Salt-induced changes on H+-ATPase activity,sterol and phospholipid content and lipid peroxidation of root plasma membrane from dwarf-cashew (Anacardium occidentale L.) seedlings

The effects of NaCl stress on the growth, water relation, gas exchange, tissue mineral content, and on H⁺-ATPase activity, lipid composition and peroxidation of root plasma membrane-enriched fractions of two genotypes (CCP06 and BRS189, sensitive and tolerant to salt stress, respectively) of dwarf-precocious cashew were studied. Growth reduction was higher in CCP06 than in BRS189. Net photosynthesis decreased in both genotypes, CCP06 being more affected. Roots of BRS189 accumulated higher amount of Na⁺ than those of CCP06 at both salt treatments, whereas Cl⁻ increase was higher only at 8 dS m⁻¹. NaCl at 8 dS m⁻¹ did not modify the plasma membrane H⁺-ATPase activity in CCP06 roots, but significantly increased it in BRS189 roots. Lipid peroxidation was lower in BRS189 than in CCP06 roots. Salinity induced higher accumulation of proline in BRS189 roots. Total phospholipids and free sterols content increased significantly in root plasma membrane of CCP06. However, in BRS189, a slight reduction of free sterols content and no changes in total phospholipids content were observed. Thus, the results suggest that the ability of cashew seedlings to adapt to salt stress is, at least in part, dependent upon the maintenance of integrity and protection against oxidative damage of plasma membrane, which could favor the activation of plasma membrane H⁺-ATPase, as a cellular mechanism to regulate ion exclusion from the shoot.