NCERT Class 11 Biology Chapter 15 Notes Plant Growth And Development- Download PDF Notes

CBSE Quick Revision Notes Class 11 Biology Chapter 13: Plants, like all living organisms, grow and develop over time. Growth in plants is an irreversible and permanent increase in size accompanied by cell division, elongation and differentiation. Unlike animals, plants exhibit indeterminate growth, meaning they continue to grow throughout their life. Development in plants involves various physiological and biochemical changes that lead to maturity and reproduction. Plant growth and development NCERT Notes for Class 11 Biology help you revise these major concepts given in the book in a short period of time for Board exam preparation. CBSE Class 11 Biology Chapter 13 notes will help you with quick revision. Having revision notes and NCERT Solutions handy saves you time.

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This Story also Contains

1. NCERT Class 11 Chapter 13 Class Notes
2. Plant Growth And Development
3. Plant Growth Regulators: Auxins, Gibberellins, Cytokinins, Abscisic acid, Ethylene
4. Benefits of NCERT Class 11 Biology Chapter 13 Notes:
5. Tips to learn NCERT Class 11 Biology Chapter 13 Notes:
6. Most Important Questions Class 11 Biology Chapter 13
7. Approach to Solve Questions of Class 11 Biology Chapter 13

The chapter explores different aspects of plant growth, including phases of growth, growth, regulators, differentiation, and plant growth regulators. Understanding these processes is important for comprehending how plants adapt, survive, and reproduce in various environments. Download the CBSE Notes for Class 11 Biology to use offline anywhere. Students must go through each topic in the most effective way possible with the help of NCERT Notes for Class 11.

Also, students can refer,

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

NCERT Class 11 Chapter 13 Class Notes

The summarised notes are given below-

Plant Growth And Development

Growth is an irreversible, permanent increase in an organ's size, one of its parts, or even a single cell's size is referred to as growth. Generally, it is accompanied by metabolic processes (both anabolic and catabolic) that occur at the cost of energy. Therefore, for example, the expansion of a leaf is growth.

Growth

Growth in plants refers to an irreversible, increase in size volume or mass due to cell division and enlargement throughout life and is observed in various structures such as roots, leaves and flowers. It is influenced by both internal and external factors. Unlike animals, plant growth is continuous and occurs at a specific region such as Meristems. This dynamic process helps plants adapt to environmental changes and ensure survival and reproduction.

Plant Growth Generally Is Indeterminate

Unlike animals, plants exhibit indeterminate growth, meaning they continue growing throughout their lifespan. This is due to the presence of meristematic tissues at the shoot and root tips, which divide continuously to produce new cells. Some parts such as leaves and flowers, exhibit determinate growth, meaning the growth with a specific size, but the structures like roots and stems, maintain the growth potential infinitely, allowing plants to regenerate and adapt efficiently.

Growth Is Measurable

Since growth involves an increase in size and mass, it can be measured quantitatively by various parameters such as length (stem elongation), volume (fruit expansion), surface area (leaf expansion), and dry weight (biomass accumulation) to help assess plant growth. Instruments like auxanometers measure shot elongation, while dry weight estimation provides insights into overall biomass production. Growth measurement helps in studying plant responses to different environmental and genetic factors

Phases Of Growth

• There are 3 broad phases of growth namely, the meristematic phase, an elongation phase, and maturation phase.
• The meristematic phase has actively dividing cells that are present at the root and shoot tips.
• The elongation phase has newly formed cells that increase in size due to water, absorption, protoplasm expansion, and cell wall modification
• In the maturation phase, the cells differentiate into specialised tissues like the xylem, and phloem, achieving their final functional form.

Growth Rates

Growth in plants can be classified into arithmetic and geometric growth, both of which describe how plant cells divide and expand over time. In arithmetic growth, one daughter cell continues to divide while the other is divided into specialised tissue and stops dividing. This type of growth is linear and constant over time, leading to a steady increase in size. In geometric growth, both daughter cells retain the ability to divide, leading to exponential growth. Initially, growth is slow (lag phase), followed by a rapid increase (lag phase) and finally, growth slows down (stationary phase) as nutrients or space become limiting.

The mathematical form of Arithmetic and Geometric Growth are explained below-

L_t = L₀ + rt

L_t = length at time ‘t’

L₀ = length at time ‘zero’

r = growth rate/elongation per unit time.

The exponential growth can be expressed as:

W₁ = W₀ e^rt

W₁ = final size (weight, height, number etc.)

W₀ = initial size at the beginning of the period

r = growth rate

t = time of growth

e = base of natural logarithms

Growth Between Organs Can Be Compared Either In:

1. Absolute terms i.e., total growth in unit time, or,

2. Relative terms i.e., growth of system per unit time expressed on a common basis.

Conditions for Growth

Plant growth depends on both internal and external factors. There are various factors affecting plant growth. The internal factors such as genetic makeup, hormones and metabolic activity regulate growth and development. They can either help in the development or also inhibit the growth. External factors such as light, temperature, water, oxygen and nutrients are essential for various plant processes, such as photosynthesis, respiration, and cell division. The optimal conditions make sure healthy plant development, flowering, fruiting, and seed production are achieved.

