Effects of Auxin on Photosynthetic Pigments and Some Enzyme Activities during Dark-induced Senescence of Tropaeolum Leaves

Effects of indole acetic acid (IAA), indole butyric acid (IBA) and naphthalene acetic acid (NAA) were investigated on some physiological parameters in detached leaves of Tropaeolum majus L., during dark-induced senescence. Auxin accelerated the loss of chlorophyll (Chl) and carotenoid content whereas it retarded the loss of protein amount at the end of senescing period in leaves significantly. Auxin (IAA and IBA) decreased meaningfully catalase (CAT; EC 1.11.1.6) activity at the second day of senescencing period but increased it at the end of senescence compared to the control group. On the other hand, peroxidase (POD; EC 1.11.1.7) activity was not changed with auxin application. H2O2 levels in leaves were unstable during senescing period in both treated and control groups however they were higher in treated leaves than the control group at 6 day of experiment. NAA was found to be the most effective auxin on protein and pigment destruction.