Morphological and palynological assessment of taxonomically problematic genus Paspalum based on light and scanning electron microscopy.

Present research work was carried out to clarify the variations among species of genus Paspalum morphologically and palynologically as this genus is taxonomically difficult due to having multiple similar morphologically overlapping characters which make it difficult to identify. Henceforth present research work was carried out to delimit taxa within the same genus by morphological and palynological tools through light microscopy (LM) and scanning electron microscopy (SEM). Both these tools are considered as the most useful taxonomic characters for taxonomically problematic genera. The results showed a lot of variations among morphological characters. In Paspalum dilatatum, the upper glume was ovate whereas in the other two species, the upper glume was elliptic. The upper glume apex found in P. dilatatum and Paspalum scrobiculatum was obtuse whereas in Paspalum distichum, upper glume apex was acute. Glume nerves showed variation in all three species. Paspalum distichum was 3 nerved, P. scrobiculatum was 5-7 nerved, and P. dilatatum was 5-9 nerved. All three species showed variation in lemma nerves. Paspalum scrobiculatum had 3 nerved lemma whereas in P. distichum 3-5 nerved and P. dilatatum 5-9 nerved lemma were present. In polar and equatorial view, pollen grains ranged from 25 (20-30) to 37.5 (30-45) µm. Paspalum distichum appeared to be the smallest in size whereas P. dilatatum was the largest. Exine thickness ranged from 0.75 (0.5-1) to 1.35 (1.2-1.5) µm. The higher value of pollen fertility was found in P. scrobiculatum as 87.69% and the lowest value was in P. distichum as 78.08%. Morphological keys were also given for correct identification.

Micro morphological foliar taxonomic studies of genus Paspalum based on scanning electron microscopy.

Paspalum is one of the 10 largest genera in Poaceae and is considered as a complex and taxonomically difficult genus due to its similar morphological characters within the species which makes it difficult to delimit taxa within the same genus. The current research work establishes the distinction among species of this genus and resolves taxonomic confusions among this genus. And this distinction is done by micro morphological foliar anatomical characterization by light and scanning electron microscopy. Both the abaxial and adaxial epidermal cuticles of three different species of genus Paspalum were studied and their phytoliths were observed through elemental dispersive spectrophotometric analysis by SEM first time in Pakistan. Results showed great variation in studied anatomical features. P. dilatatum Poir. was comprised of macro-hairs in the intercostal regions only whereas no macro-hairs were found in P. distichum Linn. and P. scrobiculatum Linn. Beak-shaped prickles were found in the intercostal regions on adaxial surface only in P. distichum Linn. and P. scrobiculatum Linn. whereas in P. dilatatum Poir., knife-shaped prickles were present in intercostal regions only on both abaxial and adaxial surfaces of leaf epidermis. No papillae were seen in P. dilatatum Poir whereas in P. distichum Linn. and P. scrobiculatum Linn. papillae were found abundantly. In genus paspalum, P. dilatatum Poir. phytoliths showed lowest mass percentage of silicon as 15.13% whereas P. distichum Linn. phytoliths showed highest mass percentage of silicon as 22.00%. Based on micro morphological foliar characteristics a taxonomic key of studied species is also provided to delimit the taxa.