Secondary metabolism modulating in vitro plant morphogenesis
Metabolites are classified as either primary or secondary based on how vital they are to organism survival or growth. While many classical plant growth regulators would be considered primary metabolites, a number of secondary compounds are known to impact plant growth and development. This thesis aimed to investigate the roles of selected secondary metabolites in modulating plant growth and development in in vitro systems. Three individual studies were conducted using a diverse group of plant species (Pisum sativum, Plagiomnium cuspidatum, Scutellaria baicalensis, and Solanum tuberosum), explant types, and tissue culture systems (seedlings cultures, bryophyte gametophyte cultures and shoot cultures) to evaluate the effect of disrupting/altering secondary metabolism to evaluate the morphogenetic consequences. These studies involved the exogenous application of enzymatic inhibitors such as 2-aminoindan-2-phosphonic acid and/or supplementation of secondary metabolites such as phenylpropanoids, indoleamines and alkaloids either alone or in combination. Morphogenetic changes, phytochemical and plant growth regulator profiles were evaluated to determine the developmental impact and elucidate the underlying mode of action. Key findings include, inhibition of phenylpropanoid biosynthesis in P. sativum induced a cytokinin-like effect, potentially related to the the documented modulation of auxin transport by certain phenolics, novel and yet to be characterized interactions between indoleamines and phenylpropanoids in mediating stem formation in P. cuspidatum, and conclude no significant role of exogenous purine alkaloid supplementation in modulating morphogenesis. Collectively, these results demonstrate the complex nature of plant growth regulators and the need to revisit the classification of metabolites and the rationales used to group them.