CONTROL OF EVAPORATIVE DEMAND ON TRANSPIRING PLANTS : I. SENSITIVITIES OF EVAPORATIVE DEMAND TO ENVIRONMENTAL FACTORS

Effects of environmental factors on evaporative demand (ED) were analyzed, and control characteristics of ED were simulated. ED was affected by the respective environmental factors of irradiance, air temperature, humidity and wind velocity, and the respective effects on ED appeared in different processes. In particular, the effects of irradiance and humidity appeared more remarkable as compared with those of air temperature and wind velocity: ED increased almost linearly with increase in irradiance and with decrease in humidity, but the effect of air temperature was not so large under moderate conditions, and the effect of wind became smaller at the higher velocities. Thus, ED was more sensitive to irradiance and humidity than to air temperature and wind velocity. In a phytotron glass room (constant air temperature and wind velocity), it can be possible to control ED by manipulating humidity even under remarkable variation in irradiance