Compared with the measureable but limited K isotope variation in geological samples,biological samples have much larger variations in δ^41 values：from-1.3‰ to＋1.1‰ relative to the international K standard NIST SR...Compared with the measureable but limited K isotope variation in geological samples,biological samples have much larger variations in δ^41 values：from-1.3‰ to＋1.1‰ relative to the international K standard NIST SRM 3141a.Notably,higher plants generally have δ^41 values that are lower than igneous rocks,whereas sea plants（algae）have δ^41 values that are higher than seawater;the range in δ^41K values of plants encompasses the δ^41 values of both igneous rocks and seawater.Plant cells utilize different K uptake mechanisms in response to highand low-K conditions.In a low-K environment,plant cells use energy-consuming ion pumps for active uptake of K;plant cells in high-K environments use non-energy-consuming ion channels.Based on these facts and on K isotope data from sea 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 could be attributed to preferential transport of isotopically light K in the energy-consuming active uptake process by K ion pumps in the membranes of plant root cells.On the other hand,the enrichment of heavy K isotopes in algae may be caused by a combination of the lack of K isotope fractionation during K uptake from seawater via ion channels and the preferential efflux of light K isotopes across the 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.展开更多
基金supported by"1000-talent Program"of China,and National Science Foundation of China(Grant No.41622301)to WL
文摘Compared with the measureable but limited K isotope variation in geological samples,biological samples have much larger variations in δ^41 values：from-1.3‰ to＋1.1‰ relative to the international K standard NIST SRM 3141a.Notably,higher plants generally have δ^41 values that are lower than igneous rocks,whereas sea plants（algae）have δ^41 values that are higher than seawater;the range in δ^41K values of plants encompasses the δ^41 values of both igneous rocks and seawater.Plant cells utilize different K uptake mechanisms in response to highand low-K conditions.In a low-K environment,plant cells use energy-consuming ion pumps for active uptake of K;plant cells in high-K environments use non-energy-consuming ion channels.Based on these facts and on K isotope data from sea 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 could be attributed to preferential transport of isotopically light K in the energy-consuming active uptake process by K ion pumps in the membranes of plant root cells.On the other hand,the enrichment of heavy K isotopes in algae may be caused by a combination of the lack of K isotope fractionation during K uptake from seawater via ion channels and the preferential efflux of light K isotopes across the 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.
