smokinrav, here is a link to Mel Franks book and his referenced discussion of stress and potency in the Cannabis plant.
http://www.sky.org/data/grow/c19.html
and this on the enzymatic nature of cannabinoid production and the effects of environment on the said, the 'Kansas' study...
http://www.druglibrary.org/schaffer/.../seasonal.html
OzGrowa