That branch of botanical sciences that strives to understand how the vegetable life lives and functions: The primary objective of plant physiology is to explain the life processes of plants with a limited number of comprehensive principles that exist in chemistry, physics, and mathematics.

In agreement with the major characteristics of organisms plant physiology is usually divided into:

• The nutrition and metabolism of plants that deals with the uptake, transformations, and release of materials, and also their movements within and between the cells and organs of the plant.
• The environment of plants which strives to understand the various responses of plants to the environment.
• The part of the environment that deals with the effects of and adaptations to adverse conditions is called stress physiology.