Abstract:

We explored effects of four nitrogen (N) treatments (0, 1, 8 or 16 mmol·L^-1) on the photosynthesis, antioxidant defense systems and lipid peroxidation in Vetiver leaves. Our results show that the net photosynthetic rate (Pn), the maximum photochemical efficiency of PSII reaction centres (Fv/Fm), quantum efficiency of PSII electron transport (ФPSⅡ), photochemical quenching (qP), non-photochemical quenching（NPQ）, superoxide dismutase (SOD) and peroxidase(POD) activities rose firstly and then declined when N concentrations increased from 0 mmol·L^-1 to 16 mmol·L^-1. They reached biggest at 8 mmol·L^-1 N and were minimum at 16 mmol·L-1 N .During the two types of treatments (1 and 8 mmol·L^-1 N), Pn, Fv/Fm, ФPSⅡ, qP ,NPQ,SOD and POD activities did not show difference significantly. Catalse activity and malondialdehyde (MDA) content reduced firstly and then enhanced while proline (Pro) accumulated with increasing N supply. These results indicate that vetiver leaves have a higher Fv/Fm、ФPSⅡ、qP and activities of antioxidant enzymes under the low nitrogen conditions.

Key words: Vetiver, Net photosynthetic rate, Chlorophyll fluorescence parameter, Enzyme of antioxidant