Chemical Coordination In Plants

Question 1

What are hormones of plants known as?

Answer 1

Phytohormones

Question 2

What is the main auxin found in plants?

Answer 2

IAA (Indole 3 acetic-acid)

Question 3

What is Tropism?

Answer 3

The biological phenomena of growth or body movements of an organism in response to an environmental stimulus is known as tropism

Question 4

What is Phototropism?

Answer 4

Phototropism is the movement of plants towards the stimulus of light.
Shoots of plants are positively phototropic (they move towards light) whereas the roots of plants are negatively phototropic (move away).

Question 5

What is geotropism?

Answer 5

It means growing of plants towards the earth’s gravity. Also known as Gravitropism. Plant parts growing towards gravity are positively geotropic (e.g root tip) and those parts that grow away from gravity are negatively geotropic (e.g. shoot tip)

Question 6

What is Hydrotropism?

Answer 6

The movement of plant parts in response to water or moisture.
Positively Hydrotropic - Roots
Negatively Hydrotropic - shoots

Question 7

What is thigmotropism?

Answer 7

The growth movement of plant parts in response to touch stimulus.
Eg. Cuscuta and vines have tendrils which coil around other plants.

Question 8

What is ChemoTropism?

Answer 8

ChemoTropism is the phenomenon of growth of plant organs in response to chemicals.
Eg. Movement of pollen tube of angiosperms and gymnosperms towards sugars and peptones secreted by neck canal cells of the female gametophyte.
- movement of fungi growing towards the areas Richer in foods
- tentacles of drosera towards source of nutrition.

Question 9

What is heliotropism?

Answer 9

•Exhibited by Sunflowers.
•sunflower heads follow the sun from east to west direction
•caused due to auxins sensitive to light.

Question 10

What is parthenocarpy?

Answer 10

Fruit formation without fertilization. Caused by auxins. Eg. Apples, tomatoes, bananas.

Question 11

State four functions of auxins

Answer 11

1. It delays leaf senescence
2. It promotes growth of stems, roots and fruits by cell- elongation
3. Auxins promote the growth of apical buds and inhibit growth of lateral buds.
4. Auxins induce rooting in the cutting of some plants like rose, bougainvillea

Question 12

Which form of Gibberelin is most studied?

Answer 12

GA3 form

Question 13

Where are gibberlins mainly found in plants?

Answer 13

Meristematic regions like stem-apex, root-apex, buds, seeds

Question 14

State 4 functions of gibberelins

Answer 14

1. main function is to promote growth of internodes by cell elongation
2. they break seed dormancy and initiate germination
3. promote fruit growth and capable of parthenocarpy
4. delay senescence

Question 15

Who discovered cytokinins?

Answer 15

Discovered by Skoog and Miller in 1950

Question 16

Where are cytokinins found?

Answer 16

Seeds, developing fruits, embryo

Question 17

State 4 functions of cytokinins

Answer 17

1. They break seed dormancy
2. Stimulate plant growth by cell division
   (Auxins and gibberlins - cell elongation)
3. Expansion of cotyledons in seeds
4. Promote chlorophyll synthesis in chloroplast and delay senescence
5. Inhibit Apical Dominance

Question 18

Which is the ham hormone at room temp.? What are its two main processes?

Answer 18

Ethylene.
Tow main processes are -
•Reduction in stem elongation
•acceleration of senescence

Question 19

Which hormone is most widely used in Agriculture?

Answer 19

Ethylene

Question 20

State 4 functions of ethylene

Answer 20

1. Ripening of fruits
2. Initiating germination in peanut seeds
3. Sprouting of potato tuber
4. Promoting root growth and root hair formation
5. Inducing flowering in mango

Question 21

Which is the growth Retarding Hormone?
It what kind of plants is it found?

Answer 21

Abscisic Acid (ABA). It’s found in Angiosperms, gymnosperms, pteridophytes, and some mosses. Fruits and seeds contain highest amount of ABA

Question 22

State 4 functions of ABA

Answer 22

1. Induces dormancy of buds and seeds
2. Inhibits seed-germination and development
3. Stimulates closing of stomata
4. Accelerated

Question 23

What is the site of synthesis for auxins?

Answer 23

Synthesized in shoot apical meristems and young leaves

Question 24

What is the site of synthesis for gibberelins?

Answer 24

Meristems of apical buds and roots

Question 25

What is the site of synthesis for cytokininsv

Answer 25

Roots and transported to other organs

Question 26

What is the site of synthesis for Ethylene?

Answer 26

In senescent leaves and flowers, germinating seeds and ripening Fruits.

Question 27

What is the site of synthesis for abscisic acid?

Answer 27

In green fruits and seeds at beginning of wintering period