Changes induced by NaCl in lipid content and composition, lipoxygenase, plasma membrane H + -ATPase and antioxidant enzyme activities of tomato (Lycopersicon esculentum. Mill) calli

摘要

Tomato (Lycopersicon esculentum Mill. cv. Pera) calli tolerant to 50 mM NaCl were obtained by successive subcultures in NaCl supplemented medium. Salt-tolerant calli showed an increase of fresh and dry weight respective to control calli. When control and 50 mM NaCl-tolerant calli were stressed with 100 mM NaCl for 48 h, a decrease in respiration rate of 32 and 9%, respectively, was observed. Relative proportions of phospholipid fatty acids and free-sterol molecular species were the same in both control and NaCl tolerant calli. While the content of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) increased in salt-tolerant calli, the free sterol content was similar in both cases. A substantial increase of vanadate- sensitive ATP-dependent H superior + pumping activity without any modification in specific phosphohydrolytic activity and in passive H superior + conductance was detected in microsomes from salt-tolerant calli, which could be explained by an increased coupling between H superior + pumping and ATP hydrolysis. The higher lipoxygenase and antioxidant enzyme activities such as superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase and glutathione-S- transferase in 50 mM NaCl-tolerant calli as compared to controls also suggest that salt-tolerant calli has a high capacity of polyunsaturated fatty acid hydroperoxide formation and active oxygen species scavenging.