draw a well labelled diagram of storage of germination in a bean seed
Answers
The following three points will highlight the three main types of seed germination.
The three main types are: (1) Hypogeal Germination (2) Epigeal Germination and (3) Vivipary (Viviparous Germination).
Type # 1. Hypogeal Germination:
In this kind of germination, the cotyledons do not come out of the soil surface. In such seeds the epicotyl (i.e., part of embryonic axis between plumule and cotyledons) elongates pushing the plumule out of the soil. All monocotyledons show hypogeal germination (Fig. 4.3, 4.4, 4.5). Among dicotyledons, gram, pea (Fig. 4.2), groundnut are some common examples of hypogeal germination.
Distinction between epigeal and hypogeal type of germination
In monocotyledons (e.g., wheat, maize, rice, coconut) radicle and plumule come out by piercing the coleorrhiza and coleoptile respectively. The plumule grows upward and the first leaf comes out of the coleoptile. The radicle forms the primary root which is soon replaced by many fibrous roots.
(i) Germination of Pea Seed:
The seed imbibes water and swells. The radicle comes out and first penetrates the soil and forms root system by giving out secondary branches. It is the epicotyls which grows first. It arches out and carries the plumule above ground. The plumule soon forms the aerial shoot. The cotyledons remain under the soil throughout (Fig. 4.2).
Successive stages of hypogeal germination of dicotyledonous exalbuminous seed of pea
(ii) Germination of Maize Grain:
The grain imbibes water from moist soil. The coleorhiza pierces the base of caryopsis (fruit) and appears as a shining knob. After sometimes, the coleorhiza gets ruptured due to growth of radicle. After sometime coleoptile comes out.
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