MULTIPLE APPROACHES FOR TAXONOMIC STUDY OF SELECTED ARTEMISIA L. SPECIES FROM PAKISTAN

Abstract

Pakistan hosts rich biodiversity including 42 species of genus Artemisia (Asteraceae) which are found in all phytogeographical regions of Pakistan. Current doctoral thesis reviews ethnobotany, morphology, leaf epidermal anatomy, palynology, phytogeography, molecular phylogeny and elemental diversity of this economically important vegetation. During ethnobotanical survey, it was found that these species (A. absinthium L., A. annua L., A. brevifolia Wall. ex DC., A. dracunculus L., A. dubia Wall. ex Besser, A. herba-alba Asso., A. japonica Thunb., A. maritima L. ex Hook.f., A. moorcroftiana Wall. ex DC., A. roxburghiana Wall. ex Besser, A. santolinifolia Turcz. ex Krasch., A. scoparia Waldst. and Kit. and A. vulgaris L.) are used by the indigenous population as fodder, food condiments, ornaments, fumigants and medicines. The morphology of this genus is complex and confusing. It is noted that the same species shows different forms under certain ecological conditions. Therefore, it was imperative to revise the morphology of the genus. 52 morphological characters of 42 taxa were selected for phylogenetic analysis of the genus and the resulted cladogram validated Artemisia as a monophyletic assemblage. Our data analysis envisages that the Seriphidium clade somehow over the years, under different climatic condition has evolved from Artemisia. Therefore, it is contended that it can be treated as a section of Artemisia instead of a separate genus. Micromorphology in 24 taxa was studied using light microscopy (LM) and scanning electron microscopy (SEM). The glandular and nonglandular trichomes are classified into 16 main types. Among glandular trichomes, capitate glands had wild distribution on the both surfaces of leaves with notable variations. In case of non-glandular trichomes, T-shaped hairs are abundant. LM and SEM observation data have identified six stomata types. Leaf epidermal cells have shown variations in their shape and size on abaxial and adaxial surfaces. From this study and information already available in the literature suggests that leaf epidermal features are valuable taxonomic traits and can be utilized to address the taxonomic issues within Artemisia genus. The palynological study of 22 taxa has reveled that pollen grains of Artemisia are tricolporate showing globular symmetry (3-lobed round in polar view and ellipsoid ball shaped in equatorial view) which are marked by reduced spinules on their surfaces. Eight morphological characters (pollen shape, spinules arrangement, exine sculpture, spinules base, polar length, equatorial width, exine thickness and colpus width) of pollen grains were subjected to cluster analysis (CA) which divided Artemisia species into five groups. Our SEM studies have supported the notion that the presence of spinules is a diagnostic feature for Artemisia limb of tribe Anthemideae of family Asteraceae. The phylogenetic analysis of pollen traits is indicative of evolutionary associations among four classical sections of the Artemisia and confirms the reunion of genus Seriphidum with Artemisia. The molecular studies using internally transcribed spacer (ITS) and externally transcribed spacer (ETS) sequences of nuclear ribosomal deoxyribonucleic acid (nrDNA) were conducted to know the phylogeny of 26 local species. The molecular data has verified first time that western Himalayan Artemisia species are the distant migrants from the neighboring areas. Current research further confirms the phylogenetic relationships of Seriphidium with Artemisia which has established in the evolution of both. Therefore, genus Seriphidium must be considered as a section of genus Artemisia. This research also has revealed that section Artemisia is polyphyletic in origin. Elemental composition of 17 indigenous species of Artemisia was determined for the first time using atomic absorption spectrophotometery. Investigated elements include nine trace elements (Zn, Cu, Cr, Ni, Co, Cd, Pb, Mn, and Fe) and four major elements (K, Na, Ca and Mg). Eight Artemisia species had concentrations of heavy metals above limits as recommended by the International Safety Standard. Cluster analysis (CA) and Principal Component analysis (PCA) of elemental data suggests two groups of Artemisia species.