Abstract
Under aerobic conditions the fungal toxin fusicoccin (FC) and the plant hormone auxin (IAA) induce rapid cell elongation in excised coleoptile segments of etiolated rye seedlings ( Secale cereale L.). The timecourse changes in the rates of oxygen uptake in darkness were measured polarographically using a Clarktype electrode. The FC-induced growth response was accompanied by a rapid enhancement in the rate of dark respiration (+ 75% within 30 min of FC-treatment). Under identical conditions IAA had no significant effect on respiration of the cells of the rye coleoptile. These results provide additional evidence for the acid-growth hypothesis of FC action. It is concluded that the FC-induced rise in the rate of mitochondrial dark respiration represents a indirect consequence of the activation of the plasma membrane H + -ATPase by the phytotoxin.
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