Biology 5090 · O Level · Sexual reproduction in plants

Sexual reproduction in plants — practice question

The diagram presents a pollen grain with a pollen tube extending from it. Pollen grains taken from the same plant species were added to sucrose solutions of varied concentrations and left there for a set period. Once that period had passed, the pollen grains and tubes were viewed under a microscope. For each sucrose concentration, the observations recorded were: • how many pollen grains had germinated to form a pollen tube, • the length of every pollen tube. The table gives the findings from the investigation.
(a(i))[1]

There were 12 pollen grains placed in the 20% sucrose solution altogether. Using the table, calculate how many pollen grains germinated and produced a pollen tube in the 20% sucrose solution.

(a(ii))[1]

Suggest why the mean pollen tube length was worked out for each sucrose concentration.

(a(iii))[3]

Use the information in the table to suggest the optimum (best) sucrose concentration for pollen tube germination and growth. Explain how the table entries led you to that conclusion.

(a(iv))[3]

Germination of a pollen grain to form a pollen tube depends on water moving into the pollen grain from its surroundings. Suggest why placing a pollen grain in a solution with a higher sucrose concentration than the one you gave in a(iii) may lead to a lower percentage of germination.

(b)[4]

Describe the path followed by a developing pollen tube in a plant and explain why this route is important in plant reproduction.

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