Question

Biology discussion explain monocot dicot seed strucutre

Answer 1

Answer:

i. Maize Grain:

The maize grain is really a one-seeded fruit and not a seed, hence it is called a grain. The seed coat and the fruit wall or pericarp are inseparably united in the maize grain to form the outer pale yellowish coat.

A whitish deltoid area is noticed on one side of the grain which marks the position of the embryo. The embryo can be clearly seen if the grain is cut into two parts along the longer axis. It occupies only a very small portion of the grain, the remaining part being endosperm or stored food.

The embryo has an axis with radicle and plumule. The radicle is surrounded by a sheath called radicle sheath or coleorhiza, and the plumule has a similar sheath called plumule sheath or coleoptile.

A shield-shaped body, called scutellum, lies between the axis of the embryo and the endosperm, thus divi­ding the grain into two unequal parts. Scutel­lum is the single coty­ledon of the maize grain. It absorbs food from the endosperm for the embryo to be used during germina­tion. Maize grain is monocotyledonous albuminous (Fig.22).

Structure of maize grain

Germination of Maize Grain:

During germinations of the maize grain the radicle at first comes out boring through the coleorhiza or radicle sheath and forms the primary root. This root does not persist but dies and is replaced by a tuft of adventitious fibrous roots from the base of the stem. In the meantime the plumule goes upwards with the plumule sheath or coleoptile.

After growing to some extent the plumule pierces the sheath and grows up to produce the green aerial organs. Scutellum or the single cotyledon continues to supply food matters to the growing embryo during germination. The mode of germination in maize grain is also hypogeal (Fig. 29). Rice (Fig. 30) and other grains also have this type of germination.

Stages in the germination of maize grain

In cocoanut the innermost layer of fruit wall is the shell having three eye-like scars, and the embryo lies below one of the scars. The white kernel including the milk is the endosperm. During germina­tion the lower end of the embryo—the cotyledon begins to grow as a spongy structure to absorb food materials stored in the endosperm.

The upper end of the embryo grows through the eye carrying the spongy structure to absorb food materials stored in the endosperm. The upper end of the embryo grows the eye carrying the radicle and the plumule; pierces through the fibrous coat and ultimately establishes itself.

Special Type of Germination:

Plants growing in saline marshes or near sea-shore show a peculiar type of germination known as vivipary. In that case, the seeds begin germination before their liberation from the fruits (Fig. 31). The radicle becomes elongated and considerably swollen.

Then the seed gets detached from the parent plant and comes vertically downwards. The radicle pierces the muddy soil below and thus gets fixed. Lateral roots are soon formed for anchorage, and the plumule is kept above the surface of Valine water. Examples: Rhizophora, Ceriops.

Viviparous germination

Answer 2

Answer:

Dicots have two seed leaves inside the seed coat. They are usually rounded and fat, because they contain the endosperm to feed the embryo plant. When a monocot seed germinates, it produces a single leaf. It is usually long and narrow, like the adult leaf. Mark brainliest