| Phosphorus is one of the essential nutrients required by plants for growth and development, and to a large extent lack of P in the soil affected crop yield and quality. That about 20%-80% of total soil P exists in organic forms plays a pivotal role in soil P library. Inositol penta- and hexaphosphates (phytate) and their derivatives account for a major component of the soil Po (about 50%). Phytate-Po is hardly absorbed by crops directly, as invalid P, and a potential P source. Implement the expectation that advancing the potential of soil phytate uptake for crops. If so, this development has vital significances for improving crop P nutrition and promoting the capacity of sustainable utilization of P resource. Wild barley has an abundant of genetic diversity as a kind of germplasm resources for barley breeding. The study on utilization mechanisms for Po in P-efficient wild barley genotypes has important significance to the genetic improvement of P nutrition in wild barley production. The P-efficient wild barley genotypes that had been identified in early screening, which were studied in pot and solution experiment. In order to explore the physiological mechanisms for uptaking Po in P-efficient wild barley genotypes, we studied systematically the characteristics of rhizosphere soil, root developmental adaptation and physiological metabolism in response to Po condition. The main results obtained were as follows:(1) Dry matter and phosphorus accumulation of wild barley in the different treatments was ranked as:Pi> Pi+Po> Po> CK. In addition, dry matter yield and phosphorus uptake of P-efficient wild barley genotypes exhibited significantly greater than that of P-inefficient genotype, higher 23%～55% and 12%～57%, respectively. The concentration of soil available phosphorus in P-efficient genotypes was significantly higher than that of P-inefficient genotype, and that showed deficiency in the rhizosphere soil under different phosphorus sources. The concentration of inorganic phosphorus fractions in soil was showed as follows:Caio-P> O-P> Fe-P> Al-P> Ca2-P> Ca8-P. The concentration of Ca2-P in the rhizosphere soil of P-efficient genotypes was especially lower than that of P-inefficient genotype, however, the tendency of Ca8-P, Al-P and Fe-P was opposite, there was not genotypic differences of Caio-P and O-P contents. The concentration of organic phosphorus fractions in soil was showed as follows:moderate labile organic phosphorus> moderate resistant, resistant organic phosphorus> labile organic phosphorus. The concentrations of labile and moderate labile organic phosphorus enriched in rhizosphere soil, but the moderate resistant and resistant organic phosphorus appeared decrease in rhizosphere soil of P-efficient genotypes. The concentrations of labile and moderate labile organic phosphorus in rhizosphere soil of P-efficient genotypes were significantly higher than that of P-inefficient genotype under various phosphorus source conditions. However, moderate resistant and resistant organic phosphorus concentrations had no significant difference among genotypes.(2) The biomass production and P accumulation of different P efficiencies wild barley were significantly increased, while root/shoot ratio had the decreasing tendency by supplying phytate-Po. The biomass, P accumulation and root/shoot ratio of P-efficient genotypes were higher than those of P-inefficient genotype, In addition, the rate of increase in biomass and P accumulation of P-efficient genotypes were higher than that of P-inefficient genotype by supplying phytate-Po.(3) Acid phosphatase and phytase activity in soil increased significantly with increasing concentration of phytate-Po. Furthermore, the enzyme activities in the rhizosphere soil of P-efficient genotypes were 1.23～1.33 times and 1.15～1.30 times than those of P-inefficient genotype under all Po levels. The concentration of soil available phosphorus increased significantly with supplying phytate-Po, and the concentration in the rhizosphere soil of P-efficient genotypes was significantly higher than those of P-inefficient genotype. The concentration of organic phosphorus fractions in rhizosphere soils were increased by supplying Po. The labile organic phosphorus and moderate labile organic phosphorus of P-efficient genotypes were observably lower than those of P-inefficient genotype. However, on moderate resistant organic phosphorus and resistant organic phosphorus, there was no significant difference among different P efficiencies genotypes. The results showed that the concentration of organic phosphorus fractions in rhizosphere soils were higher than those of non-rhizosphere soils due to the depletion of organic phosphorus. The waning of labile organic phosphorus and moderate labile organic phosphorus in rhizosphere soils of P-efficient genotypes was found, and the amount of deficiency were 0.64～1.12 mg·kg-1 and 13.8～33.9 mg·kg-1, respectively.(4) It showed that total root length, surface area and volume had an increase trend with decreasing Po concentration, higher 139.7%～146.0%,83.5%～117.5% and 80.7%～ 119.3% than those in normal Po concentration (0.4 mmol·L-1), respectively. At low Po application rates, root morphological parameters of the P-efficient genotypes were greater than that of the P-inefficient genotype, and root length and surface area of diameter< 0.16 mm in P-efficient genotypes were higher 156.8%-161.5% and 114.9%-147.1% than those in normal Po concentration, respectively. In the case of root and root exudates APase and phytase activity, a persistence of sharp increase was observed in P-efficient genotypes with respect to the decreasing Po concentrations in the growth media. At low Po application rates, root APase and phytase activity of P-efficient genotypes increased 163.3%～172.2% and 98.6%～121.2%, and higher 14.4%～41.2% and 23.1%～37.2% than those of P-inefficient genotype, respectively. Furthermore, root exudates APase and phytase activity of P-efficient genotypes increased 157.8%-193.4% and 172.4%～ 183.4%, and higher 20.2%-45.7% and 24.7%～51.4% than those of P-inefficient genotype, respectively. |
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