To investigate the key growth and physiological mechanisms underlying the adaptation of different families of Choerospondias axillaris to low phosphorus stress, so as to provide theoretical basis for the subsequent cultivation of high phosphorus efficiency and excellent varieties.

High-phosphorus-efficient families (L56, LF001) and low-phosphorus-sensitive families (L44, R27) were selected as experimental materials. A pot experiment was conducted under two phosphorus levels: normal phosphorus (16.0 mg/g, NP) and low phosphorus (0.2 mg/g, LP). Growth and physiological indices, including ground diameter, plant height, biomass, tissue phosphorus content, root activity, the activities of acid phosphatase (ACP), superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and nitrate reductase (NR) in rootswere measured to analyze the responses of morphological and physiological traits of different families to low phosphorus stress at the seedling stage.

1) Under LP stress, the growth of four families was significantly inhibited, while the root-to-shoot ratio, root activity, POD activities and phosphorus use efficiency (PUE) increased significantly. ACP and NR activities showed a decreasing trend, whereas SOD and CAT activities tended to increase. The responses of these indicators to LP stress exhibited significant variation among families; 2) Under low phosphorus stress, except for seedling height, the growth indexes such as ground diameter, root dry matter mass, total dry matter mass accumulation, root activity, ACP, SOD, NR activity and PUE of family L56 and LF001 were significantly higher than those of family L44 and R27; 3) There were obvious family differences in the response of antioxidant enzyme system (SOD, POD, CAT) to low phosphorus stress: L56 showed extremely high SOD activity and high POD and CAT activity; lF001 showed extremely high POD activity and high SOD and CAT activity. R27 showed higher POD activity, but lower SOD and CAT activity. L44 showed higher CAT activity, but lower POD and SOD activity; 4) Correlation analysis showed that there was a significant positive correlation between root-shoot ratio, root activity and antioxidant enzyme activity (SOD, POD, CAT) of Choerospondias axillaris at seedling stage. There was a significant positive correlation between NR and ACP, ground diameter, root dry weight, aboveground part dry weight and other growth indexes. The aboveground P accumulation was significantly positively correlated with aboveground part dry matter, but significantly negatively correlated with PUE.

L56 and LF001 belong to the synergistic and efficient type of high accumulation and high efficiency.