Sweetpotato tolerance to drought is associated to leaf concentration of total chlorophylls and polyphenols

The present study aimed to evaluate the effects of water deficiency on the growth, and antioxidant metabolism of two sweetpotato cultivars [Ipomea batatas (L.) Lam. cvs. Canadense (CAN) and Arapey Uruguaia (URU)] during the initial tuberization stage. 20 and 100% soil field capacity water content was used to obtain drought-stressed and well-watered plants, respectively. Water deficiency decreased growth of both cultivars (as measured by their biomass and leaf area), but URU showed lower plant growth than CAN, indicating that URU has lower tolerance to drought. The leaves of drought-stressed plants of both cultivars showed increments in the concentration of carotenoids and anthocyanins, evidencing that these plant responses are common between both cultivars. However, only CAN exhibited an increased chlorophyll concentration in leaves of water-deficient plants when compared to the well-watered plants. While the concentration of phenolic compounds was decreased in URU grown in soil with water deficiency, it was maintained in CAN. Temporal evaluations of gas exchange-related variables showed that the low water supply to plants reduced photosynthesis, transpiration and stomatal conductance rates. We concluded that the short exposure to water deficiency reduces growth of sweetpotato plants, but the degree of drought-induced impacts depends on cultivar-specific protective responses that are mainly related with each genotype to maintain chlorophyll status and to modulate antioxidant compounds in their leaves.