Effect of excess copper on tomato plants: Growth parameters, enzyme activities, chlorophyll, and mineral content

In this work, the effect of excess copper (Cu) on tomato plants grown in hydroponic solutions for up to 15 days was studied. The solutions contained different Cu concentrations ranging from 0.05, 0.15, 0.20, and 0.35 mM Cu. Dry mass, root length, and foliar area decreased with time and Cu solution concentration. Copper accumulated more heavily in roots than in leaves. Mineral uptake was affected by increasing Cu concentrations in solution with calcium (Ca), iron (Fe), and zinc (Zn) contents in leaves decreasing. Except for Ca, the concentrations of these elements in the roots also decreased, which indicated that root uptake was affected and the translocation to upper plant parts was disrupted. Iron leaf deficiency was the probable cause of the observed chlorosis and decrease in chlorophyll levels. The activities of three enzymes studied in leaves (guaiacol peroxidases (GPOD), catalase (CAT), and polyphenol oxidase (PPO)) increased transiently, probably as an early response mechanism against Cu induced oxidative stress. At higher Cu concentrations, this defense mechanism broke down and the activities of the enzymes decreased accordingly.