The relationship between the air humidity and the rate of the net photosynthesis,ten-dency of respiration and the compensation point of light quantum of saplings of four conifer-ous species. Namely . Platycladus orientaris , Pinus sylvestris var. mongolica , P. tabulaeformisand Picea meyeri were measured and studied by using 225MK₃IRGA(ADC) under the con-trolled indoor conditions. The results show that all the rates of net photosynthesis in thefour species of salings declined with decreasing air humidity an...