The Effect of Coumarins on Root Elongation and Ultrastructure of Meristematic Cell Protoplast

The effect of coumarin, umbelliferone and xanthotoxin on root elongation, as well as their influence on the cell structure of root meristem, was investigated in cucumber, maize and garden pea. Umbelliferone retarded the growth of roots less strongly than coumarin and xanthotoxin, which arrested elongation and markedly thickened cortical cells. Response to coumarin and xanthotoxin varied depending on the plant species. Cucumber seedlings were much more sensitive to coumarin than was maize, but garden pea was resistant. In sensitive plants coumarin and xanthotoxin affected the endomembrane system, mostly dictyosomes and the endoplasmic reticulum. They stimulated the fragmentation of endoplasmic reticulum cisternae and decreased the number of dictyosomes, which became less active. The mitochondrial matrix became condensed, indicating a possible energy shortage in the cell.