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Plant Movement & Hormones (Plant Hormones (Plant hormones are…
Plant Movement & Hormones
Ways of Communication
Two ways - Electrical Impulses & Chemicals
Electrical impulses convey information rapidly but it has limitations
Lim 1:
Electrical impulses only reach cells that are connected by nervous tissue and not to all cells
Lim 2:
Once an electrical impulse is generated & transmitted the cell takes some time to reset itself before a new impulse is generated & transmitted
Hence multicellular organisms also use
chemical communication
using
hormones
Chemical Communication
A cell responds to a stimulus by releasing a chemical compound rather than creating an electrical impulse
This compound diffuses all around the cell
If surrounding cells have special molecules on their surface (receptors) to detect the chemical compound, they get the information & can even transmit it
This information can reach all the cells of the body even though slower
Plant Hormones
Plant hormones are chemicals that regulate cell processes
1. Auxins
promote growth of the stem by promoting cell elongation
They help in growth & responding to stimuli in the environment
When growing plants detect light, auxin is synthesized at the shoot tip and helps the cells to grow longer
When light comes from one side, auxin diffuses to the shady part of the shoot
The cells grow longer on the shady side and the plant appears to move bend towards the light
2. Gibberelins
also promote growth of the stem
4. Abscisic acid
inhibits growth
3. Cytokinins
promote cell division
They are found in fruits & seeds where cells are dividing rapidly
It causes wilting of leaves