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.

(a) Induce rooting in a twig – Auxins(b) Quickly ripen a fruit – Ethylene(c) Delay leaf senescence – Cytokinins(d) Induce growth in axillary buds – Cytokinins(e) Bolt a rosette plant – Gibberellic acid(f) Induce immediate stomatal closure in leaves – Abscisic acid

Question 1

Heterophylly is shown in the following plants

Accepted Answer

Heterophylly is one of the methods of plasticity in which plant follow several pathways in response to the external environment. Plants like cotton, coriander, larkspur and buttercup have leaves in juvenile phase which are entirely different from the mature phase. Also, differ in either the plant is aquatic or terrestrial.So, the correct option is 'All of the above'.

Question 2

Which one of the following pairs is not correctly matched?

Accepted Answer

Tryptophan and Indole are the precursors of IAA. Terpenes are usually precursors of steroids. Some insects such as termites or swallow tail butterflies, which emit terpenes from their osmeteria. They are often strong smelling.

Question 3

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.

Accepted Answer

(a) Induce rooting in a twig &#8211; Auxins(b) Quickly ripen a fruit &#8211; Ethylene(c) Delay leaf senescence &#8211; Cytokinins(d) Induce growth in axillary buds &#8211; Cytokinins(e) Bolt a rosette plant &#8211; Gibberellic acid(f) Induce immediate stomatal closure in leaves &#8211; Abscisic acid

Question 4

Describe briefly: Arithmetic growth (b) Geometric growth (c) Sigmoid growth curve (d) Absolute and relative growth rates.

Accepted Answer

(a) Arithmetic growthIn arithmetic growth, one of the daughter cells continues to divide, while the other differentiates into maturity following mitotic cell divsion. The rate of growth is constant and increase in growth occurs in arithmetic progression, i.e., 2,4,6,8,10,.. Example: Elongation of roots at a constant rate(b) Geometric growthIn geometric growth,growth is slow in the initial stages (lag phase) whereas rapid during the later stages (log or exponential phase). The daughter cells formed as a result of mitosis retain the ability to divide, but slow down due to limited supply of nutrients. The size or number increases in multiplicative fashion, i.e., 2,4,6,8,16,32,..(c) Sigmoid growth curveIt is an S-shaped graph produced on plotting growth of living organisms in their natural environment against time. This curve is divided into three phases: lag phase, log phase or exponential phase of rapid growth, and stationary phase.Exponential growth can be expressed as:W1 = W0 e^rtwhere,W1 = Final sizeW0 = Initial sizer = Growth ratet = Time of growthe = Base of natural logarithms(d) (i) Absolute growth rate: It refers to the measurement and comparison of total growth per unit time.     (ii) Relative growth rate: It refers to the growth of a given system per unit time, expressed on a common basis.

Question 5

Formation of which tissue is example of dedifferentiation?

Accepted Answer

Differentiation is the ability of the cells to get specialised. Dedifferentiation is the ability of the cells which can regain its capacity for cell division under certain conditions. Formation of interfascicular cambium and cork cambium from fully differentiated parenchyma cells is an example of dedifferentiation.So, the correct answer is option A.

Question 6

ABA acts antagonistic to

Accepted Answer

Abscisic acid is an antagonist to gibberellins as shown in the table given below:Abscisic acidGibberellic acidIt inhibits growth.It promotes growth.It promotes the dormancy of seeds, buds, and tubers.It overcomes the natural dormancy of seeds, tubers, etc.It inhibits the synthesis of RNA and proteins.It promotes the synthesis of RNA and Proteins.Causes abscission of flowers and fruits.Promotes the development of fruits.Promotes leaf senescence.Prevents leaf senescence.Promotes stomata! closure.Promotes stomatal opening.Prevents amylase activity.Promotes amylase activity during seed germination.

Question 7

Abscisic acid controls

Accepted Answer

Abscisic acid a plant hormone that plays important role abscission of leave. It inhibits stem elongation by inhibiting gibberellic acid. It prevents loss of dormancy in seeds. Thus, the correct answer is option B.

Question 8

Ethylene is used for _________________.

Accepted Answer

Ethylene is a fruit ripening hormone. It stimulates the biochemical changes which take place upon fruit ripening.

Question 9

Auxin promotes

Accepted Answer

Auxins are plant hormones produced at the shoot tips. Indole-3-acetic acid is the main auxin found in plants. Auxins promote growth in fruits, they induce dormancy in seeds and buds and also cause opening of stomata. So, the correct answer is, 'All of these'.

Question 10

IAA helps in formation of

Accepted Answer

Auxin is a plant hormone. It is involved in fruit development. It stimulates fruit growth and development and delays fruit senescence. IAA, a type of auxin helps flowering, fruit formation and ripening of the fruits.Thus, the correct answer is option C.