Simulation of transpiration rate of cucumber growth in greenhouse based on climatic resistance

By using the To-Ta model(To and Ta represent leaf temperature and air temperature respectively) based on energy balance equation and vapor diffusive theory, the stomata diffusive resistance(ri) on sunny and cloudys days was respectively calculated according to continuously monitoring the leaf temperature, air temperature, air humidity, and radiation in the greenhouse in northern China. The climatic resistance(r^*) was calculated based on the microclimatic data and the laminar boundary layer resistance was measured too. The analysis result showed that the positive relationship was remarkable between the ri/re and r^*/re, i.e. ri/re=1.207r^*/re-0.326(n=328, r=0.8055) on sunny days and ri/re=0.169r^*/re+0.278(n=222, r=0.8076) on overcast days. Then the transpiration rate(λE2) was estimated by substituting r^*/re for ri/re in modified P-M model, compared with the transpiration rate(λE1) which was estimated directly by ri in the same model, the identity index was very high(0.96) on both sunny days and overcast days. So it concluded that these relationships between ri/re and r^*/re could be used to simulate the transpiration rate of greenhouse cucumber in the northern China.