Plant Growth and Development Test

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Plant Growth and Development Test - 36

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Question 1
1 / -0

What causes a green plant to bend towards light as it grows?

A
Because green plants need light to carry on photosynthesis.

B
Because green plants are phototropic.

C
Light stimulates plant cell on the lighted side to grow faster.

D
Auxin accumulates on the shaded side.

Solution

According to most widely accepted view for phototropism, the phytohormone auxin accumulates on the shady side of stem and stimulates growth. This causes the plant stem to grow towards the light (positive phototropism).
Thus, the correct answer is option D.
Question 2
1 / -0

2, 4-D is a synthetic

A
Auxin

B
Gibberellin

C
Cytokinin

D
Florigen

Solution

Auxin is a group of several natural and artificial plant hormones; the most common and physiologically important auxin is indoleacetic acid (IAA). Some manufactured, or synthetic, auxins have structures similar to that of IAA. The synthetic auxin naphthalene acetic acid stimulates root development on stem cuttings and is used for asexual propagation, particularly of woody plants with horticultural importance. The synthetic auxins 2,4-D and 2,4,5-T have been used as selective herbicides (weed killers). These compounds kill plants with broad leaves but, for reasons not completely understood, do not kill grasses. Both herbicides are similar in structure to IAA and disrupt the plants normal growth processes. Because many of the worlds most important crops are grasses (such as wheat, corn, and rice), 2,4-D and 2,4,5-T can kill broad leaf weeds that compete with these crops.
Thus, the correct answer is option A.
Question 3
1 / -0

Which of the following is a weed killer?

A
2, 4-D

B
NAA

C
GA

D
ABA

Solution

Auxin is a group of several natural (and artificial) plant hormones; the most common and physiologically important auxin is indole acetic acid (IAA). Some manufactured, or synthetic, auxins have structures similar to that of IAA. The synthetic auxin; naphthalene acetic acid, stimulates root development on stem cuttings and is used for asexual propagation, particularly of woody plants with horticultural importance. The synthetic auxins; 2,4-D and 2,4,5-T have been used as selective herbicides (weed killers). These compounds kill plants with broad leaves but, for reasons not completely understood, do not kill grasses. Both herbicides are similar in structure to IAA and disrupt the plants normal growth processes. Because many of the worlds most important crops are grasses (such as wheat, corn, and rice), 2,4-D and 2,4,5-T can kill broad leaf weeds that compete with these crops.
Thus, the correct answer is option A.
Question 4
1 / -0

Which of the following induces femaleness in plants?

A
Auxin and ethylene

B
Ethanol

C
ABA

D
Gibberellin

Solution

Ethylene is a fruit ripening hormone. It also induces femaleness in plants. Auxins are the hormones responsible for cell elongation in plants. High auxin concentration increases the synthesis of ethylene and hence help to promote femaleness in dioecious plants. Thus the correct answer is option A.
Question 5
1 / -0

Which of the following auxins are widely used as herbicides?

A
2, 4-D and 2, 4, 5-T

B
2, 4-D and cytokinin

C
2, 4-D and 2, 4-T

D
2, 4, 5-T and GA

Solution

Auxins like indole-3-acetic acid (IAA) and indole butyric acid (IBA) have been isolated from plants. NAA (naphthalene acetic acid) and 2, 4-D (2, 4-dichlorophenoxyacetic acid) are synthetic auxins. All these auxins have been used extensively in agricultural and horticultural practices. Auxins are widely used as herbicides. 2, 4-D and 2,4,5-T are commonly used to kill dicotyledonous weeds, it does not affect mature monocotyledonous plants. It is used to prepare weed-free lawns by gardeners.
Thus, the correct answer is option A.
Question 6
1 / -0

The compounds that inhibit the action of auxin are known as

A
Antiauxins

B
Auxins promoters

C
Auxin precursors

D
Both (A) and (B)

Solution

Auxins are the most common plant growth promoting phytohormones, which is known to cause rapid changes in gene expression. The receptor for auxin is located in the plasma membrane and has a three-dimensional shape that binds to the auxin molecule. Any substance that inhibits auxin by competing for the same receptors is called as an antiauxin.
Thus, the correct answer is option A.
Question 7
1 / -0

The movement of auxin is largely

A
Acropetal

B
Basipetal

C
Lateral

D
Centripetal

Solution

Auxins are synthesized in shoot tips and move towards base. The unidirectional movement of auxins towards base is also called as polar transport.
Thus, the correct answer is option B.
Question 8
1 / -0

Which of the following prevents the fall of fruits?

A
GA$$_{3}$$

B
NAA

C
Ethylene

D
Zeatin

Solution

NAA (Naphthalene acetic acid) is a synthetic auxin. It is produced artificially. It inhibits the abscission. It prevents the formation of a layer called abscission layer which is formed between the organs like fruits, flowers, etc. and the stem. It is a layer of dead cells which causes fruit fall. As NAA prevents the formation of this layer, so it prevents the fall of fruits. Thus, the correct answer is B.
Question 9
1 / -0

Which of the following is not an enzyme?

A
Oxidase

B
Pepsin

C
Auxin

D
Trypsin

Solution

Enzymes are biological catalysts which catalyze biochemical reactions during cellular metabolism. The enzymes are mostly made up of proteins except for a small minority of catalytic RNA molecules. The catalytic RNA molecules are called as ribozymes. Enzymes are different from hormones. Hormones do not catalyze biological reactions and are used up or metabolised completely in the physiological response they modulate but enzymes are not used up in metabolic reactions and are recovered unchanged at the end of reaction. An oxidase is any enzyme that catalyzes an oxidation-reduction reaction, especially one involving molecular oxygen (O$$_2$$) as the electron acceptor. Pepsin and trypsin are enzymes of digestive system. They digest proteins in our alimentary canal. Auxin is a plant hormone or phytohormone.
Thus, the correct answer is option C.
Question 10
1 / -0

Richmond Lang effect is due to .........................

A
Cytokinin

B
Auxin

C
ABA

D
All of the above

Solution

Cytokinins are the phytohormones which can delay plant senescence by the stimulation of cell division. Cytokinins also prevent the destruction of chlorophyll and consequently the plant parts do not turn yellow. This is known as Richmond Lang effect after the workers who discovered it.

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Plant Growth and Development Test - 36

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Plant Growth and Development Test - 36

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SHARING IS CARING

Question 1

Because green plants need light to carry on photosynthesis.

Because green plants are phototropic.

Light stimulates plant cell on the lighted side to grow faster.

Auxin accumulates on the shaded side.

Solution

Question 2

Auxin

Gibberellin

Cytokinin

Florigen

Solution

Question 3

2, 4-D

NAA

GA

ABA

Solution

Question 4

Auxin and ethylene

Ethanol

ABA

Gibberellin

Solution

Question 5

2, 4-D and 2, 4, 5-T

2, 4-D and cytokinin

2, 4-D and 2, 4-T

2, 4, 5-T and GA

Solution

Question 6

Antiauxins

Auxins promoters

Auxin precursors

Both (A) and (B)

Solution

Question 7

Acropetal

Basipetal

Lateral

Centripetal

Solution

Question 8

GA$$_{3}$$

NAA

Ethylene

Zeatin

Solution

Question 9

Oxidase

Pepsin

Auxin

Trypsin

Solution

Question 10

Cytokinin

Auxin

ABA

All of the above

Solution

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