Biology Module 3 - 2.sexual reproduction in flowering plants 2.6 explain the sequence of events from pollination to fertilization

2.6 explain the sequence of events from pollination to fertilization. diagrams required


diagram of fertilization

source

• Pollination - pollen grains land on stigma which they then absorb water and sucrose and germinate

• a pollen tube emerges from one of the pores through the exine and grows on the stigmatic tissue and then down through the style towards the ovule
• genes in the tube nucleus are transcribed and translated to provide proteins needed for the growth of the tube

• enzymes are secreted by the tube to digest a pathway

• during the growth, the generative tube nucleus divides by mitosis to give two haploid male gamete nuclei

• the tube enters the micropyle and the tip of the tube break down so male gamete nuclei can enter the embryo sac

• one of the nuclei fuses with the ovum nucleus to form the diploid zygote nucleus and the other fuses with diploid nucleus in the center of the embryo sac to form a triploid endosperm. This is double fertilization.

NB Diploid nucleus in the center of the embryo sac is the diploid nucleus which was formed from the fusion of the two polar nuclei.