Leaf Phytoliths Research Articles

Palm reading: a pilot study to discriminate phytoliths of four Arecaceae (Palmae) taxa

A pilot study of an opal phytolith morphotype series diagnostic for palms (Arecaceae), using modern specimens of four economically important palm species ( Areca catechu L., Calamus aruensis Becc., Cocos nucifera L., and Metroxylon sagu Rottb.), was undertaken to identify distinctive features of leaf phytoliths from each taxon. Our univariate and multivariate analyses documented that although it was not possible to identify individual palm phytoliths unambiguously to taxon, interspecific differences in phytolith morphology significantly outweighed intraspecific variation, revealing the potential value of further research in this area and the possible utility of assemblage-level analysis to palm phytoliths in archæological assemblages. The methods are applied to archæological phytoliths from Watom Island, East New Britain, Papua New Guinea, and directions for further research outlined.

Effects of silicon on copper toxicity in Erica andevalensis Cabezudo and Rivera: a potential species to remediate contaminated soils

The influence of silicon on responses to copper excess was studied in plants of Erica andevalensis. Plantlets were grown in nutrient solutions containing two Cu (1 and 500 µM) and three Si concentrations (0, 0.5 and 1 mM). Plant growth, water content, and mineral nutrient concentration were determined. Plants grown with 500 µM Cu showed differences in growth and shoot water content depending on Si supply. The addition of 1 mM Si in high-Cu nutrient solutions significantly improved plant growth and reduced water loss preventing plant death related to Cu-excess. Silicon supply reduced significantly leaf Cu concentration (up to 32%) and increased Cu concentration in roots. Phytoliths isolated from leaves were analysed by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. Such phytoliths consisted in silica deposits associated with Cu and other elements (K, Ca, P). Improvement by Si of Cu tolerance in E. andevalensis was clearly related to the inhibition of Cu upward transport. The leaf phytoliths formed in Si-treated plants might have some contribution to tolerance by Cu immobilisation and inactivation.

Phytolith analysis of Chusquea ramosissima Lindm. (Poaceae: Bambusoideae) and associated soils

Chusquea ramosissima Lindm. is dominant in the understory of the Misiones province forests (Argentina); it colonizes open natural areas and gaps created by timber extraction. The aim of this study is to analyze both the phytolith assemblage produced by leaves, culms, and roots of C. ramosissima and the one deposited on soil surface. This information will be used in future phytolith studies of the Misiones forest soils, which will contribute to understanding the dynamics of this species in the past. Phytoliths were extracted from plant organs by using a calcination technique and morphotypes were identified in plant tissue by anatomical observations. Soil samples were collected from two sites with a different history of use and vegetal cover. The three organs produced different phytolith morphotypes; leaf was the main producer. From the soil samples, only leaf phytoliths were observed. Although concave dumb-bells are the characteristic phytoliths of C. ramosissima, their greater robustness and higher preservation in soil—even where this species is nowadays absent—do not help to discriminate clearly between sites with and lacking this species. On the other hand, the panicoid dumb-bell (bilobated flat/concave ends short cell) and Chusquea bulliform (cubic/parallepipedal bulliform cell) phytoliths seem to be more sensitive to changes in the presence/absence of this species. Results from this research will provide useful information for future studies of late Pleistocene–Holocene reconstruction in this region.

Identifying the δ 18O signature of precipitation in grass cellulose and phytoliths: Refining the paleoclimate model

Cellulose and silica phytoliths were extracted from the leaves and stems of Calamovilfa longifolia, a C 4 grass, grown under varying climatic conditions across the North American prairies. The oxygen-isotope compositions of both cellulose and silica record a complex signal of the isotopic composition of the soil water that feeds the plants and the relative humidity conditions that influence transpiration rates, stomatal conductance, and ultimately the 18O-enrichment of leaf water. As the initial stages of cellulose formation occur in the leaves, cellulose in both the leaves and stems forms primarily from leaf water and does not differ greatly in its oxygen-isotope composition between these locations. In contrast, the δ 18O values of leaf phytoliths are significantly enriched in 18O relative to stem phytoliths, reflecting the varying isotopic composition of the water in these tissues. The oxygen-isotope compositions of leaf cellulose may be used as a proxy for the isotopic composition of water involved in leaf phytolith formation, while the δ 18O values of stem phytoliths can be used to determine the δ 18O values of stem water involved in partial exchange reactions during the transport of carbohydrates through the plant. A comparison of the isotopic compositions of phytoliths with cellulose allows for the deduction of soil and leaf water δ 18O values as well as temperature and relative humidity conditions during plant growth. This approach has application in paleoclimate studies that traditionally have required estimations of one or more of these variables because direct measurements were unavailable.

An overview of leaf phytolith production patterns in selected northwest Australian flora

Phytolith occurrence in predominantly the leaves of 177 non-Poaceae plant species, representing 53 families, from northwest Australia were investigated with the aim of creating a comparative collection to assist interpretations of phytolith assemblages recovered from archaeological and geological contexts. Approximately 50% of the samples examined were found to be non-phytolith producers. The remaining samples produced variable quantities of phytoliths, ranging from minimal traces to abundant amounts. A range of phytolith morphologies was observed, including both distinctive and redundant forms. Comparison of the results from this study with those conducted in other geographical locations reveals a general continuity of patterns within families, thereby suggesting a high level of genetic control for phytolith production. However, differences between the results of this study with another major Australian study [Bowdery (1996) Unpubl. Ph.D. Thesis, Aust. Natl. Univ., Canberra, (1998) BAR Int. Monogr. Ser. 695, Hadrian, Oxford] seem to indicate that environmental factors must also be considered to play an important role in determining the nature of phytolith production. It is concluded that phytoliths constitute a valuable microfossil system for the reconstruction of palaeovegetation, palaeoclimate and plant–human interactions in the tropical region of northern Australia.

