Density and distribution of calcium oxalate crystals in vegetative organs of “green” wild taro (Colocasia esculenta (L.) Schott.)

Abstract

The study’s aim was to investigate the distribution of calcium oxalate (CaOx) in vegetative organs of “green” morphotype wild taro Colocasia esculenta (L.) Schott. An anatomical study was conducted on the vegetative organs (root, corm, leaf blade, and petiole) of the “green” morphotype wild taro at different developing stages. The transverse sections were double-stained with carmine alum laque–iodin green dye to investigate the density and distribution of CaOx crystals. The four forms of CaOx crystals found in vegetative organs were druse, free needle-liked, raphide bundle, and prism crystals. Prismatic crystals were observed in the root only once. Biforine or biforine-liked cell, an unusual form of raphide bundle, was detected. These crystals were revealed in specialized cells such as epidermis, parenchyma, palisade mesophyll, and spongy mesophyll. The density, size, shape, and distribution of crystals in the vegetative organs varied depending on the type and developmental stage of the organs. The diameter of the druses and the width of the raphide bundles were both increased in the developing leaves compared to that of the young leaves. The width of the raphide bundles of the old leaves was reduced compared to that of the developing leaves. The minimum and maximum sizes of all CaOx crystals varied greatly. The density and distribution of CaOx in the vegetative organs made it facility to protect plants against herbivores. The presence of CaOx in the vegetative organs created a warning signal when used as a source of green vegetables or traditional medicine.