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 90 99 of incoming ultraviolet UV radiation in cucumbers and maize effectively acting as UV shields Caldwell M M R Robberecht and S D Flint 1983 Internal filters prospects for UV acclimation in higher plants Physiologia Plantarum 58 445 450 Additionally some allelochemicals act as storage compounds for essential plant nutrients such as nitrogen and phosphorus McKey D 1974 Adaptive patterns in alkaloid physiology The American Naturalist 108 305 320 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