Chemical Co-ord

Question 1

Define: Stimuli

Answer 1

Changes in the external or internal environment of an organism are called stimuli

Question 2

What is a response?

Answer 2

The resulting action caused by a stimulus is called response

Question 3

Fill in the blanks:
1. The main area of cell division in plants is _________.
2. ________ was the first phytohormone to be discovered.
3. The main auxin found in plants is _________.

Answer 3

1. Meristems
2. Auxins
3. IAA (Indole 3 acetic acid)

Question 4

G.R: Auxins are powerful growth stimulants

Answer 4

They are quite effective even in extremely low concentrations.

Question 5

State the location of Auxins

Answer 5

Shoot tip, root tip, lateral meristems etc.

Question 6

State the function of Auxins ( 4 m )

Answer 6

• Promote growth of shoot, root and fruits by cell elongation
• Delays leaf senescence.
• Promote growth of apical buts and inhibit growth of lateral buds.
• Induce fruit formation w/o fertilization in fruits like apples, tomatoes and bananas.

Question 7

What is apical dominance?

Answer 7

Phenomenon of the suppression of growth of lateral buds by apical buds.

Question 8

What is parthenocarpy

Answer 8

Development of fruit without fertilization

Question 9

Give two examples of plants wherein Auxins induce rooting when cut

Answer 9

rose, bougainvillea

Question 10

What is leaf senescence

Answer 10

The ageing / falling of leaves.

Question 11

What are the different forms of Gibberellins? Which is the most studied form?

Answer 11

GA1,GA2,GA3.
Gibberellic acid (GA3) is the most studied.

Question 12

State the location of Gibberellins.

Answer 12

Root tip, shoot tip, buds, seeds

Question 13

What are the functions of Gibberellin?

Answer 13

• Promote growth of internodes by cell elongation
• Break seed dormancy and initiate germination.
• Capable of inducing parthenocarpy and promote fruit growth
• delay leaf senescence.

Question 14

G.R: Gibberellins are used in horticulture and food industries.

Answer 14

They enhance longitudinal growth of internodes in dwarf plants and are used commercially to increase the length of grapes, elongate apples and improve their shape. It is also used to speed up malting process in the brewing industry.

Question 15

State the location of production of cytokinins and where they are found in the plant.

Answer 15

Cytokinins are produced in the root tips.
They are found in germinating seeds, developing fruits and embryos.

Question 16

State the functions of cytokinins.

Answer 16

• Stimulate plant growth by cell division even in non meristematic tissues
• In seeds, they cause expansion of cotyledons
• Break seed dormancy and promote germination
• Promote chlorophyll synthesis in chloroplasts and delay leaf senescence.
• inhibit apical dominance

Question 17

______ is the only hormone which is a gas at ordinary temperature.

It was first found emanating from _______.

Answer 17

Ethylene. It’s site of synthesis and site of action are the same

Oranges.

Question 18

What are the two plant processes caused by ethylene?

Answer 18

• Reduction in stem elongation
• Acceleration of senescence

Question 19

State the functions of ethylene

Answer 19

• Ripening of fruits
• initiating germination in peanut seeds
• /sprouting of potato tuber
• Inducing flowering in mango
• promoting root growth and root hair formation.

Question 20

G.R: Ethylene is most widely used plant hormone in agriculture

Answer 20

• Ripening of fruits
• initiating germination in peanut seeds
• /sprouting of potato tuber
• Inducing flowering in mango

Question 21

_____ is a growth retarding hormone. State its location.

Answer 21

Abscisic acid.
It’s located in the chloroplasts of leaves

Question 22

State the functions of ABA

Answer 22

• Acts as a growth inhibitor by slowing down plant metabolism
• Inhibits seed germination, induces seed dormancy to help the seed withstand desiccation
• Accelerates leaf senescence and abscission of buds, leaves and flowers and fruits.

Question 23

G.R: ABA is also called the “stress hormone”

Answer 23

When there in insufficient absorption of water by roots, ABA stimulates closure of stomata to prevent excessive transpiration and thereby increasing tolerance of a plant to unfavourable conditions.

Question 24

Define : Tropic movements

Answer 24

The movement of the plant part either towards or away from the direction of the stimulus

Question 25

What is phototropism?

Answer 25

movement of plant parts towards the stimulus of light.

Question 26

G.R: Auxins play an important role in phototropism

Answer 26

• they help in bending of a shoot towards source of light by getting accumulated in the region of the shoot which is not facing the light. This results in rapid cell elongation on this side causing the shoot to bend towards source of light.

Question 27

What is geotropism?

Answer 27

The movement of a plant part in response to the
stimulus of gravity.

Question 28

What is the instrument used to demonstrate geotropism?

Answer 28

Clinostat

Question 29

What is hydrotropism

Answer 29

The movement of a plant part in response to
the stimulus of water.

Question 30

what is thigmotropism? What plants is it seen in?

Answer 30

The movement of a plant part in response to
the stimulus of touch.

It is seen in sweet peas and cuscuta

Question 31

What is chemotropism? Where is it seen?

Answer 31

The movement of a plant part in response to
the stimulus of chemicals.
It is seen in the the movement of the pollen
tube towards sugars and peptones secreted by neck canal cells of
the female gametophyte