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