Levels of Selected Trace Elements, Phytohormones, and Sugars in Pseudomonas-Infected Lycopersicum esculantum Mill Plants

The present study investigated the levels of trace elements (Zn, Cu, Fe, Pb, and Cd), major elements (Ca and K), phytohormones (trans-Zeatin [t-Z] and gibberellic acid [GA]), and sugars (sucrose and glucose) following inoculation with Pseudomonas syringae pv. tomato strain. The results of the trace elements analysis showed that Fe (in the first, fourth, eighth, and tenth study days), Cd (in the fourth, eighth, and tenth study days), Cu (in the fourth and eighth study days), and Zn (in the eighth and tenth study days) increased in bacterium-infected tomato plants, compared to healthy plants. The levels of Pb, Ca, and K did not meaningfully determine a change after inoculation with pathogen. In this vein, the increase accumulation rates of Cu, Zn, and Fe in the injured plants can be an important indicator for the plant defense processes towards pathogen attack. Furthermore, in the first, fourth, eighth, and tenth study days, the glucose and sucrose contents crucially decreased in bacterium-infected plants compared to the control groups. The lowest level of sucrose in bacterium-infected plants was observed on the first day. The findings displayed that, when endogenous t-Z levels did not change after inoculation with virulent bacterium strain, there was a reduction in the first, fourth, eighth, and tenth days in the level of GA when compared with the control group levels. Therefore, there may be a link between lower GA level and enhancement in the expression of defense-related genes. The results of this study showed that there are complex relationships among levels of sugar, trace element, and endogenous phytohormone in the regulation of defense mechanisms against bacterial pathogen attacks.