PIGMENT CONTENT, CHLOROPHYLL FLUORESCENCE AND PHOTOSYNTHETIC ACTIVITY OF SPRUCE CLONES UNDER NORMAL AND LIMITED MINERAL-NUTRITION

During the vegetation period from June to October 1990 the growth, photosynthetic CO2-fixation, pigment content and chlorophyll (Chl) fluorescence characteristics were compared in die needles of 5-year-old spruce clones Picea abies (L.) Karst., cultivated for two years on the soil and the sand, with or without addition of mineral fertilizers. Mineral deficiency in the spruce clones grown on the sand instead of a humus containing soil resulted in somewhat reduced lengthwise growth of shoots and needles, lower level of Chl and carotenoids (Car), as well as lower net photosynthetic rates (P(N)) per needle area unit and in general also lower stomata conductance (g(H2O)) values. In contrast, the variable Chl fluorescence measured via the Chl fluorescence decrease ratio (R(fd) = fd/fs) was only little affected, indicating an internal functional photosynthetic apparatus even under mineral deficiency with a lower Chl content. In fact, P(N) expressed on Chl basis was even significantly higher in the newly developed 1990 needles of the sand cultures than in the soil ones. Application of a forestry fertilizer with basic minerals (K, Ca, Mg and some N) to die sand cultures increased growth of shoots and needles, levels of Chl and Car, P(N) and stomata conductance, and decreased the Chl fluorescence ratio F690/F735 and lability of the photosynthetic apparatus, as also seen in increased values of the ratio Chl/Car (a+b/x+c). The basic mineral elements are thus necessary for the photosynthetic apparatus development, as well as stability of its pigment content and physiological function.