Formation and distribution of calcium oxalate crystal idioblast in the tissues of taro [Colocasia esculenta (L.) Schott]

Abstract

Raphides (needle-like crystals) or druses (sand-like crystals) of calcium oxalate occur in the idioblast in the hypocotyl and cotyledon of taro at the young seedling stage. These crystals develop in the center of the idioblast. The raphide idioblasts differentiate into defensive or nondefensive types. Those in the defensive type are not tightly compact, but are ejected from the pole of idioblasts to the outside. The nondefensive type and druse idioblasts appear initially and their densities increase, accompanied by growth. The defensive type develops in seedlings 60 days after sowing. The densities of the raphide idioblast are highest in the leaf blade, lowest in the corm, and intermediate in the petiole. In the cross sections of the petiole and corm, the densities of raphide and druse idioblasts are higher in the outer tissue than those of the inner tissue. The densities of both raphide and druse idioblasts are high in the aerenchyma and the parenchyma in different tissues; they are more numerous in young tissues than in old ones.