Question 1

Question 1:
What is the general name of chemical substances which bring about control and coordination in plants?

Accepted Answer

Answer:
Plant hormones are chemical substances which bring about the control and coordination in plants.

Question 2

Question 2:
Which plant hormone is responsible for the wilting and falling of leaves?

Accepted Answer

Answer:
Abscisic acid is responsible for the wilting and falling of leaves.

Question 3

Question 3:
Which plant hormone makes a stem (or shoot) bend towards light?

Accepted Answer

Answer:
Auxin is a plant hormone which makes a stem (or shoot) bend towards light sources.

Question 4

Question 4:
Where is the auxin hormone made in a plant stem?

Accepted Answer

Answer:
Auxin hormone is made in the cells of the tip of a plant stem.

Question 5

Question 5:
What is the scientific name of sensitive plant?

Accepted Answer

Answer:
The scientific name of sensitive plant is Mimosa pudica.

Question 6

Question 6:
Name one plant hormone that promotes growth and another plant hormone which inhibits growth.

Accepted Answer

Answer:
Auxin is a plant hormone that promotes growth in plants and abscisic is a plant hormone that inhibits growth.

Question 7

Question 7:
Name one example of the movement of a plant part which is very quick and can be observed easily.

Accepted Answer

Answer:
Thigmonasty is the movement of plant, especially prevalent in sensitive plants, which is very quick and can be observed easily. If we touch the leaflets of a sensitive plant, they fold up and droop immediately.

Question 8

Question 8:
Name the type of chemical substances that control the growth in plants.

Accepted Answer

Answer:
Plant hormones are the chemical substances that control growth in plants. Auxin, gibberelins, cytokinins and abscisic acid are examples of plant hormones.

Question 9

Question 9:
What is the stimulus in : (a) phototropism? (b) geotropism? (c) chemotropism? (d) hydrotropism? (e) thigmotropism?

Accepted Answer

Answer:
The stimulus in
(a) Phototropism: Light
(b) Geotropism: Gravity
(c) Chemotropism: Chemicals
(d) Hydrotropism: Water
(e) Thigmotropism: Touch

Question 10

Question 10:
Give the scientific terms used to represent the following :
(a) Bending of a shoot towards light.
(b) Growing of roots towards the earth.
(c) Growth of a pollen tube towards ovule.
(d) Bending of roots towards water.
(e) Winding of tendril around a support.

Accepted Answer

Answer:
(a) Phototropism
(b) Geotropism
(c) Chemotropism
(d) Hydrotropism
(e) Thigmotropism

Question 11

Question 11:
Give one example of the movement of a plant part which is caused by the loss of water (or migration of water).

Accepted Answer

Answer:
The folding of leaves in sensitive plants is an example of the movement of a plant parts. It is caused by loss of water (or migration of water).

Question 12

Question 12:
Give one example each of a plant part :
(a) which is positively hydrotropic as well as positively geotropic.
(b) which is positively phototropic but negatively geotropic.

Accepted Answer

Answer:
(a) Roots are positively hydrotropic as well as positively geotropic.
(b) Shoots are positively phototropic but negatively geotropic.

Question 13

Question 13:
Which of the following is a growth movement and which is not?
(a) folding up of leaves of sensitive plant on touching with hand.
(b) folding up of petals of dandelion flower when light fades.

Accepted Answer

Answer:
Neither of them are growth movements. They are nastic movements.
(a) This is a thigmonastic movement.
(b) This is a photonastic movement.

Question 14

Question 14:
Name the plant part :
(a) which bends in the direction of gravity but away from light
(b) which bends towards light but away from the force of gravity

Accepted Answer

Answer:
(a) Roots bend in the direction of gravity but away from the light.
(b) Shoots bend towards the light but away from the force of gravity.

Question 15

Question 15:
To which directional stimuli do :
(a) roots respond?
(b) shoots respond?

Accepted Answer

Answer:
(a) Roots of a plant respond to gravity.
(b) Shoots of a plant respond to light.

Question 16

Question 16:
Fill in the following blanks :
(a) A plant's response to light is called ..........
(b) A plant's response to gravity is called ........
(c) Plant shoot grows upward in response to ........
(d) Plant roots grow downward in response to ........
(e) Tendrils wind around a support in response to .......
(f) Plant roots grow towards........ and in the direction of force of .........
(g) A root of a plant grows downward. This is known as ........
(h) ...... is the hormone that causes phototropism in plants
(i) The response of leaves to the sunlight is called ..........

Accepted Answer

Answer:
(a) A plant's response to light is called phototropism.
(b) A plant's response to gravity is called geotropism.
(c) Plant shoot grows upward in response to light.
(d) Plant roots grow downward in response to gravity.
(e) Tendrils wind around a support in response to touch.
(f) Plant roots grow downwards and in the direction of the force of gravity.
(g) The root of a plant grows downward. This is known as geotropism.
(h) Auxin is the hormone that causes phototropism in plants.
(i) The response of leaves to sunlight is called phototropism.

Question 17

Question 17:
Plant parts show two types of movements, one dependent on growth and other independent of growth. Give one example of the movement in plant parts :
(a) which depends on growth
(b) which does not depend on growth

Accepted Answer

Answer:
(a) Phototropism depends on growth. It is the growth of plant stem in response to sunlight.
(b) Thigmonasty does not depend on growth. It is a non directional movement of plant part, such as leaves, in response to touch.

Question 18

Question 18:
What is a plant hormone? Name four plant hormones. State one function of each.

Accepted Answer

Answer:
The chemicals that perform the function of control and coordination in plants are called plant hormones.
The four plant hormones and their functions are as follows:
1) Auxin: It promotes cell enlargement and cell differentiation in plants.
2) Gibberellins: It breaks the dormancy in seeds and buds.
3) Cytokinins: It promotes cell division in plants.
4) Abscisic acid: It promotes closing of stomata.

Question 19

Question 19:
(a) What does a root do in response to gravity? What is this phenomenon known as?
(b) What does a stem (or shoot) do in response to light? What is this phenomenon known as?

Accepted Answer

Answer:
(a) The roots of a plant always grow downwards in response to gravity. This phenomenon is known as geotropism.
(b) The stem of a plant grows upwards in response to light. This phenomenon is known as phototropism.

Question 20

Question 20:
(a) What does a stem (or shoot) do in response to gravity? What is this phenomenon known as?
(b) What does a root do in response to light? What is this phenomenon known as?

Accepted Answer

Answer:
(a) Stem always grows up and away from the pull of gravity. This phenomenon is known as negative geotropism.
(b) Root always grows downwards and away from light. This phenomenon is known as negative phototropism.

Chapter 2 : Control and Coordination