Chlorophyll fluorescence induction, chlorophyll content, and chromaticity characteristics of leaves as indicators of photosynthetic apparatus senescence in arboreous plants

Parameters of chlorophyll fluorescence induction (CFI) are widely used for assessment of the physiological state of higher plant leaves in biochemical, physiological, and ecological studies and in agricultural applications. In this work we have analyzed data on variability of some CFI parameters — Φ PSII max = F v / F m (relative value of variable fluorescence), q NPQ (non-photochemical quenching coefficient), R Fd (“vitality index”) — in autumnal leaves of ten arboreous plant species of the temperate climatic zone. The correlation between the chlorophyll content in the leaves and fluorescence parameters characterizing photosynthetic activity is shown for two representative species, the small-leaved linden Tilia cordata and the rowan tree Sorbus aucuparia . During the period of mass yellowing of the leaves, the Φ PSII max value can be used as an adequate characteristic of their photochemical activity, while in summer the q NPQ or R Fd values are more informative. We have established a correlation between the Φ PSII max value, which characterizes the maximal photochemical activity of the photosystem II, and “chromaticity coordinates” of a leaf characterizing its color features. The chromaticity coordinates determined from the optical reflection spectra of the leaves serve as a quantitative measure of their hues, and this creates certain prerequisites for a visual expert assessment of the physiological state of the leaves.