Studies of the reactions of photosynthesis and transfer in the bioaccumulation of tritium into the organic matter of vegetables

Plants (Phaseolus vulgaris L.) were exposed in the laboratory to tritium water vapor or to carbondioxide labelled with 14C. The samples were freeze-dried and then extracted in such a way that the entire exchangeable tritium was retained and separated from non-exchangeable tritium. These experiments revealed two compartments in the dry matter, the one consisting of exchangeable organic tritium, the other of non-exchangeable one. The former may consist of up to 44% of the hydrogen in dry matter, a value which corresponds to the proportion of hydrogen in exchangeable positions. The non-exchangeable tritium represents only about 3 - 5% of total hydrogen and is derived from the fixation of tritium by photosynthesis as is also shown by the 3H/14C ratio. It is noteworthy that the exchangeable organic tritium is very unstabile and that the normally determined organic tritium is non-exchangeable. (author)