Infraspecific variation of leaf anatomy inOriganum vulgaregrown wild in Greece

Abstract

The histological components of the leaf were studied in dried herbarium material of the threeOriganum vulgaresubspecies (subsp.hirtum, subsp.viridulumand subsp.vulgare) grown wild in Greece. These three, geographically distinct, taxa showed remarkable differences in their leaves. The leaves of subsp.hirtumgrown in the Mediterranean climatic zone of Greece are characterized by thick cutinized outer walls of the epidermal cells and a thick mesophyll with highly developed chlorophyllous tissues. Peltate glandular trichomes and stomata are numerous on both leaf surfaces. The thickness of the mesophyll decreases in the other two subspecies grown in the northern part of the country, where a Continental type of climate occurs. The number of glandular trichomes and stomata also decreases. Besides these differences, a noticeable reduction in the size of the essential oil-accumulating subcuticular chamber of the glandular trichomes and in the number of the peribasal cells, has also been recorded in the plants of subsp.vulgareandviridulum.