Germination of Seeds

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A seed consists essentially of a seed coat, stored food and a young plant, the embryo. The seed coat may be made of inner tegmen and outer testa. On the seed coat a scar (hilum) is present which shows the place of attachment of a seed in the fruit is present. At one end of the hilum is the micropyle. Through micropyle the seed absorbs water during the process of germination.

The embryo consists of epicotyl,one or two seed leaves called cotyledons, and a hypocotyle. The portion of the embryo above the point of attachment of cotyledons to embryo axis, and below the plumule is called epicotyl. The plumule forms shoot.the portion of the embryo below the point of attachment of cotyledons to embryo axis but above the radicle, is called hypocotyls. The radicle forms root.

The seed also contain the food, derived from the endosperm tissue. The food may remain as such or may be digested and stored in the cotyledons. Thus the cotyledons become thick due to the presence of stored food. This food is supplied to the developing plant during the process of germination of seeds. In the grain of maize, the cotyledon is modified into an organ called scutellum a term that comes from the Latin word meaning “Shield”. The food stored in scutellum is used first during germination of seed. Later on scutellum absorbs the food of endosperm and supply it to the developing embryo.

“The maize grain is infact a single seeded fruit in which seed coat fruit wall is fused.”

Practical Work: investigating structure of seed of gram and maize

With the help of hand lens locate micropyle and hilum of the two seeds. With the help of scalpel cut the seeds longitudinally and observe different parts of the embryo along with endosperm with the help of (fig 16.11)

1. What is the function of micropyle?

2. Why can’t you find endosperm in gram seed?

Fig. 16.11 Structure of seed of gram (a) and maize grain (b)

16.5.1 Seed germination

During germination (growth and development)...
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