Differentiation, Dedifferentiation, and Redifferentiation

The processes are explained below-

Differentiation

Differentiation is the process where unspecialised cells develop into specialised tissues like xylem, phloem, and epidermis. It is important for plant structure and function, enabling efficient transport of nutrients and water. Cells undergo morphological and physiological changes to perform specific roles, ensuring overall plant efficiency.

Dedifferentiation

Dedifferentiation occurs when mature specialised cells revert to an undifferentiated state to regain the ability to divide. For example, parenchyma cells transform into meristematic cells to form vascular cambium. This ability allows plants to repair injuries, regenerate lost parts and sustain secondary growth.

Redifferentiation

Redifferentiation is when previously differentiated regain their specialised function. For example, vascular cambium for secondary xylem and phloem during the secondary growth. This process is important for regeneration, healing wounds, and producing new tissues and mature plants.

Development

Development in plants includes all changes from germination to senescence involving growth, differentiation and reproduction. It is controlled by various factors such as genetic, environmental and plant hormones. The developmental process includes seed, germination, flowering, fruiting, and ageing, ensuring the plant completes its full life cycle.

Plant Growth Regulators: Auxins, Gibberellins, Cytokinins, Abscisic acid, Ethylene

The characteristics of different plant hormones are given below-

Characteristics:

Plant growth regulators (PGRs) are chemical messengers that regulate growth and development. They can be growth promoters such as auxins, gibberellins and cytokinins or growth inhibitors such as abscisic acid and ethylene. These hormones influence processes such as cell division, elongation, flowering, dormancy, and stress responses.

The Discovery of Plant Growth Regulators

• The Discovery of all of the 5 major PGRs was by chance.
• Charles Darwin and Francis Darwin conducted experiments on coleoptiles of canary grass and observed that the tip of the coleoptile was responsible for bending towards light. Therefore, the hypothesis is that a chemical signal was transmitted from the tip of the flower to the lower part of the plant. Went then isolated this growth-promoting substance from the coleoptile and named it auxin.
• Elichi Kurosawa was a scientist studying the foolish seedling disease in Rice plants. This disease is caused by the fungus Gibberella fujikuroi, which leads to the excessive elongation of rice seedlings. Yabuta and Sumuki isolated the active compound responsible for this abnormal growth and named it Gibberellins.
• Skoog and Miller discovered a growth promoting substance while studying the effect of coconut milk and yeast extract on tobacco pith cells. They identified the first cytokinin, called kinetin, from the herring sperm DNA.
• Addicott and colleagues identified growth-inhibiting hormones in leave abscission and seed dormancy. They named abscisic acid because it was first associated with leaf abscission.
• Dimitry Nelijubov discovered that ethylene gas released from burning gas lamps caused the triple response in plants,i.e., elongation of seeds, swelling of stems and horizontal growth instead of vertical growth. Then, R. Gane, in 1934, confirmed that ethylene is a naturally occurring plant hormone responsible for fruit ripening, leaf abscission and senescence.

Physiological Effects of Plant Growth Regulators

Auxins

Auxins are growth-promoting hormones that regulate elongation, root initiation and apical dominance. They are mainly synthesised at shoot tips and young leaves and promote phototropism and gravitropism. They promote cell elongation, apical dominance and vascular differentiation. They are also used in tissue culture, fruit development, and weed control.

Gibberellins

Gibberellins stimulate cell elongation, germination, fruit development, and seed dormancy and promote flowering in the Long-Day plants. Long- Day Plants are the kind of plants that require a longer duration of sunlight than normal plants. They also stimulate cell elongation, seed germination and bolting in rosette plants. They also break seed dormancy and enhance fruit size and yield.

Cytokinins

Cytokinins are plant hormones that promote cell division, delay leaf senescence and enhance shoot growth. They work in coordination with auxins to regulate root and shoot development. Naturally occurring cytokinin is zeatin, found in young fruit seeds and roots. Synthetic cytokinins like kinetin are used in plant tissue culture.

Ethylene

Ethylene is a gaseous hormone that regulates fruit ripening, leaf abscission and stress response. It also promotes seed germination and flowering. It is widely used in commercial agriculture to promote fruit ripening and ensure flower longevity.

Abscisic Acid

Abscisic Acid is a stress hormone that helps plants survive unfavourable conditions by inducing seed dormancy, closing stomatal pores to prevent water loss and regulating leaf abscission. It plays an important role in drought resistance by signalling the closure of stomata during water deficiency.

Chapter-Wise NCERT Class 11 Notes Biology

The chapter-wise Notes for class 11 biology are given below:

Benefits of NCERT Class 11 Biology Chapter 13 Notes:

• Understanding the phases of plant growth and development ensures concept clarity.
• The notes help in answering direct application-based questions in exams.
• There are also important NEET exams. Plant Physiology is a key topic in competitive exams.
• Understanding how plant growth regulators are used in farming gives agricultural insights.
• They are important for genetic engineering and plant breeding.

