Certain plant species are able to absorb heavy metal contaminants that are dissolved in soil water and then move them through the plant. In plant cells, these heavy metals build up in the vacuole. Which of the following suggestions about the transport and accumulation of heavy metals are valid? 1 After first entering the root, some of the heavy metals may cross the tonoplast and be kept in the vacuole of cortical cells. 2 The heavy metals follow an apoplastic route in the xylem, but at the endodermis they have to use a symplastic route. 3 The rate at which heavy metals accumulate in leaf cells will be greater at night, when photosynthesis is not taking place, than in the daytime. 4 The presence of the heavy metal will interfere with active transport, so the transpiration stream will slow and the transpiration rate will be reduced.
- A1 and 2
- B1 and 4
- C2 and 3
- D3 and 4