Sexual reproduction in plants — Cambridge IGCSE Combined Science

Revision notes

4 short notes, in the order of the specification. Each one in short:

1. Structure of an insect-pollinated flower

   Practical

   An insect-pollinated flower has a male part, the stamen, and a female part, the carpel. The anther in the stamen produces pollen grains containing the male gametes, and the filament holds it up. The stigma receives pollen, the style holds it up, and the ovary contains ovules, which develop into seeds after fertilisation. Petals attract insects.

2. Insect- and wind-pollinated flowers

   Supplement

   Insect-pollinated flowers have bright petals, nectar and sticky pollen; wind-pollinated flowers have small petals, light pollen and feathery stigmas.

3. Pollination and fertilisation

   Pollination is the transfer of pollen grains from an anther to a stigma; fertilisation is the fusion of a pollen nucleus with a nucleus in an ovule.

4. Germination

   Practical

   Germination is when a seed begins to grow into a new plant, and it needs water, oxygen and a suitable temperature. Water makes the seed swell and activates its enzymes, oxygen is needed for aerobic respiration, and enzymes work best at a suitable temperature. Light is not needed for most seeds, so investigation tubes are kept in the dark.