Light Microscopic and Scanning Electron Microscopic Techniques to Characterize Nutlets of Some Indian Cyperoideae (Cyperaceae) and Their Taxonomic Significance.

Abstract

In the present investigation, nutlet morphological and micro-morphological characters were analyzed using Light Microscope (LM) and Scanning Electron Microscope (SEM) in 38 taxa under 13 genera from the sub-family Cyperoideae of Cyperaceae to find out whether these characters are taxonomically important or not. Nutlet morphology and surface characters of the representative taxa from all the possible tribes under the sub-family Cyperoideae namely, Fuireneae, Cypereae, Cariceae, Abildgaardieae, Eleocharideae, Pseudoschoeneae, Schoenoplecteae, and Sclerieae were evaluated for their taxonomic significance. Cluster analysis was employed considering nutlet morphological characters to determine the overall similarity among the taxa based on 153 character states. Except in few specified cases, grouping of the taxa in the clusters is in accordance to the taxonomic treatments made by recent Cyperologists. Nutlets in the tribe Abildgaardieae showed maximum level of variability in size, shape, and surface ornamentation at the level of higher taxon, but showed specificity at the species level. Tuberculate, striate-reticulate, and transversely wavy ridged surface ornamentations were found in different species of Fimbristylis. Previously described cryptic variation, and effect of different ploidy level were not reflected in nutlet surface morphology and micromorphology in Fimbristylis dichotoma and F. ovata complexes which was previously made the taxa taxonomically very difficult. Serrulate anticlinal wall in F. bisumbellata was the most unique in Fimbristylis. Species under the megadiverse genus Carex representing the tribe Cariceae showed very unique type of surface ornamentation. Surface walls of all the studied species of Carex were characterized by polygonal epidermal cells with single conical silica body (2-3 per cell in C. speciosa) of variable length and sizes. Most interestingly, in C. nubigena, presence of the central silica body and peripheral satellites was not consistent. Based on the presence and absence, two different variants under the species were identified. In C. nubigena, when silica body was present, epidermal cells were characterized by central conical silica body surrounded by variable number of satellites. The present investigation first time reports this novel nutlet surface character in C. nubigena. Among the studied characters, length and height of conical, height of apex, and width of apex are variable among Carex species. On the other hand, exclusion of the genera Schoenoplectiella and Schoenoplectus from tribe Scirpeae s.l. and placement under the tribes Pseudoschoeneae and Schoenoplecteae (respectively) was also supported by the present investigation. The present study also confirms that nutlet morphological and micro-morphological characters are useful in identification and arrangement of different taxa under the subfamily Cyperoideae of Cyperaceae. Result of the present investigation was correlated and discussed in comparative manner with the treatments of the recent past.