The effect of systox on rubidium absorption by excised barley leaf tissue

The influence of various concentrations of the thiol isomer of Systox on Rb absorption by excised barley leaf tissue was compared with the effect of DNP and DCMU. Rb absorption, regardless of the external salt concentration, was progressively reduced as the Systox concentration in the external solution was increased from 0.25 to 1.0 mM. Under anaerobic conditions, light-enhanced Rb absorption by leaf tissue was not influenced by Systox treatments. DNP treatment reduced ion absorption by leaf tissue. In the dark, the relative inhibitory effect of DNP and Systox treatment on Rb absorption was greater than in the light. The combination of Systox plus DNP inhibited Rb absorption more than did separate treatment with either compound. DCMU treatments in the light resulted in a reduction of light-enhanced Rb uptake. Also in the light, the combination of DCMU with Sytox, DNP, or both, inhibited Rb uptake more than did separate treatments of Systox, DNP, or Systox plus DNP. It is suggested that the inhibitory effect of Systox on Rb absorption by leaf tissue is due to partial inhibition of oxidative phosphorylation. Moreover, since light-enhanced Rb absorption is not affected by Systox, it is concluded that Systox has no effect either on the photophosphorylation reactions or on the utilization of high-energy phosphorylated compounds.