Abstract
BackgroundCalcium oxalate crystals, which are found in many organs of plants, have different morphological forms: as druses, prism, styloids, raphides and crystal sand. In this study, the distribution, type and specific location of calcium oxalate crystals in the leaves and stems of the eight species of poisonous plants and one species of nonpoisonous plant were investigated with light microscopy. During study special attention was given to the possible correlation between the presence and types of calcium oxalate crystals and toxic plant organs. The plants examined in this study were Hedera helix L. (Araliaceae), Aristolochia clematitis L. (Aristolochiaceae), Humulus lupulus L. (Cannabaceae), Saponaria officinalis L. (Caryophyllaceae), Chelidonium majus L. (Papaveraceae), Hypericum perforatum L. (Hypericaceae), Tribulus terrestris L. (Zygophyllaceae), Cynanchum acutum L. (Asclepiadaceae), and Nerium oleander L. (Apocynaceae).ResultsThree types of crystals: druses, prismatic crystals and crystal sands were observed. Druses were identified in the leaves and stems of six species of studied plants. In contrast to druses, crystal sands and prismatic crystals were rare. Prismatic crystals were observed in the leaf mesophlly cells of both Nerium oleander and Cynanchum acutum. However, crystal sands were observed only in the pith tissue of Humulus lupulus. On the other hand, leaves and stems of Chelidonium majus, Aristolochia clematitis and Hypericum perforatum were devoid of crystals.ConclusionThere is no absolute correlation between the presence and type of calcium oxalate crystals and toxic plant organs. However druse crystals may function as main irritant in toxic organs of the plants.Electronic supplementary materialThe online version of this article (doi:10.1186/1999-3110-55-32) contains supplementary material, which is available to authorized users.
Highlights
Calcium oxalate crystals, which are found in many organs of plants, have different morphological forms: as druses, prism, styloids, raphides and crystal sand
In angiosperms crystal formation is generally intracellular and crystals form inside the vacuoles of specialized cells called idioblast
Crystal formation in idioblasts is usually related with membranes, chambers, or inclusions found within the vacuoles
Summary
Calcium oxalate crystals, which are found in many organs of plants, have different morphological forms: as druses, prism, styloids, raphides and crystal sand. During study special attention was given to the possible correlation between the presence and types of calcium oxalate crystals and toxic plant organs. There are several toxicologically significant plant constituents such as oxalates, alkaloids, glycosides, amino acids, proteins, minerals, acids, terpenes, phytotoxins, photosensitizing compounds, phenolics and tannins. These are generally known as secondary metabolites (Frohne and Pfander 1984). In angiosperms crystal formation is generally intracellular and crystals form inside the vacuoles of specialized cells called idioblast. Crystal idioblasts have different shapes, sizes and intracellular structures than non-crystal- forming cells of the same tissue (Horner and Wagner 1995) and may contain, tubules modified plastids and enlarged nuclei (Franceschi and Horner 1980). The idioblasts undergo ultrastructural modifications depending on crystal precipitation
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