Taxonomic Studies of Dicot flora Using Microscopy in Thal Desert, Punjab-Pakistan

Abstract

This project is confined to presenting taxonomic information on angiosperms plant species from the Thal Desert Punjab-Pakistan. This study elucidates the micromorphological characterization of Dicot flora adapted to arid environment. We hypothesized that comparative micromorphological attributes of pollen, seed, and the leaf of Dicot floral species were analyzed using light (LM) and scanning electron microscope (SEM). A total of 111 Dicot floral species were categorized into 80 genera and 26 dicot families. Pollen grains of dicot species were acetolyzed, observed and measured through statistical software. Dicot species showed variation in shape, type, aperture, and exine sculpturing. Amaranthaceae was the dominant family revealed smooth sparsely granulate, scabrate-spinulose, micro-spinulose perforate, micro-echinate scabrate to meta-reticulate, granulate, nano-spinulate, and micro echinate perforate exine stratification. Exine thickness was noted highest in Salsola tragus 2.15 µm and lowest in maranthus. graecizens 0.78 µm. The maximum number of pores was examined 32-36 in Digera muricata. Taxonomic utility of seed microstructural features has been explored using scanning microscopy. Seeds varied in shape from elliptical to obovate, D-shaped, reniform, rhomboid, and ellipsoidal. The periclinal boundaries, and sculpture pattern of the anticlinal wall were generally rugulate, reticulate, and striate, papillate and rugose, and undulate granulate. The phenetics of 109 character-states using principal component and dendrogram statistics supported the affinities among desert species. Foliar micromorphology of leaf and petiole vasculature of dicot species were analyzed. Both surfaces of the leaves exhibited differences in the microanatomy of stomata, epidermis, anticlinal wall, and diversity of trichomes. Stellate trichomes were observed on both surfaces of Aerva lanata while capitate trichomes in the inter-coastal zone in Alternanthra sessilis. The largest trichome length was measured for Alternanthera sessilis (127 µm) along adaxial side, while along abaxial surface was calculated for Amaranthus graecizans (117.5 µm). Petiole transverse sectioning of Amaranthaceous and Euphorbiaceous taxa showed petiole and vascular bundle shape, petiole length, trichomes, layers of collenchyma, and shape of parenchyma cells. Petiole shapes observed are cordate, slender, spherical, and ovoid. The annular shape was dominant in collenchymatous cells. The taxonomic keys were also developed to reveal micromorphological markers for the correct identification. The identified micromorphological traits provide base for correct identification of dicot angiosperms and their systematics relationships.