Abstract:

Quercus liaotungensis, a special Quercus species of China, is one of the dominant species in the warm temperate deciduous broad-leaved forests, China. Gomphidius viscidus and Russula foetens are two species of ectomycorrhizal fungi being symbiosis and formation of ectomycorrhizae with Q. liaotungensis in the natural circumstance. The positive effect of the inoculation with G. viscidus and R. foetens on Q. liaotungensis seedling growth, and the improvement induced by co-inoculation with a mixed inoculum of G. viscidus and R. foetens have been reported in our early work. In the present paper, a controlled experiment was conducted in pots to investigate the effects of different inoculation amounts and different inoculation ratios of G. viscidus and R. foetens. Q. liaotungensis seeds were collected in autumn of 2001 from the natural forest of Mt. Donglingshan in the Beijing area. Before germination, seeds were rinsed in running tap water overnight, surface disinfected by shaking for 60 min in 0.5% KMnO4 and washed in four changes of sterile distilled water. Seeds were germinated in sterile sand, and seedlings were transplanted to pots (diameter 20 cm, depth 20 cm) with a sterile mixture of soil and sand in a greenhouse. The sterile mixture had a pH of 6.9, an organic matter content of 3.76%, and total N, P, K levels of 0.30%, 0.12% and 2.61%, respectively. On June 2, 2002, every 15 pots of Q. liaotungensis seedlings were randomly grouped for inoculation treatment. Three levels of inoculation amount of 12, 18 and 24 g·pot-1 were created at the ratio of 1∶1 of G. viscidus∶R. foetens, and three ratios of 2∶1, 1∶1 and 1∶2 of G. viscidus∶R. foetens were inoculated at the inoculum amount of 18 g·pot-1. After 3 months of inoculation, the mycorrhizal infection rate and the percentages of G. viscidus and R. foetens mycorrhizae were observed. The height, dry weight, nitrogen and phosphorus contents of root, stem and leaf, net photosynthesis rate of the mycorrhizal seedlings and non-mycorrhizal seedlings were measured, and biomass, nitrogen and phosphorus contents of the whole plant, root/shoot ratio and leaf water content were calculated.The infection rate of mycorrhizae of Q. liaotungensis seedlings and the percentage of G. viscidus mycorrhizae increased but the percentage of R. foetens mycorrhizae decreased when the inoculation amount was higher. The maximum biomass, height, net photosynthesis rate and total nitrogen and phosphorus contents of whole plant of Q. liaotungensis seedlings all showed in plants with inoculation amount of 18 g·pot-1. As to inoculation ratio, with the inoculum ratios of 2∶1, 1∶1 and 1∶2 of G. viscidus and R. foetens, the infection rates of total ectomycorrhizae were 96.54%, 91.02% and 92.13% respectively, and no significantly difference among them. As the proportion of G. viscidus in the inoculum decreased, the percentage of G. viscidus mycorrhizae decreased from 42.49% to 23.33%, and that of R. foetens mycorrhizae rose from 57.51% to 76.67%. With an inoculation amount of 18 g·pot-1 at a ratio of 1∶1 G. viscidus∶R. foetens, the seedlings of Q. liaotungensis have maximal biomass, net photosynthesis rate, and total nitrogen content of the whole plant which was significantly higher than seedlings under other inoculation ratio conditions. Total phosphorus content of the whole plant of Q. liaotungensis was enhanced by the increasing ratio of R. foetens.