Calcium Crystals in Apple Stem, Petiole and Fruit Tissue1

Single crystals and clusters of crystals or druses found by polarized light microscopy in tissues of Pyrus malus L. cv. Jonathan were found to contain Ca using the electron microprobe. Crystals insoluble in 20% acetic acid occurred in cells adjacent to the vascular tissues near the pedicel in mature fruit and in dormant flower buds, stems, petioles, shoot apex, roots and callus tissue. Because of deposition of calcium as crystals, calcium supplies to cortical cells of apple fruit may be limited and may result in an increased incidence of internal breakdown due to low Ca levels in those cells.