Water use strategies of seedlings of three Malagasy Adansonia species under drought

Adansonia species, known by the common name “baobab,” have a very low regeneration rate in Madagascar. In order to determine if Malagasy Adansonia seedlings' vulnerability to drought may account for this low rate of regeneration, we compared growth, photosynthetic behavior and water use strategy of three species of Malagasy Adansonia (A. grandidieri, A. madagascariensis, A. rubrostipa). Our results indicated that drought depressed the growth, net assimilation rate, stomatal conductance and transpiration rate of Adansonia seedlings but increased their water use efficiencies. Adansonia species are able to withstand drought by reducing water loss through stomatal closure and their ability to store water within roots. Interspecific differences were attributed to diversity in water-use strategies, relative water content and biomass allocation. A. rubrostipa and A. grandidieri appeared to be more adapted to arid environments than A. madagascariensis. Ecological implications of these results are discussed.

► We studied Malagasy Adansonia seedlings tolerance to short-term drought. ► Seedlings growth and photosynthetic parameters were depressed by water stress. ► Seedlings could withstand drought by efficient water use and biomass allocation. ► Adansonia arid species were more drought-tolerant than sub-humid species.