Question 1

Hormone responsible for plant and seed dormancy during drought is

Accepted Answer

Abscisic acid (ABA) is called as stress hormone or dormin, as it induces dormancy and helps to overcome conditions of stress. Due to this hormone, plants respond to stress conditions like cold, drought. It increases the tolerance of plants towards various stresses. It is found in high concentration in roots during drought and later translocated to leaves. It causes stomatal closure during water stress. It also promotes seed dormancy under adverse condition.

Question 2

Phytohormone commonly called stress hormone is

Accepted Answer

Abscisic acid is commonly called stress hormone because the production of this hormone is stimulated by drought, water logging and other adverse environmental conditions.

Question 3

Which one of the following is a natural growth inhibitor?

Accepted Answer

ABA (abscisic acid) is a naturally occurring growth inhibitor in plants. Hormones like Abscisic Acid (ABA), ethylene are growth inhibitors. These hormones accelerate abscission process and are involved in inhibition of growth.

Question 4

ABA was discovered during

Accepted Answer

ABA was discovered during mid 1960’s.During mid 1960s, three independent researches reported the purification and chemical characterization of three different kinds of inhibitors as inhibitor B, abscission II and dormin. Later, the three were proved to be chemically identical and named Abscisic Acid (ABA).

Question 5

Which one of the following acids is a derivative of carotenoids?

Accepted Answer

Abscisic acid is a derivative of carotenoids. It was called "abscisin II" originally because it was thought to play a major role in abscission of fruits. At about the same time another group was calling it "dormin" because they thought it had a major role in bud dormancy.

Question 6

I. Antagonist to GAII. Promotes bud dormancyIII. Promotes stomatal closureIV. Promotes abscission layerIdentify the hormone/s which promote/s all these events in plants and choose the correct option

Accepted Answer

Abscisic acid (ABA). Its important functions are
(i) Promot abscission             (ii) Promot dormancy
(iii) Plant growth inhibitor  (iv) Inhibit seed germination
(vi) Seed development          (vi) Antagonist to GA
(vii) Stomata closure

Question 7

Which plant hormone promotes seed dormancy, bud dormancy and causes stomatal closure?

Accepted Answer

Abscisic acid is a natural growth inhibitor. It promotes stomatal closure, i.e., it is a stress hormone and helps the plant to cope with adverse environmental conditions especially drought. It also induces dormancy of seeds and buds. These seeds sprout only when ABA is overcome by GA.

Question 8

Choose the incorrect pair.

Accepted Answer

Abscisic acid is a naturally occurring growth inhibitor. It acts as a ‘stress hormone’. It causes abscission of leaves and promotes senescence. It initiates flowering only in certain short day plants.

Question 9

Which one of the following pairs is not correctly matched?

Accepted Answer

Kinetin is a type of cytokinin, a plant hormone. Cytokinin is an adenine derivative. It helps in cell division. Gibberellic acid is a terpene chemically. It helps in stem elongation, germination and overcomes genetic dwarfism. Abscisic acid is a plant hormone which is a carotenoid derivative. It causes abscission of leaves. It is also called as a stress hormone. IBA (indoleacetic acid) is an indole compound. It is a plant hormone which acts as a growth promoter.

Question 10

Which phytohormone has viral inhibitory property?

Accepted Answer

Abscisic acid (ABA) inhibits synthesis of RNA and proteins. It has been shown that ABA regulates the expression of certain genes during seed maturation and certain stress conditions such as  heat shock, adaptation to low temperature and tolerance.

Question 11

In most situations, ABA acts as the

Accepted Answer

ABA plays an important role in seed development, maturation and dormancy. By inducing dormancy, ABA helps the seeds to withstand desiccation and other factors. As we can compare that most of ABA effects are opposite to GA., thus, in most situations, ABA is considered as an antagonist to GA.

Question 12

Select the incorrect statement.

Accepted Answer

Phytohormones display synergistic effect when two hormones act together and contribute to same function. Auxin promote apical dominance in plants, but ethylene promotes internode elongation. These two hormones do not exhibit synergistic action.

Question 13

Which of the following is not a function of gaseous hormone?

Accepted Answer

ABA stimulates the closure of stomata and increases the tolerance of plants to various kinds of stresses.

Question 14

Among the following features of ethylene, how many are antagonistic to abscisic acid?a. Horizontal growth of seedlingsb. Promotes abscission of plant organsc. Effective in fruit ripeningd. Breaking seed and bud dormancye. Initiates germination in some seeds

Accepted Answer

Breaking seed and bud dormancy and initiating seed germination are the functions of ethylene that are antagonistic to ABA.Abscisic acid (ABA) promotes seed and bud dormancy by inhibiting growth.Abscisic acid (ABA) reversibly arrests embryo development at the brink of radicle growth initiation, inhibiting the water uptake which accompanies embryo growth.

Question 15

Consider the following statements :A) Abscisic acid is known as stress hormone.B) ABA acts antagonistically to gibberellic acid. Select the correct option :

Accepted Answer

ABA helps the plants to tolerate the stress period of growth by inducing several structural and physiological changes, e.g., seed dormancy. Thus, it is called stress hormone. In most cases, ABA acts antagonist to gibberellins. For example, gibberellins promote the formation of shoot and root apical meristem, while ABA inhibits the same by inducing seed dormancy.

Question 16

Which one of the following acids is a derivative of carotenoids?

Accepted Answer

Biosynthesis of abscisic acid (ABA) in most plants occur indirectly by degradation of certain carotenoids present in chloroplasts or other plastids. The biosynthetic pathway follow mevalonic acid pathway for their synthesis. The sites of synthesis are fruits, tissues, leaves, roots and seeds.

Question 17

Hormone responsible for senescence is

Accepted Answer

Abscisic acid is a growth inhibiting phytohormone. It induces senescence in leaves by promoting the degradation of chlorophyll and proteins.

Question 18

ABA is involved in

Accepted Answer

ABA is involved in dormancy of seeds.

Question 19

The hormone produced during adverse environmental conditions is

Accepted Answer

Abscisic acid is a hormone which is produced during adverse environmental conditions. It also causes the closure of stomata under conditions of water stress and also under high concentration of CO2​ in the guard cells. ABA plays an important role in plants during water stress and drought conditions. The concentration of ABA increases in the leaves of plants facing such stresses, hence it is called as a stress hormone.

Question 20

Which is produced durìng water stress that brìngs stomatal closure?

Accepted Answer

(b) : Abscisic acid is produced during water stress that brings stomatal closure. Abscisic acid is a stress hormone and it is produced during water scarcity, when the transpiration rate exceeds absorption, the plant faces water stress condition. As a result, incipient wilting occurs. Under water stress condition ABA increases which induces stomatal closure.

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