Sexual Reproduction in Flowering Plants

Wind pollination is a chance event, so wind-pollinated flowers produce enormous amounts of light, non-sticky pollen and have well-exposed stamens and large, feathery stigmas.
Such flowers often have a single ovule in each ovary and numerous flowers packed into an inflorescence, e.g., the corn cob, where each grain develops from an ovary with one ovule.
Having one ovule per ovary suits the low probability of many pollen grains landing on the same stigma.
Flowers pollinated by bees, butterflies and birds usually receive many pollen grains in a single visit and commonly have ovaries with many ovules.
Hence plants with ovaries having one or a few ovules are generally pollinated by wind.

The pollen grain has a two-layered wall: an outer hard exine made of sporopollenin and an inner thin intine made of cellulose and pectin.
The exine has prominent apertures called germ pores, where sporopollenin is absent.
When the pollen grain germinates on the stigma, the intine grows out through one of the germ pores to form the pollen tube.
The radicle emerges and water is absorbed through the micropyle of the seed, not through the germ pore; male gametes are released from the tip of the pollen tube inside the synergid.
Hence the function of the germ pore is the initiation of the pollen tube.

In over 60 per cent of angiosperms, pollen grains are shed at the two-celled stage (a vegetative cell and a generative cell).
In such plants the generative cell divides to form the two male gametes during the growth of the pollen tube in the stigma and style.
So two male gametes are still delivered to the embryo sac: one fuses with the egg (syngamy) and the other with the two polar nuclei (triple fusion), i.e., double fertilisation does take place.
Therefore the statement that double fertilisation does not take place when pollen is shed at the two-celled stage is wrong.
The other statements are true: the intine is made of cellulose and pectin; the vegetative cell is bigger, with abundant food reserve; and pollen of some members of Rosaceae, Leguminosae and Solanaceae remains viable for months.
Hence the wrong statement is 'When pollen is shed at two-celled stage, double fertilization does not take place'.