NCERT Solutions for Class 11 Biology Chapter 15 Plant Growth and Development

According to the CBSE Syllabus 2025-26, this chapter has been renumbered as Chapter 13.

NCERT Solutions for Class 11 Biology Chapter 13- The chapter explains plant growth, differentiation, and response to external and internal factors. This chapter focuses on various growth phases, plant hormones, and environmental influences on development. Understanding these topics with the help of Plant Growth and Development Class 11 questions and answers can enhance conceptual clarity. For students preparing for exams, mastering the chapter is essential for scoring well. The NCERT solutions prove very useful for students in their board exams.

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This Story also Contains

1. Download PDF of NCERT Solutions for Class 11 Biology Chapter 13: Plant Growth and Development
2. NCERT Solutions for Class 11 Biology Chapter 13: Plant Growth and Development (Solved Exercise)
3. Important Topics of NCERT Solutions for Class 11 Biology Chapter 13 – Plant Growth and Development
4. Class 11 Biology Chapter 13 Plant Growth and Development- Concepts
5. NCERT Solutions for Class 11 Biology: Chapter-wise

Plant growth occurs in three different phases. Various factors, including genetic makeup and external conditions, influence these phases. Plant hormones play an important role in regulating growth and development. NCERT-based Chapter 13 Biology Class 11 questions and answers explain key topics like seed dormancy, vernalisation, and photoperiodism effectively. Referring to Chapter 13 NCERT Class 11 Solutions Biology provides step-by-step explanations of key concepts.

Download PDF of NCERT Solutions for Class 11 Biology Chapter 13: Plant Growth and Development

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Also, Read

• NCERT Notes for Class 11 Biology Chapter 13 Plant Growth and Development
• NCERT Exemplar for Class 11 Biology Chapter 13 Plant Growth and Development

NCERT Solutions for Class 11 Biology Chapter 13: Plant Growth and Development (Solved Exercise)

The solved exercise questions are given below:

Q 1. Define growth, differentiation, development, dedifferentiation, development, redifferentiation, determinate growth, meristem and growth rate.

Solution:

Growth:

It is a permanent, irreversible increase in the size of an organ, one of its components, or even a single cell. Metabolic processes that are taking place as a result of the energy support growth.

Differentiation:

A localized qualitative change in the size, biochemistry, structure, and function of cells, tissues, or organs, such as mesophyll, a leaf, a fibre, a vessel, a trachea, or a sieve tube, is known as differentiation. As a result, both the form and the physiological activity change. It leads to specialization in certain functions.

Development:

Development refers to all the changes an organism experiences over the course of its existence.

Dedifferentiation:

Plants that have lost the ability to divide can regain it under specific circumstances. Dedifferentiation is the term used to describe this phenomenon. Example: meristem formation.

Redifferentiation:

It is referred to as redifferentiation when cells produced by dedifferentiation mature to carry out particular functions but once more lose the ability to divide.

Determinate growth:

Determinate growth is the capacity of a cell, tissue, or organism to grow for a specific amount of time. The majority of plants grow indefinitely; however, some plants reach a certain size before ceasing to expand.

Meristem:

The term "meristem" refers to plant tissue made up of undifferentiated cells (meristematic cells).

Growth rate:

A growth rate is an increase in growth per unit of time.

Q 2. Why is not any one parameter good enough to demonstrate growth throughout the life of a flowering plant?

Solution:

An increase in protoplasm production leads to growth. The parameters used to measure protoplasmic growth include changes in height, weight, number of cells, fresh tissue sample, length, area, volume, etc. As a result, it is challenging to identify a single growth parameter that characterizes a flowering plant's development over its lifetime.

Q 3. Describe briefly.

(a) Arithmetic growth

(b) Geometric growth

(c) Sigmoid growth curve

(d) Absolute and relative growth rates

Solution:

(a) Arithmetic growth

Only one daughter cell divides during arithmetic growth, while the other differentiates and matures. A root extending at a constant rate is the most basic illustration of arithmetic growth.

