Question

What does the pollen tube carry?

Answer 1

Hint: Pollen tube is a long tube-like structure that is present in the female structure. It is a passage for the male gamete towards the ovary of the female. Transferring of the gamete takes place in the process of gamete transfer.

Complete answer:
Let us first infer about the process of gamete transfer :
After the formation of the male and female gamete, they must be in physical contact so as to facilitate fusion. In the majority of the organisms, the male gamete is motile whereas the female gamete is stationary except in a few cases of a few fungi and algae. In seed plants, pollen grains are the carriers of male gamete and ovules have the egg. Pollen grains produced in anthers, therefore, have to be transferred to the stigma before it can lead to fertilisation.

In bisexual self-fertilising plants eg, peas, transfer of pollen grains to the stigma is relatively easy as anthers and stigma are located close to each other: pollen grain soon after they are shed come in contact with the stigma.

But in cross-pollinating plants, a specialised event called pollination facilitates the transfer of pollen grain to the stigma. Pollen grains germinate on the stigma and the pollen tubes carrying the male gametes reach the ovule and discharge male gametes near the eggs. Successful transfer and coming together of gametes is essential for the most critical event in sexual reproduction, fertilization.

Pollen tubes are mainly the product of male gametophytes which pass through the style and help in the transportation of pollen grains to the ovules, which are present at the base of the pistil in the ovary. It is mainly situated in the style.

Note: Pollen grains are the male reproductive part that is usually spherical in shape. It has a prominent two-layered wall, the hard outer called the exine which is made up of sporopollenin and the inner intine which is thin and continuous made up of cellulose and pectin. Pollen grains of many species can cause severe allergies and bronchial infections in some people often leading to chronic respiratory disorders like asthma, bronchitis etc.