Acetaldehyde emission by the leaves of trees – correlation with physiological and environmental parameters

The leaves of trees emit significant amounts of acetaldehyde which is synthesized there by the oxidation of ethanol. In the present study, we examined plant internal and environmental factors controlling the emission of acetaldehyde by the leaves of young poplar ( Populus tremula × P. alba ) trees. The enzymes possibly involved in the oxidation of ethanol in the leaves of trees are catalase (CAT; EC 1.11.1.6) and alcohol dehydrogenase (ADH; EC 1.1.1.1), both expressed constitutively in the leaves of poplars. Inhibition of ADH in excised leaves caused a significant decrease of acetaldehyde emission accompanied by an increased ethanol emission. Since inhibition of CAT by aminotriazole did not affect acetaldehyde and ethanol emission, it is concluded that the oxidation of ethanol in the leaves is mediated by ADH rather than by CAT. Further studies indicated that aldehyde dehydrogenase (ALDH; EC 1.2.1.5) seems to be responsible for the oxidation of acetaldehyde. The present results demonstrate that acetaldehyde emission is clearly dependent on its production in the leaves as controlled by the delivery of ethanol to the leaves via the transpiration stream. Environmental factors that control stomatal conductance seem to be of less importance for acetaldehyde emission by the leaves.     

Seeing the forest beyond the trees

In a recent paper (Mitchard et al. 2014, Global Ecology and Biogeography, 23 , 935–946) a new map of forest biomass based on a geostatistical model of field data for the Amazon (and surrounding forests) was presented and contrasted with two earlier maps based on remote‐sensing data Saatchi et al. (2011; RS1) and Baccini et al. (2012; RS2). Mitchard et al. concluded that both the earlier remote‐sensing based maps were incorrect because they did not conform to Mitchard et al. interpretation of the field‐based results. In making their case, however, they misrepresented the fundamental nature of primary field and remote‐sensing data and committed critical errors in their assumptions about the accuracy of research plots, the interpolation methodology and the statistical analysis. By ignoring the large uncertainty associated with ground estimates of biomass and the significant under‐sampling and spatial bias of research plots, Mitchard et al. reported erroneous trends and artificial patterns of biomass over Amazonia. Because of these misrepresentations and methodological flaws, we find their critique of the satellite‐derived maps to be invalid.     

Seeing the forest with the leaves – clues to canopy placement from leaf fossil size and venation characteristics

Although a variety of leaf characteristics appear to be induced by light environment during development, analysis of ontogenetic changes in living broad leaved trees has suggested that a number of other traits also lumped into the classic 'sun' versus 'shade' morphological distinctions, including leaf size, shape, and vein density, are instead controlled largely by local hydraulic environment within the tree canopy. The regularity in how these traits vary with canopy placement suggests a method for addressing a classic paleobotanical quandary: the stature of the source plant – from herb or shrub to canopy tree – is typically unknown for leaf fossils. The study of Ginkgo here complements previous work on Quercus that indicated that leaves throughout the crown are identical in size and venation at the time of bud break and that morphological adaptation to the local microenvironment takes place largely during the expansion phase after the determination of the vascular architecture is complete. Hence, variation in vein density does not reflect differential vein production so much as the distortion of similar vein networks over different final surface areas driven by variation in local hydraulic supply during expansion. Unlike the diffusely growing leaves of the angiosperm, Quercus , the marginally growing leaves of Ginkgo do show some potential for differential vein production, but expansion effects still dominate. The approach suggested here may prove useful for assessing the likelihood that two distinct fossil morphospecies actually represent leaves of the same plant and to gather information concerning canopy structure from disarticulated leaves.     

Utilization of evergreen and decidous oaks by the Californian oak moth Phryganidia californica

Summary The deciduous oak Quercus lobata was a better quality food source than the evergreen oak Q. agrifolia for the California oak moth Phryganidia californica: it supported higher growth rates, produced higher fecundity and survivorship, and higher efficiency of conversion of ingested food (ECI), efficiency of conversion of digested food (ECD) and efficiency of nitrogen utilization (NUE). Total polyphenols and astringency were similar in both oak speices, whereas water content was lower and leaf specific weight higher in Q agrifolia than in Q lobata. Nitrogen was higher in new leaves of Q agrifolia but higher in mature leaves of Q. lobata. Contrary to most other studies, total polyphenols and astringency were higher in new than in mature leaves. These results confirmed my hypothesis that the differences in leaf quality associated with the evergreen or deciduous life form would translate into food of differing quality for herbivores.     

Zinniol induces chlorophyll retention in barley leaves: the selective action of a non host-specific phytotoxin

A biologically active compound was isolated from liquid cultures of Alternaria tagetica and identified as zinniol. The selective action of zinniol, a non host-specific phytotoxin which induces necrosis in a number of unrelated plant species, has been demonstrated: enhanced chlorophyll retention occurs in zinniol-treated leaf tissue of three cereal species.     

Detecting hydrogen peroxide in leaves in vivo – a comparison of methods

Four hydrogen peroxide detecting probes, 3,3′‐diaminobenzidine (DAB), Amplex Red (AR), Amplex Ultra Red (AUR) and a europium–tetracycline complex (Eu₃Tc) were infiltrated into tobacco leaves and tested for sensitivity to light, toxicity, subcellular localization and capacity to detect H₂O₂ in vivo. In the absence of leaves, in water solutions, AUR was very much sensitive to strong light, AR showed slight light sensitivity, while DAB and Eu₃Tc were insensitive to irradiation. When infiltrated into the leaves, the probes decreased the photochemical yield (Φ_PSII) in the following order of effect AR > DAB > AUR > Eu₃Tc. With the exception of Eu₃Tc, all probes stimulated the build‐up of non‐photochemical quenching either temporally (DAB, AUR) or permanently (AR), showing that their presence may already limit the photosynthetic capacity of leaves, even in the absence of additional stress. This should be taken into account when using these probes in plant stress experiments. Confocal laser scanning microscopy studies with the three fluorescent H₂O₂ probes showed that the localizations of Eu₃Tc and AUR were mainly intercellular. AR partly penetrated into leaf chloroplasts but probably not into the thylakoid membranes. Photosynthesis‐related stress applications of AR seem to be limited by the low availability of internal leaf peroxidases. Applications of AR for kinetic H₂O₂ measurements would require a co‐infiltration of external peroxidase, imposing another artificial modifying factor and thus taking experiments further from ideal, in vivo conditions. Our results suggest that the studied H₂O₂ probes should be used in leaf studies with caution, carefully balancing benefits and artifacts.     

开发木本油料植物作为生物柴油原料的研究

本文根据德国、欧盟和美国制定的生物柴油标准制定了以碘值、十六烷值和脂肪酸组成等参数作为植物油质量的评价体系。通过四条标准,即51<十六烷值<65、碘值<115、亚麻酸<12%和十八碳四烯酸<1%、碳链长度为C12-C22,对国产118种种子含油量超过30%的木本油料植物进行评估,共筛选出53种木本油料植物的种子油可作为发展生物柴油最适合的原料。其中油茶、杏、无患子、臭椿、白檀、海州常山分布广,是值得推广种植的生物柴油植物。富油大科山茶科和无患子科植物的种子油一般都适合发展生物柴油,而富油大科樟科、松科和卫矛科植物的种子油不适合作生物柴油原料。我国各省区可因地制宜选择合适的能源树种,发展生物柴油产业。