Abstract:

Phosphorus (P) deficiency is one of the main factors that influences plant productivity in agricultural and forestry systems. Fertilization and soil improvement are the primary measures used to meet the P demands of crops in traditional agriculture and trees in forestry management. Recently, plants with high phosphorus use efficiency have been discovered and used to replace traditional measures for improving phosphorus use efficiency of corps. Chinese fir (Cunninghamia lanceolata), a fast-growing, evergreen conifer tree with high yield and excellent wood quality, is the most important tree species of timber plantations in subtropical China. In order to understand the P demands of Chinese fir clones, levels of acid phosphatase (APA) activity were studied in the leaves and rhizosphere soil of different potted Chinese fir clones under different levels of phosphorus additions. The potted Chinese fir clones were subjected to four P supply levels: normal P supply (16 mg•kg－1), slight P deficiency (8 mg•kg－1), medium phosphorus deficiency (4 mg•kg－1) and heavy phosphorus deficiency (0 mg•kg－1). The results showed that the activities of APA in the leaves and rhizosphere soil under the P-deficiency treatment were higher than those under normal P treatment, and there were significant differences in the levels of APA activity among the 8 Chinese fir clones. The activities of APA in the leaves and rhizosphere soil of clones 8, 24 and 37 under the P-deficiency treatment were much higher than those under normal P treatment. Compared with the APA levels in leaves, the activities of APA in the rhizosphere soil of clones 5 and 9 under the P-deficiency treatment had higher amplitudes than those under normal P treatment. The clones 3, 23 and 34 were insensitive to P stress, and there were no significant treatment effects on APA levels for these clones. Under the P-deficiency treatment, the activities of APA in the leaves and rhizosphere soil of different Chinese fir clones increased in response to the P stressed environment, and there were significant differences in the abilities of the different Chinese fir clones to adapt to low P levels. Therefore, more research is needed in order to determine whether APA level is an important index for evaluating and selecting Chinese fir clones with high phosphorus use efficiency.