Effects of lead and copper application on some ecophysiological parameters and antioxidant defense system of Cucurbita moschata Duch.

Geological factors, anthropogenic activities, mining and agricultural practices cause heavy metal pollution, which has become an important ecological problem all over the world. Due to their sessile nature, plants are the most affected by this abiotic stress. Plants exposed to heavy metal stress suffer from loss of quality in products and decrease in productivity. For this reason, plants have developed various mechanisms at the ecological, physiological and molecular level to survive in soils contaminated with heavy metals. In this study, the effects of two different concentrations of lead (25 mM and 50 mM) and copper (50 mM and 100 mM) on pumpkin plants were investigated. Root and stem length, root and stem fresh-dry weight, root and stem biomass, lead and copper tolerance index, chlorophyll a, b and total chlorophyll amount, lipid peroxidation, total protein amount, SOD, CAT, APX enzyme activities and changes in gene expression levels of these enzymes were determined in pumpkin samples exposed to lead and copper. As a result, it was found out that lead and copper stress had a positive effect on the ecological parameters of the stem in pumpkin, and negatively affected the ecological parameters of the root. It was observed that both metal applications increased chlorophyll a, b and total chlorophyll amounts, but only high concentrations of metal applications (50 mM Pb and 100 mM Cu) increased the MDA content. It was determined that the activities and gene expressions of SOD and CAT enzymes increased in all experimental groups treated with lead and copper, while APX activity and gene expression increased at 50 mM Pb and 100 mM Cu concentrations. According to the obtained ecological, physiological and molecular parameters, it has been revealed that the pumpkin plant has a high antioxidant defense capacity and shows a very high tolerance to the applied lead and copper concentrations.