Stabilization by glutaraldehyde of high-rate electron transport in isolated chloroplasts

Treatment of isolated chloroplasts with glutaraldehyde affects their ability to photoreduce artificial electron acceptors. The remaining rate of O₂ evolution approaches zero with methyl viologen, is low with ferricyanide, but nearly normal with lipophilic Photosystem II acceptors, like oxidized p-phenylenediamine and oxidized diaminodurene. Since Photosystem I donor reactions are also affected, a specific site of inhibition of electron transport to Photosystem I is indicated. At the same time, glutaraldehyde prolongs the longevity of the chloroplasts stored in dark. In control samples the half-life of Photosystem II activity varied between 5 days at 4 °C and 1 day at 25 °C. Glutaraldehyde treatment increased these half times approx. 3-fold. The glutaraldehyde doses required to induce inhibition and stabilization were very similar.