Short-term pigment changes in Norway spruce needles

The photosynthetic pigment contents and the chlorophyll fluorescence induction in Norway spruce [ Picea abies (L.) Karst.] needles were monitored at 3 h intervals over a 10 day period. This covered 6 days of high insolation, one day of low insolation, followed by three more days of high insolation. During the first six days only small changes in mean pigment contents were observed but we interpret them as suggesting a daily rhythm in total chlorophyll content with two maxima and minima. The day of low insolation was paralleled by larger pigment changes, mostly an increase in chlorophyll b along with a decrease in carotenoid content. With the resumption of high insolation, pigments gradually return to their previous levels. During the entire period chlorophyll a fluorescence induction remained relatively constant. These short-term responses may reflect features of thylakoid organization in relation to pigment content and suggest possible long-term adaptive mechanisms in non deciduous conifers.