Ontogeny and the process of biomineralization in the trichomes of Loasaceae

PREMISE OF THE STUDY: South American Loasaceae have a morphologically complex trichome cover, which is characterized by multiple biomineralization. The current study investigates the ontogeny of these complex trichomes and the process of their biomineralization, since both are very poorly understood. METHODS: The development of stinging trichomes on various parts of the plants and the process of mineralization were studied using scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDX). KEY RESULTS: Trichomes are initiated very early in organ development and the different trichome types begin developing their distinctive morphology at a very early developmental stage. Biomineralization in the stinging trichomes starts with the deposition of silica or calcium phosphate in the apex and then proceeds basipetally, with a more irregular, subsimultaneous mineralization of the base and the shaft. Mineralization of the scabrid-glochidiate trichomes starts on the surface processes and in the apex (silica, calcium phosphate), with a subsequent mineralization of the shaft with calcium carbonate. CONCLUSION: Mineralized trichomes in Loasaceae provide an excellent model for the study of biomineralization. The overall sequence of mineralization is typically from distal and peripheral to proximal and central. Typically, three biominerals-silica, calcium carbonate, and calcium phosphate-are differentially and sequentially deposited in different parts of each unicellular stinging trichome.