Class 11 Biology - WEST-BENGAL
Plant Growth and Development
The chapter 'Plant Growth and Development' in Class 11 Biology explores the irreversible permanent increase in size, differentiation, and morphogenesis of plants. Students learn about the fundamental characteristics of plant growth, indeterminate growth, and the phases of cell division, elongation, and maturation. It covers the crucial roles of plant growth regulators (PGRs) such as auxins, gibberellins, cytokinins, ethylene, and abscisic acid, which control physiological responses. Additionally, the chapter details photoperiodism, vernalization, and seed dormancy. For WBBSE board exams, this is a high-scoring unit frequently featuring direct questions on hormone functions and experimental definitions.
Start Learning FreeKey Concepts
Plant Growth
An irreversible, permanent increase in size, dry weight, or volume of an organism, driven primarily by mitotic cell division and elongation.
Phases of Growth
Growth occurs in three distinct phases: the meristematic phase (constant division), the elongation phase (cell enlargement and vacuolation), and the maturation phase (tissue differentiation).
Plant Growth Regulators (PGRs)
Small, simple chemical molecules that act as plant hormones—categorized into promoters (auxins, gibberellins, cytokinins) and inhibitors (abscisic acid, ethylene).
Photoperiodism
The physiological response of plants to the relative lengths of light and dark periods (day length) that determines flowering behavior (short-day, long-day, and day-neutral plants).
Vernalization
The phenomenon where the flowering of certain plants is promoted or dependent on exposure to low chilling temperatures during their early stages of growth.
Seed Dormancy
A condition in which seeds fail to germinate even under favorable environmental conditions due to internal seed coat barriers or presence of germination inhibitors.
Important Formulas
Board Exam Info
In the West Bengal (WBBSE) Class 11 Annual Examination, this chapter typically carries around 4 to 6 marks. Questions usually include 1-mark Multiple Choice Questions (MCQs), 2-mark short answer questions on hormone functions (like 'physiological effects of gibberellins'), and 3-mark descriptive questions explaining photoperiodism or the mathematical representation of geometric growth.
Frequently Asked Questions
What is the difference between arithmetic and geometric growth?
In arithmetic growth, only one daughter cell continues to divide while the other differentiates, resulting in a linear increase (Lt = L0 + rt). In geometric growth, both daughter cells continue to divide, resulting in an exponential increase in size (W1 = W0 * e^(rt)).
Why are auxins and abscisic acid considered antagonists?
Auxins generally promote plant growth, cell elongation, and apical dominance, whereas Abscisic Acid (ABA) acts as a potent growth inhibitor that promotes leaf senescence, stomatal closure, and seed dormancy.
What is 'bolting' and which plant hormone induces it?
Bolting is the premature internode elongation just prior to flowering in rosette plants (like cabbage). It is primarily induced by Gibberellins (GA).
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