Microanatomy of leaf trichomes: opportunities for improved ampelographic discrimination of grapevine (Vitis vinifera L.) cultivars

Background and Aims: Trichome('hair') density on the underside of grapevine leaves has long been used in classifying Vitis species and identifying grapevine ( Vitis vinifera L.) cultivars. Grapevine leaf trichomes, however, are of two types but few studies have examined their microanatomy and relative spatial distribution. This study addresses those aspects. Methods and Results: The anatomy and spatial distribution of erect and prostrate trichomes on abaxial surfaces of leaves of 13 V. vinifera cultivars were examined microscopically. Erect trichomes are conical, ca. 300 mu m long. Prostrate trichomes are cylindrical, ca. 2000 mu m long, becoming senescent and flattened as leaves age. The relative abundance and spatial density of each trichome type varies among grapevine cultivars. When both types become entangled they form a 'hair coat', ca. 1.5 times thicker than the leaf lamina, supported by erect trichomes. Conclusions: Grape leaf trichomes are non-glandular, uniseriate structures of two distinct types, 'erect' and 'prostrate'. Both types arise from the epidermis but both the arrangement of their basal cells forming the point of attachment and their fluorescent properties differ markedly. Significance of the Study: The microanatomical features and fluorescent characteristics of grape leaf trichomes may facilitate improved ampelographic discrimination of grapevine cultivars.