13. Sperm cell behaviour during double fertilization in Arabidopsis can be stated as follows. Identify the INCORRECT statement:
    (1) Pollen tube bursts and discharges sperm cells.
    (2) Pollen cells produce pollen tubes and enter into female gametophyte.
    (3) The receptive antipodal cells break down when pollen tube enters the female gametophyte.
    (4) One sperm nucleus fuses with the egg cell and the other fuses with the central cells.

The incorrect statement regarding sperm cell behavior during double fertilization in Arabidopsis is:

(3) The receptive antipodal cells break down when pollen tube enters the female gametophyte.

This is incorrect because antipodal cells are located at the chalazal end of the embryo sac and generally degenerate on their own later; the pollen tube interacts with synergid cells, not antipodal cells.

The other statements are correct:

(1) Pollen tube bursts and discharges sperm cells.

(2) Pollen cells produce pollen tubes and enter into female gametophyte.

(4) One sperm nucleus fuses with the egg cell and the other fuses with the central cell.

---

---

Introduction

Double fertilization in Arabidopsis involves the coordinated delivery of two sperm cells by the pollen tube into the female gametophyte. Understanding the specific interactions and roles of different cells within the embryo sac clarifies fertilization mechanisms and dispels misconceptions, especially regarding antipodal cells.

Correct Sperm Cell Behavior in Arabidopsis Fertilization

• The pollen tube penetrates the embryo sac and bursts to release two sperm cells as stated in (1).

• Pollen cells generate pollen tubes that grow through the style into the female gametophyte, facilitating sperm cell delivery (2).

• One sperm fertilizes the egg cell, forming the embryo, while the other fertilizes the central cell to generate the endosperm as in (4).

• Pollen tube entry occurs through a synergid cell, not an antipodal cell.

Clarifying The Role of Antipodal Cells

• Antipodal cells are located at the chalazal end of the embryo sac opposite the micropyle and generally degenerate naturally during or after fertilization.

• They do not serve as receptive structures for the pollen tube or contribute directly to fertilization, unlike synergid cells.

---

Summary Table: Fertilization Interaction in Arabidopsis

---

Conclusion

Among the given statements regarding sperm cell behavior during double fertilization in Arabidopsis, statement (3) involving antipodal cell role is incorrect. The pollen tube interacts with synergid cells, releasing sperm for fusion with egg and central cells, while antipodal cells are largely passive.