how is pollen tube formed?
Answers
Vegetative cells in the plant produce and develop the pollen tube.
Pollen grains settle on pistils and germinate in presence of sugary fluids and lipids produced by stigma of plants. Multiple pollen grains stimulate a quick growth of pollen tube. The vegetative cells produce the pollen tube or a simple protrusion from the pollen grain. After germinating the pollen tube drills its way. It does not cause much damage to the tissue of the plant on its way. It curls and is rich in nutrients too. Then it reaches the bottom of the ovary and reaches the ovule. Then two sperm cells (male gametes) are delivered together with some thrust. Thus the egg cell is fertilized.
Pollen tube polymerizes quickly and so grows very fast. It extends always from its top. The growth happens in pulses ie., in bursts.