16.3 Sexual reproduction in plants

Flower structure of insect-pollinated flowers (sepals, petals, stamens — anther + filament — and carpels — stigma + style + ovary + ovules) and the functions of each named part. Pollination as transfer of pollen from anther to stigma. Fertilisation as the fusion of a pollen nucleus with a nucleus in an ovule. Distinction between insect- and wind-pollinated flowers — their structural adaptations and pollen grain features. Environmental conditions affecting germination (water, oxygen, suitable temperature). HL extension: self-pollination vs cross-pollination and their effects on population variation; growth of the pollen tube down the style into the ovule.