Abstract
<p>The taxonomic value of phytolith assemblages and their degree of variability within different species of the same genus is still an undervalued issue in the botanical range of phytolith studies. However the understanding of grass phytolith variance and its implications to plant systematics is doubtless.</p><p>In the present study phytoliths of the lateral shoots (leaves) of nine, globally distributed <em>Poa</em> species (Pooideae – Poaceae) are described. Phytoliths were recovered from <em>Poa</em> specimens by the dry ashing technique. Altogether 6223 disarticulated phytoliths were counted (approximately 500–700 phytoliths per species) in 54 plant samples, which cover six shoots of nine species. Not only the relative frequency of each morphotype was calculated, but measurements were conducted to determine the biogenic silica content of <em>Poa</em> lateral shoots. A phytolith reference collection for the nine selected species of a worldwide importance was also compiled. The description of the most significant phytolith morphotypes and their taxonomic relationships are given here.</p><p>Results suggest that the biogenic silica content of the <em>Poa</em> lateral shoots was determined to be relatively high within all nine species. Phytolith assemblage data was subjected to multivariate statistical analyses (e.g., CA and PCA) in order to find differences and similarities among the nine <em>Poa</em> species. Results show that the two closely related <em>Poa</em> of the <em>P. pratensis</em> species group, namely the <em>P. pratensis</em> and <em>P. angustifolia</em>, only slightly differ from the other <em>Poa</em> species if we consider their rondel-trapeziform short cells (SC) phytolith frequencies.</p>
Highlights
Many plants deposit hydrated SiO2 in cell walls, cells and characteristic structures in intercellulars [1,2]
The aim of this study is to describe the phytolith assemblage in lateral shoots of nine Poa species, looking for potential species level phytolith characters that could be useful in palaeocecology and, in parallel, to start collecting reference material to make comparisons with other grass species and genera
There may be some correlation between the biogenic silica content (bSi) content and width of the leaves of the studied species because the higher bSi content was coupled with narrower leaves, but the negative correlation is not significant
Summary
Many plants deposit hydrated SiO2 in cell walls, cells and characteristic structures in intercellulars (silica bodies, phytoliths) [1,2]. Several studies link phytolith morphotypes to plant families and subfamilies (in Poaceae) [3,4,5,6,7,8]. It has been shown that there is a correlation between phytolith morphotypes and the C3 and C4 photosynthetic pathways and this allows the reconstruction of plant communities and climate through time [7,8]. Some cases are known in which the phytolith shapes of plant reference material allowed the correct identification. For example Mejia-Saules and Bisby [10] found distinguishing silica bodies in the lemmae of Melica species. Form and position of phytoliths, which are not greatly influenced by environmental factors but are genetically controlled, may have considerable systematic potential [11,12,13]
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