Plant Behaviour

Plant Behaviour

Plant Behaviour • External factors, such as light, gravity and touch have an influence on plant growth and development.

Plant Behaviour • External factors, such as light, gravity and touch have an influence on plant growth and development. • The growth of a plant in response to a stimulus such as light or water is called a tropism.

Types of Tropism • stimulus

tropism

shoot

gravity

unilateral light

geotropism

phototropism

negative

positive

water

hydrotropism

no response

response root

positive

negative

positive

Tropisms • Growth of a plant in a specific DIRECTION

Tropisms • Growth of a plant in a specific DIRECTION • Positive tropism =TOWARDS THE STIMULUS

Tropisms • Growth of a plant in a specific DIRECTION • Positive tropism =TOWARDS THE STIMULUS • Negative tropism =AWAY FROM THE STIMULUS

Importance of Phototropism •

Enables leaves to be in a position to receive as much sunlight as possible for photosynthesis

Tropisms

Auxin •

Commonest plant hormones

Auxin Commonest plant hormones • Regulates growth & other physiological processes in plants •

Auxin Commonest plant hormones • Regulates growth & other physiological processes in plants • Produced by root tip / shoot tip •

Auxin Commonest plant hormones • Regulates growth & other physiological processes in plants • Produced by root tip / shoot tip • They affect the elongation region of the tip •

Auxin

Auxin • If light is concentrated on one side of the plant, then auxin moves away from the light source to the darker side of the tip and becomes more concentrated in the cells in that region.

Auxin • If light is concentrated on one side of the plant, then auxin moves away from the light source to the darker side of the tip and becomes more concentrated in the cells in that region. • The increased concentration of auxin means they grow more quickly than cells nearer the light.

Auxin • If light is concentrated on one side of the plant, then auxin moves away from the light source to the darker side of the tip and becomes more concentrated in the cells in that region. • The increased concentration of auxin means they grow more quickly than cells nearer the light. • The uneven growth results in the bending

Phototropism in Shoot •

The shoot tip produces auxin which diffuse downward

Phototropism in Shoot The shoot tip produces auxin which diffuse downward • The auxin diffuse to the shaded side due to the presence of unilateral light •

Phototropism in Shoot The shoot tip produces auxin which diffuse downward • The auxin diffuse to the shaded side due to the presence of unilateral light • High auxin concentration stimulates growth in shoot •

Phototropism in Shoot The shoot tip produces auxin which diffuse downward • The auxin diffuse to the shaded side due to the presence of unilateral light • High auxin concentration stimulates growth in shoot • The shaded side grows faster than the lighted side •

Phototropism in Shoot The shoot tip produces auxin which diffuse downward • The auxin diffuse to the shaded side due to the presence of unilateral light • High auxin concentration stimulates growth in shoot • The shaded side grows faster than the lighted side • The shoot bends towards the light •

Geotropism in Root •

The root tip produces auxin which diffuse to the elongation region

Geotropism in Root •

•

The root tip produces auxin which diffuse to the elongation region The auxin diffuse to the lower side due to gravity

Geotropism in Root The root tip produces auxin which diffuse to the elongation region • The auxin diffuse to the lower side due to gravity • High auxin concentration inhibits growth in root •

Geotropism in Root The root tip produces auxin which diffuse to the elongation region • The auxin diffuse to the lower side due to gravity • High auxin concentration inhibits growth in root • The lower side grows slower than the upper side • •

Geotropism in Root The root tip produces auxin which diffuse to the elongation region • The auxin diffuse to the lower side due to gravity • High auxin concentration inhibits growth in root • The lower side grows slower than the upper side • The root bends downward •

The End