Pollination

In the syllabus and the exam

Pollination opens the topic of sexual reproduction in flowering plants and is one of the terms most frequently confused with fertilisation, so nearly every examination touching this area tests whether candidates can separate the two clearly: pollination is purely the physical transfer of pollen grains from an anther to a stigma, while fertilisation is the later fusion of nuclei that only becomes possible after a pollen tube has grown down to the ovule. Candidates are expected to distinguish self-pollination, where pollen moves from the anther to the stigma of the same flower or another flower on the same plant, from cross-pollination, where pollen moves between flowers on genetically different plants, and to state that cross-pollination is generally linked to greater genetic variation in the offspring. Structured questions often ask candidates to identify features of a flower adapted for either insect pollination or wind pollination, such as bright petals and scent versus small, dull, feathery flowers with exposed anthers and stigmas. A common error is stating that pollination directly produces a seed or a zygote; pollination only brings pollen into contact with the stigma, and several further steps, including pollen tube growth and fertilisation, must still occur before a zygote or seed can form. Candidates should also be able to explain why cross-pollination is generally considered more advantageous for a species over time than continuous self-pollination, linking the resulting greater genetic variation to a population's ability to survive changing environmental conditions or new diseases. This is also why some crops grown in enclosed greenhouses rely on introduced bees or manual pollen transfer by hand, since the usual wind or insect pollinators found outdoors may not reach the flowers under such controlled growing conditions.

Example

Distinguishing pollination from fertilisation, a candidate writes: 'Pollination is the transfer of pollen grains from the anther to the stigma, which must happen before fertilisation, the fusion of the male and female nuclei, can take place.'

Related terms

AntherStigmaFertilisation

Source:SRC-DSKP-EN