Mucilage ultrastructure in mucilage cells within the order Malvales

摘要

Mucilage ultrastructure in leaves of 30 species belonging to 18 genera of the Malvales has been studied. Two types of mucilage (fibrillar and granular) were revealed by means of transmission electron microscopy. Both mucilage types may be present in dense or loose forms. There are irregularly distributed transparent areas within the dense mucilage, round of elongated in shape. We call such structure porous mucilage. Both fibrillar and granular mucilages can form porous structure. In the dense mucilage, silica compounds have been found in amorphous and crystal forms. The latter may be present either as separate crystals or arranged in rays. The forms of silica depositions affect differently the mucilage structure of the Malvales. Silica compounds in crystalline form take part in the formation of layers within the mucilage. They can be distinguished by means of light microscopy. Silica compounds do not take part in forming of porous mucilage, which is specific of the Malvales.