The possible bottleneck effect of polyamines' catabolic enzymes in efficient adventitious rooting of two stone fruit...

Adventitious rooting is an important plant physiological response utilized in cutting propagation, a procedure with high financial significance. Many endogenous factors are involved, such as plant growth regulators, carbohydrates, minerals, polyamines etc. The objective of the present study was to investigate the role of polyamines and polyamine catabolic enzymes in the bases of softwood cuttings of two Prunus rootstocks, during the early phases of rhizogenesis. An easy-to-root and a difficult-to-root rootstock were studied, concerning their polyamine content (in free, soluble conjugate and insoluble bound form), polyamine catabolic enzyme activities (polyamine oxidase, PAO and diamine oxidase, DAO) and catalase activity, with and without the effect of indole-3-butyric acid as rooting hormone, during the early phases of rhizogenesis. Putrescine, spermine and their catabolic product, H₂O_2, were applied to test their function to rescue the rooting percentage of the recalcitrant species. Spermine was not detected in the difficult to root rootstock, which exhibited higher titer of putrescine and spermidine, PAO and catalase activity, but lower DAO activity compared to the easy-to-root one. The rooting percentage of the recalcitrant species was doubled under spermine and H₂O₂ application. The results obtained, highlighted the role of polyamine catabolic enzymes and indirectly the role of the polyamine catabolic product H₂O₂ as more significant than the polyamine content per se in adventitious rooting of the specific stone fruit rootstocks.