Affiliations: The Key Laboratory of Industrial Biotechnology,
Ministry of Education, Southern Yangtze University, Wuxi 214036, China | School of Biotechnology, Southern Yangtze University,
Wuxi 214036, China | College of Chemistry and Environmental Science,
Nanjing Normal University, Nanjing 210097, China
Abstract: Effect of cerium (Ce^{3+}) on the growth,
photosynthesis and antioxidant enzyme system in rape seedlings (Brassica juncea
L.) exposed to two levels of UV-B radiation (T_1: 0.15
W/m^2 and T_2:0.35
W/m^2) was studied by hydroponics under laboratory
conditions. After 5 d of UV-B treatment, the aboveground growth indices were
obviously decreased by 13.2%–44.1%(T_1) and
21.4%–49.3%(T_2), compared to CK, and except active
absorption area of roots, the belowground indices by
14.1%–35.6%(T_1) and
20.3%–42.6%(T_2). For Ce+UV-B treatments, the
aboveground and belowground growth indices were decreased respectively by
4.1%–23.6%, 5.2%–23.3%(Ce+T_1) and
10.8%–28.4%, 7.0%–27.8%(Ce+T_2), lower
than those of UV-B treatments. The decrease of growth indices appeared to be
the result of changes of physiological processes. Two levels of UV-B radiation
induced the decrease in chlorophyll content, net photosynthesis rate,
transpiration rate, stomatal conductance and water use efficiency by
11.2%–25.9%(T_1) and
20.9%–56.9%(T_2), whereas increase in membrane
permeability and activities of antioxidant enzymes including superoxide
dismutase(SOD), catalase (CAT) and peroxidase (POD) by 6.9%, 22.8%, 21.5%,
9.5%(T_1) and 36.6%, 122.3%, 103.5%,
208.9%(T_2), respectively. The reduction of the
photosynthetic parameters in Ce+UV-B treatments was lessened to
3.2%–13.8%(Ce+T_1) and
4.9%–27.6%(Ce+T_2), and the increase of membrane
permeability and activities of antioxidant enzymes except POD in the same
treatments were lessened to 2.4%, 8.4%, 6.6%(Ce+T_1)
and 30.1%, 116.7%, 75.4%(Ce+T_2). These results
indicate that the regulative effect of Ce on photosynthesis and antioxidant
enzymatic function is the ecophysiological basis of alleviating the suppression
of UV-B radiation on growth of seedlings. Furthermore, the protective effect of
Ce on seedlings exposed to T_1 level of UV-B radiation is
superior to T_2 level.
