trace and explain the step involved in the formation of seed
Answers
Seed germination begins when the first root breaks through the seed wall and ends when the first pair of true leaves begin the process of photosynthesis. The three stages in-between are when the primary root, which is called the radicle, develops root hairs, the first young shoot rises emerges from the soil and the first pair of true leaves form to begin to manufacture food for the plant.
Successful germination depend on several factors occurring in harmony with one another. The seed must first be viable, or alive, and in most cases, it must have undergone a period of cold temperatures. This process is called stratification. When the right combination of water and warmth is present, the seed coat ruptures, allowing the radicle to emerge. This initial root also serves to anchor the seedling to the soil so that small amounts of water and wind pose less of a threat to its survival.
After the radicle develops small root hairs that begin to take nutrients from the soil, the first shoot, called the plumule, emerges from the soil. The plumule will contain two cotyledons, which are not true leaves but rather photosynthetic material that is actually formed during the embryonic period. Cotyledons are larger than true leaves and serve to photosynthesize as much energy as possible for the growing plant. When the cotyledons begin to grow smaller and turn yellow, the first true leaves begin to emerge from the plumule.
Soon after the true leaves emerge, the cotyledons will shrivel up and fall from the plant. Germination is complete when the new leaves begin to photosynthesize energy from the sun to promote the plant's growth.
→ A flower consists of two parts. One is male part and another is female part.
* Male parts consists of long, stalk part called Filament and upper broad portion called Anther. Anther contains pollen grains.
* Female parts consists of upper broad portion called Stigma. Middle thin part called Style and the lower portion called Ovary. Ovary conatins ovule.
→ When a pollen grain reach the stigma of the flower then it secretes some liquid substance which is absorbed by pollen grain. After it they form a pollen tube which ultimately reach the ovule of the ovary.
→ Now, the two male gamates (pollen grains) start travelling through this pollen tube amd reach the ovule of the ovary, which contains egg and two polar nuclei.
→ When a male gamate fuse with egg then it forms zygote by the process of fertilization and this type of fertilization in plants is known as Syngamy. And when a another male gamate fuse with two polar nuclei, it is known as triple fussion; then it form primary endosperm nucleus.
* Since, the fusion occurs two times. So, this type of fusion is known as as Double Fusion.
→ After is the zygote develops into the embryo and the primary endosperm nucleus into endosperm which provides nourishment to the growing embryo.
* After it the ovule develops into seed and ovary into fruit.
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