Adaptive responses to drought of two<i>Retama raetam</i>subspecies from Tunisia

Abstract Aims The survival and ecological distribution of plants in arid habitats are mainly conditioned by water availability physiological adaptations to withstand drought. In the present study, we have compared responses drought two Retama raetam (retama) subspecies from Tunisia, one them living under desert climate (subsp. raetam) other growing on coast bovei). Methods To physiologically characterize R. subspecies, elucidate their main mechanisms underlying tolerance stress, parameters related seed germination, growth, photosynthesis (net photosynthetic rate, intracellular CO2 concentration, transpiration stomatal conductance water-use efficiency) accumulation osmolytes (proline, glycine betaine [GB] soluble sugars) were determined 4-month-old subjected stress for up 1 month. Important Findings Drought significantly inhibited growth all evaluated parameters. Plants subsp. bovei severely affected after 3 weeks treatment when rates 7-fold lower than controls. At same time, proline GB accumulated with irrigated controls, but much less raetam; latter increased levels 24- 6-fold higher, respectively, corresponding summary, population region exhibited stronger that adapted semiarid littoral climate, suggesting is dependent osmolytes.