HYDROGEN ISOTOPE PARTITIONING DURING PLANT-GROWTH

The intrinsic rate of natural growth as well as the growth increment o f the hydrogen isotopes H-1 and H-3 in non-exchangeable organically bo und states of maize and barley (representatives of C4- and C3-plants) are determined. In contrast to the kinetic isotope effect, the heavy i sotope is preferred instead of retarded not only in the growth rate bu t also in the growth increment. Local accumulation of the heavy hydrog en isotope in exchangeable hydrogen positions during growth and subseq uent relocation in non-exchangeable positions can be concluded. Struct ural hydrogen bonds, which are abundant in carbohydrates, proteins, DN A, etc., have to be taken into account. The usually employed isotope a nalysis of isolated plants or plant organs cannot reveal these facts. (C) 1997 Elsevier Science Ltd.