Unusual patterns in the distribution of calcium oxalate in spruce needles and their possible relationships to the impact of pollutants

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Abstract
Summary: The patterns of distribution of calcium oxalate crystals in spruce needles have been investigated in healthy needles and those subjected to either acid precipitation (ph 2.5) or various ozone fumigations. In the acid treatment, deposits of Ca oxalate were lacking in the outer walls of the epidermal cells. Under the impact of ozone, unusual complexes of Ca oxalate crystals embedded in a matrix of callose and cellulose projected from the walls inwards into the cells, filling the lumina of epidermal and hypodermal cells completely. In mesophyll cells, the complexes projected more or less from the walls into the vacuoles. In other cases, crystals appeared within the vacuoles of mesophyll cells. In dead cells, precipitates of Ca oxalate or phosphate apparently indicate destruction of the cytoplasm after a major influx of Ca2+. It is speculated, that the physiological significance of enhanced calcium leaching has been overestimated. With regard to ozone impact, it seems that the major problem of thereby enhanced membrane permeabilities may not be an increased efflux of mineral elements, but rather an increased influx of Ca into the symplast and subsequent disturbances in metabolism.