Effect of fresh spent coffee grounds on the oxidative stress and antioxidant response in lettuce plants
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Fundação para a Ciência e Tecnologia (FCT) através do Projeto PTDC/AGR-AAM/102447/2008.
Spent coffee grounds (SCG) are widely used in the domestic cultures, apparently as fertilizer and due to its repellent effect. However, scientific evidences about their effect on plants remain unknown. The high residual amounts of caffeine (about 0.2%) in SCG, together with tannins and chlorogenic acids, might impose some toxicity to the plants.
The aim of this study was to evaluate the oxidative stress response of lettuce plants to fresh SCG. The roots of one month-old lettuces plantlets cv. “Wonder of four seasons” were immersed in aqueous solutions with different fresh SCG concentrations [0%, 5%, 10% and 15% (w/v)]. During the first 24 hours of elicitation, the roots and leaves were periodically harvested and the levels of hydrogen peroxide (H2O2), as well as the activities of superoxide dismutase (SOD) and catalase (CAT), were determined.
The results indicated that fresh SCG induce oxidative stress in lettuce plants. An increase of reactive oxygen species (ROS), namely on H2O2, was more evident within the first 12 h of elicitation with increasing fresh SCG concentrations. This pattern was coincident with an increase of SOD activity, but not of CAT. Oxidative stress induction by fresh SCG was observed in both roots and leaves, being more noticed in the former. Altogether, the results show that the fresh SCG modify the equilibrium between production and scavenging of ROS, causing oxidative stress in lettuce plants, especially at the root level.