Subject Wise NCERT Exemplar Solutions

• NCERT Exemplar Class 11 Solutions
• NCERT Exemplar Class 11 Maths
• NCERT Exemplar Class 11 Physics
• NCERT Exemplar Class 11 Chemistry
• NCERT Exemplar Class 11 Biology

Tips to learn NCERT Class 11 Biology Chapter 13 Notes:

• Use of mnemonics to remember plant hormones and their functions using short phrases.
• Diagram-based learning to study the growth, curves and meristematic regions.
• Creation of flow charts for differentiation, dedifferentiation and redifferentiation.
• Testing yourself with questions and practice quizzes.

Most Important Questions Class 11 Biology Chapter 13

Plant Growth and Development is an important NEET and board exam chapter explaining how plants develop, grow, and control their physiological processes using internal and external factors. It has extremely important points like phases of growth, rate of growth, differentiation, dedifferentiation, redifferentiation, and the function of plant hormones such as auxins, gibberellins, cytokinins, ethylene, and abscisic acid. If one comprehends this chapter, it is quite possible to face questions on tropisms, seed dormancy, seed germination, flowering, and stress responses, and thus, conceptual understanding as well as achieving good marks becomes mandatory.

Question: Which of the following plant hormones is mainly responsible for cell elongation?

1. a) Cytokinin

2. b) Gibberellin

3. c) Auxin

4. d) Ethylene

Answer: Auxin

Question: Which hormone is reported to induce seed germination by removing seed dormancy?

1. a) Abscisic acid

2. b) Ethylene

3. c) Gibberellin

4. d) Cytokinin

Answer: Gibberellin

Question: Which of the following is a growth inhibitor in plants?

1. a) Auxin

2. b) Gibberellin

3. c) Cytokinin

4. d) Abscisic acid

Answer: Abscisic acid

Question: What is growth in biological terms?

Answer: Growth refers to a long-lasting and unidirectional growth in the volume, size, and dry matter of a living organism, frequently coupled with differentiation.

Question: Write down the term "differentiation" in plants.

Answer: Differentiation refers to the process by which unspecialized cells become specialised cells that have precise functions in plants, like being xylem, phloem, or leaf cells.

Question: Make the distinction between photoperiodism and vernalisation.

Answer: Photoperiodism refers to the plant's physiological reaction to day and night length, affecting flowering. Vernalisation refers to the stimulation of a plant's flowering process by cold temperatures for an extended period.

Question: What is the function of ethylene in plants?

Answer: Ethylene controls activities like fruit ripening, flower wilting, leaf fall (abscission), and it also induces senescence.

Question: Define the term "apical dominance."

Answer: Apical dominance refers to the tendency of the dominant central stem of the plant to dominate (i.e., to grow more than) other side stems, primarily regulated by auxin synthesised at the shoot tip.

Question: Match the following:

A. Auxin – i. Apical dominance

B. Gibberellin – ii. Stem elongation

C. Abscisic acid – iii. Inhibition of growth

Options:

1. A-i, B-ii, C-iii
2. A-ii, B-iii, C-i
3. A-iii, B-i, C-ii
4. A-i, B-iii, C-ii

Answer: Option 1: A-i, B-ii, C-iii

Question: What is the importance of the lag phase of plant growth?

Answer: The lag phase is the first slow growth phase when cellular metabolism is actively occurring, but there is minimal visible increase in size or weight.

Question: Define "plasticity" in plant development.

Answer: Plasticity is the capacity of plants to change their shape (morphology) and structure under environmental conditions.

Approach to Solve Questions of Class 11 Biology Chapter 13

This chapter has a mix of direct, conceptual, and application-based questions. To prepare well:

• Read the NCERT and Exemplar very well for understanding growth phases, growth curves, processes of plant differentiation, and roles and mechanisms of various plant hormones such as auxins, gibberellins, cytokinins, ethylene, and abscisic acid.
• Practice drawing and labelling diagrams of sigmoid growth curves, experiments of auxin-mediated phototropism, and diagrams depicting seed dormancy and germination.
• Memorise the sequence of plant growth phases (meristematic, elongation, maturation), the major physiological impacts of each hormone, and notable terms including differentiation, dedifferentiation, redifferentiation, vernalization, and photoperiodism.
• Complete all exemplar questions with emphasis on differences among plant hormones (growth promoters vs. growth inhibitors), aspects influencing seed germination, and phenomena like apical dominance and senescence.

Subject-Wise NCERT Solutions

• NCERT Solutions for Class 11 Mathematics
• NCERT Solutions for Class 11 Chemistry
• NCERT Solutions for Class 11 Physics

• NCERT Solutions for Class 11 Biology

The study of plant growth and development is essential for understanding how plants function and adapt to their environment. From the basic phases of growth to the role of plant hormones and environmental factors, this chapter provides valuable insights into plant physiology. Mastering the notes will help in the clarification of concepts that will help in academic exams and also lay a foundation for careers in botany, agriculture and biotechnology. By applying effective learning strategies and understanding real-life applications, students can understand the topic efficiently and apply the knowledge and practical fields.