Which one of the following statements is not true ?

Megaspore divides twice to form an eight nucleate embryosac

The correct answer is Option (3) - Megaspore divides twice to form an eight-nucleate embryo sac.

The statement that is not true is Megaspore divides twice to form an eight-nucleate embryo sac.

In flowering plants, the megaspore mother cell undergoes meiosis and forms four haploid megaspores. One of these megaspores is functional and undergoes three rounds of mitosis to form the mature embryo sac. The mature embryo sac contains seven cells and eight nuclei.

The other statements are all true.

• Pollen grains are released from anthers at a 2-celled state. The two cells are the vegetative cell and the generative cell.
• The sporogenous cell directly behaves as the microspore mother cell. As the anther develops, the cells of the sporogenous tissue undergo meiotic divisions to form microspore tetrads.Each one is a potential pollen or microspore mother cell. The process of formation of microspores from a pollen mother cell (PMC) through meiosis is called microsporogenesis. The microspores, as they are formed, are arranged in a cluster of four cells–the microspore tetrad.
• Endosperm is triploid. Endosperm is formed by triple fusion in which male gamete fuses with the diploid secondary nucleus and results in the formation of a triploid primary endosperm mother cell which develops into endosperm. So, the endosperm is triploid.