Document Type : Research Paper
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Abstract
Salinity is one of the most important causes in reduction of agricultural products and depletion of natural vegetation in many parts of the world, like Iran. Sesbania aculeata is a palatable forage and relatively salt tolerant species from Fabaceae family that can be used for reclamation of semi- saline rangelands. The study was performed to evaluate the salinity resistance of this in view of ions accumulation and anatomical changes. S. aculeata seeds were planted in sand under greenhouse conditions and irrigated with Hougland nutrient solution. A completely randomized design including three levels of salinity (control, 75 and 150 mM NaCl) was applied and plants were harvested after two months. According to the results, fresh and dry weight of roots and shoots and relative water content were decreased under salinity. With increment of salinity level, Na+ and Cl- accumulation increased in all organs of plants which were more obvious in shoots. Furthermore, the potassium concentration and K+/Na+ ratio decreased in shoots and roots while total amino acids and soluble carbohydrates increased in plants in response to the salinity. Salinity also increased the palisade parenchyma cells thickness and total thickness of leaves, while spongy parenchyma cells thickness decreased under salinity. In addition, ratio of cortex to stele decreased in roots of plants grown under salinity. The results reveal that S. aculeata probably accumulates Na+ and Cl- mostly in vacuoles and amino acids and sugars in cytosol of thick leaf cells with palisade parenchyma through which osmotic adjustment and water absorption by plants is done with minimum energy. Increase of stele area in comparison with cortex in root may also facilitate water uptake under salinity.
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