Calcium oxalate crystals in the stem of Sida hermaphrodita(L.) Rusby (Malvaceae)

Observations of calcium oxalate crystals of the stem of an energetic plant S. hermaphrodita(L.) Rusby from the Malvaceae family, were performed using LM, DIC, and CLSM microscopes.The transversal and longitudinal sections showed the presence of calcium oxalate crystals in theparenchymal tissue distributed in various layers of the stem. The crystals occurred only in the formof druses. In the innermost part of the stem, i.e. in the pith, the calcium oxalate crystals occurredsingly in individual cells. In the parenchyma cells separating sclerenchyma fibres and adjacent to thexylem, the crystals were observed individually in single cells, but the cells containing druses formedrows consisting of even several cells. The cortex contained the different-size druses scattered randomlywithin the cells. Druses differ in shape and size but they do not protrude beyond the cells althoughthey very often fill them completely. The functions of calcium oxalate crystals are discussed.