Concepts to Remember - Plant Growth and Development

1. Meristems:

• Apical meristems:
• Located at the tips of roots and shoots, responsible for primary growth.
• Lateral meristems:
• Found on the sides of stems and roots, responsible for secondary growth.

2. Cell Division:

• Mitosis:
• Cell division that produces two genetically identical daughter cells.
• Meiosis:
• Cell division that produces four genetically diverse daughter cells, crucial for sexual reproduction.

3. Differentiation:

• The process by which unspecialized cells become specialized to perform specific functions.
• Results in the formation of various tissues.

4. Primary Growth:

• Occurs due to the activity of apical meristems.
• Involves the elongation of stems and roots.

5. Secondary Growth:

• Occurs due to the activity of vascular cambium (produces secondary xylem and phloem) and cork cambium (forms cork).
• Increases the girth of the plant body.

6. Tissues:

• Meristematic tissue: Responsible for cell division and growth.
• Epidermal tissue: Forms the outer protective layer of plants.
• Vascular tissue: Transports water, minerals, and nutrients throughout the plant.
• Ground tissue: Provides support, stores food and water, and performs photosynthesis.

7. Roots:

• Primary roots: Develop from the radicle of the embryo.
• Secondary roots: Develop from the stems or older roots.
• Root hairs: Tiny, finger-like projections that increase the surface area for water and nutrient absorption.

8. Stems:

• Herbaceous stems: Green, non-woody stems found in non-woody plants.
• Woody stems: Brown, hard, and lignified stems found in trees and shrubs.
• Nodes: Regions where leaves attach to the stem.
• Internodes: The regions between nodes.

9. Leaves:

• Leaf blade: The flat, expanded portion of the leaf where photosynthesis occurs.
• Petiole: The stalk that connects the leaf blade to the stem.
• Veins: Transport water, minerals, and nutrients within the leaf.

10. Flower:

• Sepals: Leaf-like structures that form the outermost layer of the flower bud.
• Petals: Colorful structures that attract pollinators.
• Stamen: Male reproductive organ consisting of anther and filament.
• Pistil: Female reproductive organ consisting of stigma, style, and ovary.
• Floral diagram: A symbolic representation of the arrangement of flower parts.

11. Pollination:

• The transfer of pollen from the anther to the stigma.
• Can be self-pollination (within the same flower or plant) or cross-pollination (between different flowers or plants).
• Agents of pollination: Wind, insects, birds, mammals, and even water.

12. Fertilization:

• The union of the male gamete (pollen) with the female gamete (egg).
• In flowering plants, double fertilization occurs, leading to the formation of a zygote and an endosperm.

13. Seed:

• Consists of an embryo, a food reserve (cotyledons), and a protective seed coat.
• Seed dormancy: A period of metabolic inactivity that prevents premature germination.
• Seed germination: The resumption of metabolic activity, leading to the growth of a seedling.

14. Fruit:

• The mature ripened ovary of a flower, along with other associated structures.
• Various types: Simple fruits, aggregate fruits, multiple fruits, and accessory fruits.
• Significance: Protection, dispersal, and attraction of animals for seed dispersal.

15. Plant Hormones:

• Chemical messengers that regulate various physiological processes in plants.
• Auxins: Promote cell elongation and root growth.
• Gibberellins: Stimulate stem elongation, seed germination, and fruit growth.
• Cytokinins: Promote cell division and shoot development.
• Abscisic acid: Involved in seed dormancy, abscission, and stress response.
• Ethylene: Regulates fruit ripening, senescence, and responses to environmental stresses.

16. Photoperiodism:

• The response of plants to the length of day and night.
• Short day plants: require long nights to flower (e.g., poinsettia).
• Long-day plants: require long days to flower (e.g., roses).
• Day-neutral plants: flower regardless of day length (e.g., marigold).

17. Vernalization:

• The requirement for a period of cold weather for the flowering of some plants (e.g., winter wheat).
• Enables plants to synchronize their life cycle with favorable seasons.

18. Senescence and Abscission:

• Senescence: The natural aging and deterioration of plant parts before they fall off.
• Abscission: The process by which leaves, flowers, and fruits are shed from the plant.