Potential phenolic bioherbicides from Cladonia verticillaris produce ultrastructural changes in Lactuca sativa seedlings

• Cladonia verticillaris produces a despide, atranorin, and two depsidones, fumarprotocetraric and protocetraric acids.
• The biological activity of these phenolics permits their use as natural bioherbicides.
• The roots of lettuce seedlings grow more rapidly in the presence of the phenols than in their absence.
• Nevertheless, intergranal lamellae of leaf chloroplasts disappear as a consequence of phenolic addition.
• Mitochondria disorganize their internal membranes.

The possibilities for using phenolics, extracted from the lichen Cladonia verticillaris with different organic solvents, as bioherbicides have herein been studied through observation of the ultrastructural changes produced in Lactuca sativa seedlings. The different extracts mainly contain protocetraric and fumarprotocetraric acids and very small amounts of atranorin. It has been observed that the roots of lettuce seedlings grow more rapidly in the presence of the phenols than in their absence. This fact is supported by a minor number of lobes and less indentation of the parenchymatous cells as well as a major appearance of active dictyosomes in their cytoplasm.Nevertheless, seedling leaves developed in the presence of these extracts show drastic degenerative changes. Intergranal lamellae of chloroplasts disappear whereas thylakoids are melted in amorphous masses. In some cases, the number of dictyosomes increases in parenchymatous cells and mitochondria disorganize their internal membranes, though in a minor degree of that observed for chloroplasts.