Vital effects of K isotope fractionation in organisms:observations and a hypothesis
Compared with the measureable but limited K isotopic variation in geological samples,biological samples have much larger variations in δ41K values,ranging from-1.3‰ to+1.1‰ relative to the international K standard NIST SRM 3141a.Notably,higher plants generally have δ41K values that are lower than the igneous rocks,whereas sea plants(algaes)have δ41K values that are higher than the seawater.Plant cells utilize different K uptake mechanisms in respond to high and low K conditions,that in a low K concentration environment,plant cells use energy-consuming ion pumps for active up take of K,whereas non energy-consuming ion channels are used by plant cells in environments of high K concentrations.Based on this fact and the measured K isotope data from sea plants and land plants,it is hypothesized that the different K uptake mechanisms are accompanied by distinct K isotope fractionation behaviors or vital effects.The enrichment of light K isotopes in terrestrial plants is attributed to preferential transport of isotopically light K in the energy consuming active K uptake process by K ion pumps in membrane of plant root cells.The enrichment of heavy K isotopes in algaes is caused by a combined effect of the lack of K isotope fractionation during K uptake from seawater via ion channels and the preferential efflux of light K isotopes across cell membrane back to the seawater.The large variation of K isotope compositions in biological samples therefore may reflect the diversity of isotopic vital effects for K in organisms,which implies the great potential of K isotopes in biogeochemical studies.
Weiqiang Li
School of Earth Sciences and Engineering,Nanjing University,Nanjing 210046,Peoples Republic of China;Institute of Lunar and Planetary Sciences,Nanjing University,Nanjing 210046,Peoples Republic of China
国际会议
The 11th International Symposium on Geochemistry of the Earths Surface(GES-11)(第十一届地球表层地球化学国际研讨会)
贵阳
英文
1-5
2017-06-11（万方平台首次上网日期，不代表论文的发表时间）