Peroxidase and Glucose-6-phosphate Dehydrogenase Levels in Cotyledons ofCucumis sativus(L.)

Peroxidase and glucose-6-phosphate dehydrogenase become increasingly active in cucumber cotyledons excised from the plant although there is a fall in total protein content. The increases are inhibited by dinitrophenol, D, and L-threo-chloramphenicol, cycloheximide, puromycinj and actinomycin D, and it is concluded that the enzymes are synthesized de novo. Disc electrophoresis of cotyledon extracts revealed three bands of peroxidase, one of which becomes much enhanced in excised cotyledons. Citrulline accumulates markedly in excised cotyledons. If the shoot of cucumber plants is cut away above the cotyledons, very large increases in peroxidase and glucose-6-phosphate dehydrogenase are observed although yellowing and protein loss are delayed.