i think that this is the bit you are talk about there are several alternative explanations for the presence of allelochemicals in plants evidence suggest that flavonoids and cuticle waxes absorb between of incoming ultraviolet uv radiation in cucumbers and maize effectively acting as uv shields caldwell m m r robberecht and s d flint internal filters prospects for uv acclimation in higher plants physiologia plantarum additionally some allelochemicals act as storage compounds for essential plant nutrients such as nitrogen and phosphorus mckey d adaptive patterns in alkaloid physiology the american naturalist sorry i had meant to move it here but forgot i couldn't find any good place to put it but feel free to add it back if you know where it should go