It can be mathematically expressed as:

Lt = Lo + rt

Lt = length of time ‘t’

Lo = length at the time ‘zero’

R = growth rate/elongation per unit of time

(b) Geometric growth

The initial phase of geometric growth is slow (lag phase), and the subsequent exponential or logarithmic phase sees a rapid increase. Here, both of the progeny cells that result from mitotic cell division are still able to divide. Due to the insufficient nutrient supply, the growth slows down and enters a stationary phase. In geometric growth, the number grows in a multiplicative pattern.

If we plot the growth parameter against time for geometric growth, we obtain a typical sigmoid or S-curve.

Exponential growth can be expressed as:

W1 = Wo ert

W1 = final size

Wo = initial size of the period;

r = growth rate

t = time growth

e = base of natural logarithms

'r' stands for relative growth and the efficiency index, which measures how well plants can produce new plant materials. Wo's initial size determines the final size of W1, thus.

(c) Sigmoid growth curve

Plotting growth against time results in an S-shaped graph that has four main parts: a slow lag phase, exponential phase or rapid phase, stage of diminishing growth, and stationary phase.

(d) Absolute and relative growth rates

The net growth per unit of time is known as the absolute growth rate. The growth rate per unit of time per unit of initial growth is known as the relative growth rate.

Q 4. List five main groups of natural plant growth regulators. Write a note on the discovery, physiological functions and agricultural/horticultural applications of any one of them.

Solution:

Plant growth regulators are the intercellular intrinsic factors (chemical substances) that are responsible for the growth and development of plants.

The following are the top five categories of natural plant growth regulators (PGR):

• Auxins
• Gibberellins
• Cytokinins
• Abscisic acid
• Ethylene

These PGRs are synthesized in various plant parts and regulate various developmental and differentiation processes that occur throughout a plant's life cycle.

Gibberellins

Discovery:

• One of the first gibberellins to be found, designated as GA1, GA2, and GA3, is gibberellic acid, which is acidic.
• More than 100 gibberellins have been identified in a variety of different sources, including fungi and other higher plants.

Physiological functions:

• Plants respond physiologically to gibberellins in a variety of ways.
• They have the ability to increase the length of the axis, which can result in an increase in the length of grape stalks.
• Fruits like apples elongate and acquire a better shape as a result of their presence.
• They are in charge of putting off the senescence process.

Agricultural/horticultural applications:

• The fruits can be left on the tree for longer to increase the market period because the senescence process is delayed.
• Gibberellic acid, or GA3, is a substance that is used to accelerate the malting procedure in the brewing industry.
• By spraying the sugarcane crop with gibberellins, which lengthen the stem and increase yield by up to 20 tonnes per acre because sugarcane stems store carbohydrates as sugar, the crop is able to store more carbohydrates as sugar.
• Spraying GAs on young conifers can shorten their maturation period and promote early seed production.
• Additionally, it encourages the bolting process in plants like cabbage and beets. The elongation of the internode that occurs just before flowering is known as bolting.

Q 5. Why is abscisic acid also known as stress hormone?

Solution:

Abscisic acid is responsible for stimulating the closure of stomata in the epidermis and raising the tolerance of plants to different types of stresses. This is why it is also known as the stress hormone. In order to ensure that seeds germinate under favourable conditions, abscisic acid is in charge of promoting seed dormancy. This makes it easier for seeds to withstand desiccation and induces dormancy in plants near the end of the growing season, which encourages the abscission of fruits, leaves, and flowers.

Q 6. ‘Both growth and differentiation in higher plants are open.’ Comment.

Solution:

Due to the presence of meristems at specific locations of their bodies, higher plants have the ability to retain the capacity to have indefinite growth throughout their life span. Because of these meristems, the cells have the ability to divide and grow on their own. This explains why the growth in higher plants is open. Following several rounds of cell division, some of these cells go through differentiation. Therefore, differentiation is also open.

Q 7. ‘Both a short-day plant and a long-day plant can produce flowers simultaneously in a given place.’ Explain.

Solution:

In a few plants, flowering depends on the relative durations of light and dark periods. Under the condition that they receive enough photoperiod, both long-day and short-day plants can bloom in the same location.

Q 8. Which one of the plant growth regulators would you use if you were 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.