The oxygen isotopic compositions of silica phytoliths and plant water in grasses: implications for the study of paleoclimate

Information about climatic conditions during plant growth is preserved by the oxygen-isotope composition of biogenic silica (phytoliths) deposited in grasses. The oxygen-isotope composition of phytolith silica is dependent on soil-water δ 18O values, relative humidity and evapotranspiration, and temperature during plant growth. Phytolith and plant-water δ 18O values for C3 ( A. breviligulata) and C4 ( C. longifolia) grasses from natural and greenhouse sites in southwestern Ontario were used to compare the isotopic fractionation between biogenic silica and water in various parts of these living plants. For non or weakly transpiring tissues (rhizomes, stems, sheaths) in both grass species, the Δ 18O silica-plant water remained constant at ∼34‰, and the δ 18O and δD values of plant water collected from pre-dawn and mid-day samplings showed little variation. These plant waters were only slightly enriched in 18O and D relative to water provided to the grasses. Isotopic temperatures calculated from the silica and plant-water isotopic data matched measured growing temperatures for the region. By comparison, the upper leaf water was extremely enriched in oxygen-18 and deuterium at maximum rates of transpiration relative to water from non-transpiring tissues, as were the calculated, steady-state values for leaf-water δ 18O and δD. Silica produced in the transpiring tissues (leaf, inflorescence) has higher δ 18O values than silica from non-transpiring tissues, but the enrichment is modest compared to upper leaf water under mid-day conditions. Leaf phytoliths have formed from plant water typical of average conditions in the lower leaf, where the extreme 18O-enrichment is not encountered. C. longifolia was also collected from Alberta and Nebraska, where growing conditions are different from southwestern Ontario. Phytoliths at all three sites have a similar pattern of δ 18O values within the plants, but the isotopic separation between leaf and stem silica increases from 4 to 8‰ as average relative humidity decreases. The difference between actual growing temperature and that calculated using measured δ 18O values for stem silica and local meteoric water became progressively larger as relative humidity decreased, likely because of evaporative 18O-enrichment of soil water. Such effects are most pronounced in arid environments and pertinent in grasslands where much of the active rooting zone can be situated at the shallower depths most affected by the 18O-enrichment of soil water.

FITOLITOS DE POACEAE DE ARGENTINA. III. FITOLITOS FOLIARES DE ESPECIES DEL GÉNERO PASPALUM (PANICEAE) EN LA PROVINCIA DE ENTRE RÍOS

Zucol A. F. 2000. Phytoliths of Poaceae from Argentina: III. Leaf phytoliths of some species of the genus Paspalum (Paniceae), from Entre Rios province. Darwiniana 38(1-2): 11-32. Foliar phytolith morphology of 8 species of Paspalum: P. dilatatum Poir., P. lividum Trin. ex Schltdl., P. nicorae Parodi, P. notatum Flugge, P. plicatulum Michx., P. saurae Parodi, P. unispicatum Nash and P. urvillei Steud., present in the prairie of Entre Rios Province, was described. Cluster analysis (UPGMA) and ordination by principal component analysis (PCA) were performed on 49 morphological characters from the 8 phytolith assemblages (OTUs). Three groups were found, the first one with P. unispicatum, the second one with P. lividum and the third group with (P. dilatatum + (P. notatum + P. saurae)) and (P. nicorae + (P. plicatulum + P. urvillei)) assemblage subgroups. The 8 phytolith assemblages show Panicoid affinity (sensu Twiss, 1992). This analyses supported the infrageneric classification, with an exception in the Dilatata group assemblages ( P.dilatatum and P.urvillei).

Oxygen isotopic composition of opaline phytoliths: Potential for terrestrial climatic reconstruction

Opaline mineralized bodies are produced by many terrestrial plants and accumulate in certain soils and archaeological sites. Analyses of the oxygen isotopic compositions of these so-called phytoliths from stems and leaves of wheat plants grown in a greenhouse showed a linear relationship with stem and leaf water isotopic compositions and hence, indirectly, rain water isotopic composition. Analyses of wheat plants grown in fields showed that stem phytoliths isotopic composition directly reflects the seasonal air temperature change, whereas leaf phytoliths isotopic composition reflects both temperature and relative humidity. Temperature and the oxygen isotopic composition of stem phytoliths were related by an equation similar to that proposed for marine opal. Oxygen isotopic compositions of fossil phytoliths, and in particular those from stems, could be valuable for reconstructing past terrestrial climate change.

PSEUDOFAGUS IDAHOENSIS, N. GEN. ET SP. (FAGACEAE) FROM THE MIOCENE CLARKIA FLORA OF IDAHO

A new genus and species of Fagaceae are established for compressed leaves and attached fruits which represent one of the dominant taxa in the rich Miocene Clarkia flora of northern Idaho. The leaf and fruit morphology, cuticular and pericarp anatomy, and leaf phytoliths fall within the range of variation of the subfamily Fagoideae. The unique fruit consists of a large, exposed, distinctly keeled, trigonous nut and a diminutive basal cupule. The cupule has an apical frill of free, petiolate, leaflike appendages but lacks other ornamentation, and there is no evidence of a distinct Valvation. As no other genus of the Fagaceae has fruits with this combination of characters, a new genus is established and is referred to the subfamily Fagoideae. The Miocene genus seems most closely related to the extant genus Fagus.