Songklanakarin Journal of Science and Technology (SJST) (Nov 2004)
Effect of available soil water on leaf development and dry matter partitioning in 4 cultivars of peanut (Arachis hypogaea L.)
Abstract
Water stress brings about changes in growth and dry matter partition in peanut plants and the changes vary depending on peanut cultivars. The objectives of this study were to investigate the effect of 3 regimes of available soil water on leaf development and dry matter partitioning of 4 peanut cultivars. A 4×3 factorial experiment in randomized complete block design with four replications was used. Treatments were combinations of 4 peanut cultivars; Tainan 9, Khon Kaen 60-3, ICGV 98308 and ICGV 98324, and three soil water regimes; field capacity (FC; 20% soil moisture content), 1 2 available soil water ( 1 2 AW; 8.6% soil moisture content) and 1 4 available soil water ( 1 4 AW; 4.3% soil moisture content). On day 75 after seedlingemergence, depleting available soil water from FC to 1 4 AW significantly (p<0.01) reduced leaf areas of peanut plants. There were also significant differences (p<0.01) in leaf areas among peanut cultivars. At harvest, 1 2 AW caused more reduction in leaf area but resulted in an increase in weight of fallen leaves thandid 1 4 AW. On day 75 after seedling emergence, there was a significant effect (p<0.01) of available soil water on root:shoot ratios. As available soil water became limited, there was a significant increase (P<0.01) in root:shoot ratios. At harvest, there were interactions between available soil water and peanut cultivars for root:shoot ratio, harvest index and shelling percentage. At FC, there were no significant differences in root: shoot ratio among peanut cultivars. However, at 1 2 AW and 1 4 AW, there were significant differences in root:shoot ratios and the magnitude of differences varied depending on peanut cultivars. At 12 AW and 1 4 AW, Khon Kaen 60-3 had root:shoot ratios of 0.55 and 0.48 while ICGV 98324 had the ratios of 0.35 and 0.32, respectively. There were no significant differences in harvest index and shelling percentage among peanut cultivars when available soil water was at FC. At 1 2 AW and 1 4 AW, there was a large decrease in harvest index of Khon Kaen 60-3 and the indices were 0.03 and 0.01, respectively. At the corresponding available soil waters, ICGV 98324 had harvest indices of 0.33 and 0.23, respectively. Shelling percentages at 1 2 AW and 1 4 AW for Khon Kaen 60-3 were 24.9 and 6.8, respectively, while those for ICGV 98324 were 62.3 and 46.6, respectively. Our results indicated that under water stress the partitioning of dry matter into pod yields is more sensitive in drought-sensitive cultivars. Under drought conditions, mobilization of reserved assimilates in leaves could be crucial for supporting pod growth and yields in drought-tolerant cultivars.
