Biology: Plant Growth and Development (Solved Examples Part 1)

Transform your understanding of Plant Growth and Development with PracBee's exclusive collection of 25 solved examples for NEET preparation. Our comprehensive guide covers everything from growth indices to hormone crosstalks, making complex concepts like apical dominance and parthenocarpy easily digestible. Each solution is crafted by NEET experts, featuring detailed explanations of key experiments like went's classical experiment and biological clock mechanisms. Perfect your knowledge of growth regulators, flowering physiology, and plant movements through real NEET questions. Whether you're studying abscisic acid functions or vernalization requirements, these handpicked examples ensure thorough topic mastery.

1. Most widely used hormone in agriculture

A . Can increase yield of sugarcane crop

B . Can induce flowering in LDP

C . Initiates seed germination in peanut

D . Inhibits horizontal growth of seedlings

Solution:

Ethylene is one of the most widely used PGR in agriculture. Since ethylene regulates many physiological processes like flowering, fruit ripening, initiating germination, synchronising fruit-set, rapid internode/petiole elongation, breaking seed/bud dormancy etc.

Correct Answer : C

2. Which of the following are not secondary metabolites in plants?

A . Morphine, codeine

B . Amino acids, glucose

C . Vinblastin, curcumin

D . Rubber, gums

Solution:

Amino acids and Glucose are primary metabolites but not secondary metabolites as they have some known functions.

Correct Answer : B

3. Growth by cell elongation in plants occurs by the activity of

A . Apical meristem

B . Intercalary meristem

C . Secondary meristems

D . Primary meristems

Solution:

Cell division occurs primarily in regions of undifferentiated cells known as meristems. Cell division in the apical meristems and subsequent elongation and maturation of the new cells produces primary growth.

Correct Answer : D

4. The induction for photoperiodic stimulus in plants is received by

A . Meristematic tissue

B . Young leaves

C . Mature leaves

D . Cotyledons

Solution:

The induction for photoperiodic stimulus in plants is received by Mature leaves.

Correct Answer : C

5. Which one among the following chemicals is used for causing defoliation of forest trees?

A . Maleic hydrazide

B . 2,4D

C . Amo1618

D . Phosphon D

Solution:

2,4D is a famous herbicide or weedicide which especially kills broad leaved weeds. It kills weeds perhaps by over stimulated root growth. Other auxins like 2,4,5 T have also been used as defoliants during early sixties.

Correct Answer : B

6. Select incorrect statement w.r.t. abscisic acid

A . Acts as an inhibitor of plant metabolism

B . In most situation acts as an antagonist to GAs

C . Has its role in seed maturity and dormancy but no role in seed development

D . Promotes flowering in some short day plants in non-photoinductive periods

Solution:

ABA plays an important role in seed development, maturation and dormancy.

Therefore, it is also called the stress hormone. ABA plays an important role in seed development, maturation and dormancy. By inducing dormancy, ABA helps seeds to withstand desiccation and other factors unfavourable for growth. In most situations, ABA acts as an antagonist to GAs.

Correct Answer : C

7. Which among the following is product of redifferentiation?

A . Cortex

B . Vascular bundles

C . Cork

D . Endodermis

Solution:

Redifferentiation is the event of losing the ability to divide by dedifferentiated cells. Interfasicular cambium and cork cambium are also examples of redifferentiation.

Correct Answer : C

8. Plants which respond to cold treatment

A . Do not require photoperiod

B . Require anaerobic condition

C . Respond as per the age of plant

D . Cannot overcome this stimulus

Solution:

Plants respond to cold temperatures by activating metabolic pathways that protect their cells from cold and freezing conditions.

Correct Answer : C

9. Importance of day length in flowering of plants was first shown in

A . cotton

B . Petunia

C . Lemna

D . tobacco.

Solution:

The effect of photoperiods or daily duration of light hours (and dark periods) on the growth and development of plants, especially flowering, is called photoperiodism. Photoperiodism was first studied by Garner and Allard (1920) in 'Maryland Mammoth' variety of tobacco.

