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Question
Assertion :Endosperm is a nutritive tissue and it is triploid. Reason: Endosperm is formed by fusion of secondary nucleus to second male gamete. It is used by developing embryo.
Assertion :Endosperm is a nutritive tissue and it is triploid. Reason: Endosperm is formed by fusion of secondary nucleus to second male gamete. It is used by developing embryo.
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Solution
The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
The eight nucleate female gametophytes of flowering plants have an egg apparatus at micropylar end which in turn has one egg cell and two flanking cells. The flanking cells are known as synergids and serve as site for entry of pollen tube. Three cells present at chalazal end of embryo sac are called as antipodals. One nucleus from each pole migrates to middle and forms diploid secondary nucleus. Pollen tube penetrates the stylar canal and enters the ovule through micropyle chalaza or integument followed by discharge of male gametes in embryo sac. One male gamete fuses with egg nucleus (syngamy) to form diploid embryo. And the other male gamete fuses with diploid secondary nucleus/central cell (triple fusion) to form triploid primary endosperm nucleus which in turn divides to form large nutritive endosperm. Assertion is correct. Endosperm serves as source of food material to the growing embryo and also to seedling. Reason is correct as endosperm is triploid because of being the product of triple fusion between diploid secondary nucleus and haploid male gamete. Thus, the correct answer is option A.
The eight nucleate female gametophytes of flowering plants have an egg apparatus at micropylar end which in turn has one egg cell and two flanking cells. The flanking cells are known as synergids and serve as site for entry of pollen tube. Three cells present at chalazal end of embryo sac are called as antipodals. One nucleus from each pole migrates to middle and forms diploid secondary nucleus. Pollen tube penetrates the stylar canal and enters the ovule through micropyle chalaza or integument followed by discharge of male gametes in embryo sac. One male gamete fuses with egg nucleus (syngamy) to form diploid embryo. And the other male gamete fuses with diploid secondary nucleus/central cell (triple fusion) to form triploid primary endosperm nucleus which in turn divides to form large nutritive endosperm. Assertion is correct. Endosperm serves as source of food material to the growing embryo and also to seedling. Reason is correct as endosperm is triploid because of being the product of triple fusion between diploid secondary nucleus and haploid male gamete.
Thus, the correct answer is option A.
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