Pollen morphology and its taxonomic potential in some selected taxa of Caesalpiniaceae observed under light microscopy and scanning electron microscopy

• Published in: Microscopy research and technique 2022-04, Vol.85 (4), p.1410-1420
• Main Authors: Ullah, Farhat, Ahmad, Mushtaq, Zafar, Muhammad, Parveen, Bushra, Ashfaq, Shomaila, Bahadur, Saraj, Safdar, Qura‐tul‐ain, Safdar, Luqman Bin, Alam, Fakhre, Luqman, Muhammad
• Format: Article
• Language: English
• Subjects: Caesalpinia; Caesalpiniaceae; Caesalpiniaceae taxa; Classification; Diameters; Fertility; Granulation; Light microscopy; light microscopy and scanning microscopy; Microscopy, Electron, Scanning; Optical microscopy; Pakistan; Pollen; Pollen - anatomy & histology; pollen micromorphology; Scanning electron microscopy; Species; Species classification; Structure-function relationships; Taxa; taxonomic significance; Taxonomy; Variation
• ISSN: 1059-910X; 1097-0029
• DOI: 10.1002/jemt.24004

Pollen micromorphology is not only used to check the functional and structural evolution in plants but also to solve the taxonomic problem related to the classification of plants. Therefore, keeping in view the significance of pollen traits, selected taxa of the subfamily Caesalpiniaceae was collected from different geographical regions of Pakistan. The species were then analyzed under both light microscopy and scanning electron microscopy techniques to investigate the importance of micromorphological characters of pollen in the identification and classification of species. Great variation was recorded in equatorial shape, surface ornamentation, tectum, polar diameter, equatorial diameter, and exine thickness. However, little variation was observed in pollen type, polar shape, and fertility of pollen. The equatorial shape of five types was observed: prolate, prolate‐spheroidal, spheroidal‐subprolate, subspheroidal‐prolate, and subspheroidal. Four types of surface ornamentation, psilate, granulate, clavate, and perforate, were recorded. Tectum of five types, intactate, reticulate regulate, medium reticulate, tactate, and striate, was observed. Sexine was thicker than nexine in all studied species. The largest polar diameter was observed in Caesalpinia pulcherrima 64.1 μm while the smallest in Parkinsonia aculeata 26.1 μm. The largest equatorial diameter was found in C. pulcherrima of 70.25 μm whereas the smallest in P. aculeata 27.57 μm. All the pollens analyzed were tricolporate. All studied species have a fertility ratio of more than 90%. A taxonomic key was developed to show the variation in pollen features and delimit species for the correct identification. In conclusion, the pollen traits were found useful to define species boundaries at various taxonomic ranks and will strengthen the taxonomy of this subfamily. Besides, this study also explored the palynological traits and their implication in the taxonomy of the subfamily Caesalpiniaceae. Pollen study of some selected taxa of Caesalpiniaceae was performed by using light microscopy and scanning electron microscopy. A significant variation was observed in exine sculpturing that was found useful to define species boundaries. Both qualitative and quantitative features were assessed for the identification and discrimination of these taxa. Pollen features were found to have significant taxonomic potential and can be used as an additional tool for the characterization of Caesalpiniaceae taxa.