LED lights increase an antioxidant capacity of Arabidopsis thaliana under wound-induced stresses.

A comparison among four light emitting diode (LED) lights including red LED (R), blue LED (B), red (70%) + blue (30%) LED (RB) and white LED (W) as well as fluorescent (F) light was made on antioxidative capacity of Arabidopsis thaliana (L.) Heynh. in response to wounding. Under wound-stress condition, LED-exposed plants, especially RB-irradiated plants, maintained significantly higher shoot dry weight and antioxidant enzymes activities compared with those irradiated with fluorescent lights. The highest amounts of both chlorophyll a and b were observed in the leaves treated with B light. Also, the concentration of H2O2 was higher under the condition of RB and B lights compared with the other light environments. The highest amount of malondialdehyde was measured in plants exposed to F and B lights. Similarly, wounded leaves under F and B light conditions showed the maximum lipoxygenase activity, whereas R-exposed leaves had the lowest lipoxygenase activity. In contrast, the highest level of phenolic compounds was found in R and RB exposed leaves in response to wounding. Among the five light treatments, RB and B lights were more effective in stimulating anthocyanin synthesis; however, RB-exposed plants were more efficient in the late-induction of the PAL gene (phenylalanine ammonia lyase catalyses the first step of the general phenylpropanoid pathway). Collectively, we reasoned that RB light condition gives a superior capacity to Arabidopsis thaliana to tolerate wound-stress. Also, we propose the probable signalling role of ROS in light-stimulated wound responses in Arabidopsis.