Tropisms (or Tropic Movements)
Tropisms (or Tropic Movements): Overview
This topic discusses tropism and its use through an example. Tropism is the direction of the movement and growth of plants in a particular direction as a response to an external stimulus. The five types of tropism in plants are explained in detail.
Important Questions on Tropisms (or Tropic Movements)
Name the plant part that bends towards the light but away from the force of gravity.
Name the plant part that bends in the direction of gravity but away from light.
To which directional stimuli do the roots respond?
Which of the following is a growth movement and which is not?
a) folding up of leaves of the sensitive plant on touching with hand.
b) folding of petals of a dandelion flower when the light fades.
Give one example of a plant part that is positively phototrophic as well as negatively geotropic. (Root/Shoot)
A potted plant is growing in a transparent glass jar. In this plant, X and Y are the two growing parts having a lot of meristematic tissue. It is observed that the part X of this plant exhibits positive geotropism but negative phototropism. On the other hand, part Y of this plant exhibits negative geotropism but positive phototropism.
(b) Name the part Y of plant.
Name the plant organ which is negatively geotropic.
Name the plant organ which is positively phototropic.
Plant parts show two types of movements, one dependent on growth and the other independent of growth. Give one example of the movement in plant parts which does not depend on growth.
Plant parts show two types of movements, one dependent on growth and the other independent of growth. Give the name for the movement in plant parts which depends on growth. (Write in two words. Example: _____ movement.)
A potted plant is growing in a transparent glass jar. In this plant, X and Y are the two growing parts having a lot of meristematic tissue. It is observed that part X of this plant exhibits positive geotropism but negative phototropism. On the other hand, part Y of this plant exhibits negative geotropism but positive phototropism.
Which part of the plant, X or Y, can have tendrils on it?
A potted plant is growing in a transparent glass jar. In this plant, X and Y are the two growing parts having a lot of meristematic tissue. It is observed that the part X of this plant exhibits positive geotropism but negative phototropism. On the other hand, part Y of this plant exhibits negative geotropism but positive phototropism.
(c) Which part of the plant, X or Y, will exhibit positive hydrotropism?
A potted plant is growing in a transparent glass jar. In this plant, X and Y are the two growing parts having a lot of meristematic tissue. It is observed that part X of this plant exhibits positive geotropism but negative phototropism. On the other hand, part Y of this plant exhibits negative geotropism but positive phototropism.
Name the part X of the plant. (Root/ Stem)
The chemical substance P is made and secreted by the meristematic tissue at the tip of stem (or shoot) of a plant. The chemical substance P is responsible for a phenomenon Q in plants in which the stem bends towards a source of light. The same chemical substance P has an opposite effect on the root of a plant. It causes the root of a plant to bend away from the source of light in a process called R.
(d) What is the name of process (i) Q and (ii) R?
The climbing organs of plants like tendrils grow towards any support which they happen to touch and wind around the support. This is an example of
The growth movement of a plant part in response to the touch of an object is called
Which of the following acts as a stimulus in the process of hydrotropism?
A growing seedling is kept in a dark room. A burning candle is placed near it for a few days. The top part of seedling bends towards the burning candle. This is an example of :
The stimulus in the process of thigmotropism is :
The bending of the shoot of a plant in response to light is called:
