CA NUTRITION OF CONIFERS

Ca nutrition of trees has received increased attention in the past yea rs. In this paper the ambivalent role of the mineral element Ca in for est tree nutrition is discussed in regard to uptake, translocation, an d metabolism. External influences of different supply and fertilizatio n on Ca metabolism of trees are described. Total Ca contents in plant tissues only partitially allow conclusions about the nutritional statu s. This is emphasized by distinguishing three different physiological fractions of Ca bonds. Water soluble and pectate bound Ca contents rem ain constant in spite of very different total Ca contents of the needl es. These differences are explained by various amounts of Ca-oxalate. After fumigation with ozone and exposure to acid rain, changes in the distribution pattern of Ca-oxalate in spruce needles are described at a microscopical level.