Question

Pollination of pollen grains in Pinus takes place at
A)One celled stage
B)Two celled stage
C)Three celled stage
D)Four celled stage

Answer 1

Hint: Pollination in the pinus involves the transport of pollen by the wind. The pale-yellow pollen grains are caught by the female cone and then it transfers to the pollen tube present in the cone to the micropyles of the ovules.

Complete answer:
The cones of coniferous pines contain the male and female gametophyte. Because female gametophyte is larger than the cones of male gametophyte and their position towards the top of the tree. the male cones present on the lower side of the tree because it shed pollen grains that are blown by the wind. Due to this arrangement of the cones of pine, it is difficult for a gymnosperm to self pollinate.
-There is a central axis on the male cone, where the modified type of leaf that is bracts are attached known as microsporophylls. These are the sites where the microspores will develop inside the microsporangium.
-The microscopes are the wind in the finals and consists of two prothallial cells. The prothallial cells start to disintegrate before the pollination takes place.
-Pollination in the finals takes place at the four-cell stage i.e two prothallial cells, a generative cell, and a tube cell.
-Two non-motile male gametes developed from generative cells are present in the pinus without any cilia. Pinus will take about one full year to complete the entire process of male gametophyte.
-the pollens are hanging downwards into the archegonial chamber of the pinus and function as a sperm carrier.

Additional Information: -The pollen grains are produced in a very large number and they are transported to a very long distance by air currents.
-At the time of pollination, the ovuliferous scales separated from the megastrobili and pollen grains that trapped in the pollination droplet of the micropyles of the ovules.
-The pollen grain transferred through the micropyle by contraction and reaches to a surface of a small depression called pollen chamber present at the tip of the megasporangium.
-As the germination of pollen grains takes place it forms a tube through the megasporangium and arrives at the female gametophyte. The female gametophyte matures into several archegonia. The pollen tube discharge is sperm nuclei into the archegonia and in this way, fertilization is done.
So, the correct answer is, "four celled stages".

Note: -At the time of shedding of the pollen grains, the microspore has only one prothallial cell or two prothallial cells and later liberated at the three-cell stage and Four celled stages.
-The pinus is popularly called as 'sulfur showers' because pollination especially takes place in the spring season when trees are shedding off their pollen grains.