Role of Cell Wall Stiffening Enzymes in Internode Development of Merremia Emarginata

Merremia emarginata plants were treated with different plant growth regulators (PGRs): naphthyl acetic acid (NAA), phenyl acetic acid (PAA) and gibberellic acid (GA 3). To determine the role of wall stiffening enzymes in internode elongation, IAA oxidase and peroxidase in the presence of different hydrogen donors like caffeic acid, chlorogenic acid and guaiacol were assayed. The levels of total, mono-and dihydroxy phenols were also determined together with the assay for the presence of IAA protectors. There was no significant difference in internode length upon PGRs treatment. Peroxidase assayed using caffeic acid as a hydrogen donor after GA 3 treatment showed inhibition in both cytoplasmic and wall-bound fraction. Promotion in the activities of the cytoplasmic and wall-bound fractions was observed in NAA and PAA-treated internodes with the other two substrates. IAA oxidase activity was significantly inhibited by GA 3 treatment in the wall-bound fractions.The IAA protectors correlated well with length in control internodes. Total phenols and diphenols showed almost similar contents in control and treated internodes while monophenols were remarkably inhibited by hormone treatments. The possible role of these parameters in elongation growth of the internodes is discussed.