Plants respond to things like light, gravity, touch, water etc. These are environmental stimuli for a plant. Plants coordinate their behavior by using their hormones and respond to the environmental changes. This they do by affecting the growth of a plant.

1. CONTROL AND
COORDINATION IN
PLANTS
Radiate

3. PHYTO-HORMONES
The hormones present in plants are called phyto-hormones.
1. Auxin:-
It is present on tip of plants.
It helps in growth of plant (cell multiplication, cell enlargement and cell
maturation), breaks seed dormancy. (auxin breaks dormance seed which
plants germinate more seed).
2. Gibberellins:-
It is also growth hormone.
It also promotes growth of plants as it increases the height of plant.
3. Ethylene:-
It helps in ripening of fruits and vegetables.
4. Cytokinin:-
It helps in closing of stomata, breaks seed dormancy.

4. PHYTO-HORMONES
5. Abscisic acid(ABA):-
It is a negative hormone.
It retards growth of plant, it promotes senescence (it promotes toward
death), it cause premature falling of fruits and vegetables.

5. PHYTO-HORMONES

6. Tropic movements:-
The movements caused in plant in response to stimulus.
The stimulus can be; light, chemical, gravity and water etc.
Phototropism:-
The movements caused in plant or plant pats in response to light. [Response
of the plant to the direction of plant] i.e., Plants moves toward the light.

7. PHOTOTROPISM

8. WHY PLANT DROOP WHEN IT IS KEPT INSIDE
THE ROOM?
The plant droop when it is kept inside the room as it doesn’t get complete
sunlight, so auxin get accumulated only at one side.
Therefore the growth occurs in only that region where auxin accumulates
hence the plant droops. (whereas the auxin does not get equally distributed
so therefore the plant droops)

9. Geotropism:-
The movement caused in plant in response to gravity.
Chemotropism:-
The movement caused in plant in response to chemical.
Nastic movements:-
This is the movements that occurs in the direction of stimulus.
For examples: it is seen in touch me not plant (mimosa pudica).
The stimulus for it is touch when touch leaf closes.

10. GEOTROPISM

11. CHEMOTROPISM

12. NASTIC MOVEMENTS

13. PHOTO-PERIODISM
It is the period of light to which the plant is exposed to sunlight.
Actually there is a blue-green pigment called phyto-chrome in plants that
responds to light.
Some plants need more light, some need less light or some need neither
more nor less sunlight, i.e., moderate.
Accordingly plants are classified as:
1. Long day plants
2. Short day plants
3. Day neutral plants

14. PHOTO-PERIODISM