Seed Structure
விதை அமைப்பு
Do not mistake a seed for a mere dormant structure. It is a biological time capsule, protecting the embryo until environmental conditions trigger germination. If the seed coat fails, the embryo dies. NEET examiners love to test your knowledge of the embryonal axis and cotyledon counts.
The idea
A seed consists of a seed coat and an embryo. The embryo comprises a radicle, an embryonal axis, and one or two cotyledons. Seeds are classified as endospermic (albuminous) or non-endospermic (ex-albuminous) based on the presence or absence of residual endosperm. This structural distinction is fundamental to plant classification.
Why it matters
Seeds serve as the primary unit of dispersal and survival for plants, protecting the embryo until favorable conditions for germination occur.
NEET lens
Focus on the list of endospermic vs non-endospermic seeds provided in NCERT. NEET frequently asks to identify examples like Castor (endospermic) versus Bean (non-endospermic). Do not confuse the radicle with the plumule. Memorize the specific examples; this is a high-yield area for direct questions.
Clinical significance
Seed proteins and storage reserves are the primary source of human nutrition. Failure in endosperm development leads to crop yield collapse, directly impacting global food security. Understanding these storage proteins is also vital for managing food allergies, such as those caused by specific seed storage globulins.
Introduction
A seed consists of seed coat (testa + tegmen), cotyledons (1 in monocot, 2 in dicot), embryonal axis (plumule + radicle), and endosperm (food storage).
Core concept
Dicot seed (bean): testa, tegmen, hilum (scar), micropyle, cotyledons (2, food-storing), embryonal axis. Monocot seed (maize): pericarp fused with seed coat, single cotyledon = scutellum, endosperm (separate food storage), coleoptile (covers plumule), coleorhiza (covers radicle).
Go deeper
In maize: scutellum absorbs nutrients from endosperm. Aleurone layer (outermost endosperm) produces enzymes that digest endosperm during germination. Embryonic axis = coleoptile + plumule + radicle + coleorhiza.
From Class 10
Seeds are mature ovules after fertilization. They contain an embryo and stored food. Seed structure varies between monocots and dicots.