EFFECT OF VARIOUS TEMPERATURES IN THE ROOT ZONE AND LIGHT INTENSITIES ON PHOTOSYNTHESIS AND TRANSPIRATION OF TOMATO PLANTS

Photosynthetic intensity, transpiration and stomatal resistance (R_s) of tomato plant leaves were studied at various light intensities and temperatures in the root zone. Temperature regime had an insignificant effect on a gas exchange of plants at an irradiation of 900μmol m^<-2> s^<-1>. Less irradiation, 180μmol m^<-2> s^<-1>, resulted in a relatively greater effect of temperature on CO_2 uptake. Transpiration rate and stomatal resistance to CO_2 varied slightly within a wide range of temperature changes. An increase and decrease of R_s were observed only at low (<14) and high (>28℃) temperatures, respectively. Reverse dependence was found for the process of transpiration. The highest transpiration coefficient Ph/T was observed at 20℃. The results indicate that it is necessary to take all the aspects of plant activity into account for determining optimal growth conditions