Taxonomic significance of palynological studies for identification of two morphologically similar Malva species.

Abstract

Pollen studies can assist in distinguishing different plant taxa on the basis of pollen diameter, exine thickness, spines length, spine shape, number of rows of spines between colpi, shape of pollen, P/E ratio, pollen class and aperture type. Light microscopy (LM) and scanning electron microscopy (SEM) was used to compare and differentiate two Malva species on the basis of different pollen characteristics. Pollen in Malva neglecta and Malva parviflora had punctate and subpsilate, and, granulate and verrucate sculpturing between spines respectively. Both species pollen had bulbous spine base, but were more swollen in M.parviflora. M.neglecta had more pollen size, spine length and distance between spine base and spine apex, except spine base and pore diameter. The scatterplot matrix showed a wide variation among sculpturing types and other pollen attributes of both species. In PCA biplot, pore diameter and spine length were linked to M.parviflora while other pollen attributes were clearly linked to M.neglecta, indicating the taxonomic significance of the observed characters. It was concluded that the palynological studies can act as an identification tool and are of great significance in delimiting Malva and different plant taxa. RESEARCH HIGHLIGHTS: Taxonomic identifications is a big problem in morphologically identical Malva neglecta and Malva parviflora. The usefulness of pollen morphology (pollen diameter and exine thickness) and wall ornamentation in identification through light microscopy (LM) and scanning electron microscopy (SEM) was confirmed. Pollen of M.neglecta can be differentiated from M.parviflora by its sculpturing patterns. Spine base and pore diameter of M.parviflora is a taxonomically important feature.