TAXONOMIC SIGNIFICANCE OF NUTLET AND LEAF CHARACTERS IN HYMENOCRATER, NEPETA SECT. PSILONEPETA AND LOPHANTHUS (NEPETINAE, NEPETOIDEAE: LAMIACEAE)

Hymenocrater (Lamiaceae) in Iran was studied using morphological characters of nutlets and leaves. The species of the genus Nepeta sect. Psilonepeta and a few species of the genus Lophanthus were also examined for comparison. Scanning electron micrographs showed the surface of the nutlets and trichome types on leaves in detail. Two types of nutlets including smooth and sculptured were recognized. Among the species with smooth nutlets H. incanus is very characteristic having an absolutely smooth nutlet surface. Sculptures may be prominently tuberculate e.g. in H. bituminosus and H. calycinus or verrucose e.g. in H. sessilifolius and N. sessilifolia. Most species have constant features in nutlet surface, but minor differences could be identified within a few species, i.e. H. elegans and H. yazdianus. Leaf surfaces in studied group are covered with dense or laxe trichomes. Different trichome types are observed including glandular and non-glandular trichomes. Two different glandular trichomes were identified: peltate or sub-sessile glands and capitate or stalked glands. Non-glandular trichomes consist of short or long trichomes with (1)2-8(11) cells. Relationship among the species of the three genera was investigated based on data provided from morphological features, using cluster and PCA analysis. Three species groups are provided by the cluster analysis. Sculptured nutlets and peltate glands with two- or multi-celled head are characteristic features of most species grouped in the first cluster. Most species of the second and third clusters have smooth nutlets. Micro-papillate trichomes and capitate glands with a long, one- or multi-celled stalk are significant respectively in species of second and third clusters. Characters with the most variation were identified using FA based on PCA. Closely placement of Hymenocrater species together with Nepeta and Lophanthus species in obtained phenogram and ordination supports the affinity of these genera. It also reveals that the morphological features are not significant for defining the boundaries of the studied genera but raised the proposal of very close relationships among the studied species and the possibility of re-circumscribing the genera within Nepetinae.