Describe structure of dicotyledonous seed.
Answers
Peas and grams are examples of dicotyledons. In dicotyledons, the embryo consists of an embryo axis and two cotyledons. Cotyledons are generally swollen part which acts as a food reserve for the developing seedling. The embryo axis has two ends. The one which forms the shoot tip is called plumule and the portion at the lower end which forms the root tip is called radicle. The whole content is enclosed within a protective cover, seed coat. The seed coat is made up of an outer layer called testa and an inner layer called tegmen. And a seed is attached to the fruit through a structure called hilum.
Endosperm is the third component of the seeds, others being embryo and seed coat. It is formed by the double fertilization. It consists of reserved food materials. In some plants, as the seeds mature, the endosperm is fully used by the embryo. Such seeds are devoid of endosperm and are called non-endospermous seeds; also called non-albuminous seeds (e.g. peas, beans, and groundnut).
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Answer:-
★ Structure of dicotyledonous seed:-
→ The outermost covering of a seed is the seed coat.
→ Seed coat has 2 layers: outer testa and inner tegmen.
→ The hilum is a scar on the seed coat through which the developing seeds were attached to the fruit.
→ Above the hilum is a small pore called the micropyle.
→ Within the seed coat is the embryo, consisting of an embryonal axis and two cotyledons.
→ The cotyledons are often fleshy and full of reserve food materials. At the two ends of the embryonal axis are present the radicle and the plumule.
→ 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 seeds are non-endospermous where endosperm is not seen in mature seeds.
★ Note:- Look into the attechment for the diagram.
