The influence of leaf senescence on light dependence of chlorophyll fluorescence of radish leaves

Chlorophyll fluorescence as an indicator of age-dependent changes in photosynthetic apparatus of wheat leaves

“…We showed ear lier that the ratio F v /F m , characterizing the maximal quantum efficiency of PSII photochemistry, under goes only slight (~8%) age dependent changes under normal growth conditions [12,14], whereas the ratio F p /F t (F p and F t are fluorescence intensities at the peak level P and under steady state, respectively [1]) exhib its age dependent changes with an amplitude of at least 40% [14]. Furthermore, the age dependence could be enhanced or weakened depending on the conditions of measurements [7,12,14]. Abbreviations: CFI-chlorophyll fluorescence induction; F 0 and F m -minimal and maximal levels of chlorophyll fluorescence after dark adaptation; and F t -minimal, maximal, and stationary levels of chlorophyll fluorescence in the light adapted state; F p -fluorescence intensity at the peak of CFI curve recorded under actinic illumination after preliminary dark adap tation; F v /F m -the ratio of variable (F v = F m − F 0 ) to maximal (F m ) fluorescence representing the maximal photochemical quantum yield of PSII; NPQ-non photochemical quenching in PSII; PAM-pulse amplitude modulated (fluorometry); PAR-photosynthetically active radiation; PFD-photon flux density; PSI and PSII-photosystem I and II; PSA-photosyn thetic apparatus; qN-coefficient of non photochemical quenching of chlorophyll fluorescence; qP-coefficient of pho tochemical quenching of PSII fluorescence; R fd -vitality index; Yield = − F t )/ -effective photochemical quantum yield, i.e., the fraction of light energy used by PSII complexes for electron transport.…”

“…Our studies with radish and wheat plants revealed a signifi cant impact of leaf senescence on the light response curves for F p /F t ratio. Leaf senescence was accompa nied by changes in shape and quantitative parameters of the light response curves for F p /F t [12,14].…”

“…It is known that these parameters are affected by stress factors [3][4][5][6] and undergo changes during natural senescence of plant leaves [5,[7][8][9][10][11][12]. The age dependence of chlorophyll fluorescence parameters is a well established fact.…”

“…However, the extent of this dependence for individual parameters remains poorly examined; in many cases researchers were satisfied by simple comparison of fluorescence characteristics in mature and senescent leaves using rough estimates of leaf age [7][8][9][10][11]13]. We showed ear lier that the ratio F v /F m , characterizing the maximal quantum efficiency of PSII photochemistry, under goes only slight (~8%) age dependent changes under normal growth conditions [12,14], whereas the ratio F p /F t (F p and F t are fluorescence intensities at the peak level P and under steady state, respectively [1]) exhib its age dependent changes with an amplitude of at least 40% [14]. Furthermore, the age dependence could be enhanced or weakened depending on the conditions of measurements [7,12,14].…”