Chlorophyll fluorescence kinetic depends on age of leaves and plants

Recently, parameters of chlorophyll (Chl) fluorescence induction kinetics have often been used as characteristics of stress effect on plant photosynthesis. In these determinations, age of tested leaves and plants is only exceptionally taken into account. Nevertheless, photosynthetic activities markedly change during life span of leaves and plants, they even vary at individual places of the leaf blade that differ in relative age of cells and chloroplasts. These changes are reflected in Chi fluorescence kinetic, and the ontogenic differences in its parameters may be larger than those induced by stress. Comparison of values from the literature has shown that relatively independent of leaf age is the often used ratio of variable and maximum fluorescence F-v/F-m: it rapidly declines only at leaf senescence, when its value is related to the Chi content in leaves.