IS PROLINE A COMPATIBLE SOLUTE IN CALLI FROM NACL-SENSITIVE LYCOPERSICON-ESCULENTUM AND NACL-TOLERANT L PENNELLII

When cultured on a 140 mmol/L NaCl medium, calli of the salt sensitive Lycopersicon esculentum (Mill) cv. P-73 accumulated more proline (PRO ) than the salt tolerant L. pennellii (Correll), D'Arcy, accession PE 47. Soluble peroxidase (PRX, EC. 1.1.1.7) activity of both species was also enhanced in both salt treated species, while salinity did not mo dify cell wall PRX from L. esculentum or decreased cell wall PRX from L. pennellii. The ability of proline, NaCl and various organic solutes (glucose, glycerol, glycine betaine and sucrose) to affect in vitro t he activity of soluble and cell wall PRX of these species has been the refore compared. In vitro, the overall PRX were quite tolerant to NaCl , a 20 % decrease being only observed for soluble PRX extracted from c ontrol L. esculentum in presence of 50 mmol/L NaCl. In both species, 5 0 % of cell wall and soluble PRX activities were recovered when sucros e and glycine betaine were added in vitro to the assay medium. In L. e sculentum, addition of glucose enhanced both PRX activities. Proline d ecreased soluble PRX activity of L. esculentum at acidic pH (from pH 4 .5 to 6.5), but had a positive effect at alkaline pH; on the contrary, PRO had no inhibitory effect on soluble PRX from control and salinize d L. pennellii and on cell wall from control and salinized L. esculent um. The PRX/PRO interaction was also markedly dependent on the culture media of calli from which the extracts were derived. Changes in PRX a ctivities under salinity stress and the consequences of osmolyte effec ts are discussed for each species as regards the NaCl responses.