INDUCED VARIABILITY DURING THE PROCESS OF ADAPTATION IN SORGHUM-BICOLOR

The coefficient of variation of some anatomical and physiological para meters has been measured in plants of Sorghum bicolor (L.) Moench expo sed to conditions inducing adaptation to salt, The kinetic analysis of the variability of shoot DW and shoot Na+ concentration revealed a sp ecific phase of increase in variability between days 6 and 16 followin g exposure to salinity. The increase in variability observed in a popu lation of adapted plants, as compared to a population of control plant s, appeared as a whole plant process since variability for most of the parameters were positively correlated. Variability within plant popul ations of 11 Sorghum genotypes, each presenting a different capacity f or adaptation, was determined during the middle of the adaptation proc ess. A strong linkage between the level of adaptation and the increase in variability was observed. The relatively low level of variability observed in populations of Sorghum varieties which did not adapt to sa linity suggested that the increase in variability was not a direct con sequence of exposure to stress conditions, but that it was specificall y related to the adaptation process, The data presented suggest the oc currence of modifications at the level of genome expression during the adaptation process.