Asian Research Thesis Index

Abstract

This thesis attempts to update the taxonomic knowledge of the grass family Poaceae inhabiting in the Potohar region of Pakistan. The present studies were conducted during 2007 -2012 in the taxonomy lab of Quaid-i-Azam University Islamabad. Taxonomic studies of four subfamilies comprising 10 tribes, 36 genera and 52 species of Poaceae have been completed from Potohar. The genus Cenchrus, Eragrostis, Setaria and Poa each have 3 species from this area. Paniceae and Andropogoneae are the largest tribes represented by 16 and 10 species respectively. All other tribes contain less than 10 species. The present work describes morphological, palynological and anatomical variations in grasses and their potential in resolving relationship at subfamilies, tribal, generic and species levels. Different exomorphic characters like height of culm, length of ligule, leaf sheath and various other aspects of leaf, while reproductive characters like type of inflorescence, length of glumes, nerves on glumes and other features are helpful to identify plants at generic and specific level. It is the first time that a comprehensive study of grasses of Potohar region is conducted from taxonomic point of view. Additional characters have also been studied such as shape, length and width of caryopsis and length of stigma and anther. The objective of the study was to assess the potential of grass features in the area and to identify and classify the grasses on the basis of morphological, anatomical and palyonological features and their palatability status with the help of local peoples and personal observations of area. Palyonological studies showed that pollens in grasses are monad, spheroidal to sub spheroidal, prolate to sub prolate, circular to triangular to inter semi angular, monoporate and psilate. Pollen sculpturing is verrucate or scabrate. Exine thickness ranged from 0.8 micrometer to 1.5 micrometer. Pollen characters in some tribes like paniceae are helpful to differentiate taxa at genera and species level. The study was conducted with light microscope and scanning electron microscope. Leaf epidermal studies showed variations at the species, genus and tribe level. Taxonomically interesting correlations and differences were observed in different genera and tribes. Problematic species like Pennisetum orientale that is confused with Cenchrus ciliaris, can be differentiated by the presence of short cells with rounded papillae, which are absent in Cenchrus species. Different type and occurrence of microhairs helps to distinguish different xxii   tribe .e.g. Panicoideae. In Enneapogon persicus of the tribe Pappophoreae special type of macrohairs with narrow stalk cell are seen that are absent in other tribes of subfamily Chloridoideae. In Andropogoneae and Paniceae, a variety of silica bodies is seen. Bicellular microhairs with thin walled distal cells are observed in tribe paniceae and andropogoneae. Most of the species belonging to tribes of subfamily Pooideae are distinct in having numerous long cells with straight walls to differentiate it from other tribes of subfamily.

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