What the roots bring

The idea

Terrestrial plants take up water through roots, and nitrogen, phosphorus, iron and magnesium from the soil; nitrogen, essential for making proteins, is taken as inorganic nitrates or nitrites or as organic compounds made by bacteria from atmospheric nitrogen.

Plants in the field

A wheat plant grows in a field. Its roots are in the soil.

Which of these do roots take up?

• Water and minerals
• Sunlight
• Only air

Soil or not?

Sort each item: does a land plant take it up from the soil?

Soil as a store

Land plants (terrestrial plants) take up water through their roots. Nitrogen, phosphorus, iron and magnesium also come from the soil. Nitrogen is essential for making proteins and other compounds. The plant takes it as nitrates or nitrites, which are inorganic, or as organic compounds that bacteria have prepared from the nitrogen of the air.

Terrestrial plants take up water through roots, and nitrogen, phosphorus, iron and magnesium from the soil; nitrogen, essential for making proteins, is taken as inorganic nitrates or nitrites or as organic compounds made by bacteria from atmospheric nitrogen.

Notes

Land plants take water through roots and nitrogen, phosphorus, iron, magnesium from the soil; nitrogen (for proteins) comes as nitrates or nitrites, or as organic compounds made by bacteria from atmospheric nitrogen.

Check yourself

Which element from the soil is essential for making proteins?

In what form can a plant take up nitrogen?

Which part of a land plant takes up water from the soil?

Which of these do the roots of a land plant take up from the soil?

• Iron. Iron is also taken from the soil, but the book names nitrogen as the element essential for making proteins.
• Magnesium. Magnesium is also taken from the soil, but the book names nitrogen as the element essential for making proteins.
• Nitrogen — correct. Yes!
• As inorganic nitrates or nitrites, or as organic compounds made by bacteria — correct. Yes!
• As starch made in its own leaves. Starch is the internal energy reserve made from carbohydrates; it is not how nitrogen is taken up.
• As water from the roots. Water is taken up for photosynthesis; nitrogen comes as nitrates, nitrites or organic compounds.
• The stomata. Stomata are tiny pores on the leaf surface where gases are exchanged.
• The roots — correct. Yes!
• The chloroplasts. Chloroplasts are green organelles that contain chlorophyll; they do not absorb water from the soil.
• Sunlight. Sunlight is the energy source absorbed by chlorophyll, not a material from the soil.
• Carbon dioxide for photosynthesis. Carbon dioxide gas is exchanged through the stomata of the leaves.
• Magnesium — correct. Yes!