Data analysis
All data were analyzed for statistical significance of treatment effects by one-way analysis of variance (ANOVA) using the software program PASW Statistics 16.0 (SPSS company, Chicago, IL, USA). The least significant difference (LSD) at p <0.05 was used to compare the treatment means. Plots were drawn using the software Origin 9.0 (Origin Lab Corporation, Northampton, Massachusetts, USA).