Taxonomic Studies of selected Euphorbiaceae species from Pakistan using basic and modern approaches

Abstract

In the current research, the diversity among twenty members of family Euphorbiaceae collected from different areas of Pakistan was observed by utilizing both the modern and basic techniques. Plant taxonomy is the most essential field to find the new industrial and medicinal plants. Basic approaches such as palynological, morphological and anatomical characteristics are of immense importance and are used for the identification of various plants species. Morpholoical, anatomical and palynological investigation was done by utilizing light microscopy and scanning electron microscopy (LM &SEM). Moreover, DNA barcoding of the Euphorbiaceae species was also done for the identification of various plant resources comprising on short, gene standard sequences in a precise, rapid and feasible manner. Morphological investigation was done by using various floras and herbaria. Anatomy of leaf epidermis is considered as one of the essential tool used to get more accurate taxonomic information. Characters i.e. types of epidermal cells, types of stomata, types of trichomes, epidermal cells length and width, guard cells, subsidiary cells and presence of trichomes on both abaxial and adaxial side of epidermis were identified. Mostly species had irregular or polygonal shape epidermal cell, only 5 species had epidermal cells hexagonal in shape which are E. neriifolia L., E. prostataAiton, Jatropha integerrimaJacq.,Vernicia fordii (Hemsl.) and Euphorbia royleanaBoiss. Large numbers of stomata were observed on abaxial epidermis as compared to the adaxial epidermis. Euphorbia pulcherrima Willd. Ex Klotzsch, Euphorbia prostate Aiton and Phyllanthus emblica L. had anomocytic type of stomata and Euphorbia cotinifolia L., Euphorbia helioscopia L., Euphorbia neriifolia L. and Ricinus communis L. had anisocytic type of stomata. Remaining species possessed paracytic type of stomata. All the guard cells were bean shaped. Very few species had trichomes including E. hirta L., E. prostate Aiton, E. pulcherrimaWilld. Ex Klotzsch and P. roxburghii Wall. These results ensured that some of the anatomical characters, such as the absence or presence of stomata, trichomes and epidermal cell shape had taxonomic value and are useful in the identification of taxa.In this research both qualitative and quantitative features of pollen of Euphorbiaceae species such as P/E ratio, polar and equatorial diameter, pollen sculpturing, exine and intine thickness, colpi presence or absence and length of colpi and pollen fertility were studied. Significant variations in these pollen features have been examined among these selected species. In polar view, Riccinus communis L. showed the maximum pollen size (264.1um) while Acalypha wilkesiana Mull Arg.(17um) exhibited smallest size of pollen. In respect of equatorial view, Riccinus communis L. showed highest pollen size (270um) while Acalypha wilkesiana Mull Arg. (18.5) exhibited the lowest size. Sapium sebiferum L. Roxb exhibited the maximum p/e ratio of 1.18 while Bischofia javanica Blume showed minimum p/e ratio i.e. 0.85. Colpi were reported in only 5 species. Pollen fertility varied from specie to specie but mostly plants exhibited the pollen fertility between 70% to 80%. DNA barcode is mostly used by taxonomist and evolutionary biologists. Universally accepted DNA barcodes include nuclear, plastidal and mitochondrial DNA fragments whose sequences are helpful in determination of different taxa of living organism. In this study three barcodes (matK, rbcl& nrITS) were used in combination for twenty different plants collected from different areas of Pakistan. All three barcodes individually were helpful in identification of family of collected samples. Barcode matK and nrITS in combination are essential for the identification of genus of the unidentified plants where as all three barcodes when used in combination lead to correct identification of species of the collected plants. As previously reported ITS barcode identifies correct species when sequence identity ranges 96.43-96.72% sequence identity whereas rbcl shows species identification threshold limits 97.62-99.73% sequence identity.