Would you expect the leaves to be sources or sinks in winter? Explain your answer.
Important Questions on Transport in Plants
The table shows the amount of starch, measured as a percentage of the dry mass of the tissues, in the leaves and roots of pine trees at three times of the year.
| Time of year | Starch in leaves/percentage of dry mass | Starch in roots/percentage of dry mass |
| spring | 15.0 | 2.6 |
| summer | 15.6 | 3.1 |
| autumn | 4.9 | 4.1 |
Describe the changes in the amount of starch in the pine tree leaves from spring until autumn.
Situation A: The changes in the amount of starch in the pine tree leaves from spring until autumn.
Situation B: The changes in the amount of starch in the pine tree roots from spring until autumn.
Suggest a reason for the changes described in situations a and b.
In summer, the researchers removed the buds from some pine trees and the leaves from other pine trees. They left some pine trees untreated, to act as controls. They measured the amount of starch in the leaves and buds of each group of trees at the end of the summer. Their results are shown in Table.
| Treatment | Starch in leaves/percentage of dry mass | Starch in buds/percentage of dry mass |
| Control | 4.9 | 7.1 |
| Buds removed | 4.9 | |
| Leaves removed | 6.5 |
Describe and explain the results shown in the table.
