User talk:NPQ

Non-photochemical quenching of chlorophyll fluorescence
In higher plants the capacity for photosynthesis tends to saturate at high light intensities while the absorption of light remains linear. Therefore there exists the potential for the absorption of excess light energy by photosynthetic light harvesting systems. This excess excitation energy leads to an increase in the lifetime of singlet excited chlorophyll increasing the chances of the formation of long-lived chlorophyll triplet states by inter-system crossing. Triplet chlorophyll is a potent photosensitiser of molecular oxygen forming singlet oxygen which can cause oxidative damage to the pigments, lipids and proteins of the photosynthetic thylakoid membrane. One photoprotective mechanism that exists to counter this problem is the so-called non-photochemical quenching of chlorophyll fluorescence (NPQ) which relies upon the conversion and dissipation of the excess excitation energy into heat. The mechanism(s) of NPQ remains one of the most hotly debated areas of modern photosynthesis research and has created a focal point for the overlap of modern photo-physics, biochemistry, molecular biology and plant physiology.