Effects of several environmental factors on sweetpotato growth

Effects of relative humidity, light intensity and photoperiod on growth of ‘Ga Jet’ and ‘TI-155’ sweetpotato cultivars, using the nutrient film technique (NFT), have been reported. In this study, the effect of ambient temperature regimes (constant 28°C and diurnal 28:22°C day:night) and different CO 2 levels (ambient, 400, 1 000, and 10 000 μL/L-400, 1 000 and 10 000 ppm) on growth of one or both of these cultivars in NFT are reported. For a 24-h photoperiod, no storage roots were produced for either cultivar in NFT when sweetpotato plants were grown at a constant temperature of 28°C. For the same photoperiod, when a 28:22°C diurnal temperature variation was used, there were still no storage roots for ‘TI-155’ but the cv. ‘Ga Jet’ produced 537 g/plant of storage roots. For both a 12-h and 24-h photoperiod. ‘Ga Jet’ storage root fresh and dry weight tended to be higher with a 28:22°C diurnal temperature variation than with a constant 28°C temperature regime. Preliminary results with both ‘Ga Jet’ and ‘TI-155’ cultivars indicate a distinctive diurnal stomatal response for sweetpotato grown in NFT under an ambient CO 2 level. The stomatal conductance values observed for ‘Ga Jet’ at elevated CO 2 levels indicated that the difference between the light- and dark-period conductance rates persisted at 400, 1 000, and 10 000 μL/L.