Preliminary Measurement on Uptake of Tritiated Methane by Plants

Uptake of atmospheric tritiated methane by plants was examined in a preliminary study. Several potted plants which differ in their photosynthetic processes were exposed to tritiated methane in an enclosed chamber. The plants were exposed to a total of 185 MBq of tritium in the form of methane. The methane carrier gas was 630 ppm. The potted plants exposed to tritiated methane included edible Chinese mustards (Komatsuna in Japanese), Indian corns, cactuses. Each pot was covered with a plastic bag to prevent the reaction of methane gas with the potted soil. Only the leaves and branches were exposed to tritiated methane. Tritium was detected in the exposed leaves of C3 and C4 plants, not only in the water soluble form but also in the organically bound tritium form. There seems to be no difference in the transfer mechanism of tritium from methane to C3 and C4 plants. CAM plants which have different photosynthetic processes, did not accumulate HTO. This means that the transfer of tritiated methane to C3 and C4 plants is general phenomena not depending on the difference of the photosynthetic processes among the C3 and C4 plants.