Class 11 Biology - TAMILNADU
Plant Growth and Development
The chapter Plant Growth and Development in Class 11 Biology under the Tamil Nadu Samacheer Kalvi syllabus explores the fundamental processes of plant life, from seed germination to senescence. Students learn about the phases of plant growth, indeterminate and determinate growth types, and the conditions necessary for growth. A major focus is placed on Plant Growth Regulators (PGRs) or phytohormones—auxins, gibberellins, cytokinins, ethylene, and abscisic acid—which control various physiological responses. Additionally, the chapter covers photoperiodism, vernalisation, and seed dormancy, making it a high-scoring and conceptually vital topic for board examinations.
Start Learning FreeKey Concepts
Plant Growth
An irreversible, permanent increase in size, volume, or weight of a plant, accompanied by metabolic processes requiring energy.
Plant Growth Regulators (PGRs)
Small, simple molecules of diverse chemical composition that act as chemical messengers in plants, categorized as promoters or inhibitors.
Photoperiodism
The physiological response of plants to the relative lengths of light and dark periods (photoperiods) that regulates flowering.
Vernalisation
The phenomenon where flowering is promoted or dependent on exposure to a low or chilling temperature treatment.
Seed Dormancy
A condition in which viable seeds fail to germinate even under optimal environmental conditions due to internal barriers.
Important Formulas
Board Exam Info
In the Tamil Nadu Samacheer Kalvi Class 11 Biology board examination, this chapter typically carries around 6 to 8 marks. Questions usually include 1-mark objective questions, 2-mark and 3-mark short answers on specific functions of plant hormones or photoperiodism, and 5-mark detailed questions describing the physiological effects of specific PGRs or the differences between arithmetic and geometric growth.
Frequently Asked Questions
What is the difference between SDD and LDD plants?
Short Day Plants (SDP) require a photoperiod below a critical day length to flower, whereas Long Day Plants (LDP) require a photoperiod above a critical day length.
Why is ethylene considered a unique plant hormone?
Ethylene is the only plant growth regulator that exists in a gaseous state at physiological temperatures and primarily promotes senescence and fruit ripening.
What are the three main phases of plant growth?
The three phases of plant growth are the lag phase (meristematic phase), the log phase (elongation phase), and the stationary phase (maturation phase).
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