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Silicon isotope fractionation in rice and cucumber plants over a life cycle: Laboratory studies at different external silicon concentrations
Author(s) -
Sun Yan,
Wu Lianghuan,
Li Xiaoyan,
Sun Li,
Gao Jianfei,
Ding Tiping
Publication year - 2016
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1002/2016jg003443
Subject(s) - silicon , fractionation , isotopes of silicon , isotope , biogeochemical cycle , isotope fractionation , stable isotope ratio , chemistry , environmental chemistry , chromatography , physics , nuclear physics , organic chemistry
Understanding the variations of silicon isotopes in terrestrial higher plants can be helpful toward elucidating the global biogeochemical silicon cycle. We studied silicon isotope fractionation in rice and cucumber plants over their entire life cycles. These two different silicon‐absorbing plants were grown hydroponically at different external silicon concentrations. The ranges of δ 30 Si values in rice were −1.89‰ to 1.69‰, −1.81‰ to 1.96‰, and −2.08‰ to 2.02‰ at 0.17 m M , 1.70 m M , and 8.50 m M silicon concentrations, respectively. The ranges of δ 30 Si values in cucumber were −1.38‰ to 1.21‰, −1.33‰ to 1.26‰, and −1.62‰ to 1.40‰ at 0.085 m M , 0.17 m M , and 1.70 m M external silicon concentrations, respectively. A general increasing trend in δ 30 Si values from lower to upper plant parts reflected the preferential incorporation of lighter silicon isotopes from transpired water to biogenic opal. Furthermore, the active uptake mechanism regulated by several transporters might have also played an important role in the preferential transport of heavy silicon isotopes into aboveground plant parts. This suggested that silicon isotope fractionation in both rice and cucumber was a Rayleigh‐like process. The data on δ 30 Si values for the whole plants and nutrient solutions indicated that biologically mediated silicon isotope fractionation occurred during silicon uptake by roots. At lower external silicon concentrations, heavy silicon isotopes entered plants more readily than light silicon isotopes. Conversely, at higher external silicon concentrations, light silicon isotopes entered plants more readily than heavy silicon isotopes.