Laser-induced chlorophyll fluorescence induction kinetics of metal-stressed and nonstressed Norway spruce needles for forest damage assessment

Damaged spruce needles showed a smaller rise from ground level fluorescence (Fo) to maximum fluorescence (Fm) of the fast component of the Kautsky effect and a corresponding smaller decline (Fd) to the steady state fluorescence (Fs) of the slow component of the Kautsky effect relative to healthy needles. Fm/Fo and (Fm - Fs)/Fs or RFd derived photosynthesis indices were also correspondingly lower for metal-stressed versus nonstressed needles, and indicate a disfunctioning of the photosynthetic apparatus in the damaged needles and a consequent decrease in their photosynthetic capacity. A strong linear relationship occurs between the Fm/Fo indices of the fast component of the Kautsky effect and needle chlorophyll a content, although less strong relationships occur with respect to chlorophyll b and a + b contents, as well as between the RFd indices of the slow component of the Kautsky effect ad needle chlorophyll a, b, and a + b contents. The possibility exists to utilize chlorophyll fluorescence induction kinetics as a fast and reliable means to predict the chlorophyll content of plant foliage, in addition to providing an indicator of plant vitality.