Several cuttings were removed from a plant grown in 50yo D20 nutrient for 40 days. One cutting was transplanted into a culture flask containing 50% D20 nutrient solution. and the other was placed in a flask containing aqueous nutrient and no DtO. The former cutting showed no sign of developing a root system and succumbed within 3 to 4 weeks.
The latter grew a root system within 2 weeks and continued growing in a normal manner similar to a typical control plant. It was hoped that if a root system would develop in the 50% DpO medium. it would be possible to propagate a deuteriated plant; and possibly with successive cuttings in constantly increasing concentrations of D20 a plant could be grown in a highly deuteriated medium. Thus far, this has not been successful, but further work is in progress with this aspect of the investigation.
In Fig. 4 comparison is made between the deuterium content of the water distilled from the deep frozen fresh plants and the water of combustion of the dried plants.
The distilled or labile water contains deuterium from water loosely bound by the plant tissues and represents essentially completely exchangeable deuterium.
The deuterium content of the labile water from the plant is approximately 75% that of the nutrient solution in which the plant was grown. The water obtained from combustion of the dried plants, representing organically bnund exchangeable and nonexchange-83 able deuterium, contains about 50% of the deuterium content of the nutrient solution. The ratio of organically bound to labile deuterium is about 0.66, somewhat higher than that reported by Katz, el a2. (6), for certain tissues in mice. This may reflect the nonequilibrium aspects of the situation resulting from the continuous transpiration of water. The active water metabolism and the ensuing fractionation may contribute significantly to the observed isotope effects.