Fruit and Seed Structure
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Direct answer
A fruit is a ripened ovary: after fertilisation the ovary wall becomes the pericarp, differentiated into epicarp, mesocarp and endocarp, and the ovules become seeds; fruits formed without fertilisation are parthenocarpic and seedless. The apple is a false fruit because the thalamus contributes to the fruit, while aggregate fruits such as strawberry develop from many free carpels of one flower and composite fruits such as pineapple and jackfruit from an entire inflorescence. A dicot seed such as gram has two fleshy cotyledons storing food, while a monocot cereal seed such as maize is albuminous, with a single shield-shaped cotyledon, the scutellum, an endosperm and an aleurone layer.
What you must remember
- Pericarp in a drupe: in mango the epicarp is the thin skin, the mesocarp is the thick edible flesh and the endocarp is the hard stony layer; in coconut the mesocarp is fibrous and the endocarp is the hard shell.
- True and false fruits: a true fruit develops from the ovary alone; in false fruits such as apple, strawberry and cashew the thalamus also grows into the fruit.
- Aggregate and composite fruits: strawberry is an aggregate of many tiny achenes from one flower; pineapple and jackfruit (sorosis) and mulberry develop from fused flowers of an inflorescence.
- Dicot seed (gram, bean): seed coat with hilum (scar of stalk) and micropyle; embryo of two cotyledons enclosing an embryonal axis — the plumule above the epicotyl, the radicle below the hypocotyl; non-endospermic.
- Monocot seed (maize): fruit wall and seed coat fused; large endosperm covered by a protein-rich aleurone layer; single cotyledon, the scutellum; plumule sheathed by the coleoptile and radicle by the coleorhiza; endospermic (albuminous).
- Albuminous versus non-albuminous: seeds that retain endosperm at maturity are albuminous (maize, castor); those that use it up are exalbuminous (gram, pea).
Common confusion
The favourite trap is seed-versus-fruit in cereals: the maize grain is technically a fruit (caryopsis) because the fruit wall fuses with the seed coat — calling it a naked seed costs the mark. The second is cotyledon versus endosperm: in gram the cotyledons store the food (non-endospermic), but in maize the endosperm does, with the scutellum absorbing it — do not call the scutellum a food store. Distinguish coleoptile (sheath of plumule) from coleorhiza (sheath of radicle); the -optile belongs above.
Exam-focused takeaway
NEET-UG asks the pericarp layers with mango and coconut as models, the false-fruit status of apple, and the parts of the maize grain — scutellum, aleurone layer, coleoptile and coleorhiza — in labelling-style MCQs. Statement items test "parthenocarpic fruits develop without fertilisation" and "hilum and micropyle are seed-coat scars". Keep two labelled diagrams ready, the gram seed and the maize grain; nearly every question in this section is answered directly by one of them.
Frequently asked questions
What is a false fruit?
A fruit in which parts besides the ovary, typically the thalamus, contribute — apple, strawberry and cashew are the standard examples.
Name the pericarp layers and their fate in mango.
The epicarp forms the thin skin, the mesocarp the thick edible pulp and the endocarp the hard stone enclosing the seed — mango is a typical drupe.
What is the scutellum?
The single, shield-shaped cotyledon of a maize grain that absorbs food from the endosperm for the germinating embryo.
Differentiate coleoptile and coleorhiza.
The coleoptile is the protective sheath around the plumule (shoot), while the coleorhiza sheathes the radicle (root) in a monocot seed.
Why is the maize grain called albuminous?
Because it retains a large, food-storing endosperm at maturity, unlike the non-endospermic gram seed whose cotyledons store food.