ABSTRACT
Phytoliths (siliceous structures) present in the plants have been employed in the fields of taxonomy and archaeology for many decades. Rostraria cristata is an economically important grass species (Poaceae) which accumulates silica in its different organs in the form of phytoliths. In order to understand the pattern of phytolith production and biochemical architecture of silica in R. cristata, leaf epidermis (blade) using the clearing solution method and different organs using the dry ashing method, X-ray diffraction and Fourier-transform infrared spectroscopy techniques were analyzed. Both abaxial and adaxial leaf epidermis showed the presence of acute bulbosus, rectangular sinuate and stomata phytolith morphotypes. Leaf including sheath and blade had the highest silica content. Characteristic phytolith morphotypes were present in different organs. A total of 34 phytolith morphotypes were present among which nine (9) were articulated and 25 were isolated forms. The most abundant were elongate scrobiculate (48.20%) in root and rectangular sinuate (26.16%) in leaf part. Other common phytolith morphotypes present in different organs of R. cristata were articulated elongate irregular, articulated elongate scrobiculate, acute bulbosus, and polygonal rondel etc. Leaf and synflorescence had the highest similarity based on presence/absence of phytolith morphotypes (Jaccard's similarity index). XRD studies revealed the presence of cristobalite, quartz, tridymite, zeolite etc. forms of silica in different organs. FTIR spectra showed that inplane stretching vibration of Si-C was unique to root, anti-symmetric stretching vibration of C-H was unique to leaf and Al2O3.SiO2 was found in synflorescence only. Our results show the characteristic pattern of phytoliths production in R. cristata.
Subject(s)
Poaceae , Silicon Dioxide , Silicon Dioxide/chemistry , Plants , Plant LeavesABSTRACT
Acrachne racemosa (B. Heyne. ex Roem. & Schult.) Ohwi of the subfamily Chloridoideae of the family Poaceae is an economically important grass species. Grasses are characterized by deposits of silica in the cells or tissues in the form of phytoliths which protect them from various types of biotic and abiotic stresses. Owing to variable shape and specificity of morphotypes, phytolith helps in taxonomical studies, reconstruction of paleoenvironments and prediction of climate changes. The present study focussed on developing a phytolith profile of the selected species. For isolation of phytolith, Dry Ashing Method was employed, and by epidermal peeling, in-situ location of phytoliths was deciphered. In the present study, silica percentage was studied from different parts of the plant and the maximum amount was found in the leaf. Frequency and morphometric data of phytolith morphotypes from different parts of the plants were also collected and analyzed. The strongest correlation was found between phytolith types of root and culm by Pearson's correlation coefficient supported by cluster analysis. The saddle type of phytoliths had the highest frequency in the leaf; other types of phytoliths in different parts of the plant were bilobate, blocky types, elongate types, trapezoids, triangular, cross, sinuate elongate, tabular types, globular types. Functional groups and amorphous polymorphic phases of silica were also analyzed by FTIR and XRD. It was concluded that phytolith types are controlled by parts of plant body and by anatomical and environmental factors.
Subject(s)
Poaceae/chemistry , Silicon Dioxide/analysis , Cluster Analysis , Plant Leaves/chemistry , Plant Roots/chemistry , Spectroscopy, Fourier Transform Infrared , Stress, PhysiologicalABSTRACT
Background and Aims: The role and significance of phytoliths in taxonomic diagnosis of grass species has been well documented with a focus on the types found in foliar epidermis and the synflorescence. The present paper is an attempt to broaden the scope of phytoliths in species diagnosis of grasses by developing phytolith signatures of some species of the foxtail genus Setaria P. Beauv. through in situ location and physico-chemical analysis of various phytolith morphotypes in different parts of the plant body. Methods: Clearing solution and dry ashing extraction methods were employed for in situ location and isolation of phytolith morphotypes respectively. Ultrastructural details were worked out by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy. Morphometric and frequency data of phytolith morphotypes were also recorded. Biochemical architecture of various phytolith types was worked out through SEM-EDX, XRD, and FTIR analysis. Data were analyzed through Principal Component Analysis and Cluster Analysis. Key Results:In situ location of phytoliths revealed species specific epidermal patterns. The presence of cystoliths (calcium oxalate crystals) in the costal regions of adaxial leaf surface of S. verticillata (L.) P. Beauv. is the first report for the genus Setaria. Our results revealed marked variations in epidermal ornamentation and undulation patterns with a novel "Λ" (Lamda) type of undulated ornamentation reported in S. verticillata. Dry ashing method revealed species specific clusters of phytolith morphotypes. Conclusions: The study revealed that phytoliths can play a significant role in resolution of taxonomic identity of three species of Setaria. Each species was marked out by a unique assemblage of phytolith morphotypes from various parts of the plant body. Apart from in situ location and epidermal patterning, diagnostic shapes, frequency distribution, size dimensions, and biochemical architecture emerged as complementary traits that help in developing robust phytolith signatures for plant species.
