Fertilisation In plants

Learning outcome Describe the process of fertilisation in flowering plants. Starting with pollen tube growth and ending with the fusion of the nuclei

Parts of a flower

The pollen grain Male gametes are found in pollen grains Each grain contains 2 haploid nuclei – a tube nucleus and generative nucleus. Grain lands on surface of stigma = pollination If stigma is of same species, it secretes substances that allow pollen grain to germinate. Outer wall = Exine Inner wall = Intine

Part 1: Pollen germination Tough outer coating breaks down and a pollen tube grows out. Generative nucleus divides by mitosis to form 2 male gametes

Part 2: Pollen tube growth Pollen tube grows down the style. It secretes enzymes and digests style and uses products to continue tube growth. The tube nucleus controls growth of tube Tube enters the ovule through a little gap called the micropyle Pollen tube nucleus degenerates

Clip http://www.bbc.co.uk/learningzone/clips/fertilisation-in-plants/120.html

Part 3: Fertilisation One male gamete fuses with female gamete and produces a diploid zygote (2n) The other male gamete fuses with the two haploid polar nuclei to form a triploid endosperm nucleus. (3n) This becomes the endosperm (nutrient store)