Page 20 - 新思维科学学生用书9 样章

1.2 More about photosynthesis

Magnesium is needed to make the green Nitrate contains nitrogen atoms. These are

pigment, chlorophyll. If a plant does not needed so that the plant can convert carbohydrates
have enough magnesium, its leaves look to proteins. Proteins are essential for making new
yellow instead of green. It cannot grow well, cells, so that the plant can grow well. Without
because it does not have much chlorophyll to enough nitrogen, leaves die and the plant stays

absorb energy from sunlight, and so it cannot small, like these maize (corn) plants. Nitrogen is
photosynthesise as much as it should. also needed to make chlorophyll.

Farmers can test the soil in their fields to find out
exactly which minerals are lacking in each part of

the field. This tells the farmer where they need to
add fertiliser, and where it is not needed.

Farmers who can afford the latest technology can
use global positioning system (GPS) with their
machinery.

The screen in the tractor cab shows the farmer
exactly where he is in the field, as well as the

results of the soil tests. The farmer can easily
control how much fertiliser is added in each part
of the field.

Questions
3 All organisms need protein for growth. Compare the way in which plants obtain protein with the

way that you and other animals obtain protein.
4 It can be difficult, even for an expert, to tell the difference between a plant that is short of
magnesium, and one that is short of protein. Suggest why.

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