Glandular trichomes and sesquiterpene lactones of Artemisia nova (Asteraceae)

The leaves of Artemisia nova Nelson are covered with a dense layer of nonglandular trichomes that obstruct the observation of glandular trichomes on the leaf surfaces. An acid-staining technique was developed that eliminates interference from the nonglandular trichomes and stains the glandular ones red, allowing them to be seen under a light microscope. Using this method it was found that these glands develop on both leaf surfaces, except over veins, and cover 21–35% of the leaf surface area at densities of 50–70 per mm². Mature glands are sac-like structure with a thin sheath or cuticle surrounding a clear transparent fluid. This fluid contains all of the sesquiterpene lactones present in the leaves, and some of the monoterpenes. These terpenoids were responsible for the red color of the glands after acid treatment.