Abstract

The influence of growing conditions upon the pigmentation in needles from seedlings of Scots pine and Norway spruce has been studied. The plant material was grown either in the open or in plastic greenhouses. The greenhouses were covered with plastic during the vegetation periods from May to August, and during the rest of the year the 'greenhouse' grown seedlings were exposed to outdoor conditions. A pronounced seasonal variation of both chlorophyll and carotenoids was found. The content of pigments was influenced also by growing conditions, plant age, needle age and origin of the seed source. The new technique of growing coniferous seedlings in greenhouses during the vegetation period does not seem to have any harmful effect on the seedlings, as far as the pigmentation of the needles is concerned. Since the seasonal discoloration of needles is many cases can resemble changes caused by nutrient deficiencies, caution should be exercised whenever the needle color is used as an index of the physiological state of nursery stocks.