Effect of Osmotic Stress Upon Endogenous Hormone Levels in Euphorbia lathyrus L. and Vicis faba L.

Ethylene concentrations rise in stems, lacunae and roots ofEuphorbia Iathyrus subjected to osmotic stress. In contrastto other species, however, no such changes are observed in leaves.Similarly, ABA concentrations rise in the leaves of osmotically-stressedplants but little change was observed in roots. In no case wasthere any strong evidence for the existence of a threshold ofosmotic potential above which a response will not occur. Instead,marked increases in concentrations of both ABA and ethylenewere obtained in response to osmotic stresses which did notresult in significant changes in water saturation defecit (WSD)during the experiment. In Vicia faba, time course studies at constant osmotic potentialshowed that ABA concentrations increased with duration of stressand increased WSD but the effect was most marked in youngertissues for a given level of stress. Concentrations of boundABA showed a similar pattern with time but here the change wasleast marked in the younger tissues. Euphorbia Iathyrus, Vicia faba, endogenous growth regulators, osmotic stress