Question:

The arrangement of the nuclei in a normal embryo sac in the dicot plants is-

Updated On: Jul 21, 2024

3 + 3 + 2
2 + 4 + 2
3 + 2 + 3
2 + 3 + 3

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The Correct Option is C

Solution and Explanation

Megaspore is the initial cell or beginning of female gametophyte or embryo sac. The nucleus of megaspore undergoes divisions and gives rise to embryo sac or female gametophyte, which is called megagametogenesis. During development, the single nucleus of functional megaspore (of chalazal end) undergoes 3 mitotic divisions to form 8 nuclei. Out of these 8 nuclei, 4 are present at micropylar end and 4 at chalazal end. One nucleus from each group comes in centre to form 2 polar nuclei. Remaining 3 nuclei at micropylar end constitute egg apparatus and remaining 3 nuclei at chalazal end constitute 3 antipodal cells or antipodals. So it is 3 + 2 + 3 arrangement. So fully developed normal type of female gametophyte or embryo sac is 8-nucleated and 7-celled structure.

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Concepts Used:

Pre-fertilization events - Monoecious Plant

Fertilization in plants may be a process during which they undergo amphimixis in consequence of pollination and germination. During a physicochemical process, the male gametes (known as pollen) infusion with the feminine gametes (known as ovum) forms diploid zygote after carpal pollinates. The whole process happens in a zygote which later germinates into a seed. During the method, what happens is male gametes are transferred into female reproductive organs through pollinators (butterflies, birds, honey bees, bats, and flower beetles). This leads to an embryo being formed during a seed. Flowers are the reproductive organs of angiosperms and reproduce in a completely different method.

Read More: Flower Structure

The two important pre-fertilization procedures are gametogenesis and gamete transfer. The female and male reproductive forms in flowers are the androecium and the gynoecium which distinguishes and goes through development.

"Mono" means single so a monoecious plant is one that bears both male and female sex organs on same plant. The monoecious plant can produce bisexual flowers or unisexual flowers. A dioecious plant is one that bears both male and female sex organs on different plants.

Read Further: Sexual Reproduction in Flowering Plants