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

During the vegetation period from June to October 1990 the growth, pho tosynthetic CO2-fixation, pigment content and chlorophyll (Chl) fluore scence characteristics were compared in die needles of 5-year-old spru ce clones Picea abies (L.) Karst., cultivated for two years on the soi l and the sand, with or without addition of mineral fertilizers. Miner al deficiency in the spruce clones grown on the sand instead of a humu s containing soil resulted in somewhat reduced lengthwise growth of sh oots and needles, lower level of Chl and carotenoids (Car), as well as lower net photosynthetic rates (P(N)) per needle area unit and in gen eral also lower stomata conductance (g(H2O)) values. In contrast, the variable Chl fluorescence measured via the Chl fluorescence decrease r atio (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 si gnificantly higher in the newly developed 1990 needles of the sand cul tures 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 la bility of the photosynthetic apparatus, as also seen in increased valu es of the ratio Chl/Car (a+b/x+c). The basic mineral elements are thus necessary for the photosynthetic apparatus development, as well as st ability of its pigment content and physiological function.