Light-mediated Oxygen Uptake Measured in Wheat Etioplasts

An in vitro O₂ assay was used to measure early response of wheat (Triticum aestivum L.) etioplasts to light. A transient photoinducible O₂ uptake occurred when dark-grown etioplasts were initially exposed to light. The rate of inducible O₂ consumption was dependent on both the intensity of light and the quantity of organelle protein present. Higher light intensities resulted in greater O₂ utilization per minute, and a greater quantity of organelle protein in the sample resulted in an increased rate of O₂ uptake under the same light intensity conditions. Experiments with various plant tissues as well as with mitochondrial respiratory inhibitors indicated that etioplasts are the organelles responsible for the photoinduced O₂ uptake phenomenon. A preliminary action spectrum study revealed that wavelengths 640 to 680 nm resulted in maximum O₂ uptake. This indicated the presence of an etioplast red light receptor pigment which induces O₂ uptake in etioplasts.