INDUCED VARIABILITY DURING THE PROCESS OF ADAPTATION IN SORGHUM-BICOLOR

The coefficient of variation of some anatomical and physiological parameters has been measured in plants of Sorghum bicolor (L.) Moench exposed to conditions inducing adaptation to salt, The kinetic analysis of the variability of shoot DW and shoot Na+ concentration revealed a specific phase of increase in variability between days 6 and 16 following exposure to salinity. The increase in variability observed in a population of adapted plants, as compared to a population of control plants, appeared as a whole plant process since variability for most of the parameters were positively correlated. Variability within plant populations of 11 Sorghum genotypes, each presenting a different capacity for adaptation, was determined during the middle of the adaptation process. 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 salinity suggested that the increase in variability was not a direct consequence of exposure to stress conditions, but that it was specifically related to the adaptation process, The data presented suggest the occurrence of modifications at the level of genome expression during the adaptation process.