RELATIVE-HUMIDITY INFLUENCES YIELD, EDIBLE BIOMASS, AND LINEAR GROWTH-RATE OF SWEET-POTATO

Growth chamber experiments were conducted to study the physiological and growth response of sweetpotato [Ipomoeabatatas (L.) Lam.] to either 50% or 85% relative humidity (RH). Vine cuttings of T1-155 were grown using the nutrient film technique in a randomized complete-block design with two replications. Temperature regimes of 28/22C were maintained during the light/dark periods with irradiance at canopy level of 600 mumol.m-2.s-1 and a 14/10-hour photoperiod. High RH (85%) increased the number of storage roots per plant and significantly increased storage root fresh and dry weight, but produced lower foliage fresh and dry weight than plants grown at 50% RH. Edible biomass index and linear growth rate (in grams per square meter per day) were significantly higher for plants grown at 85% than at 50% RH. Leaf photosynthesis and stomatal conductance were higher for plants at 85% than at 50% RH. Thus, the principal effect of high RH on sweetpotato growth was the production of higher storage root yield, edible biomass, growth rate, and increased photosynthetic and stomatal activity.