Phosphorus Alleviates Aluminum Toxicity in Camellia oleifera Seedlings
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2019 Friends Science Publishers. Camellia oleifera Abel. (oiltea) is an edible oil tree and mostly distributed in red acid soil areas. High aluminium (Al) and low phosphorus (P) are often coexisting as two important factors limiting plant growth in acidic soils. This study evaluated plant growth, Chl a fluorescence, and P and Al contents of oiltea seedlings cultivated in sand with a toxic Al level at 4 mmol/L Al and P concentrations at 0, 0.5, 1.0 or 1.5 mmol/L in a pot experiment. Leaf photosynthesis and dry weights of shoots and roots of oiltea seedlings were increased linearly as P concentration increased. Contents of P in shoots and roots increased with P addition in the cultural solutions and peaked at 1.0 mmol/L, while Al contents in shoots and roots decreased. Under the toxic level of Al, the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) increased as P concentration increased. Twenty-eight, twenty, sixteen and nine organic compounds were identified by GC-MS in root exudates of plants subjected to 0, 0.5, 1.0 and 1.5 mmol/L P treatments, respectively. Hematoxylin staining showed that adding P increased root tip Al accumulation and transport. These results suggest that P treatment can partially alleviate Al toxicity. In addition, triethyl citrate in root exudates can serve as an indicator of Al stress.
