Date post: | 18-Jan-2017 |
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COORDINATION IN PLANTS
Dr.U.P.PaniPGT(Biology)JNV Raipur
Class - X
All living organisms respond to environmental stimuli.
Animals have nervous system and endocrine system for
control and coordination.
Plants also respond to stimuli by secreting chemicals.
Plants exhibit some movements.
Coordination in Plants
Movements of Plants
Directional or Tropic movements
Non-directional or Nastic movement
Occur in the direction of the stimulus
Non growth movement,
independent of stimulus
The movements do not depend on the direction from the stimulus acts.
Example - when someone touches the leaves of mimosa, the leaves begin to fold up and droop.
Non-directional or Nastic
Movement
Mimosa plant
Leaves before touching
Leaves after touching
Mechanism of Leaf drooping
The drooping of Mimosa leaves is independent of the direction from which the leaves are touched.
Such movements usually happen due to change of water balance in the cells.
When leaves of mimosa are touched, the cells in the leaves lose water and become flaccid which results drooping of leaves.
Plants respond to stimuli slowly by growing in a particular direction.
Example - Plants like the pumpkin, cucumber etc. plant climb up fences by means of tendrils.
Directional or Trophic movements
Types of Trophic movements
Phototropism (light)
Geotropism (gravity)
Hydrotropism (water )
Chemotropism (chemicals)
Thigmotropism (touch)
Phototropism is the growth of plants in response to light.
Positive phototropism – Shoots respond by bending towards light.
Negative phototropism - Roots respond by bending away from light.
Phototropism
Response of the plant to
the direction of light
GeotropismGeotropism is the
movement of a plant in response to gravity (either downwards or upwards).
Positive geotropism – Roots grow towards the ground
Negative geotropism - Shoots by growing away from the ground.
Plant showing Geotropism
Hydrotropism
Hydrotropism is a growth response in which the direction is determined by the stimuli of water.
Example - Roots grow towards the source of water.
Plant showing Hydrotropism
Chemotropism is a growth movement of a plant part in response to chemical stimulus.
Example - Growth of pollen tubes towards ovules
Chemotropism
Flower showing Chemotropism
Thigmotropism is the directional growth of a plant part in response to the touch stimulus of an object.
Climbers produce tendrils which move towards a source of support in order to coil around it and help the plant to climb.
Thigmotropism
Plant showing Thigmotropism
Plants hormones, also called Phytohormones, are chemicals produced within the plant in a low concentrations and diffuse all around the cell.
Phytohormones regulate plant growth, development and response to the environment.
Plants Hormones
Types of PhytohormonesAuxinsGibberellinsCytokininsAbscisic acidEthylene
Plant HormonesAuxins are synthesised by the growing apices
of the stem and root. It promotes cell elongation and growth of stem
and root.It causes apical dominance. It induces rooting on stem cutting.Gibberellins are hormones that help in the
growth of the stem, seed germination, bolting, and flowering.
It induces parthenocarpy.It’s application overcomes the genetic
dwarfism.It breaks up the dormancy of seeds.
Cytokinins are hormones present in the areas of rapid cell division, such as fruits and seeds.
It promotes cell division and cell enlargement. It promotes the germination of seeds.
Abscisic acid is a hormone that inhibits the growth in various parts of plants.
It inhibits cell growth and cell division.It causes dormancy of buds and seeds. It induces wilting of leaves and closure of stomata.
Ethylene is a gaseous plant growth regulator.It plays role in ripening of fruits.
Plant Hormones