Chlorophyll fluorescence measurement is a widely used technique to determine photosynthetic performance. Light energy absorbed by a chlorophyll molecule can be dissipated by driving photochemical energy conversion, as heat in non-photochemical quenching processes, or it is re-emitted as fluorescence. The loss of light energy as chlorophyll fluorescence is primarily derived from photosystem II. Photosystem II is a thylakoid-embedded multiprotein complex which provides the high redox potential needed to oxidize water. Within photosystem II photons of light are captured and used to energize electrons. Energized electrons are fed into the linear electron transport chain and photosystem II replenishes lost electrons with electrons from splitting of water. Chlorophyll fluorescence yield can be quantified using a modulated fluorometer device. In such a device, a modulated measuring light beam (switched on and off at a high frequency) and the parallel detection of fluorescence exclusively excited by the measuring light allows chlorophyll fluorescence measurements in the presence of photosynthetic (actinic) light. In addition, high intensity, but short duration light flashes (saturating pulses) are used to determine maximum fluorescence yields in dark and light adapted leaves. In this protocol the procedure to receive a typical fluorescence graph of Arabidopsis wild-type leaves is given. Furthermore, this procedure can be used to identify Arabidopsis mutant plants affecting photosystem II, on the basis of the respective fluorescence graphs and values.

Arabidopsis (拟南芥)

Phtotosynthesis (phtotosynthesis)

Photosystem II (光系统II)

Chlorophyll fluorescence (叶绿素荧光)

Pulse Amplitude Modulation PAM (脉冲振幅调制)