Rice uptake of soil adsorbed amino acids under sterilized environment

Plants can directly absorb intact amino acid molecules. However, it has not been widely accepted that amino acids can be readily adsorbed to the soil solid phase and that the adsorbed amino acids quantity is more than that of free amino acids. This experiment examined the effects of soil adsorbed glycine on plant glycine uptake, uptake efficiency, and nutritional contribution as an N source for rice seedling growth under sterilized environment. The silt loam soil from Xiaoshan site had higher glycine sorption capacity than clay loam soil from Xianju site. Soil sorption capacity was closely related to soil physical and chemical properties. Our results revealed that soil adsorbed glycine improved plant biomass compared with ammonium. The content of adsorbed glycine had a positive effect on plant glycine uptake and glycine uptake efficiency in the treatments with different ratios of adsorbed glycine and ammonium. About 4.8–11.6% and 10.9–32.2% of the adsorbed glycine in soil from Xiaoshan and Xianju, respectively, were found in rice seedling leaves and roots after 21 days of incubation. Glycine uptake accounted for about 15.7–47.3% of plant total N uptake in the treatments with different ratios of adsorbed glycine and ammonium. Glycine nutritional contribution was independent of soil sorption capacity. Therefore, we speculated that soil adsorbed amino acids can serve as an important potential N source for plant growth, and should not be overlooked in the study of nitrogen cycling in different ecosystems.