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

Tomato (Lycopersicon esculentum Mill. cv. Pera) calli tolerant to 50 mM NaC l were obtained by successive subcultures in NaCl supplemented medium. Salt -tolerant calli showed an increase of fresh and dry weight:eight 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 3? and 9%;. r espectively, was observed. Relative: proportions of phospholipid Fatty acid s and free-sterol molecular species were the same in both control and NaCl tolerant calli. While the content of phosphatidylcholine (PC) and phosphati dylethanolamine (PE) increased in salt-tolerant calli, the free sterol cont ent was similar in both cases. A substantial increase of vanadate-sensitive ATP-dependent H; pumping activity without any modification in specific pho sphohydrolytic activity and in passive H conductance was detected in micros omes from salt-tolerant calli, which could be explained by an increased cou pling between Ht pumping and ATP hydrolysis. The higher lipoxygenase and an tioxidant enzyme activities such as superoxide dismutase. catalase, ascorba te peroxidase, glutathione reductase and glutathione-S-transferase in 50 mM NaCl-tolerant calli as compared to controls also suggest that salt-toleran t calli has a high capacity of polyunsaturated fatty acid hydroperoxide for mation and active oxygen species scavenging. (C) 1999 Elsevier Science Irel and Ltd. All rights reserved.