Effects of inoculating nitrogen fixing bacteria Klebsiella sp.120on photosynthetic characteristics and mineral nutrient contents of sugarcane

【Objectives】 Sugarcane (Saccharum officinarum L.) isan important sugar and energy crop with high biomass and high productivity. However, application of large amount chemical nitrogen fertilizer in sugarcane is very common in China, which not only increases the production cost, but also causes environmental pollution.A possible method of reducing sugarcane nitrogen fertilization is inoculation of nitrogen fixation bacteria. The nitrogen fixing bacteria (NFB) strain Klebsiella sp.120 was isolated from surface-sterilized roots of sugarcane cultivar ROC22.Its effect on photosynthetic characteristics and mineral nutrient accumulation in sugarcane was investigated.【Methods】 Four sugarcane cultivars were planted in pots. The strain Klebsiella sp.120 was inoculated to the plants by root watering at the tillering stage. Effects of the inoculation on photosynthetic characteristics and mineral nutrient accumulation of the four cultivars were studied after the treatment of 30 and 60 days, respectively.【Results】 The results show that the photosynthetic rates and chlorophyll contents of different cultivars are affected differently by the inoculation with Klebsiella sp.120.After 30 days inoculation increases signiticantly the chlorophyll contents in leaves of sugarcane cultivar ROC22 (increased by 23%),slightly in the other three sugarcane cultivars B8, GT21 and GT28, compared to the uninoculated controls. The net photosynthetic rates of sugarcane cultivar ROC22 and B8 are higher than the controls after 30 days, and there are significant differences. The net photosynthetic rates of the four sugarcane cultivars inoculated the strain after 60 days are higher than those after 30 days. The net photosynthetic rates of the four sugarcane cultivars are significantly higher than controls after the treatment 60 days. The effects of inoculation on the net photosynthetic rates are better in the cultivars ROC22 and GT21. The effects of the inoculation treatments on the nutrient element contents are different. The contents of N in the NFB inoculation treatment group are all higher than control group for the four sugarcane cultivars, especially incultivar ROC22(increased by 59.8%). There are no differences in the contents of P and K in all the cultivars between the inoculation treatment group and the control group. Among the four cultivars, the Zn content in leaves of ROC22 and the Cu contents in leaves of ROC22 and B8 are improved significantly by inoculating, compared with the control. 【Conclusions】 The effects of inoculating Klebsiella sp. 120 on the photosynthetic characteristics and mineral contents depend on sugarcane cultivars. The effect is most obvious in the sugarcane cultivar ROC22 among the selected four sugarcane cultivars.Therefore,experiment should be carried out for different sugarcane cultivars for the effective performance ofthe strain Klebsiella sp.120.