ligase, chalcone-flavanone isomerase, a glucosyl transferase, an apiosyltransferase, UDPapiose
synthetase and an O-methyltransferase. The first three enzymes have as substrates
phenylpropanoid derivatives and the enzymes reach a peak and start to decline within 15
hr after the onset of continuous illumination. The remaining enzymes which are all concerned
with flavonoid synthesis reach a maximum 24 hr after illumination and only then do the
levels decline. Regulation of the levels of these two sets of enzymes thus appear to be different.
So far this is the most complete study of flavonoid biosynthesis at the enzyme level
and the parsley cell culture system holds some promise of being suitable for elucidating the
mechanisms of control of flavonoid synthesis.