NEET BIOLOGY

Detailed explanation-1: -The pollen grain contains two nuclei the generative and tube nucleus. The pollen tube develops from the pollen grain that falls on the stigma and grows towards the ovary. Nuclei of the pollen enter the pollen tube and travel along to reach the ovary.

Detailed explanation-2: -A pollen grain has two nuclei-a generative nucleus and tube nucleus. The generative nucleus divides in the pollen tube to form two male gametes. The tube nucleus eventually disintegrates.

Detailed explanation-3: -Most pollen grains consist of three distinct parts. The central cytoplasmic part is the source of nuclei responsible for fertilization. The other parts constituting the wall of the grain are an inner layer, the intine, and an outer layer, the exine. The intine consists, at least in part, of cellulose or hemicellulose.

Detailed explanation-4: -The germ nucleus or generative nucleus undergoes fertilization. The tube nucleus is the vegetative nucleus that guides the growth of the pollen tube when it enters the pistil. The main function of a tube nucleus is to control and direct the growth of the pollen tube.

Detailed explanation-5: -Pollen-tube pathway During the pollination process of higher plants, after the pollen germinates on the stigmatic surface, a pollen tube is formed from the pollen and extends down the style into the ovule; nuclei from the pollen travels through the pollen tube to fertilize the ovule.