Temperature Effects on Sweetpotato Growth and Development

Sweetpotato [Ipomoea batatas L (Lam.)] storage root initiation and subsequent growth are sensitive to temperature conditions. Little specific information is available on sweetpotato growth and physiological responses to wide range of temperature levels, both at early and late seasons. Two experiments were conducted to quantify the effects of temperature using the cultivar, Beauregard. In experiment I, slips were transplanted in pots at five day/night temperatures of 20/12, 25/17, 30/22, 35/27 and 40/32 °C for 55 days. In experiment II, same temperature treatments except 20/12 °C were imposed after initiation of storage roots, 18 days after transplanting at 30/22 °C, for 74 days. In Experiment I, plants were harvested on regular intervals and growth and development including storage root formation were monitored. In both the experiments final destructive harvest was carried to record number of storage and non-storage roots, and total and plant-component dry weights. Gas exchange and other physiological measurements were recorded during the last three weeks of the experiments. Temperature did not affect total number of roots formed. However, the number of storage roots formed changed significantly, when treatments imposed at the beginning of planting. Storage root number increased linearly up to 20 °C and declined linearly with increasing temperature. The time to reach 50% of storage roots formed, and size and quality of the storage roots, however were significantly affected by temperature. Total biomass produced increased up to 30/22 and 35/27 °C and declined slightly at the 40/32°C. Storage root biomass increased with increase in temperature up to 30/22 °C, and declined by 11% and 90% at 35/27 and 40/32 °C, respectively. When temperature treatments were imposed after the storage roots are formed, the number of total and storage roots produced was not affected by temperature, but the size and quality of storage roots were significantly affected. The optimum temperature for total biomass production was 30/22 °C and declined by 9% at 35/27 °C and 27% at 40/32 °C. The optimum temperature for storage root growth was 25/17 °C and declined linearly by 31 g per 1 °C increase in temperature. The data obtained and functional algorithms developed using these studies will be useful in assisting management decisions on field planting to optimize yield.