Relations entre la résistance membranaire et la composition en lipides foliaires sous l'effet d'un stress hydrique chez deux variétés de Soja

Apres 35 jours de developpement, la resistance membranaire de deux varietes de Soja (Harosoy et Adoc) a ete etudiee en mesurant le flux d'electrolytes (par conductiVite) et le flux de phosphate inorganique lors de la rehydratation des disques foliaires prealablement soumis, pendant 4 h, a un choc osmotique (en presence de polyethylene-glycol). La resistance membranaire etant inversement correlee aux flux d'ions, il a ete ainsi demontre que les plantes de la variete Adoc sont plus resistantes a une secheresse moderee que celles de la variete Harosoy. L'analyse des lipides foliaires a montre qu'un defi ci t hydrique modere (-0,9 a -1,1 MPa) provoque une augmentation de la quantite d'acides gras totaux (plus importante chez la variete Adoc) et notamment celle de l'acide linolenique dans les triacylglycerols et les phosphatidylcholines. Relationships among membrane resistance and the leaf lipid compositions oftwo varieties of Soya under hydrie stress After 35 days of development, membrane resistance was determined in two varieties (Harosoy and Adoc) by mesuring ion flux (by conductimety) and inorganique phosphate, during rehydration of foliar disks which had been submitted for 4 hrs to an osmotic shock (in presence of polyethylene glycol). Membrane resistance being inversely related to ion effiux, it has been shown that plants from the Adoc variety were more resistant to moderate drought than those from the Harosoy variety. Analysis ofIeafIipids has shown that moderate water deficit (-0,9 to -1,1 MPa) induced an increase in the quantity of total fatty acids more prononced in Adoc plants than in Harosoy plants. This is accompanied by an increase oflinolenic acid in triacylglycerols and in phosphatidylcholines.