SALINITY-INDUCED ENHANCEMENT OF L-MYO-INOSITOL 1-PHOSPHATE SYNTHASE IN RICE (ORYZA-SATIVA L)

The salt-tolerant varieties of rice (Oryza sativa L.) exhibit enhanced activity of the chloroplast form of L-myo-inositol 1-phosphate syntha se (EC 5.5.4.1) under NaCl treatment either during the seedling stage or in fully grown plants during field growth, The salt-induced enhance ment was noticeable only in chloroplasts from light-grown plants, The effects of these treatments on the cytosolic inositol synthase activit y were less pronounced, While the effect of salt on the activity of th e two forms was marginal in the salt-sensitive varieties during seedli ng growth, salinity affected the chloroplast inositol synthase activit y adversely in these varieties during growth of the plants under field conditions, The salt-enhanced activities of inositol synthase(s) in t he highly salt-tolerant varieties studied were found to be comparable to that observed in Porteresia coarctata, a halophytic wild rice speci es, The implications of these findings, which suggest a role of the in ositol pathway in osmoregulation, are discussed.