Which form(s) of nitrogen is(are) unusable by plants?

Name: Which form(s) of nitrogen is(are) unusable by plants?
Brand: Quizplus
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Question

Quizplus · Accepted Answer

Nitrogen gas (N2) makes up about 78% of the Earth's atmosphere and is unusable by most plants because they cannot directly fix atmospheric nitrogen into a form they can absorb. Plants primarily absorb nitrogen in the form of ammonium (NH4+) and nitrates (NO3-), which are produced from nitrogen gas by the process of nitrogen fixation carried out by certain bacteria and industrial processes.

Which Form(s) of Nitrogen Is(are) Unusable by Plants