you are close but science has yet to prove your "k" theroy
here is a patent for light modulation a snippit of it shows light can affect gene expression and overall plant expression :
"Specific wavelengths of light provide discrete information to the plant leading to particular responses. For instance, blue light (400-500 nm) controls phototropic growth, leaf expansion, stem growth inhibition and accumulation of anthocyanin pigments. Red light (-660 nm) controls many responses including germination, functions of the chloroplast, stem and petiole growth. Far-red light (>700 nm) is an important signal in a shaded environment, and has a central role in modulating red light responses. All of these light wavelengths have effects on flowering and gene expression."
now if light has that much to do with expression . could pest pressure be the key to modulaion of terpens . like the expression of the SAR response on oil producion in plant *HINT*