title: Silicon uptake and transport is an active process in Cucumis sativus.
abstract: Cucumis sativus is a species known to accumulate high levels of silicon (Si) in the tops, though the mechanism for its high Si uptake is little understood. In a series of hydroponic experiments, we examined uptake and xylem loading of Si in C. sativus along with Vicia faba at three levels of Si (0.085, 0.17 and 1.70 mm). Measured Si uptake in C. sativus was more than twice as high as calculated from the rate of transpiration assuming no discrimination between silicic acid and water in uptake. Measured Si uptake in V. faba, however, was significantly lower than the calculated uptake. Concentration of Si in xylem exudates was several-fold higher in C. sativus, but was significantly lower in V. faba compared with the Si concentration in external solutions, regardless of Si levels. Silicon uptake was strongly inhibited by low temperature and 2,4-dinitrophenol, a metabolic inhibitor, in C. sativus but not in V. faba. It can be concluded that Si uptake and transport in C. sativus is active and independent of external Si concentrations, in contrast to the process in V. faba.
authors.affiliation: Institute of Soil and Fertilizer, and Ministry of Agriculture Key Laboratory of Plant Nutrition and Nutrient Cycling, Chinese Academy of Agricultural Sciences, Beijing 100081, China. ycliang@caas.net.cn
authors.forename: Yongchao
authors.initials: Y
authors.lastname: Liang
authors.forename: Jin
authors.initials: J
authors.lastname: Si
authors.forename: Volker
authors.initials: V
authors.lastname: Römheld
mesh_terms: D019297:2,4-Dinitrophenol / Q000494:pharmacology; D001693:Biological Transport, Active / Q000187:drug effects; D018553:Cucumis sativus / Q000187:drug effects / Q000378:metabolism*; D012825:Silicon / Q000378:metabolism*; D014475:Uncoupling Agents / Q000494:pharmacology; D031307:Vicia faba / Q000187:drug effects / Q000378:metabolism; D014867:Water / Q000378:metabolism
chemical_list: D014475:Uncoupling Agents; D014867:Water; D019297:2,4-Dinitrophenol; D012825:Silicon