Role of Auxin

Q. Dr F. Went noted that if coleoptile tips were removed and placed on agar for one hour, the agar would produce a bending when placed on one side of freshly - cut coleoptile stumps. Of what significance is this experiment?

1. It made possible the isolation and exact identification of auxin.
2. It is the basis for quantitative determination of small amounts of growth - promoting substances.
3. It supports the hypothesis that IAA is auxin.
4. It demonstrated polar movements of auxins

Q.

What causes a green plant exposed to the light on only one side to bend toward the source of light as it grows?

1. Auxin accumulates on the shaded side, stimulating greater cell elongation there.

2. Green plants need light to perform photosynthesis.

3. Green plants seek light because they are phototropic.

4. Light stimulates plant cells on the lighter side to grow faster.

Q. Which of the following is not a function of auxin?

1. It helps in seed germination
2. It can be used as weedicides
3. It promotes apical dominance
4. It helps in the initiation of flowering

Q.

Which one of the plant growth regulators would you use if you are asked to:

(a) Induce rooting in a twig

(b) Quickly ripen a fruit

(c) Delay leaf senescence

(d) Induce growth in axillary buds

(e) 'Bolt' a rosette plant

(f) Induce immediate stomatal closure in leaves.

Q.

What Plant Hormone Is Most Commonly Used In Plant Tissue Culture?

Q.

Assertion (A): Decapitation of shoot tip in plants induces the growth of their lateral buds

Reason (R): Accumulation of auxins in lateral buds causes inhibition of their growth

1. Both A & R are true and R explains A

2. Both A & R are true and R does not explain A

3. A is true and B is false

4. Both A & B are false

Q. Scientists use various combinations of auxin and cytokinin in plant tissue culture experiments. Choose the correct statement from the options given below regarding the role of both hormone in plant culture medium.

1. High cytokinin-auxin ratio promotes shoot formation
2. High cytokinin-auxin ratio promotes root formation
3. Low cytokinin-auxin ratio promotes root formation
4. Low cytokinin auxin ratio promotes shoot formation

Q. Which of the following auxin is commonly used as a selective weedicide for dicot weed?

1. 2, 4-D
2. IAA
3. NAA
4. IPA

Q.

Mention few roles of auxins in plant growth.

Q.

Why is auxin present in human urine?

Q. Xylem differentiation is facilitated by

1. auxin
2. cytokinin
3. gibberellin
4. ethylene

Q.

A gardener finds some broad-leaved dicot weeds growing in his lawns. What can be done to get rid of the weeds efficiently?

Q. The pre-harvest fruit drop is due to the

1. decrease in the level of ABA
2. increase in the level of auxin
3. decrease in the level of gibberellin
4. decrease in the level of auxin

Q.

One of the following is a natural cytokinin?

1. 2, 4-D

2. Zeatin

3. BAP

4. ABA

Q. Synthetic hormone used as a weedicide is

1. PAA

2. NAA

3. 2, 4-D

4. IBA

Q.

Parthenocarpic fruits can be produced by

1. treating the plants with phenyl mercuric acetate.

2. treating the plants with gibberellic acid.

3. raising the plants from vernalized seeds.

4. None of these.

Q.

One hormone hastens maturity period in juvenile conifers, second hormone controls xylem differentiation, while the third hormone increases the tolerance of plants to various stresses. They are respectively

1. Gibberellin, Auxin, ABA

2. Gibberellin, Auxin, Ethylene

3. Auxin, Gibberellin, Cytokinin

4. Auxin, Gibberellin, ABA.

Q. The diffusible substance synthesised in the coleoptile tip causes phototropic bending. This was confirmed by

1. Boysen-Jensen

2. F.W Went

3. Paal

4. Charles Darwin and Francis Darwin

Q. Which plant hormone is responsible for the induction of the parthenocarpy of tomatoes?

1. Auxin
2. Ethylene
3. Cytokinins
4. Gibberellins

Q. Avena coleoptile curvature test is for

1. Isolation of auxins

2. Identification of phytohormones

3. Quantitative measurement of auxins

4. Studying movement of auxins

Q. Who demonstrated that the severed tip of canary grass would resume phototropic sensitivity, when placed back in its position?

1. Darwin
2. Went
3. Boysen-Jensen
4. Paal

Q.

Who among the following coined the term photoperiodism?

1. F.W. Went

2. Varner and Allard

3. Lysenko

4. Boysen - Jensen

Q.

Parthenocarpy can be induced by

Q. Match the following:
$\begin{array}{cc}& \\ \text{Column I}& \text{Column II}\\ \text{a. Weedicide}& \left(i\right)G{A}_3\\ \text{b. Bolting}& \left(ii\right)\text{Cytokinin}\\ \text{c. Thinning of cotton}& \left(iii\right)\text{Ethylene}\\ \text{d. Lateral shoot growth}& \left(iv\right)2,4-D\end{array}$

1. a-(iii), b-(ii), c-(iv), d-(i)
2. a-(iv), b-(i), c-(iii), d-(ii)
3. a-(iv), b-(i), c-(ii), d-(iii)
4. a-(iv), b-(ii), c-(iii), d-(i)

Q.

Question 4:

Match the following.
$\begin{array}{cc}\text{Column~I}& \text{Column~II}\\ A.IAA& 1.HerringspermDNA\\ B.ABA& 2.Bolting\\ C.Ethylene& 3.Stomatalclosure\\ D.GA& 4.Weed-freelawns\\ E.cytokinins& 5.Ripeningoffruits\end{array}$
Codes
$\begin{array}{ccccc}A& B& C& D& E\\ \left(a\right)4& 3& 5& 2& 1\\ \left(b\right)5& 3& 4& 2& 1\\ \left(c\right)4& 1& 4& 3& 2\\ \left(d\right)5& 3& 2& 1& 4\end{array}$

Q. What is geotropism? Draw a labelled diagram of a potted plant showing positive geotropism and negative geotropism.

Q. One hormone hastens maturity period in juvenile conifers, a second hormone controls xylem differentiation, while the third hormone increases the tolerance of plants to various stresses. They are respectively:

1. Auxin, Gibberellin, Cytokinin
2. Gibberellin, Auxin, ABA
3. Auxin, Gibberellin, ABA
4. Gibberellin, Auxin, Ethylene

Q. Increased availability of abscisic acid stimulates

1. lipid formation
2. protein formation in cell
3. starch synthesis in guard cells
4. cellulose synthesis

Q. Negative geotropism in horizontal stems is caused by

1. accumulation of auxins on the lower side
2. accumulation of auxins on the upper side
3. cell shrinkage on the lower side
4. cell enlargement on the upper side

Q. Choose the correct answer from the alternatives given.
The classical experiments performed by FW Went on auxins was on

1. Oryza
2. Avena
3. Zea
4. tomato