Chapter 13 - Plant Growth and Development

Plant Growth and Development explains how plants increase in size, form new structures, undergo differentiation and respond to internal and environmental signals. NCERT Class 11 Biology Chapter 13 connects patterns of growth with plant growth regulators, photoperiodism, vernalisation, dormancy and senescence.

Teachoo’s Chapter 13 category includes clear notes, NCERT exercise solutions, graph explanations, important questions and NEET MCQs. The content is organised around a central question: how does an immobile organism coordinate growth and development throughout its life?

Growth is a permanent and irreversible increase in size, often accompanied by an increase in dry mass, volume or cell number. In plants, growth is generally indeterminate because meristems retain the capacity to divide. Root and shoot growth can be divided into phases of cell division, elongation and maturation.

Students compare arithmetic and geometric growth. Arithmetic growth increases by a constant amount and produces a linear graph. Geometric growth initially increases exponentially and may later form a sigmoid curve when resources become limiting. Absolute growth rate measures total increase, while relative growth rate expresses increase in relation to the initial size.

Growth depends on water, oxygen, nutrients, temperature and light. These external factors operate along with internal genetic and chemical controls.

Differentiation occurs when cells mature and become specialised. Living differentiated cells may regain the ability to divide through dedifferentiation and later specialise again through redifferentiation. Development is the broader term covering all changes from germination to senescence and includes growth, differentiation and maturation.

Plants show plasticity, the capacity to follow different developmental pathways in response to environment or life stage. Heterophylly, in which a plant forms different kinds of leaves, illustrates this ability.

The chapter examines five principal groups of plant growth regulators:

• Auxins

• Gibberellins

• Cytokinins

• Ethylene

• Abscisic acid

Students learn their physiological effects rather than labelling each hormone simply as a promoter or inhibitor. Auxins influence cell elongation and apical dominance; gibberellins promote stem elongation and can break dormancy; cytokinins promote cell division and delay senescence; ethylene promotes fruit ripening and affects growth responses; abscisic acid promotes dormancy and stress responses.

Photoperiodism is the response of plants to the relative duration of light and dark, especially in flowering. Vernalisation is the promotion of flowering by exposure to low temperature. These processes demonstrate how environmental signals regulate developmental transitions.

Teachoo’s resources support questions involving:

• Growth phases and growth curves

• Arithmetic versus geometric growth

• Absolute and relative growth rates

• Differentiation and dedifferentiation

• Development and plasticity

• Hormone functions and agricultural uses

• Apical dominance, dormancy and senescence

• Photoperiodism and vernalisation

• NCERT solutions and NEET statement questions

Students should prepare a comparison table of hormones with their source, major effects, practical uses and interactions. For growth graphs, understand what each axis represents and why the curve takes its shape. This approach supports both school answers and application-based MCQs.