Physio-morphological responses of sweet potato [Ipomoea batatas (L.) Lam.] genotypes to water-deficit stress

Abstract

Roots of sweet potato [Ipomoea batatas (L.) Lam.; Convolvulaceae] are rich source of carbohydrates, vitamins and other nutrients; however, root storage and productivity is very sensitive to water deficit stress. We, therefore, investigated the light harvesting complexes (photosynthetic pigments) and activities (chlorophyll fluorescence), and photosynthetic abilities in three genotypes of sweet potato in response to decreased soil water content (SWC). Single vine cutting was propagated and then water withheld in different soil water contents. Osmotic potential, free proline, chlorophyll pigments, chlorophyll fluorescence, net photosynthetic rate and growth characters were measured. Free proline in the leaf tissues was enriched depending on a degree of water deficit, genotypes and their interaction. Physio-morphological characteristics of water-deficit stressed plants in each genotype of sweet potato were significantly inhibited. Osmotic potential in leaf tissues of water-deficit stressed plants of Tainung 57 sharply declined (-0.044x) when compared to PROC 65-3 (-0.027x) and Japanese Yellow (-0.025x). Chlorophyll a (Chla), chlorophyll b (Chlb), total chlorophyll (TC), photon yield of PSII (ΦPSII), stomatal conductance (gs), transpiration rate (E), vine length and number of leaves in cv. PROC 65-3 grown under water deficit were maintained better than those in cvs. Japanese Yellow and Tainung 57. A positive relationship between photosynthetic pigments and photosynthetic abilities was observed (R2 > 0.9) and it correlated directly with net photosynthetic rate (Pn). Free proline enrichment may play a key role as osmotic adjustment in sweet potato cv. PROC 65-3, grown under water deficit stress. Photosynthetic pigments, chlorophyll fluorescence activities, net photosynthetic rate and transpiration rate in cv. PROC 65-3 under water deficit condition were retained better than those in cvs. Japanese Yellow and Tainung 57, resulting in maintain growth performance.