Page 19 - 新思维科学学生用书9 样章

1 Photosynthesis and the carbon cycle

Questions

1 The cells inside a plant leaf use up carbon dioxide when they photosynthesise. Use what you have
learnt about diffusion to explain how carbon dioxide diffuses into the leaf.
2 The cells inside a plant leaf produce oxygen when they photosynthesise. Suggest what happens to

this oxygen.

Minerals and plant growth

The farmer in the picture is adding fertiliser to a field of wheat.

Farmers add fertiliser to their fields because it makes the crops grow larger and produce a higher yield.
Yield is the quantity of crop that the farmer harvests.

Fertilisers contain minerals. Like the minerals that we need in our diet, plants need only quite small
quantities of minerals. They get these minerals from the soil, through their roots. But sometimes the
soil does not contain enough of certain minerals. This stops the plants growing to their full potential.

Two important minerals for plants are magnesium and nitrate.

18