Development and Structure of Seeds
Seed Formation:
Fertilization: After fertilization in the female gametophyte, the zygote undergoes mitotic divisions to develop into an embryo.
Ovule Transformation: The ovule transforms into a seed, completing the sexual reproduction process in seed plants.F
Seed Structure:
Embryo: The developing plant within the seed, consisting of the radicle (root), plumule (shoot), and cotyledons (seed leaves).
Endosperm: A tissue that stores nutrients for the developing embryo.
Seed Coat: A protective layer that surrounds the embryo and endosperm.
Seed Coat:
Protection: The seed coat protects the embryo from mechanical injury and desiccation.
Hilum: The point where the seed was attached to the ovary wall.
Micropyle: A small opening in the seed coat through which water and oxygen can enter.
Embryo:
Radicle: Develops into the primary root.
Plumule: Develops into the shoot.
Cotyledons: Seed leaves that store nutrients and aid in photosynthesis.
Endosperm:
Nutrient Storage: Contains a reserve of nutrients (starch, oil, or protein) for the developing embryo.
Absorption: In many seeds, the endosperm's nutrients are absorbed by the cotyledons.
Seed Germination:
Conditions: Seeds require favorable conditions (moisture, temperature, oxygen) to germinate.
Embryo Growth: The embryo begins to grow, utilizing the stored nutrients in the endosperm or cotyledons.
Root and Shoot Development: The radicle emerges and develops into the root system, while the plumule grows into the shoot.
In conclusion, seeds are essential for the survival and dispersal of plants. They provide protection, nutrients, and a mechanism for the next generation to establish itself in new environments.
Seed Germination: The Process of Growth
Seed germination is the process by which a seed embryo develops into a seedling. It requires suitable conditions and involves several key steps.
Conditions for Germination:
Internal Conditions: A live embryo and sufficient food storage within the seed.
External Conditions: Water, oxygen, and favorable temperatures.
Germination Process:
Water Absorption: The seed absorbs water, causing it to swell and split the seed coat.
Embryo Activation: The absorbed water activates the embryo's metabolic processes.
Root Emergence: The radicle, the embryonic root, emerges from the seed and grows downward to anchor the plant and absorb water and nutrients.
Shoot Emergence: The plumule, the embryonic shoot, grows upward and emerges from the soil.
Types of Germination:
Epigeal Germination: The hypocotyl (the part of the embryonic stem below the cotyledons) elongates, forming a hook that pulls the cotyledons above the ground. Examples: beans, cotton, papaya.
Hypogeal Germination: The epicotyl (the part of the embryonic stem above the cotyledons) elongates, leaving the cotyledons underground. Examples: peas, maize, coconut.
Importance of Germination Conditions:
Water: Water is essential for the digestion of stored food, the softening of the seed coat, and the elongation of the embryo.
Oxygen: Oxygen is required for the respiration of the embryo's cells.
Temperature: The optimum temperature for germination varies among different plant species, but most seeds germinate best within a specific temperature range.
In summary, seed germination is a complex process influenced by both internal and external factors. The availability of water, oxygen, and suitable temperatures are crucial for successful germination and the establishment of a new plant.
Seed Germination: The Process of Growth
Seed germination is the process by which a seed embryo develops into a seedling. It requires suitable conditions and involves several key steps.
Conditions for Germination:
Internal Conditions: A live embryo and sufficient food storage within the seed.
External Conditions: Water, oxygen, and favorable temperatures.
Germination Process:
Water Absorption: The seed absorbs water, causing it to swell and split the seed coat.
Embryo Activation: The absorbed water activates the embryo's metabolic processes.
Root Emergence: The radicle, the embryonic root, emerges from the seed and grows downward to anchor the plant and absorb water and nutrients.
Shoot Emergence: The plumule, the embryonic shoot, grows upward and emerges from the soil.
Types of Germination:
Epigeal Germination: The hypocotyl (the part of the embryonic stem below the cotyledons) elongates, forming a hook that pulls the cotyledons above the ground. Examples: beans, cotton, papaya.
Hypogeal Germination: The epicotyl (the part of the embryonic stem above the cotyledons) elongates, leaving the cotyledons underground. Examples: peas, maize, coconut.
Importance of Germination Conditions:
Water: Water is essential for the digestion of stored food, the softening of the seed coat, and the elongation of the embryo.
Oxygen: Oxygen is required for the respiration of the embryo's cells.
Temperature: The optimum temperature for germination varies among different plant species, but most seeds germinate best within a specific temperature range.
In summary, seed germination is a complex process influenced by both internal and external factors. The availability of water, oxygen, and suitable temperatures are crucial for successful germination and the establishment of a new plant.
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