i(+)-Adenosine Activity lnhibited by D(-)-Adenosine
Various controls were used to rule out artifacts in the
protocol. Perhaps the best evidence for the lack of artifacts
was obtained from application of synthetic D(-)-adenosine,
the enantiomer of L(+)-adenosine. Tomatoes were excised 5
s after spraying with 25 different concentration combinations
of t(+)-adenosine and D(-)-adenosine. concentrations of
L(+)-adenosine that increased cation pulses were inhibited
by as little as 0.01 pg L-’ of D(-)-adenosine (Fig. 3). A11concentrations of L(+)-adenosine (up to 1000 pg L-’) were
inhibited by 10.0 pg L-’ of D(-)-adenosine. Thus, D(-)-
adenosine, the primary form of adenosine found in plants,
inhibits the activity of L(+)-adenosine when the two are
applied together exogenously. Further research will be necessary
to determine the specific mode of inhibition.