1. Comparison of Rhizospheric Impacts of Wheat (Triticum aestivum L.) Genotypes Differing in Phosphorus Efficiency on an Acidic and an Alkaline Soil Acknowledgments We are grateful to National Basic Research Program of China (2007CB109302). Wen Ke Liu, Xiaoying Zhan,Shuxiang Zhang* Materials and Methods A glasshouse study was conducted to compare the rhizospheric characteristics of two wheat (Triticum aestivum L.) genotypes, Xiaoyan54 (XY54, P- efficient ) and Jing411 (J411, P- inefficient ), with two contrasting pH values in an alkaline (Fluvo- aquic) from Shaanxi and an acidic ( red ) soil from Hunan. Two P treatments with different level (P0: No P addition and P1: 100 mg KH 2 PO 4 ·kg -1 soil). Objective The exploitation of phosphorus (P) use efficient genotypes of crops and understanding of their rhizospheric effects are essential to develop the management practice for sustainable agriculture under the condition of different P input. Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences/ Ministry of Agriculture Key Laboratory of Crop Nutrition and Fertilization, Beijing 100081,China. Tel +86-10 82106202 *Email:sxzhang@caas.ac.cn Conclusion P application increased P content of shoot, biomass of shoot and root for two wheat lines alkaline soil was a principal significantly on alkaline; but P fertilization only enhanced P content of shoot for acidic soil. The acidification on alkaline soil was a principal rhizospheric mechanisms for XY54 to acquire more P under no P addition, and resulted higher root uptake. The glasshouse experiment clearly demonstrated that both soil type and P level affect the growth, P uptake and rhizospheric properties of wheat genotypes with different P use efficiency. Table 1 Physical and chemical properties of the two soils tested Soils pH Total P g·kg -1 Total K g·kg -1 Total N g·kg -1 Organic matter g·kg -1 Available P mg·kg -1 Organic P mg·kg -1 Fluvo- aquic soil 8.000.5811.060.419.729.081.2 Red soil 4.940.589.050.9715.4130.0131.2 Soils P level Genotypes Biomass (g·pot -1 ) P content (mg·pot -1 ) ShootRootShootRoot Fluvo- aquic soil P0P0 XY548.29c4.44bc0.13e0.08a J4118.12c3.48c0.12e0.04b P1P1 XY5410.49a5.46ab0.31a0.10a J41110.59a4.99abc0.25b0.08a Red soil P0P0 XY549.39b6.57a0.17d0.07ab J41110.35a6.38a0.18d0.07ab P1P1 XY549.48b5.73ab0.23bc0.07ab J41110.71a5.14ab0.21c0.06ab The P content in root for XY54 with no P addition was higher than J411 in the Fluvo-aquic soil, not for the red soil. P application significantly increased P content in shoot and the whole plant, but not in root for these two wheat lines on these two contrasting soils. The higher phosphatase activity for XY54 was higher than that of J411 on red soil under two P levels, which did not resulted higher P uptake. On Fluvo-aquic soil, J411 and XY54 demonstrated the similar rhizoshpheric phosphatase activity irrespectively of soil P level and rhizosphere site (data omitted). Table 2 Wheat biomass and P content of XY54 and J411on Fluvo-aquic and red soils Figure 2 Rhizospheric pH of the two wheat genotypes at two P levels on Fluvo-aquic Vertical bars indicate standard error (n=4),same as in the Figure 3. Figure 3 Rhizospheric phosphatase activity of the two wheat genotypes at two P levels on Red soils (mg phenol·kg -1 soil). Notes: In the same column, the different letters following the averages indicated significantly differences between treatments at P<0.05 level, the same letters following the averages indicated no differences between treatments at P<0.05 level. Results The rhizobox are 20 cm×7 cm×20 cm (length×height×width), the 3cm for inner compartment for wheat growth. In the seedling stage, biomass and P content of different wheat, pH and the phosphatase activity of rhizosphereic and non- rhizosphereic soil samples were measured (Figure 1). Under no P addition, the significant decrease of pH was greater in the XY54 rhizosphere than in the J411 rhizosphere, but not for P addition under the Fluvo-aquic soil. The same situation did not existed in the red soil (data omitted). Figure 1 Schematic figure of the rhizobox. R1 to R5 in two outer compartments means 0-5 mm from root surface, 1mm rhizosphere soil made up a sample. BS means non-rhizosphere soil.