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Evaluation · Q44

Q.'The endosperm of angiosperm is different from gymnosperm'. Do you agree? Justify your answer.

Tamil Nadu DgeTextbookSubjectiveImportance★★★★★
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Step 1. In angiosperms, the chapter shows that endosperm forms specifically from the Primary Endosperm Nucleus (PEN), itself the product of triple fusion - the second male gamete fusing with the two polar nuclei (or secondary nucleus) of the central cell.

Step 2. Because triple fusion combines three haploid nuclei, the angiosperm PEN, and the endosperm it develops into, is triploid (3n).

Step 3. Critically, this angiosperm endosperm cannot exist until AFTER fertilization has occurred, since triple fusion is itself part of the double-fertilization event.

Step 4. In gymnosperms, by contrast, there is no double fertilization at all - only one male gamete is used, fusing with the egg to form the zygote - so what is loosely called 'endosperm' in a gymnosperm seed is actually the haploid (n) female gametophyte tissue, which develops from the megaspore BEFORE fertilization and simply persists afterward to nourish the embryo. …

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