Tuber formation in yam (Dioscorea spp.): effect of moisture stress; contribution of the parent sett

Abstract

SUMMARYSetts of water yarn (Dioscorea alata) weighing 75 g each were pre-sprouted in sawdust and then grown in soil. The plants were subjected to moisture stress by withholding water from day 15 to 35, or day 36 to 56 or by watering only once every 14 days. In all cases, tuber initiation was delayed, the greatest delay being in the plants that were watered once every 14 days.Some setts of D. rotundata that were placed in moist sawdust were seen to produce new tubers without their shoots emerging above the sawdust level. This was taken to indicate that some of the photosynthate in the sett was being transferred into the new tuber. This could offer a partial explanation for the greater tuber yield that results from larger setts.