Role of Plant Pigments in the 24-epibrassinolide Ameliorating Salt Stress in Canola

This study evaluated effects of foliar spraying 24-epibrassinoide(24-EBL) on the growth of salt-stressed canola and plant pigment role played in canola salt tolerance.The seedlings were grown in the presence of 150 mmol·L-1 NaCl and sprayed with different concentration of 24-EBL(1 000,10,0.1,0.001 nmol·L-1) for 15 days.The plant biomass,electrolytic leakage percentage(ELP),net photosynthetic rate(Pn),contents of photosynthetic pigments,phenolics,flavonoids and anthocyanins,and total antioxidant capacity(T-AOC) of these plant pigments were determined.The results showed that:(1)24-EBL could ameliorate these adverse effects induced by salt on biomass,Pn,contents of chlorophyll(Chl) and carotenoid(Car),MDA level and ELP.0.1 nmol·L-1 24-EBL(EBL3) was chosen as the optimal concentration for growth promotion and used in a subsequent experiment.(2)The levels of β-carotene(β-Car) and lutein(Lut) in different parts of leaves were sharply decreased under salinity,but β-Car content in upper leaves,Lut content in upper and middle leaves were reversed with varying degrees by EBL3.The treatment of EBL3 could promote the contents of phenolics in all leaves and petioles,and the contents of flavonoids in petioles of seedlings under salt stress.However,the anthocyanin contents of all plant organs were increased significantly induced by EBL3.(3)The treatment of EBL3 induced the T-AOC of carotenoid(Car) extracts in the upper and middle leaves.However,it induced the T-AOC of phenolics extracts in all plant organs of canola seedlings under salt stress.(4)Correlation analysis indicated that the T-AOC of carotenoids' extracts was all highly positively related to their contents of Car,β-Car and Lut.While,T-AOC of phenolics' extracts showed a positive correlation with contents of phenolics and anthocyanins in upper leaves,a very positive correlation with contents of phenolics and flavonoids in stems,and anthocyanins' contents of mid-leaves,petioles and stems.Sum up,foliar spraying 24-EBL could promote adaptation of the canola seedling to salt stress,which was due mainly to its increase of photosynthetic and antioxidant capacities induced by 24-EBL.Also,the increase of photosynthetic pigment and anthocyanin levels induced by 24-EBL played an important role in anti-oxidation of canola seedlings.