NCERT Class 11-Biology: Chapter –15 Plant Growth and Development Part 2

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Question 10:

ABA acts antagonistic to

a. Ethylene

b. Cytokinin

c. Gibberlic acid

d. IAA

Answer: (c)

Question 11:

Monocarpic plants are those which

a. Bear flowers with one ovary

b. Flower once and die

c. Bear only one flower

d. All of the above

Answer: (b)

Question 12:

The photoperiod in plants is perceived at

a. Meristem

b. Flower

c. Floral buds

d. Leaves

Answer: (d)

Very Short Answer Type Questions

Question 1:

Fill in the places with appropriate word/ words.

a. A phase of growth which is maximum and fastest is __________.

b. Apical dominance as expressed in dicotyledonous plants is due to the presence of more ________ in the apical bud than in the lateral ones.

c. In addition to auxin, a ________ must be supplied to culture medium to obtain a good callus in plant tissue culture.

d. ________ of a vegetative plants are the sites of photoperiodic perception.

Answer:

a. A phase of growth which is maximum and fastest is the log phase or exponential phase.

b. Apical dominance as expressed in dicotyledonous plants is due to the presence of more auxins in the apical bud than in the lateral ones.

c. Cytokinin- kinetin, zeatin, and 6-benzylaminopurine

Leaves of a vegetative plants are the sites of photoperiodic perception.

Question 2:

Plant growth substances (PGS) have innumerable practical applications. Name the PGS you should use to

a. Increase yield of sugar cane.

b. Promote lateral shoot growth.

c. Cause sprouting of potato tuber.

d. Inhibit seed germination.

Answer:

Plant growth substances are small molecules having diverse chemical composition. PGS of one group called plant growth promoters is involved in growth promotion like cell division or cell enlargement, flowering, fruiting, etc. Example: Auxins, Gibberellins. The other group has a role to play in plant responses to different stresses it is exposed to and also participates in growth inhibiting activities like dormancy. Eg: Ethylene.

a. Increase yield of sugar cane: Giberellins (Spraying sugarcane crop with gibberellins increases the length of the stem and hence increases the yield of sugarcane by about 20 tonnes per acre).

b. Promote lateral shoot growth: Cytokinins (These are generated in regions where rapid cell division occurs).

c. Cause sprouting of potato tuber: Ethylene (It breaks seed and bud dormancy and aids in initiation of sprouting of potato tubers)

d. Inhibit seed germination: Abscisic acid (It acts as a growth inhibitor hormone. It inhibits seed germination and promotes closure of stomata thus increasing the tolerance of plants in different stress conditions hence it is also known as stress hormone).

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