315 to 400nm is UVA. UVB has been shown to stimulate resin and cbd production and protect plants from insects.mold and fungus but true uvb diodes are very expensive ($122 for a 1/4 watt diode) mercury arc tubes and sunlight contain a small amount of UVB and at low levels (>%3) are beneficial thru the entire grow
http://en.wikipedia.org/wiki/Ultraviolet and also see
http://www.plantphysiol.org/content/160/1/145 a VERY SMALL reptile light would would be beneficial thru the entire grow.MH and fluorescent lights contain a small amount of UVB so supplemental UVB lighting would not be useful with these lights
