THEORY OF EVAPOTRANSPIRATION: 1. Transpiration and its quantitative description

Basic information about the evapotranspiration and its components is presented. System of equations describing the transport of water and energy in the soil - plant continuum is analyzed. The system of five differential equations with five unknowns is proposed, describing transport of heat and water vapour within the plant canopy, including exchange processes among the leaves and the atmosphere, vertical transport of the heat, water vapour and the energy balance.