The attempt has been undertaken in the paper to describe plant transpiration in relationship to leaves temperature. There was analysed as well mutual correlation between resistance of water vapour transfer from leaves to surrounding atmosphere and their temperature. The experimental work was carried out in the greenhouse where tomatoes were planted. Obtained results were presented in graphic form and correlations were found which described changes of transpiration and physiological resistance depending on temperature of leaves. Vital relationships were observed between transpiration of plants as well as physiological resistance value and temperature of leaves. Additionally it was proved that using minimum quantity of parameters of surrounding environment and cultivated plants, which are described by standard measuring instruments, one could approximately estimate required mass of nutrient for their root system.