The Nitrogen Cycle

Front

In what form do plants absorb the majority of nitrogen from the soil?

Back

Nitrates

Front

Why do plants need to absorb nitrogen from the soil?

Back

Plants require nitrogen to synthesize important nitrogen-containing compounds, like proteins.

Front

The picture shows root nodules on a pea plant. Those root nodules are colonized by nitrogen-fixing bacteria. The relationship between the bacteria and the pea plant is described as mutualistic; what does this mean?

Back

Both the bacteria and the pea plant benefit from this relationship.

Front

Legumes (e.g., pea plants) are able to increase the level of soil nitrogen where they are planted. What is a benefit this provides?

Back

There is more nitrogen available in the soil for other crops that are planted there.

Front

Which organisms convert nitrates in the soil back into atmospheric nitrogen?

Back

Denitrifying bacteria

Front

Which organisms in the nitrogen cycle convert ammonium ions into nitrites and then into nitrates?

Back

Nitrifying bacteria

Front

Which organisms in the nitrogen cycle convert proteins, contained in urea and the bodies of dead organisms, into ammonia?

Back

Decomposers

Front

Why can plants not absorb nitrogen directly from the atmosphere?

Back

Gaseous nitrogen is too unreactive to be absorbed and used by plants.

Front

Which organisms involved in the nitrogen cycle convert nitrogen gas into nitrogen compounds in the soil?

Back

Nitrogen-fixing bacteria

Front

Technique where each year a different crop is planted in different fields in a fixed order to maintain soil nitrogen levels.

Back

Crop rotation