. What do you mean by Zygote and its Germination


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ZYGOTE AND ITS GERMINATION

Disappearance of flagella from quadriflagellate zygote of isogamous or anisogamous species is followed by the formation of a wall around it. The two nuclei fuse and it becomes a spherical structure, which undergoes a period of rest. It secretes a thick wall, which may be smooth and spiny. The resting zygote enlarges to 2-5 times of its original size, owing to the accumulation of reserve food material during photosynthesis. However, there are few species, in which there is no increase in size of the resting zygote that develops a red pigment, called hematochrome. In C. eugametos, however, zygotes remain green.

 

When the resting period is over and the conditions are favourable, the zygote germinates. The diploid nucleus undergoes reduction division and forms four nuclei and the cytoplasm gets accumulated around each nucleus. The daughter protoplasts are liberated to the outside by the breaking up of the zygote wall. Thus, the new cells formed are usually four in number, from a single zygote. But in some species, there may be eight (c. reinhardi) or 16 to 32 (c. intermedia) biflagellate zoospores.

 

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