Does lightning affect photosynthesis and cause plants to grow and turn greener?

Answer 1

Nitrogen is an essential element (for the production of amino acids), it does not directly influence photosynthesis. Plants can not directly use the nitrogen out of the air.

Some plants (eg legumes, cycads and casuarina) have nitrogen fixing bacteria (rhizobium,cyanobacteria and frankia respectively) in their roots that can turn the nitrogen in the air into ammonia using the enzyme nitrogenase. Others have to rely on nitrogen from decomposition or from nitrogen fixed by free living nitrogen fixing microbes, from industrial nitrogen fixation (chemical fertilizers like ammonium nitrate) or from lightening

The enormous energy of lightning breaks nitrogen molecules and enables their atoms to combine with oxygen in the air forming nitrogen oxides. These dissolve in rain, forming nitrates, that are carried to the earth. Lightning plays an important role in the nitrogen cycle, returning nitrogen to the soil that is lost by denitrifying bacteria.

So lightning indirectly affects photosynthesis, by "fertilising" plants allowing them to grow greener (they have more chlorophyll) and thus are better photosynthesisers, the net effect of which is that they grow faster.

Answer 2

Lightning puts atmospheric nitrogen into the ground for plants to use. It doesn't affect photosynthesis, but it does "fertilize" the ground.