Biology · Oct / Nov 2018 · Paper 22 · Question 3

The diagram shows a pollen grain with a pollen tube growing from it. Pollen grains from the same type of plant were placed in sucrose solutions of different concentrations for a fixed amount of time. After this time, the pollen grains and tubes were examined using a microscope. The following observations were made for each concentration of sucrose: • the number of pollen grains that had germinated to produce a pollen tube, • the length of each pollen tube. The table shows the results of the investigation. % sucrose concentration % of pollen grains germinated mean pollen tube length / mm 1 6 0.005 2 13 0.008 4 25 0.015 8 56 0.040 10 31 0.030 20 25 0.018 40 13 0.006

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