Question

Plants need the help of certain bacteria to absorb nitrogen. Why cannot plants absorb nitrogen directly from the atmosphere ?

Answer 1

Answer:

Plants cannot use atmospheric nitrogen directly because they lack the required enzymes and metabolic pathways. Only a few bacterial families can actually deal directly with atmospheric nitrogen.

It just makes things easier when there is already an organism that can do a favour to the plant and in turn get nutrition from it. That's called a symbiotic relationship.

Many plants that cannot involve in such symbiosis are insectivorous - not because they cannot photosynthesise, only to get the required nitrogen through insects.

So, your answer is, the plants aren't evolved to be so.... but maybe they can evolve in the future....

Good question though!!!

Thanks, hope I was atleast near to answering your question!!

P.S : Just found a website that answers your question:

"Plants do not get their nitrogen directly from the air. Although nitrogen is the most abundant element in the air, every nitrogen atom in the air is triple-bonded to another nitrogen atom to form molecular nitrogen, N2. This triple bond is very strong and very hard to break (it takes energy to break chemical bonds whereas energy is only released when bonds are formed). As a result, even though nitrogen in the air is very common, it is energetically unfavorable for a plant to split the nitrogen molecule in order to get the raw atoms that it can use. The strong triple bond of N2 also makes it hard for molecular nitrogen to react with most other chemicals. This is, in fact, part of the reason there is so much nitrogen in the air to begin with."