Correct Answer : D

10. Mark the incorrect one (w.r.t. Phytochrome)

A . Isolation by Butler

B . Responsible for flowering only

C . Present in two forms

D . Open tetrapyrrole present

Solution:

Phytochromes are a class of photoreceptor in plants, bacteria and fungi used to detect light.

Correct Answer : B

11. What will happen if seeds of winter varieties are allow saw in spring:-

A . No flowering

B . Flowering occur but no seed setting

C . Neither flowering nor seed setting

D . Either No flowering or Flowering occur but no seed setting

Solution:

In contrast to the spring variety, the winter variety will not flower or produce grains within the flowering season if planted in spring. They need period of cold or vernalisation to flower in the subsequent months.

Correct Answer : D

12. Coiling of garden pea tendrils around any support is an example of

A . thigmotaxis

B . thigmonasty

C . thigmotropism

D . thermotaxis

Solution:

The growth movement in response to touch, or contact of a foreign body, in plants is called thigmotropism or thigmotropic movement. The stems and tendrils of the climbers are positively thigmotropic in their response.

Correct Answer : C

13. Most widely used PGR in agriculture

a. Is formed from methionine

b. Can fit in both categories i.e. inhibitor and promoter of growth

c. Causes femaleness in Cucumber

d. Induces flowering in LDP

A . a and d are incorrect

B . b and c are incorrect

C . a and c are incorrect

D . Only d is incorrect

Solution:

Ethylene is one of the most widely used PGR in agriculture. Since ethylene regulates many physiological processes like flowering, fruit ripening, initiating germination, synchronising fruit-set, rapid internode/petiole elongation, breaking seed/bud dormancy etc. it is used in agriculture.

Correct Answer : D

14. Phytochrome is a

A . flavoprotein

B . glycoprotein

C . lipoprotein

D . chromoprotein.

Solution:

Phytochrome is a chromoprotein, plant pigment that can detect the presence or absence of light. It consists of a light detecting portion, called a chromophore, linked to a small protein and exists in two interconvertible forms with different physical properties.

Correct Answer : D

15. Some cells are left behind from shoot apical meristem during the formation of leaves and elongation of stem which constitutes

A . Leaf primordium

B . Axillary bud

C . Intercalary meristem

D . Apical meristematic zone

Solution:

Those cells from the apical meristem which do not help in elongation of shoot tip form the axillary bud. These axillary buds are found at nodes of a plant.

Correct Answer : C

16. In plants growth is open ended because?

A . There is continuous cell differentiation

B . Produced meristem cell can take part in division and can differentiate in mature cells

C . It is not covered by primordial.

D . On maturation meristem cell can attain any of the shape & function

Solution:

In plants growth is open ended because on maturation meristem cell can attain any of the shape & function.

Correct Answer : D

17. Effect of low temperature which shortens vegetative period and hastens flowering is called _____.

A . photoperiodism

B . transpiration

C . vernalization

D . photolysis

Solution:

Vernalization is the cooling of seed during germination in order to accelerate flowering when it is planted.

Correct Answer : C

18. Find odd one w.r.t. developmental plasticity

A . Larkspur

B . Coriand

C . Cotton

D . Buttercup

Solution:

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.

Correct Answer : D

19. Growth in plants is largely restricted to specialised regions of active cell division, characterised by

A . Large vacuolated cells

B . Abundant ergastic materials

C . Absence of intercellular spaces

D . Presence of thin wall and plastids

Solution:

Meristem growth in plants is largely restricted to specialised regions of active cell division called meristem. A meristem is a localised region in which actual cell division occurs.

Correct Answer : C

20. Dr. F W 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?

A . It made possible the isolation and exact identification of\(\text{auxin}\)

B . It is the basis for quantitative determination of small amounts of growth-promoting substances

C . It supports the hypothesis that IAA is auxin

D . It demonstrated polar movement of auxins

Solution:

Auxin bioassay is quantitative test as it measures concentration of auxin to produce the effect and the amount of effect.

Correct Answer : B