Solution:

The plant growth regulators for the related events are listed below:

(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. – Gibberellins

(f) induce immediate stomatal closure in leaves. – Abscisic acid

Q 9. Would a defoliated plant respond to the photoperiodic cycle? Why?

Solution:

No, a defoliated plant will not respond to the photoperiodic cycle. This is due to the fact that the leaves serve as the sites where dark or light duration is perceived. Therefore, plants would not respond to light if leaves were not present.

Q 10. What would be expected to happen if:

(a) GA3 is applied to rice seedlings.

(b) dividing cells stop differentiating.

(c) a rotten fruit gets mixed with unripe fruits.

(d) you forget to add cytokinin to the culture medium.

Solution:

(a) If GA3 is applied to rice seedlings:

The rice seedlings will show internode-elongation, and hence, an increase in height will be observed.

(b) If dividing cells stop differentiating:

The various plant parts, including the stem and leaves, will not form if the dividing cells stop differentiating.

(c) If rotten fruit gets mixed with unripe fruit:

When unripe fruits are combined with rotten fruits, the unripe fruits ripen more quickly due to the ethylene produced by the rotten fruits, which is a plant growth regulator.

(d) If you forget to add cytokinin to the culture medium:

The processes of cell division, differentiation, and growth will be muted and slow down if cytokinin is not added to the culture medium.

Important Topics of NCERT Solutions for Class 11 Biology Chapter 13 – Plant Growth and Development

The important topics and subtopics given in the chapter are discussed below:

13.1 Growth

13.1.1 Plant Growth Generally is Indeterminate

13.1.2 Growth is Measurable

13.1.3 Phases of Growth

13.1.4 Growth Rates

13.1.5 Conditions for Growth

13.2 Differentiation, Dedifferentiation and Redifferentiation

13.3 Development

13.4 Plant Growth Regulators

13.4.1 Characteristics

13.4.2 The Discovery of Plant Growth Regulators

13.4.3 Physiological Effects of Plant Growth Regulators

13.4.3.1 Auxins

13.4.3.2 Gibberellins

13.4.3.3 Cytokinins

13.4.3.4 Ethylene

13.4.3.5 Abscisic acid

NCERT Solutions for Class 11: Subject-wise

Class 11 Biology Chapter 13 Plant Growth and Development- Concepts

The NCERT Class 11 Solutions for Biology offers students explanations of all the chapters in a downloadable format. The questions and answers educate students on some of the controlling factors for the various plant developmental processes.

The chapter discusses the various topics:-

Growth

• The topic explains that growth is a permanent and irreversible process.
• The process occurs via division, elongation and differentiation.
• Growth can be measured and is influenced by both internal and external factors.

Differentiation, Dedifferentiation and Redifferentiation

• The topic explains how plants undergo structural and functional changes to form specialised tissues.
• Dedifferentiation is when mature cells gain the capability to divide, while redifferentiation is the process of change of dedifferentiated cells into new specialised forms.
• The process is helpful in plant growth, regeneration and repair.

Development

• The topic discusses the changes that plants undergo from germination to senescence.
• The changes include growth, differentiation and maturation.
• The processes are influenced by internal as well as external factors.

Plant Growth Regulators

• The topic explains the involvement of hormones that control growth and development.
• The hormones include auxins, cytokinins, giberellins, ethylene and abscisic acid.
• These hormones influence cell division, elongation, flowering and fruit ripening.

NCERT Solutions for Class 11 Biology: Chapter-wise

NCERT solutions for all the class 11 biology chapters are given below:-

Class 11 Biology NCERT Solutions are framed following the textbook data. Answers are provided to all the questions about the chapter. The questions are given in the same order as provided in the textbook. These explanations are the ultimate resource for all the academic requirements of students in the CBSE session. The Plant Growth and Development questions and answers are provided in the most efficient and effective pattern. The conceptual knowledge of students can be assessed while referring to the NCERT.

Check the NCERT Books and NCERT Syllabus here:

• NCERT Books Class 11 Biology
• NCERT Syllabus Class 11 Biology
• NCERT Books Class 11
• NCERT Syllabus Class 11