UPTAKE, TRANSPORT, AND STORAGE OF CALCIUM AND MAGNESIUM IN SPRUCE (PICEA-ABIES [L] KARST) AND PINE (PINUS-SYLVESTRIS L) AS AFFECTED BY VARIABLE NUTRITION AND POLLUTANT STRESS

In regard to the discussion about the ''new-type forest decline'' and the practical importance of the nutrient elements Ca and Mg in forest practice, statements about the dynamic processes of uptake, transport, and deposition of Ca and Mg in norway spruce and Scots pine are made in this paper. It is generally considered that Ca and Mg behave simila rily in uptake and transport within the tree. Concerning the storage o f these elements it is shown, however, that there are great difference s in their functional importance in cell metabolism. There is evidence that the role of Mg in enzyme and protein metabolism is of far greate r significance for the understanding of Mg-deficiency symptoms than it s function as the central atom of the chlorophyll complexes. In regard to the transport and especially to the incorporation of Ca into the n eedles differences between species were evident, expressing the specia l status of pine among the gymnosperms. With increasing needle age an accumulation of Ca-oxalate crystals, which are physiologically inert, could be proved for the studied conifers. This was interpreted as a '' detoxication'' from surplus Ca to hold constant the level of the physi ologically active fraction. Accordingly, the low Ca-contents of yellow ed needles are not expressing a deficiency level. It is therefore ques tionable, that the increase of total Ca-contents caused by liming is r eflecting a physiologically improved nutritional status of conifers. T he study of spruce needles exposed to ozone showed that instead of the until now considered increased Ca-efflux from the cells caused by hig her membran permeability an increased Ca-influx should be assumed. The experimental exposition of spruces to simulated acid rain reveals inc reased leaching of Ca from the epidermal cell walls instead of the pre cipitation as Ca-oxalate crystals, having no major negative impact on foliage physiology.