Question 1 Name two types of movements shown by plants?
Question 2 Define the term phototropism?
Question 3 What is positive stimulus?
Question 4 What is negative stimulus?
Question 5 Define the term geotropism?
Question 6 Define the term chemotropism?
Question 7 Define the term hydrotropism?
Coordination in Plants
Plants do not have nervous system, muscles and sense organs but still they respond to various environmental stimuli such as light, water, gravity, touch, chemicals etc.
Plants show 2 types of movement in response to various stimuli:
(1) Movement independent of growth
(2) Movement dependent on growth
Plants coordinate their response against environmental stimuli by using hormones.
Hormones coordinate in 2 ways:
(1) Effecting the growth of plant and as a result part of plant show movement.
(2) Affecting the shape of plant cell by changing amount of water in them(shrinking or swelling)
The plants use electrical chemical means to convey the information from cell to cell.
Tropic movement or tropism
Directional movement of specific part of plant in response to external stimuli is called tropism. These movements are very slow. The movement of plant part can be either towards or away from stimulus. If the movement of plant is towards stimulus, it is called positive stimulus.
If the movement of plant is away from stimulus, it is called negative stimulus.
It is the directional movement of plant part in response to light stimulus.
If plant part move towards light it is called as positive phototropism.
For Example : Stem or shoot
If plant part move away from light it is called as negative phototropism.
For Example : Roots
It is the response to gravity.
If the plant part moves in the direction of gravity it is called positive geotropism
For Example : Roots grow downwards.
If the plant part moves against the direction of gravity it is called negative geotropism.
For Example : Stem grows upwards
Response to chemical stimuli.
If Plant part move towards chemical stimuli it is positive chemotropism.
If plant part move away from chemical stimuli it is negative chemotropism.
Response to water