การประชุมวิชาการระดับชาติ ครั้งที่ 16
มหาวิทยาลัยราชภัฏนครปฐม

Paclobutrazol, a growth retardant, was applied to increase drought stress tolerance in plants. The objective was to study the effect of paclobutrazol on the growth of Rayong 86-13 cassava variety, which was planted by mini-cutting (5 cm), under water deficit conditions. The strip plot design with 4 replications was adopted to experiment. The irrigation (30-90 days after planting (DAP)) used as vertical plot, irrigated every 3 days (3D) compared which water deficit conditions, irrigated every 6 days (6D) and irrigated every 9 days (9D). The horizontal plot was 4 concentrations of paclobutrazol (PBZ) (0, 25, 50, and 75 ppm). The result showed that irrigation was significant on plant height at 90 DAP, the plant height of 3D and 6D were higher than 9D. PBZ concentration showed a significant difference in plant height at 30 DAP, PBZ 25, 50, and 75 ppm were lower than 0 ppm. On fresh weight at  90 DAP, 3D showed higher stem, stump, root, and whole plant fresh weight (37.5, 13.4, 30.6, and 173.4 g plant^-1, respectively) than 6D and 9D. The highest root fresh weight was found on PBZ at 50 ppm (28.4 g plant^-1). PBZ 50 ppm was the recommended concentration from the result in plant height decrease, which reduced cassava water use, and root fresh weight increased when compared with 0 ppm.