| Aquilaria sinensis (Lour.) Gilg of Thymelaeaceae family, a tropical and subtropical evergreen tree species, was an important rare medical plant in China with high medicinal and economic value. Recently, many private enterprises and state-owned Forest Farm increasely invested in the establishment of A.sinensis plantation. The climate and soil conditions in mosts of tropical and subtropical areas were suitable for the growth of A.sinensis. However, the lower contents of soil available nitrogen and phosphorus element derived from soil erosion and acidification, and seasonal drought in some areas also seriously impacted on the survival rate of afforestation of A.sinensis seedlings. Exploring the nutrition demand amount of nitrogen(N) and phosphorus(P) of the A.sinensis seedlings, researching the relationship between nutrition demand and water stress tolerance, as well as selecting high capability of drought-resistance provenance are scientific issues need to be solved urgently. The effects of diffferent of N and P application amount on the growth of A.sinensis seedlings, and the accumulation of N, P, K, Ca anc Mg element were studied in two pot experiments. In addition, the effects of N and P nutrition added and water availability on the growth of A.sinensis seedlings were studied in water culture and soil culture pot experiments respe ctively.The nitrogen fertilizing experiment of A.sinensis seedlings were studied by using exponential fertilization and a completely randomized block(CRB) design with six different levels (0,100,200,400,600and800mg·plant-1). The result showd that height (H), taproot length(TL) and leaf area(LA), biomass of roots, stems, leaves and the total of A.sinensis seedlings were increased with the increasing of N supply, and reached the peak value at600mg·plant-1N. The root collar diameter(Do) was reached the peak value at800mg·plant-1N. The radio of root and shoot mass decreased with the increase of the nitrogen supply, reached the minimun at600mg·plant-1N. The N, P, K, Ca and Mg content in leaves increased generally with the nitrogen addition increased, and reached the maximum at600mg·plann-1N. It could be inferred that600mg·plants-1could be the optimal nitrogen application amount for A.sinensis seedlings.The phosphorus fertilization experiment of A.sinensis seedlings were studied by using RCB design with seven levels of P (0,200,400,600,800,1000and1200mg·plant-1.). The result showd the H, Do, LA, and biomass of roots, stems, leaves and the total of seedlings increased with the increasing of P supply, reached the maximun at800mg-plant-1. The root biomass reached the maximun at1000mg·plant-1P, but ther was no signicant difference with the treatment of800mg·plant-1P. The radio of root and shoot mass reached the minisum at800mg·plant-1P. The content of N, P, K, Ca and Mg in leave increased generally with the P addition-increased during200to800mg·plant-1P, and decreased significantly over800mg·plant-1P, It concluded that800mg·plant-1P could be the optimal nitrogen application amount for A. sinensis seedlings.An experiment of taking three A.sinensis provenances, two levels of nitrogen supply(7.5mol·L-1,15mol·L-1) and two levels of water stress (-0.04MPa,-0.63MPa) by PEG-induced, was conducted to study the response of physiological and biochemical indices. The results showed that the different nitrogen supply and water stress levels had significant effects on the relative conductivity, the superoxide dismutase(SOD) activity, proline mass fraction and malondialdehyde(MDA) molality. Under the appropriate water condition, although the high nitrogen supply was beneficial to improve the antioxidant enzyme activity and free proline mass fraction, it caused a certain degree of osmotic stress, representative by the increasing of MDA molality and relative conductivity. Under the water stress condition, the relative conductivity and the molality MDA of the high nitrogen treatment were lower than that of the low nitrogen treatment, on the contrary, for the catalase(CAT) activity and free proline mass fraction. The peroxidase(POD) activity was not actively responsed by the nitrogen supply and water stress. There was significantly difference in relative conductivity among the three Provenances. The value in Qiongzhong Provenance was higher than that of Chenmai Provenance, while Lingao Provenance in the between. Althought SOD activity and CAT activity, as well as proline mass fraction and MDA molality were some difference among the three provenances, high nitrogen supply is helpful for improving their drought resistance under-0.6MPa water stress conditions.An experiment of taking two A. sinensis provenances, there levels of phosphorus supply(0,200and800mg·plant-1) and three levels of water stress(30-35%,50-55%,70-75%media mositure), was conducted to study the response of physiological and biochemical indices. The results showed that the different P supply and water stress levels had significant effects on the malondialdehyde(MDA) molality, the superoxide dismutase(SOD) activity, proline mass fraction and root activity. The lower soil water content, MDA molality, SOD activity, CAT activity were higher. The POD activity and the proline mass fraction improved with the decrease of soil moisture, under the high and moderate P treatments. But they reached the maximum at moderate water stress, under the low P treatment. Under low P treatment, the root activity reached the maximum at normal water condition. Under moderate P treatment, it reached the maximum at moderate water stress conditions. Under high P treatment, it reached the maximum at severe water stress. Under the water stress condition, MDA molality decreased gradually, antioxidant enzyme activity increased, with the increase of P supply. Except for MDA molality, There were significant differences among the three provenances in terms of antioxidant enzyme activity, proline mass fraction and root activity. Qiongzhong provenance was significantly higher than that of Chengmai. The higher P supply could effectively improve the drought resistance of A. sinensis seedlings. |
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