Light-mediated Oxygen Uptake Measured in Wheat Etioplasts.

An in vitro O(2) assay was used to measure early response of wheat (Triticum aestivum L.) etioplasts to light. A transient photoinducible O(2) uptake occurred when dark-grown etioplasts were initially exposed to light. The rate of inducible O(2) consumption was dependent on both the intensity of light and the quantity of organelle protein present. Higher light intensities resulted in greater O(2) utilization per minute, and a greater quantity of organelle protein in the sample resulted in an increased rate of O(2) 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 O(2) uptake phenomenon. A preliminary action spectrum study revealed that wavelengths 640 to 680 nm resulted in maximum O(2) uptake. This indicated the presence of an etioplast red light receptor pigment which induces O(2) uptake in etioplasts.