High growing temperature affects the antioxidant potential of broccoli seedlings (Brassica oleracea L. convar. botrytis (L.) Alef. var. cymosa Duch.)

Due to climate change, plants are exposed to abiotic stress, especially high temperatures. To combat those stressful conditions, they developed antioxidant mechanisms which help them to reduce reactive oxygen species. To investigate how high temperature affects the antioxidant potential of broccoli seedlings (Brassica oleracea L. convar. botrytis (L.) Alef. var. cymosa Duch.), in the winter of 2021/2022, within the scope of the TEMPHYS project (IP-2020-02-7585), we cultivated three biological replicas of broccoli seedlings at high temperature (38 °C day/33 °C night) and three biological replicas at regular temperature (23 °C day/18 °C night) as a control group. Extracts of lyophilized broccoli tissue were made in 70% ethanol, and antioxidant potential was measured using four methods: ABTS, DPPH, FRAP and β- carotene bleaching. The obtained values were compared to those of standard Trolox solution of the same concentration as our extracts (i.e. 30 mg/mL for all the methods, except for FRAP which was 15 mg/mL). Based on the results of ABTS, FRAP and β-carotene bleaching method, high temperature significantly increased antioxidant potential of broccoli seedlings. However, DPPH method indicated a reduction of antioxidant potential. All the methods were significantly positively correlated with each other, except the DPPH which was negatively correlated with other methods. Both, at high and regular temperature, statistical methods principal component analysis and hierarchical clustering revealed higher similarity between second and third biological replicas, and separation of first biological replica. However, all biological replicas grown at high temperature tended to cluster together and clearly separated from those at regular temperature. In conclusion, based on three out of four used methods, high temperature significantly increased antioxidant potential of broccoli seedlings, suggesting further research into the effect on plant metabolism.