Growth and physiological responses of canola (Brassica napus) to UV‐B and CO2under controlled environment conditions

Few studies have investigated the interaction of ultraviolet (UV)‐B radiation and CO2concentration on plants. We studied the combined effects of UV‐B radiation and CO2concentration on canola (Brassica napuscv. 46A65) under four growth conditions – ambient CO2with UV‐B (control), elevated CO2with UV‐B, ambient CO2without UV‐B, and elevated CO2without UV‐B – to determine whether the adverse effects of UV‐B are mitigated by elevated CO2. Elevated CO2significantly increased plant height and seed yield, whereas UV‐B decreased them. Elevated CO2ameliorated the adverse effects of UV‐B in plant height. UV‐B did not affect the physical characteristics of leaf but CO2did. Certain flower and fruit characteristics were affected negatively by UV‐B and positively by CO2. UV‐B did not affect net photosynthesis, transpiration and stomatal conductance but decreased water use efficiency (WUE). Elevated CO2significantly increased net photosynthesis and WUE. Neither UV‐B nor CO2affected chlorophyll (Chl) fluorescence. UV‐B significantly decreased Chlband increased the ratio of Chla/b. Elevated CO2decreased only the ratio of Chla/b. UV‐B significantly increased UV‐absorbing compounds while CO2had no effect on them. Both UV‐B and CO2significantly increased epicuticular wax content. Many significant relationships were found between morphological, physiological, and chemical parameters. This study showed that elevated CO2can partially ameliorate some of the adverse effects of UV‐B radiation inB.napus.