Class 11 Biology - RAJASTHAN
Plant Growth and Development
The chapter 'Plant Growth and Development' in RBSE Class 11 Biology explores the fascinating journey of how a tiny seed transforms into a complex, mature plant. Students will learn about the indeterminate nature of plant growth, the phases of cell division and elongation, and the crucial role of plant growth regulators or phytohormones like Auxins, Gibberellins, Cytokinins, Ethylene, and Abscisic Acid. Additionally, the chapter covers photoperiodism, vernalization, and seed dormancy. This is a high-scoring chapter for Rajasthan board exams, frequently featuring direct questions on hormone functions, physiological processes, and curve-based growth patterns, making a thorough understanding essential.
Start Learning FreeKey Concepts
Plant Growth
An irreversible, permanent increase in size, volume, or weight of an organ or its parts, driven by mitotic cell division and cellular elongation.
Phytohormones
Chemical messengers synthesized in one part of the plant and transported to another to regulate physiological responses; includes both growth promoters and inhibitors.
Photoperiodism
The physiological reaction of plants to the length of day or night, categorized into short-day plants, long-day plants, and day-neutral plants.
Vernalization
The dependence of certain plants, such as winter varieties of wheat and barley, on a low-temperature stimulus to flower or complete their life cycle.
Seed Dormancy
A condition in which viable seeds fail to germinate even under favorable environmental conditions due to internal barriers like hard seed coats or inhibitors.
Important Formulas
Board Exam Info
In the Rajasthan (RBSE) Class 11 Biology board examinations, this chapter typically carries around 4 to 6 marks. Questions usually include a mix of 1-mark objective questions, 2-mark short answer questions (often asking to name specific hormone functions or discoverers), and occasional 3-mark conceptual questions explaining photoperiodism or the phases of plant 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 growth curve. In geometric growth, both daughter cells retain the ability to divide, leading to an exponential (S-shaped or sigmoid) growth curve.
Which plant hormone is known as the 'stress hormone'?
Abscisic Acid (ABA) is called the stress hormone because it increases manifold during water stress or drought conditions, leading to stomatal closure to prevent transpiration.
What triggers bolting in rosette plants?
Gibberellins (GAs) trigger internode elongation just prior to flowering in rosette plants like cabbage, a process known as bolting.
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