Scope of Plant Physiology
We know that a tree is just not a large seed. Actually growth took place in the seed and this is
accompanied by differentiation of roots, shoots, leaves, flowers and fruits, thus making it a complete
plant. A large number of diverse and complex processes take place during various stages of
development. First of all, the seeds imbibe water and swell up resulting in bursting of seed coats. Soon
after radicle and plumule emerge from the seed, the food reserves of seed are mobilized to meet the
requirements of developing radicle and plumule. The radicle penetrates into the soil and develops root
system, the plumule goes into the air and produces shoot system. Through root, water and nutrient-
salts pass into the vascular tissue and are carried through the stem to the leaves. Carbon dioxide enters
through the stomata of the leaves and with the help of sunlight, carbohydrates are synthesized from
carbon dioxide and water, in the chlorophyll bearing cells. From the carbohydrates and salts the plant
later synthesizes other compounds such as amino acids, fatty acids and vitamins. These manufactured
foodstuffs are then distributed in a solution to cells in all parts of the plant and the excess may be stored
in the seed, fruit, root and stem. Although photosynthesis occurs only in some special cells of the seed
plant, all cells of the plant body must be supplied with foods and they must be freed of cell wastes.
Plants grow using part of the food manufactured and after reaching maturity they reproduce. Growing
plants respond to gravity, to light and to chemical and other factors in their environment. Thus the root
grows downward in response to gravity, whereas the stem grows upward, the root grows away from the
light while the stem grows towards it. Movements of plants are mainly growth movements and although
they are too slow for us to be seen they can be readily demonstrated in time lapse photography. The
more rapid turgor movements can be seen in the sensitive plant Mimosa pudica. Plant physiology
covers all the vital phenomena in plants. It is the science concerned with processes and functions, the
response of plants to change in the environment and the growth and development that result from such
responses.
To describe and explain plant processes like photosynthesis, respiration, ion absorption, translocation,
stomatal opening and closing, assimilation, transpiration, flowering and seed formation is one of the
tasks of plant physiology.
There are three major tasks of plant physiology:
(a) To describe and explain plant processes like photosynthesis, respiration, ion absorption, -
translocation, flowering and seed formation is one of the tasks of plant physiology.
(b) To describe and explain the natural activity or function of each kind of an organ, tissue, cell
and cellular organelle in plant and the function of each chemical constituent is the second task
of plant physiology.
(c) Because above mentioned processes and functions are dependent on and modified by
environmental factors, so the third task of plant physiology is to describe and explain how
processes and functions respond to changes in such factors like light, temperature, humidity,
etc.
