Oxygen flux from a mixed sample

A chamber contains 2 g of photosynthetic tissue. In darkness oxygen concentration falls by 3 micromol/L/min. At a fixed light level it rises by 5 micromol/L/min. Chamber liquid volume is 0.4 L. Gas exchange with the air is negligible. Assume respiration is unchanged by light and photosynthesis is zero in darkness. In a second light trial, an electron-transfer inhibitor reduces gross photosynthetic oxygen production by 50% while leaving respiration unchanged. All rates are initially constant.