Evidence Against the Involvement of Ionically Bound Cell Wall Proteins in Pea Epicotyl Growth

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Abstract
Developing seedlings of Catharanthus roseus were analyzed for appearance of tryptophan decarboxylase (TDC), strictosidine synthase (SS), N-methyltransferase (NMT) and O-acetyltransferase (DAT) enzyme activities. SS enzyme activity appeared early after germination and was present throughout most of the developmental study. TDC activity was highly regulated and peaked over a 48 hour period achieving a maximum by day of 5 of seedling development. Both TDC and SS were present in all tissues of the seedling. NMT and DAT enzyme activities were induced after TDC and SS had peaked and these activities could only be found in hypocotyls and cotyledons. TDC, SS, and NMT did not require light for induction whereas DAT enzyme activity was increased approximately 10-fold after light treatment of dark grown seedlings.