Effect of air current speed on evapotranspiration rate of transplant canopy under artificial light

Evapotranspiration rate (ET) of a sweetpotato transplant canopy (TC) under artificial light was measured at three levels (0.1, 0.3 and 0.5m s sup(-1)) of air current speed (ACS) in a wind-tunnel -type growth chamber and at leaf area indices (L) of 0.9, 1.5, 2.6 and 4.0. The ET was measured based on the weight change over time of a transplant tray, consisting of 72 transplants, soil mixture, water and a plug tray. The Penman-Monteith model (P-M) was used for estimating aerodynamic conductance (g sub(a)) above the TC based on the measured ET and canopy conductance (g sub(c)). It was found that ET of the sweetpotato TC increased as ACS and L increased. The increase in ACS increased g sub(a) above TC. Increase in L increased the g sub(c) and also g sub(a). Understanding the effect of ACS on ET makes it possible to control ET in the transplant production system with artificial light (TPSAL) by manipulation of ACS. Effects of ACS on the net photosynthetic rate and growth of TC should be further investigated to determine the optimum ACS in the TPSAL.