Скачать или смотреть Development and Structure of Seed| Chap # 14| Biology Class 10 | Lec # 8 (PTB)

Assalam-o-Alaikum!

Seeds play a vital role in the life cycle of plants, serving as the primary means of reproduction and dispersal for many species. The development and structure of seeds are intricately designed processes that ensure the survival and propagation of plants across diverse environments.

Development of Seeds:

Fertilization: Seed development begins with the process of fertilization, where pollen from a male reproductive structure (anther) is transferred to the female reproductive structure (stigma) of a flower. This leads to the formation of a zygote within an ovule.

Ovule Maturation: The fertilized ovule undergoes a series of developmental stages, including cell division and differentiation. This results in the formation of the embryo, which will eventually develop into the new plant.

Endosperm Formation: In some plant species, the endosperm, a nutrient-rich tissue, forms through a process called double fertilization. The endosperm provides nourishment to the developing embryo.

Seed Coat Formation: As the embryo develops, layers of protective tissues, collectively known as the seed coat or testa, form around it. The seed coat helps safeguard the embryo from external environmental factors and mechanical damage.

Storage Reserves Accumulation: Nutrients such as carbohydrates, proteins, and lipids are stored within the seed's endosperm or cotyledons. These reserves serve as a source of energy and nourishment for the germinating seedling until it can establish its roots and leaves for photosynthesis.

Structure of Seeds:

Seed Coat: The outermost layer of the seed, the seed coat, is usually made up of one or more protective layers. It prevents desiccation (drying out) and physical damage to the embryo.

Cotyledons: Cotyledons are embryonic leaves that play a vital role in the early growth of the plant. They can function as storage organs for nutrients or emerge as the first photosynthetic structures upon germination.

Embryo: The embryo is the miniature form of the future plant. It consists of a shoot apex, which will give rise to the stem and leaves, and a root meristem, which will develop into the root system.

Radicle: This is the embryonic root of the plant. It is the first structure to emerge during germination and is responsible for anchoring the plant and absorbing water and nutrients from the soil.

Hypocotyl and Epicotyl: These are stem-like structures that connect the radicle and cotyledons. The hypocotyl lies below the cotyledons, and the epicotyl lies above. They aid in the emergence of the seedling from the soil.

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