FAST CHANGES IN SOLUBLE CARBOHYDRATES AND PROLINE CONTENTS IN TOMATO SEEDLINGS IN RESPONSE TO IONIC AND NONIONIC ISOSMOTIC STRESSES

Qualitative and quantitative changes in soluble carbohydrates and prol ine contents were studied in young plants of two tomato cultivars (Lyc opersicon esculentum L. Mill.) differing in their salt-tolerance (cvs. Pera and Volgogradskij). Seedlings were treated for 24 h with ionic ( 300 mmol L-1) and non-ionic isoosmotic (380 g kg(-1) polyethylene glyc ol MW 6000) stresses. Salinity provoked a decrease in the hexose conte nts and it also dramatically enhanced sucrose accumulation in all orga ns of the plants, and to a greater extent in the salt-sensitive cv. Vo lgogradskij. The PEG iso-osmotic stress, compared with saline conditio ns, only affected the hexose contents in a similar way to salinity in the cv. Volgogradskij, while it increased the sucrose content 2.5 and 4 times in the roots of Pera and Volgogradskij, respectively. Proline accumulation was more important in the salt-sensitive cultivar under b oth conditions. The contribution of these solutes to the osmotic poten tial was up to -0.3 MPa under non-ionic stress, but they had little in fluence under salinity compared with control plants. The fast changes observed in soluble carbohydrates and proline composition are discusse d in relation to the osmotic adjustment under saline and non-permeant iso-osmotic stresses.