Activation of Chlororespiration Increases Chlorophyll Fluorescence Yield in Chlorella Adapted to Darkness at High Temperature

A tenfold increase in chlororespiration during dark incubation of Chlorella perynoidosa Chick CALU-175 at high temperature doubled the initial chlorophyll fluorescence yield (F sub(0)). The presence of iodacetamide or unmetabolizable glucose analog 2-deoxy-D-glucose prevented increase in both chlororespiration and F sub(0) yield. The rates of chlororespiration and F sub(0) yield growth demonstrated a similar pattern of temperature dependence. Inhibition of electron transport between Q sub(A) and plastoquinone with diuron prevented increase in F sub(0) during dark incubation of the cells at high temperature. Apparently, a pool of plastoquinone was restored in the chlororespiratory chain during the dark incubation at 37.5-41 degree C, and plastoquinone exchanged electrons with Q sub(A). This is the cause of Q sub(A) reduction and subsequent increase in F sub(0) yield.