Effect of relative air humidity on gas exchange, stomatal conductance and nutrient uptake in miniature potted roses

摘要

The study was conducted to evaluate the effect of relative air humidity (RH) and Ca/K ratio on the physiological reactions of potted miniature roses cv. 'Parade Fiesta'. The plants were grown at constant temperature and three RH levels (70%, 80% and 90%) and fertilised with three nutrient solutions each containing a different Ca/K ratio. Decreasing the RH resulted in increasing stomatal conductance (gs) despite RH during growth being highest when subjected to lower RH during measurements of photosynthesis. Transpiration increased linearly with decreasing RH and the slope was steepest for high RH-grown plants. The net photosynthesis of high RH-grown plants was unaffected by decreasing RH. Weight loss in detached leaves was highest in 90% RH-grown plants, reaching 55% loss after 6 h compared with 36% loss in low RH-grown plants. This indicates that plants grown under constant and especially high RH have reduced ability to control stomatal closure. Low RH conditions resulted in increased uptake of Ca and K. The uptake pattern in leaves is identical to that in petals, and the increasing Mg content with decreasing Ca/K ratio reflects competition between the cations. The increased Ca content in the nutrient solution increased the Ca content in the plant and might improve post-harvest quality.