(i) Prepare the pollen germination medium by dissolving 10g sucrose, 30mg calcium nitrate and 10mg boric acid in 100ml of distilled water. Alternatively 10% sucrose solution can also be used. (ii) Take a drop of medium or 10% sucrose solution on a cover slip and sprinkle mature pollen grains on the drop.

Growth and signaling Pollen tube growth is influenced by the interaction between the stigma-style and the pollen grain. The elongation of the tube is achieved with elongation of the cytoskeleton and it extends from the tip, which is regulated by high levels of calcium in the cytosol.

Ionic elements, such as boron and calcium, that are involved in the metabolism during pollen tube growth, and at different concentrations can stimulate or inhibit it. Naturally occurring polyamines such as spermine also stimulate pollen tube germination and elongation when they are sprayed on the stigma.

During germination, the tube cell elongates into a pollen tube. In the flower, the pollen tube then grows towards the ovule where it discharges the sperm produced in the pollen grain for fertilization. The germinated pollen grain with its two sperm cells is the mature male microgametophyte of these plants.

The results of many studies indicate that calcium is a critical element that is strongly related to pollen germination and pollen tube growth.

Boric acid significantly promoted the germination of pollen and tube growth. Promotion of germination was most notable at boric acid concentration of 0.01%. Pollen germination rate and tube growth increased significantly compared with that in the boric acid-deficient media (control media).

Studies of pollen germination in vitro show that in some species the uptake of water is sufficient stimulation to initiate the germination process. In others, sugars and a few minerals are required [1].

approximately 60–65 days

The pollen tube invades the pistil, growing between the walls of the stigmatic cells, then traveling through an extracellular matrix within the transmitting tissue of the style. The pollen tube finally arrives at the ovary, where it is attracted to an ovule that contains an egg cell.

Generally, only one pollen tube is inserted into the ovule; however, we previously found that if fertilization by the first pollen tube fails, a second pollen tube could rescue fertilization via the so-called fertilization recovery system (FRS).

After the pollen tube enters the female gametophyte, it ruptures and releases two sperm cells with its contents. The two sperm cells then move toward and fuse with the egg cell and central cell to produce embryo and endosperm, respectively.

Pollen grains carry male reproductive cells (gametes) in a plant and are haploid microgametophytes.

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.

The size and appearance of pollen grains is extremely varied, with a range in size from very small (5-7 microns*) to quite large (over 200 microns), and wide variation in shape and ornamentation also. Most pollen grains probably fall in the size range of 30-40 microns.

“Pollen grains in wheat are shed at 3-celled stage while in peas they are shed at 2-celled stage.” Explain. Where are germ pores in a pollen grain?

The most striking feature of the pollen grain is the tough, resistant outer coat termed the exine which is often elaborately sculptured.

In flowering plants pollen comprises either two or three cells when shed from the flower. Both pollen types possess a large vegetative cell containing within, a single generative cell (bicellular pollen) or sperm cell pair (tricellular pollen). Pollen shows a wide variation in size, shape and surface patterning.

You experience an allergic reaction because your immune system falsely believes pollen is dangerous. In an attempt to fight against the “foreign invader”, your immune system releases antibodies to attack the pollen particles. This produces a chemical known as histamine, which causes traditional allergy symptoms.