TEMPERATURE AND LIGHT EFFECTS OF SWEETPOTATOES GROWN HYDROPONICALLY

Vine cuttings (15cm lengths) of two sweetpotato cultivars ‘Ga Jet’ and ‘TI-155’ were planted into trays using the Tuskegee University Nutrient Film Technique described by Hill et al. (1988) in four environmental growth chambers. Light intensity of approximately 400 umol m^-2s^-1, relative humidity at 70±5% and ambient CO₂₂ level were maintained in each chamber. Plants were subjected to 24h photoperiod, or 12:12h light/dark photoperiod with either constant temperature of 28°C or diurnal temperature of 28/22°C. The nutrient solution used consisted of modified half-Hoagland with N:K ratio of 1:2.4. Each growth chamber contained two channels and each channel contained four plants spaced 25cm apart. Plants were harvested 90 days after planting and yield in terms of fresh and dry weights of foliage and storage roots was measured. Results showed varietal differences in the response of ‘Ga Jet’ and ‘TI-155’ sweetpotato plants to continuous light. Continuous light combined with diurnal temperature of 28/22°C resulted in significant storage root yield increases of ‘Ga -Jet’ sweetpotato. However no storage roots were produced when ‘TI-155’ sweetpotato plants were exposed to similar conditions. Continuous light combined with constant temperature resulted in no storage root production in both cultivars. Highest foliage yield for both cultivars