关键词: 杉木, 低磷, 铝毒, 抗氧化酶, 养分吸收, 透射电镜-X-射线能谱, 亚细胞分布

Abstract: [Objective] Low phosphorus and aluminum toxicity is an important limiting factor in the productivity of Chinese fir (Cunninghamia lanceolata) plantation in southern China. Effects of phosphorus on physiological and biochemical indicators of Chinese fir seedlings under aluminum stress were studied in order to provide a scientific basis for sustainable management of Chinese fir plantation in acid soil, and to improve the productivity of plantation.[Method] We studied the effects of low phosphorus and aluminum stress on the physiological indicators of Chinese fir seedlings, the mechanism of low phosphorus aluminum stress on nutrient absorption, the subcellular distribution of elements, and the distribution of Al in the organelle of Chinese fir seedling roots was assessed through Transmission Electron Microscope and Energy Dispersive X-ray Spectroscopy (TEM-EDS) by setting different concentrations of phosphorus and aluminum in Hoagland nutrient solution.[Result] Al³⁺ resulted in abnormalities of the physiological indicators, such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and malondialdehyde (MDA) in Chinese fir seedlings. With the increase of phosphorus concentration, the above physiological abnormalities have been effectively alleviated. In addition, with the increase of phosphorus concentration, the content of Al decreased significantly in the roots, while the contents of K, Mg, Zn and P increased significantly. The contents of Al, Mg, Ca and K in leaves were also increased. It was found that the cell wall of the roots were the main sites of aluminum accumulation by TEM-EDS, and phosphorus could promote aluminum to transport to the vacuoles and deposit it as black insoluble particles in the vacuoles. Further analysis of subcellular fractions revealed that Al and P were mainly distributed in cell wall component of the roots of Chinese fir seedlings. With the increase of phosphorus concentration, the ratio of Al and P in the root cell wall fraction decreased significantly, but increased significantly in the soluble fraction, indicating that phosphorus and aluminum were transported to the vacuole at the same time. The content of K and Mg have a similar pattern to Al and P.[Conclusion] These result demonstrate that, under the aluminum stress, the roots of Chinese fir seedlings were seriously poisoned. The increase of phosphorus changed the activity of antioxidant enzymes, changed the absorption and transport of Ca, K, Mg and Zn, increased the transport of Al to vacuole, and reduced the enrichment of Al in the cell wall of root of Chinese fir. They were the reason for that Chinese fir seedlings maintained the normal structure and function of the root cell wall, alleviated the lipid peroxidation, and reduced the damage of aluminum to Chinese fir seedlings under the aluminum stress.

Key words: Cunninghamia lanceolata, low phosphorus, aluminum toxicity, antioxidase, nutrient absorption, Transmission Electron Microscope and Energy Dispersive X-ray Spectroscopy (TEM-EDS), subcellular distribution