Bihar Board - Class 11 biology - Chapter 15: Plant Growth and Development Handwritten Notes
Plant growth and development refer to the processes by which plants increase in size, differentiate, and mature into a complete organism. This chapter define the phases of development and the role of influencing growth and plant hormones in regulating these processes.
Key Points
Growth in Plants
- Definition: Irreversible increase in size, volume, or cell number in a plant.
- Growth is measured quantitatively (e.g., length, volume, or weight).
Phases of Growth
- Meristematic Phase: Active cell division occurs in meristematic tissues.
- Elongation Phase: Cells elongate, increasing the size of the plant.
- Maturation Phase: Cells differentiate and specialize to form various tissues.
Types of Growth
- Primary Growth: Increases the length of the plant, occurring in apical meristems.
- Secondary Growth: Increases the girth or thickness of the plant, occurring in lateral meristems.
Development
- Refers to the progression of a plant through various stages like germination, flowering, fruiting, and senescence.
- Involves differentiation and dedifferentiation of cells.
Plant Growth Regulators (PGRs)
- Auxins: Promote cell elongation, apical dominance, and root initiation.
- Gibberellins: Stimulate stem elongation, seed germination, and flowering.
- Cytokinins: Promote cell division and delay leaf senescence.
- Ethylene: Regulates fruit ripening, leaf abscission, and flower senescence.
- Abscisic Acid (ABA): Induces seed dormancy and regulates stress responses.
Photoperiodism and Vernalization
- Photoperiodism: The response of plants to the duration of light and dark periods, influencing flowering.
- Vernalization: The requirement of cold treatment for certain plants to flower.
Seed Dormancy and Germination
- Seed Dormancy: A period of inactivity in seeds to survive unfavorable conditions.
- Germination: The process where a seed develops into a seedling under favorable conditions like water, temperature, and oxygen.
Environmental Factors Affecting Growth
- Light: Influences photosynthesis and photoperiodism.
- Temperature: Affects enzyme activity and overall plant metabolism.
- Water and Nutrients: Essential for metabolic activities and cell expansion.
Conclusion
Plant growth and development are complex processes regulated by both internal factors like hormones and external factors such as light, temperature, and water. Understanding these mechanisms is crucial for improving agricultural productivity and managing plant health. This knowledge forms the foundation of modern plant biology and biotechnology.
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