Water Transport (Chap. 30)

Transpiration (Overview) evaporation of water that occurs mainly at leaves while stomata are open for the passage of CO 2 and O 2 during photosynthesis. the resulting flow of water through the plant is called the transpiration stream less than 1% of the water reaching the leaves is used in photosynthesis and plant growth. Most of it is lost in transpiration.

Important in order to:

Environmental factors that affect the rate of transpiration –Light –Temperature –Humidity

–Wind –Soil water

Water (and dissolved mineral ions) Transport in Roots, Stems, and Leaves Roots (Root Pressure)

then, it travels through the cortex in order to reach the xylem via two routes:

Although root pressure plays a role in the transport of water in the xylem in some plants and in some seasons, it does not account for most water transport.

Stem (Transpiration Pull) water is pulled through the xylem (tracheid and vessel element cells) by three forces that create an incredible amount of tension: –transpiration – –adhesion – –cohesion

Leaves (Transpiration)

opening of guard cells

The Big Picture