Functions of Plant Hormones
- Effect depends on size of action, stage of plant growth and hormone concentration
- Control plant growth and development by affecting division, elongation, and cell differentiation
- Hormonal signal is amplified by gene expression, enzyme activity, or membrane properties
Five types of plant hormones:
- Abscisic Acid
Auxin acts to :
Auxin is a plant hormone that causes the elongation of cells in shoots and is involved in regulating plant growth.
Promote root initiation
- Promote cell elongation
- Trigger the growth of prop roots that grow from aboveground stems
- Holds down the growth of lateral branches
- Keeps in leaf drops before leaf ages; promote leaf drop afterward
- Elongation, that travels one way
- Pattern Formation, controls where leaves will grow, whether the stems are going to lengthen, etc.
Cytokinins Acts To :
Cytokinins is any of a class of plant hormones, produced by the roots and traveling upward through the xylem, that promote tissue growth and budding and, on application, retard plant senescence.
Induce growth of shoot
- Promote cell division (recall that cytokinesis is the process of cell division after mitosis)
- Stimulate formation of adventitious buds
- Reverse suppression by auxin
- Delay senescene (ageing) of leaves by maintaining chlorophyll content
- Cell division
Gibberellins Acts To :
Gibberellins are growth hormones that stimulate cell elongation and cause plants to grow taller. Gibberellins also have a role in other plant processes, such as stem elongation, germination, flowering, and fruit ripening.
Stimulate cell clongation
- Promote cell enlargement
- Promote uptake of starch tissue by the embryos in germinating seeds
- Reverse genetic dwarfism
- Stimulate the vascular cambium to produce secondary phloem in woody plants
- Stem Elongation
- Fruit Growth
- Seed Germination