Class 11 Biology - KARNATAKA
Plant Growth and Development
The chapter 'Plant Growth and Development' explores how a tiny seed transforms into a complex, mature plant. You will study the phases of plant growth, indeterminate growth, and the crucial role of plant growth regulators (PGRs) such as auxins, gibberellins, cytokinins, ethylene, and abscisic acid. The chapter also covers photoperiodism, vernalization, and seed dormancy, which dictate how plants respond to environmental cues. For Karnataka KSEEB board exams, this is a high-scoring unit. Expect direct questions on the physiological effects of plant hormones, differentiation terms, and difference-based questions on growth curves and photoperiodism.
Start Learning FreeKey Concepts
Plant Growth
An irreversible, permanent increase in size, volume, or weight of an organ or its cells, typically accompanied by metabolic processes utilizing energy.
Phase of Growth
Growth occurs in three distinct phases: the lag phase (meristematic zone with slow growth), the log/exponential phase (rapid elongation), and the stationary/senescence phase (maturation where growth slows down).
Differentiation, Dedifferentiation, and Redifferentiation
Differentiation is when cells mature to perform specific tasks. Dedifferentiation is the reversal of maturity to form meristematic tissue (e.g., interfascicular cambium), and redifferentiation is when these cells lose division capacity again to become mature tissues.
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 developmental processes.
Photoperiodism
The physiological response of plants to the relative lengths of light and dark periods (photoperiods) which determines flowering and other developmental stages.
Vernalization
The dependence or promotion of flowering in plants by a prior exposure to prolonged cold treatments, commonly seen in winter varieties of wheat and barley.
Important Formulas
Board Exam Info
In the Karnataka (KSEEB) Class 11 Biology annual examinations, this chapter typically carries around 5 to 7 marks. Questions commonly include 1-mark fill-in-the-blanks or multiple-choice questions, 2-mark definitions (like vernalization or photoperiodism), 3-mark questions on the physiological effects of specific PGRs, and occasional 5-mark long answers requiring diagrams or explanations of growth phases and geometric growth.
Frequently Asked Questions
What is the difference between short-day plants and long-day plants?
Short-day plants (SDPs) flower when exposed to day lengths shorter than a critical period (e.g., soybean), whereas long-day plants (LDPs) require light periods longer than a critical threshold to flower (e.g., radish, spinach).
What are the physiological effects of Gibberellins?
Gibberellins stimulate internode elongation, delay senescence, break seed dormancy, induce bolting in rosette plants, and increase the length of grapes and sugarcane stalks.
Why is ethylene called a ripening hormone?
Ethylene is a gaseous PGR that promotes senescence and ripening of fruits by accelerating respiratory rates (respiratory climacteric) in climacteric fruits like bananas and tomatoes.
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