In order to ascertain whether oxidative phosphorylation in plant mitochondria is sensitive to light, coupled durum wheat (Triticum durum Desf.) mitochondria were irradiated with a low power continuous wave Helium-Neon laser (fluence: 2 Joules/cm2), with measurements made of certain processes related to ATP production. As a result of irradiation, an increase in the rate of ATP synthesis was found, as continuously monitored via luciferine/luciferase, moreover the mitochondrial ATP and ADP endogenous contents were found to increase and decrease, respectively with a 1:1 stoichiometry, as revealed by HPLC measurements. Consistently, an increase in mitochondrial rate of delta psi generation was found as measured by using the fluorescent probe safranine. Thus, this paper gives a first evidence of a novel property of plant mitochondria: the direct light sensitivity of ATP synthesis via oxidative phosphorylation.