Class 11 Biology - CBSE
Plant Growth and Development
Plant Growth and Development explores how plants grow, differentiate, and respond to internal and external signals throughout their life cycle. This CBSE Class 11 Biology chapter covers the phases of plant growth, mathematical growth rates (arithmetic and geometric), differentiation, dedifferentiation, and redifferentiation. You will also learn about the discovery, physiological effects, and agricultural applications of the five major plant growth regulators: auxins, gibberellins, cytokinins, ethylene, and abscisic acid, along with photoperiodism and vernalization. This is a high-yield chapter for board exams, frequently featuring direct questions on plant hormones, growth kinetics, and photoperiodism.
Start Learning FreeKey Concepts
Plant Growth
An irreversible, permanent increase in size, dry weight, or volume of an organism, driven primarily by cell division, elongation, and maturation.
Growth Kinetics
The rate of plant growth can be arithmetic (linear growth where only one daughter cell continues to divide) or geometric (exponential growth where both daughter cells divide).
Plasticity
The ability of plants to follow different pathways in response to environment or phases of life to form different kinds of structures, a phenomenon known as heterophylly.
Plant Growth Regulators (PGRs)
Small, simple molecules of diverse chemical composition (like auxins, gibberellins, cytokinins, ethylene, and ABA) that act as plant hormones to regulate growth and development.
Photoperiodism
The physiological response of plants to the relative lengths of light and dark periods (day length) expressed in terms of flowering.
Important Formulas
Board Exam Info
In the CBSE Class 11 Biology examination, this chapter typically carries around 4 to 6 marks. Common question types include direct functions and physiological roles of plant hormones (PGRs), distinguishing between arithmetic and geometric growth, and defining terms like dedifferentiation, vernalization, and photoperiodism.
Frequently Asked Questions
What is the difference between differentiation, dedifferentiation, and redifferentiation?
Differentiation is when cells mature to perform specific functions. Dedifferentiation is the reversion of differentiated cells back to meristematic tissue (e.g., interfascicular cambium). Redifferentiation is when these dedifferentiated cells lose the capacity to divide and mature again to perform specific functions.
Which plant hormone is gaseous in nature?
Ethylene is the only gaseous plant growth regulator, primarily involved in fruit ripening and transverse growth in seedlings.
What is the role of ABA (Abscisic Acid)?
ABA acts as a general plant growth inhibitor and stress hormone. It induces seed dormancy, inhibits seed germination, and closes stomata during water stress.
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