Water deficit stress affects photosynthesis and the sugar profile in source and sink tissues of groundnut (<i>Arachis hypogaea</i> L.) and impacts kernel quality
Keywords:Groundnut, kernel quality, mid-season drought, sugar profile, source-sink relation
Water deficit stress conditions disturb photosynthetic activity of plants and thereby affect further growth and the mobilization of assimilates towards sink tissues. The influence of mid-season drought on sugar metabolism in both source and sink tissues and its sustained effect on kernel quality across three different habit groups of groundnut was investigated. The experiment was conducted in Kharif 2012 and water deficit stress was created by withholding irrigation for 40 days between 30−70 days after sowing under rain-out shelter to simulate mid-season drought condition. Imposition of water deficit stress reduced net photosynthesis rate, which significantly altered the sugar profiles in leaf. The content of glucose, fructose and sucrose decreased in the leaf tissue, whereas the content of sugar alcohol (inositol and mannitol) and trehalose increased. The sugar profile of the sink tissue (kernel) was also altered under stress but changes were slightly different. The sugar alcohol and oligosaccharides (RFOs) showed significant increase, but the level of mono- and di-saccharides did not show significant change. The results suggest different drought tolerance strategies in source and sink tissues. The kernel quality was also affected under stress with lower oil and higher protein content. The content of oleic acid was reduced, while linoleic acid increased resulting in a decrease of the O/L ratio and oil stability. Alteration of quality traits was least in Spanish genotypes, suggesting a relatively better tolerance of this group for water deficit stress.
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