12. During reproductive development in plants:
    (A) male and female gametes are produced as a result of two mitotic divisions after meiosis
    (B) vegetative cells in pollen contribute to pollen development
    (C) antipodal provide nourishment to developing embryo
    (D) Pollen tube ruptures and releases both the male gametes in one of the degenerated
    synergids
    Which of the above statement are true?
    (1) A and B (2) B and D
    (3) B and C (4) A and D

The correct statements regarding reproductive development in plants are:

(A) Male and female gametes are produced as a result of two mitotic divisions after meiosis — This is correct. After meiosis, the microspore divides mitotically twice to produce the male gametophyte containing two sperm cells, and similarly in the female gametophyte, mitotic divisions lead to the development of the embryo sac which houses the egg cell.

(B) Vegetative cells in pollen contribute to pollen development — This is correct. The vegetative cell forms the pollen tube, facilitating sperm delivery.

(C) Antipodal cells provide nourishment to the developing embryo — This statement is incorrect. Antipodal cells are located at the chalazal end of the embryo sac and generally degenerate soon after fertilization; they have no established role in nourishing the embryo.

(D) Pollen tube ruptures and releases both the male gametes in one of the degenerated synergids — This is true. The pollen tube typically enters the embryo sac via one of the synergid cells, which degenerates to allow the release of the two sperm cells.

Hence, the correct combination is:

(2) B and D.

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Introduction

Sexual reproduction in flowering plants involves complex developmental steps leading to the formation of male and female gametes and their interaction during fertilization. Key players in this developmental phase include the vegetative and generative cells of pollen and the synergid cells within the female embryo sac. Understanding these processes clarifies the functional anatomy of plant reproduction.

Male and Female Gamete Formation

• After meiosis, the male microspore undergoes two mitotic divisions: the first produces a vegetative cell and a generative cell, and the second division of the generative cell produces two sperm cells that act as male gametes.

• The female gametophyte (embryo sac) forms through mitotic divisions from the megaspore and contains the egg cell (female gamete) and accessory cells.

Role of Vegetative Cells in Pollen

• The vegetative cell forms the pollen tube, which grows through the style to deliver sperm cells to the ovule.

• It provides metabolic support and directional growth ensuring delivery of male gametes.

Function of Synergid Cells

• Synergids are located at the micropylar end of the embryo sac and help guide the pollen tube into the embryo sac through chemical signaling.

• When the pollen tube reaches the synergid, the synergid degenerates, allowing discharge of the two sperm cells into the embryo sac for fertilization.

Antipodal Cells and Nourishment

• Antipodal cells, located opposite the micropyle, generally degenerate early and do not provide nourishment to the embryo.

• Nutritional support for the embryo mainly comes from the endosperm formed post-fertilization.

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Summary Table: Evaluation of Statements on Plant Reproductive Development

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Conclusion

Among the given statements, (B) and (D) are correct: vegetative cells are crucial for pollen tube development, and the pollen tube releases sperm cells by bursting through a degenerated synergid cell. Statements regarding gamete formation and antipodal function are incorrect or misleading.