ABSTRACT
Transpiration rate is more proportional to the conductance to water vapor than to the resistance to water vapor, and stomatal conductance is proportional to the area of the stomatal aperture, whereas stomatal resistance has an inverse hyperbolic relationship. Damage to root systems by diseases or pests results in reduced transpiration only if it either causes stomatal closure or reduces shoot growth rate such that percent ground cover is less, compared with plants whose root systems are not damaged. Plants require large quantities of water if they are to be productive. For water-limited environments, the level of daily water use that is adaptive depends on the rainfall pattern and the type of crop species. Water flow in the soil–plant–atmosphere continuum is controlled at the top of the plant: the interface between leaves and the atmosphere. The cohesion-tension hypothesis is widely believed to account for the movement of water in the xylem from roots to leaves.
