Effects of preliminary heat-shock treatment on accumulation of osmolytes and drought resistance in cotton plants during water deficiency

To elucidate how plants adapt to overheating followed by mater efficiency, experiments with two cotton (Gossypium hirsutum L.) cultivars (Ok-oltin and INEBR-85) were performed. Preliminary heat-shock (HS) treatment (45 degree s C for 1.5 h) increased resistance of both cultivars to subsequent progres sive soil drought [40 days without watering, with soil moisture gradually d ecreasing from 70 to 20% of field moisture capacity (FMC)]. HS induced accu mulation of amino acids and amides and increased their contribution to the osmotic pressure (OP) of the leaf cell sap. HS also enhanced resistance to water deficiency and to overheating of the leaves, especially in cv, INEBR- 85, the more drought resistant of the two cultivars, The results suggest th e existence of common resistance systems to both stress factors, in particu lar, accumulation of amino acids and amides (mainly arginine, proline and a sparagine) - their concentration in the cell sap increased up to 240-, 160- and 150-fold, respectively.