SIMULATED WATER-USE AND GROWTH OF NEW-GUINEA IMPATIENS (IMPATIENS-X-HB) IN SINGLE POTS USING ROOT-ZONE HEATING

Root Zone heating on New Guinea impatiens (Impatiens X hb.) in single pots was evaluated under computer controlled growth chamber conditions . The effects of root zone heating and air temperature on dry weight, fresh weight, leaf area (plant canopy temperature), and plant water us e were determined. Measured plant water use correlated highly with pla nt dry matter production for both heated (r(2) = 0.96) and controlled (r(2) = 0.93) plants. Measured plant transpiration and evaporation rat es compared favorably with values predicted by the Monteith evapotrans piration model (root-mean-square errors = 0.37 and 0.30 mm/day, respec tively). Even when air temperatures were held around 12 degrees C, a r oot temperature at 24 degrees C increased plant dry matter. Total plan t water use was significantly increased by higher root zone temperatur es.