Silicon Isotope Fractionation in Maize and Its Biogeochemical Significance

Plants that absorb silicon may induce isotope fractionation that causes relative abundance changes in biogeochemical processes in organisms and environment. Silicon isotopes (Si-28, Si-29, and Si-30) were determined with high precision using multicollector inductively coupled plasma mass spectrometer. In the present study, the silicon isotope composition was determined in maize and corresponding soil was collected from Zhejiang Province, China. The Si-30 values were from -2.7 to 3.3 parts per thousand in the plant tissues. The isotope fractionation between precipitated and dissolved silicon was 0.9976 and the silicon isotope fractionation in the plants was appeared to be Rayleigh-like process. The fractionation factors between the whole plants and the soil-water-soluble fractions were estimated to be 0.9989, indicating the presence of biochemical silicon isotope fractionation. The active uptake of silicon appeared to play an important role through which the heavy silicon isotopes were preferentially absorbed and transferred to the aboveground plant tissues. However, the roles of a passive mechanism for silicon uptake could not be ruled out through which the light silicon isotopes preferentially precipitated in various plant tissues.