Plant Responses Summarized notes

Growth and Development in Plants


Responding to the Environment – Plants


Growth and development in plants are controlled by Hormones. There are three main groups
of plant hormones: Namely: - Auxins, Gibberellins, Abscisic acid.


Auxins:
 Auxins bring about a bending reaction in plants known as tropism.
Functions:
 Stimulate cell elongation.
 Stimulate cell division (But only in the presence of other plant hormones)
 Stimulate the development of adventitious roots.
 Causes Tropism


Gibberellins:
Functions:
 Stimulates stem elongation.
 Stimulate root growth.
 Promote flowering.
 Promote the growth of lateral buds.
 Stimulate the germination of seeds.


Abscisic Acid:
Abscisic acid is a growth inhibitor that counteracts the functioning of auxins. It plays a role in
helping the plant to cope under stressful conditions. It is produced in leaves, stems, and
unripe fruit.
Function of Abscisic acid:
 Causes dormancy of terminal buds and lateral buds in winter.
 Contributes to the dormancy of seeds by inhibiting germination.
 Promotes the abscission (detachment) of leaves and fruit.
 Causes the closing of stoma when the plant wilts (drying out)




Tropism