Influence of Environmental Pollution on Leaf Properties of Urban Plane Trees, Platanus orientalis L.

To investigate whether leaves of plane trees (Platanus orientalis) are damaged by traffic pollution, trees from a megacity (Mashhad, Iran) and a rural area were investigated. Soil and air from the urban centre showed enrichment of several toxic elements, but only lead was enriched in leaves. Leaf size and stomata density were lower at the urban site. At the urban site leaf surfaces were heavily loaded by dust particles but the stomata were not occluded; the cuticle was thinner; other anatomical properties were unaffected suggesting that plane trees can cope with traffic exhaust in megacities

CURSO DIÁRIO E SAZONAL DO POTENCIAL HÍDRICO FOLIAR DE MOGNO EM SISTEMAAGROFLORESTAL1

Este trabalho objetivou avaliar o curso diário e sazonal do potencial hídrico foliar de mogno (Swietenia macrophylla King) (Meliaceae) em sistema agroflorestal (SAF). O experimento foi realizado em árvores de S. macrophylla plantadas num sistema agroflorestal instalado no Campo Experimental da Embrapa Amazônia Ocidental, Manaus, AM. Avaliou-se o potencial hídrico foliar (Ψf) dos cursos diário e sazonal nos anos 2004 e 2005, por meio da utilização de bomba de pressão tipo Scholander. Os resultados indicaram que os valores do Ψf de S. macrophylla, de modo geral, foram superiores no início da manhã e no final da tarde, com redução acentuada ao meio-dia, e que, em relação à sazonalidade de precipitação, as menores taxas foram reportadas para a época menos chuvosa, variando de -26 bar em 2004 para -31bar em 2005. Verificou-se que o potencial hídrico de Swietenia macrophylla em sistema agroflorestal sofreu reduções significativas em razão dos baixos índices pluviométricos entre junho e outubro de 2005

Ultrastructural changes in soredia of the epiphytic lichen Hypogymnia physodes cultivated with manganese

The ultrastructure of soredia of the foliose epiphytic lichen Hypogymnia physodes cultivated on agar plates for I I days with three different concentrations of MnCl2 (7 muM [control], 500 muM, 7 mM) was compared by means of transmission electron microscopy. Photobiont cells (Trebouxia jamesii) of Mn-exposed soredia had swollen and contracted thylakoids. The chloroplasts were reduced in size, and numerous lysosome-like vesicles occurred in cells with degenerated chloroplast. At 500 muM, autospores of T jamesii were more severely damaged than vegetative cells. At 7 mM, autospore formation was strongly reduced. Concentric bodies and mesosome-like structures were nearly completely absent from mycobiont cells of Mn-treated soredia at both 500 muM and 7 mM. At 500 muM, the photobiont of not grown soredia was more severely damaged compared to grown soredia (defined as soredia where division of algal cells had taken place). At 7 mM, ultrastructural damage was observed in both grown and not grown soredia. This suggests that even soredia that survived the first days of cultivation are probably not capable of fort-ning thalli on Mn-rich substrates. The ultrastructural changes in Mn-exposed soredia support the hypothesis that high Mn concentrations in bark or stemflow are a limiting factor for the abundance of H. physodes and other epiphytic lichens in coniferous forests of Europe and North America. (C) 2004 Elsevier B.V. All rights reserved

Ectomycorrhiza and hydrogel protect hybrid poplar from water deficit and unravel plastic responses of xylem anatomy

To investigate whether the performance of Populus × canescens, a water-spending species, can be improved by Paxillus involutus ectomycorrhizas (EM) and soil amendment with water-retaining polymers (hydrogel), the pre-dawn water potential, growth performance and the hydraulic architecture of well-irrigated and drought-stressed plants were studied. Roots of well-irrigated plants were about 75% colonized with P. involutus regardless the presence of hydrogel. Drought stress resulted in an about 10% loss of EM. Non-inoculated plants showed marginal EM colonization (3%). EM poplar in hydrogel-amended soil maintained the highest pre-dawn water potential under drought stress, showed lowest biomass loss and kept almost full photosynthetic activity, whereas non-EM plants in soil without hydrogel exhibited severe leaf loss under these conditions and did not show net CO2 assimilation. Non-EM plants in hydrogel-amended soil and EM plants without hydrogel showed intermediate stress symptoms. The soluble carbohydrate content of roots was correlated with the pre-dawn potential indicating osmotic regulation under drought stress. EM plants displayed larger vessel cross-sectional areas and increased radial stem growth compared with non-EM plants. EM plants contained the lowest numbers of vessels (mm−2) but the largest vessel diameters, whereas non-EM drought-stressed plants in soil without hydrogel showed the smallest vessel diameters and highest vessel numbers. Vessel diameter and vessel numbers were strictly inversely correlated suggesting strong developmental coordination between these two parameters. The finding that neither vessel diameters nor vessel numbers were correlated with the pre-dawn water potential suggests that the coordination between these wood features may be achieved by signals acting independent of acute water stress. Overall, EM and hydrogel, especially in combination, help to avoid drought stress. Thereby, these soil amendments improve plant performance and may be useful for the establishment of plantations on marginal sites