensis (Bt) (DKC 3421 YG) and its non-Bt near-isoline (DKC 3420) as well as Polish cultivar Bosman (HR Smolice) were subjected to drought stress and/or the two-spotted spider mite (Tetranychus urticae, Acarina: Tetranychidae) feeding to assess changes in the relative water content (RWC) and dry weight (DW) in leaves of different age (leaf: 7th, 8th, 9th, 10th). All plants were at the vegetative stage and grew under greenhouse conditions. The effect of both abiotic and biotic stress was analysed 4 and 6 days after treatment. The experiments conducted in two series showed that among examined maize cultivars, T. urticae feeding decreased RWC in Bosman cv. leaves only, while drought altered leaf RWC of plants in a similar manner – the older the leaf, the greater reduction of RWC. Drought alone and drought accompanied by T. urticae feeding significantly decreased RWC of maize leaves in all cultivars (DKC 3421 YG, DKC 3420, Bosman). Concluding, drought had a greater impact on leaf RWC of young maize plants than mite feeding.