ABSTRACT
The transpiration (T) is the water moving from soil layer around the roots to the atmosphere trough the plant by vascular cells and moving forward to the atmosphere as a vapor by the stomas principally. The transpirations is part of the gas interchange of the plant and can be called as the cost that the plant pay by take the carbon dioxide (CO2) for the photosynthesis. The transpiration is necessary processes in the cycle of live of the plants because by mean of transpiration the plant can take the nutrients from the soil solution, regulate his temperature, and keep growing. In the evapotranspiration (ET) process the transpiration is the water that really uses the plants, but in many cases is not easy separated of the ET complex especially in diverse agroecosystems. In the transpiration process are involve two main factors:
1. Physical factors: The physical factors include the available energy (Rn-G), the water vapor pressure deficit (VPD), wind that influence in the VPD, and the stomatical control and available water in the soil layer around the root system; and
2. Physiological factors: The physiological factors include the stomas number per unit of area and stomatical control, the leaf area, the height of the plant, and the root depth and density. The stomatical control is defined as the capacity of the stomas to keep open or close as a function of a drought or other physiological stress conditions like wind, salinity, air temperature and others.
