The comparison of two different LED exposure times in wound stress tolerance in Arabidopsis thaliana

In this experiment, we made a comparison between various 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, in addition to two lightening time (time1 and time2), on Arabidopsis plant’s response to wounding. In response to wounding, LED-exposed plants, especially RB-irradiated plants, maintained significantly higher shoot dry weight and antioxidant enzyme activities compared to those irradiated with fluorescent lights. The concentration of H2O2 was significantly higher under the condition of RB and B lights in time 1, and in B and florescent lights in time 2, compared to the other light environments. The highest amount of MDA was observed in F and B exposed plants in both times 1 and 2 of the experiment. The highest level of phenolic compounds was found in wounded leaves exposed to RB and R lights. Among the LED-irradiated plants, the highest expression level of the PAL gene in response to wounding was detected in RB-exposed plants in time 1, and in B exposed plants in time 2 of the experiment, one week after wounding. Late-induction of JA biosynthesis-associated genes (AOC and AOS) in response to wounding was observed in all LED conditions, with the highest intensity in W light-exposed plants. The results of COI1 relative expression also suggest more JA signaling in W exposed plants in comparison with other light conditions. Collectively, we concluded that LED light conditions provide a better capability for Arabidopsis thaliana to recover from wound stress mainly by increasing the antioxidant capacity and secondary metabolites production. Among LED light conditions, we candidate RB condition as the best environment for Arabidopsis growth and tolerance to wound stress, and we think, through improving antioxidant capacity, pre-treatment with LED light can provide a better condition for plants to tolerate wound stress. Different amounts of hydrogen peroxide production in response to wounding between different light-exposed plants suggests the possible signaling role of ROS in light-induced wound responses.