TAXONOMIC STUDIES OF GRASSES OF SALT RANGE OF PAKISTAN

Abstract

The research work was conducted during May 2005-2009 in the taxonomy lab of Quaid-i-Azam University Islamabad. The project involves the morphological, palynological and anatomical studies of 66 species of grasses belonging to 43 genera and 12 tribes within 4 sub families collected from Salt Range of Pakistan. Paniceae is the largest tribe having 10 genera and 22 species followed by Andropogoneae and Eragrostideae with 10 and 6 genera and 13 and 8 species respectively. Taxonomic studies of grasses are of prime importance from systematic point of view and proved helpful in delimitation of the taxa at the species, genus and tribe level. It is the first time, that a comprehensive study of grasses of any area is conducted from taxonomic point of view in Pakistan after Cope, (1982) who classified the grasses from Pakistan on the basis of morphological characters and in many species some characters are not examined which are valuable taxonomically and has not mentioned, 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 grasses in the area and to identify and classify the grasses on the basis of above mentioned studies and to study the differences among the species of the same and different genera of the same tribe and among the different tribes. Morphological markers are helpful in the identification, differentiation and classification of the species at species, genus and tribe level. Variations in different morphological characters are observed in different genera of the same tribe and among the species of the same genus. There are few characters that are constant in the different genera of the each tribe and are helpful in identification and classification of the species to the tribe level. In the present studies there are two new reports from the area. Tetrapogon cenchriformis is identified by its spatheolate inflorescence while Parapholis strigosa is identified by the length of anthers and straight spikes. Previously only one species of Parapholis (P. incurva) is reported from Pakistan, but the studies showed that another species of Parapholis (P. strigosa) is also present in the Salt Range of Pakistan. Quantitative characters of pollen are also helpful in distinguishing different taxa. Maximum polar and equatorial diameter is recorded in Bromeae followed byAndropogoneae and Paniceae, while maximum polar diameter is also observed in tribe Bromeae. Maximum exine thickness is shown by tribe Eragrostideae. SEM of pollen showed four types of sculpturing patterns that are scabrate, verrucate, rugulate and striate. Variations are also observed in features regarding leaf epidermal and transverse section studies at the species, genus and tribe level and by correlating with morphological characters are valuable in the identification and classification of different taxa. There are a few problematic species that are identified and differentiated from the resembling species by studying their anatomy. Pennisetum orientale is confused with Cenchrus ciliaris, but it can be differentiated by the presence of short cells with rounded papillae, which are absent in Cenchrus species. Distinct type of microhairs with hemispherical distal cell are found in genera of the all tribes belonging to subfamily Chloridoideae, and bulliform cells make a girder to the abaxial side that is the distinguishing character of this subfamily. In Enneapogon persicus of tribe Pappophoreae special type of macrohairs with narrow stalk cell are observed that are absent in other tribes of subfamily chloridoideae making this tribe peculiar from other tribes of subfamily Chloridoideae. In Andropogoneae and Paniceae, a complexity in structure of silica bodies is seen and distal cell is thin walled in bicellular microhairs which can be used as a tool in identification. Bulliform cells are in fan shaped or irregular groups. Most species belonging to tribes of subfamily Pooideae are distinct in having long cells with straight walls, and length of long cells is also recorded more in these tribes. Microhairs are absent and subsidiary cells are mostly parallel sided and chlorenchyma cells are diffused around the vascular bundles. There are some species that are present in the area but not mentioned previously during the vegetation study of the area due to improper identification and collection from the area. It is concluded that morphological, palynological and anatomical studies help in proper identification and classification of grasses, and to classify the previously identified vegetation of Pakistan.