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Gorai M.,Institute des Regions Arides | Ennajeh M.,Laboratoire des Biotechnologies Vegetales Appliquees A lAmelioration des Cultures | Khemira H.,Laboratoire des Biotechnologies Vegetales Appliquees A lAmelioration des Cultures | Neffati M.,Institute des Regions Arides
Acta Physiologiae Plantarum

The aim of this study was to investigate the effects of NaCl-salinity on the physiological attributes in common reed, Phragmites australis (Cav.) Trin. ex Steudel. Plants grew optimally under salinity treatment with standard nutrient solution without added salt and at NaCl concentrations up to 100 mM. Applied for 21 days, NaCl-salinity (300 and 500 mM) caused a significant reduction in growth allocation of all different tissues of P. australis. Shoot growth of reed plants displayed a highly significant correlation with plant-water relations and photosynthetic parameters. The net photosynthetic rate and stomatal conductance of reed plants treated with NaCl-salinity at varying osmotic potential (ψπ) of nutrient solutions were positively correlated, and the former variable also had a strong positive relationship with transpiration rate. Leaf water potential and ψπ followed similar trends and declined significantly as ψπ of watering solutions was lowered. The increase in total inorganic nutrients resulting from increased Na+ and Cl- in all tissues and K+, Ca2+ and Mg2+ concentrations were maintained even at the most extreme salt concentration. Common reed exhibited high K+/Na+ and Ca2+/Na+ selectivity ratios over a wide range of salinities under NaCl-salinity. These findings suggest that reed plants were able to adapt well to high salinities by lowering their leaf ψπ and the adjustment of osmotically active solutes in the leaves. © 2010 Franciszek Górski Institute of Plant Physiology, Polish Academy of Sciences, Kraków. Source

Ennajeh M.,Laboratoire des Biotechnologies Vegetales Appliquees A lAmelioration des Cultures | Vadel A.M.,Laboratoire des Biotechnologies Vegetales Appliquees A lAmelioration des Cultures | Cochard H.,French National Institute for Agricultural Research | Cochard H.,University Blaise Pascal | Khemira H.,Laboratoire des Biotechnologies Vegetales Appliquees A lAmelioration des Cultures
Journal of Horticultural Science and Biotechnology

The effects of drought on several major morphological and anatomical features of leaves were investigated in an attempt to explain the origin of the difference in drought resistance between two olive (Olea europaea L.) cultivars, ('Chemlali' and 'Meski') previously demonstrated to be drought-resistant and drought-sensitive, respectively. Under water deficit conditions, 'Chemlali' maintained higher rates of photosynthetic assimilation and lower rates of transpiration compared to 'Meski'. In the present study, we found cultivar-dependent differences in leaf morphoanatomical adaptations to drought stress. When subjected to water stress, the leaves of 'Chemlali' increased the thickness of their upper palisade and spongy parenchyma by 17% and 22%, respectively, compared with only 9% and 13% in the case of 'Meski'. A thicker palisade parenchyma could contain larger numbers of CO2-fixation sites, while a thicker spongy parenchyma could result in easier diffusion of CO2 to these sites. Furthermore, stomatal density (SD) in 'Chemlali' leaves increased by 25% (vs. 7% for 'Meski' leaves) during drought treatment, which could also enhance the external supply of CO2. Other morpho-structural traits implicated in the control of water loss were enhanced more in 'Chemlali' than in 'Meski' leaves. Under conditions of lower water availability, leaf size decreased by 24% in 'Chemlali' (vs. 15% in 'Meski'), trichome density (TD) increased by 25% (while remaining unchanged in 'Meski'), and the thickness of the upper and lower epidermis increased by 32% and 25%, respectively (while remaining unchanged in 'Meski'). The above morpho-anatomical adaptations should improve the water-use efficiency of the tree. These differential changes in leaf morphology and anatomy can explain, at least in part, the difference in drought resistance between the two cultivars. In particular, the upper palisade parenchyma, the spongy parenchyma, SD, and TD could be considered key structural features of leaves that govern the ability of a tree to withstand water stress. They could therefore be used as criteria to select olive cultivars that are more resistant to drought. Source

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