| Phosphorus is one of the inorganic nutrients required by plants for growth and development, application of fertilizer in agricultural production as a measure to improve crop yields, but poor mobility of phosphorus, soil adsorption and easily fixed, resulting reactive phosphorus utilization of scarce crops directly. Wild barley genetic resource is an important improvement of the modern cultivated barley varieties. Screening wild barley genotypes with P-efficient genetic characters, the study on the rhizosphere physiological mechanisms of P efficiency has important significance to the genetic improvement of P nutrition in wild barley production. The study collected 16 parts with a wide range of wild barley germplasm genetic differences, based on the evaluation of P efficieney in different wild barley genotypes, P-efficient genotype IS-22-30, IS-22-25 and P-ineffieient genotype IS-07-07 were screened from the population. Used the two genotypes, rhizo bag pot experiment were conducted to study systematically the genotypic differences of physiology in response to low-P stress, and then the physiological mechanisms of P efficiency were discussed. The objectives of the present study were to investigate the the effects of phosphorus on the growth of wild barley within the two genotypes; uptake and utilization of phosphorus; rhizosphere soil pH values; acid phosphatase activity; and P fraction of rhizosphere and bulk soils with pot culture, root box culture and solution culture, respectively. The main results are as follows: (1) Under low phosphorus condition, biomass, phosphorus accumulation, phosphorususe efficiency for dry matter (PUE for dry matter), phosphorus use efficiency for grain yield (PUE for grain yield) were difference among genotypes. The biomass per plant of genotypes with widely background sources ranged from 0.66-1.47g (Jointing stage)、 3.58～8.31g (Flowering staged 5.94～12.11g (Maturing stage), respectively. And the phosphorus accumulation per plant of genotypes ranged from 1.99-4.25mg (Jointing stage)、6.10-9.20mg (Flowering staged 8.86～19.96mg (Maturing stage), respectively. Significant differences was observed in PUE for dry matter (Jointing stage CV=11.6%, Flowering stage CV=12.4%, respectively) or P use efficiency for grain yield (Maturing stage CV=13.7%) among the genotypes. The grain yield of IS-22-30 and IS-22-25 were 3.10 times and 3.20 times higher than of IS-07-07, is efficient genotypes. P efficient genotypes IS-22-30, IS-22-25 not only has a high absorption capacity of the material accumulation and phosphorus, phosphorus recycling capacity is also strong.(2) The concentrations of available P and water soluble phosphorus in rhizosphere soils were lower than those of non-rhizosphere soils for the all genotypes when supplied 0 and 30 mg P kg"1 to the soils. Moreover, the water soluble P contents of P-efficient genotypes in the rhizosphere soils were lower than those of P-inefficient genotype. The concentration of inorganic P fractions showed in the order of Ca10-P>O-P>Fe-P> Al-P> Ca2-P>Ca8-P for the rhizosphere and non-rhizosphere soils, and Caio-P content of more than 80%of total inorganic phosphorus. Under 30 mg P kg-1 soil, Cas-P concentrations in rhizosphere soils of P-efficient genotypes were significantly higher than those of P-inefficient genotype during the jointing and flowering stage. However, Ca2-P concentrations in rhizosphere soils of the former were significantly lower than those of the latter. Without P supplied to the soil, the concentrations of Ca2-P and Cag-P in the rhizosphere soils of P-efficient genotypes were significantly higher than those of the P-inefficient genotype, and Caio-P concentration in rhizosphere soils decreased for the all genotypes. Fe-P and O-P concentrations in rhizosphere soils of P-efficient genotypes were significantly higher than those of P-inefficient genotype with 30 mg P kg-1 supplied to the soil. However, Al-P concentrations in rhizosphere soils of the former were significantly lower than those of the latter. Moreover, Al-P, Fe-P and O-P concentrations in rhizosphere soils of P-efficient genotypes were significantly lower than those of P-inefficient genotype without P supplied to the soil. In conclusion, the absorption capabilities of Al-P and Ca2-P in the P-efficient genotypes were greater than those of the corresponding P-inefficient genotype when exposed to the low P soils for the wild barley. The absorption capabilities of Al-P, Fe-P, Ca2-P and Cag-P in the P-efficient genotypes were greater than those of the corresponding P-inefficient genotype when exposed to the low P soils for the wild barley.(3) The activity of rhizosphere acidification of P-efficient genotypes (IS-22-30, IS-22-25) were significantly higher than that of P-inefficient genotype (IS-07-07) under low P application rates. The Effects of IS-22-30, IS-22-25 rhizosphere soil pH value range of 6 mm, while IS-07-07 is 4 mm. Under different phosphorus treatments, different categories of wild barley genotypes rhizosphere soil acid phosphatase activity significantly different. At low P application rates, P-efficient genotypes rhizosphere soil acid phosphatase activity effects range from 4 mm, while P-inefficient genotype of 2 mm. The higher soil pH decreased amplitude and effects range of acid phosphatase activity of P-efficient genotypes (IS-22-30, IS-22-25) were significantly higher than that of P-inefficient genotype (IS-07-07) under low P application rates, it showed that high phosphorus efficiency wild barley has a strong ability to adapt to low-phosphorus soil environment and soil phosphorus activation capability. Roots of acid phosphatase activity were significantly increased for different phosphorus efficiency wild barley genotypes with the decreasing P application, and P-efficient genotypes were significantly higher than that of P-inefficient genotype. Indicating that phosphorus recycling capacity in plant of P-efficient genotypes were higher than P-inefficient genotype. For wild barley genotypes of high phosphorus use efficiency and uptake efficiency, the activation capaciities of phosphorus were higher than those of wild barley genotypes of low phosphorus use efficiency and uptake efficiency. Higher acid phosphatase activity is its efficient absorption of the important characteristics of phosphorus.(4) With the increasing P fertilizer amounts, the dry matter weigh and phosphorus accumulation of different phosphorus efficiency wild barley increased, and -matter weigh and phosphorus accumulation of P-efficient genotypes were significantly higher than that of P-inefficient genotype in different P treatments. Under different phosphorus treatment, most of the phosphorus in the soil are NaOH-Pi and Residual-P which exists in two forms. Two genotypes of wild barley rhizosphere soil H2O-Pi, NaHCO3-Pi, NaOH-Pi, HCl-Pi, NaHCO3-Po and NaOH-Po six kinds of components significantly forms of phosphorus depletion phenomenon in different P treatments. P-efficient genotypes IS-22-30, IS-22-25 rhizosphere soil of the six forms of phosphorus depletion was significantly greater than P-inefficient genotype IS-07-07, this may be the IS-22-30, IS-22-25 has a high absorbing ability of different phosphorus. While the two genotypes of wild barley rhizosphere Residual-P no obvious depletion phenomenon. P-efficient genotypes roots secrete more acid phosphatase in different P treatments, in the rhizosphere soil acid phosphatase activity and NaHCO3-Po and NaOH-Po depletion of two organic phosphorus-fractions were significantly or very significantly negative correlation, description acid phosphatase activity of wild barley played a very important role in rhizosphere soil organic phosphorus mineralization process. |
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