NEET Biology Notes Morphology of Flowering Plants Seed
Seed
Seed
The fertilised ovules develop^into seeds. A seed contains seed coat upon the embryo. The embryo is made up of a radicle, an embryonal axis and one (wheat, maize) or two cotyledons (gram and pea). The outermost covering of a seed is seed coat. It has two layers, i.e. the outer testa and the inner tegmen. The hilum is a scar on the seed coat. Above the hilum is a small pore called the micropyle.
In dicot seeds, the embryo consists of an embryonal axis and two cotyledons. The cotyledons are often fleshy and full of reserve food. In some seeds, such as castor, the endosperm formed as a result of double fertilisation is a food storing tissue. In plants such as bean, gram and pea, the endosperm is not present in mature seeds, such seeds are called non-endospermous.
In monocots, seeds are endospermic but some as in orchids are non-endospermic. In the seeds of cereals such as maize, the seed coat is membranous and generally fused with the fruit wall. The endosperm is bulky and stores food. The outer covering of endosperm separates the monocot embryo by a proteinous layer called aleurone layer.
The embryo of monocot consists of one large and shield-shaped cotyledon known as scutellum and a short axis with a plumule and a radicle. The plumule and radicle are enclosed in sheaths, which are called coleoptile and coleorhiza, respectively.
Some Important Families if Flowering Plants
- Fabaceae
Vegetative characters The plants are trees, shrubs, root with root nodules, stem erect or climber, leaves alternate, pinnately compound or simple, leaf base pulvinate and venation is reticulate.
Flower characters Inflorescence is racemose, flower is bisexual, sepals five, gamosepalous, petals five, polypetalous, androecium having 10 stamens, gynoecium monocarpellary, ovary superior, fruit legume and seed non-endospermic.
Sources of pulses (gram, sem, moong, etc.), dye (Indigofera), fibres (hemp), fodder {Sesbania, Trifolium}, ornamentals, medicine (muliathi), etc.
- Solanaceae
Vegetative characters Mostly herbs, shrubs and rarely small trees. Stem is herbaceous, hairy or glabrous, underground in potato. Leaves are alternate, simple, venation is reticulate.
Flower characters Inflorescence is solitary, axillary or cymose, flower is bisexual, sepals five, united, petals five, androecium stamen five, gynoecium bicarpellary, ovary superior with many ovules. Fruits are berry or capsule. Seeds are many and endospermous.
Sources of vegetables (tomato, brinjal and potato), spice (chilli), medicine (belladonna and aswagandha), fumigatory (tobacco) and ornamentals (Petunia).
Solanaceae is a large family, commonly known as the potato family. Family-Fabaceae was earlier called Pailonoideae, a sub family of family-leguminosae.
- Liliaceae
Lily family is a characteristic representative of monocot plants. These are perrenial herbs, with underground bulbs/corms and rhizomes. Leaves are mostly basal, alternate with parallel venation.
Inflorescence is solitary/cymose, flower is bisexual, perianth tepal six (3 + 3) stamen six, gynoecium syncarpous, ovary superior with many ovules. Fruit is capsule and seeds are endospermous.
Plants of this family are good ornamentals (Tulip, Gloriosa), source of medicines (Aloe), vegetables (Asparagus) and colchicine.