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Effect of NaCl stress on root and leaf anatomy in two cowpea (Vigna unguiculata (L.) Walp.) genotypes

Abstract:

The effect of NaCl stress on leaf and root anatomy in two cowpea genotypes with differences in sensibility to that salt was studied in order to know the probable existence of histological adaptations associated to that differential behavior. Seeds of the genotypes 'I-484' (moderate sensibility to salinity) and 'I-490' (sensible to salinity) were sown on inert substrate and six days after sown they were subject to salinization with NaCl (100 mM). Fourteen days after sown, samples of the root and the primary leaves were taken and fixed in FAA until their processing. Salt stress induced succulence in the rizodermis and cortex parenchyma of the root, in higher degree in 'I-484'. Salinity also produced a reduction in the stele diameter of both genotypes, because of the decrease in number and diameter of the xylem vessels. In the primary leaves of stressed plants, were observed more glandular trichomes, less compact mesophyll and invaginations in the palisade parenchyma cells. In 'I-490' the thickness of the leaf, and that of the adaxial epidermis of palisade and spongy parenchyma, were significantly reduced. These results suggest that the anatomical mechanisms of adaptation to NaCl stress in Vigna unguiculata are related to the capacity to develop root succulence and the maintenance of foliar tissue integrity.