LA EXPANSIóN FOLIAR DEL SORGO GRANíFERO EN RESPUESTA A PERíODOS CORTOS Y SúBITOS DE ESTRéS HíDRICO

summary the behavior of the foliar area of the eleventh leaf of sorghum, sorghum bicolor (l.) moench, plants, cultivated in pots in a greenhouse, was monitored for two days, during sudden exposures to different water stress situations, accomplished by the modification of the hydric offer in the soil, and until completing their maximum foliar expansion. the final effect of water stress was observed in the maximum foliar area expansions reached by leaves that were in expansion during the experiment (10°, 11°, 12° and 13° leaves), and in the expansion time of the eleventh leaf. leaf elongation during the period of hydric stress was attained by very similar diurnal and nocturnal leaf enlongation rate (ler). treatments with less water availability showed a greater decrease in the ler, in relation to the degree of reduction of soil's water content and the foliar hydric potentials (fhp), being very severe in the maximum hydric stress (20% of water in the ground available to the plant), where leaf elongation stopped. results showed a correlation between ler and fhp during the day and between air temperature and fhp during the night. all treatments that suffered some grade of hydric stress showed a decreasing rate of foliar expansion duration and a smaller final foliar area