Relationship between leaf apoplast pH and iron chlorosis of sunflower (Helianthus annuus L.)

A hypothesis has been presented and tested that bicarbonate (HCO₃) and nitrate (NO₃) are the most important anions inducing iron (Fe) chlorosis because these anions increase the pH of leaf apoplast which in turn depresses ferric‐iron [Fe(III]) reduction, and hence, the uptake of Fe into the symplasm. Experiments with young sunflower (Helianthus annuus) plants showed that nutrition with NO₃ as the sole nitrogen (N) source induced chlorosis whereas ammonium nitrate (NH₄NO₃) did not. Monohydrogen carbonate (bicarbonate) also favoured the development of chlorosis. The degree of chlorosis was not related to the Fe concentration in the leaves. Both anion species, NO₃ and HCO₃, increased the pH of the leaf apoplast which was measured by means of the fluorescence dye 5‐carboxyfluorescein. A highly significant negative correlation between leaf apoplast pH and chlorophyll concentration in the leaves (r = ‐0.97) was found. Ferric‐Fe reduction in the apoplast—measured by means of ferrocene—provided evidence that a low leaf apoplast pH, obtained with ammonium (NH₄) supply, favoured the reduction of Fe(III) as compared with a higher leaf apoplast pH obtained with NO₃ supply. These results support the hypothesis tested.     

Natural abundance of 18O of sugar biomarkers in topsoils along a climate transect over the Central Scandinavian Mountains,Norway

Precipitation and topsoil samples from a climate transect over the Scandinavian Mountains, Norway, were analyzed for bulk and compound‐specific δ¹⁸O values. The natural abundance of ¹⁸O in the plant‐derived hemicellulose biomarkers arabinose and xylose correlates positively with δ¹⁸O of bulk soil, but not with δ¹⁸O of precipitation. This suggests that other factors than δ¹⁸O_prec, such as evaporative ¹⁸O enrichment of leaf water, exert a strong influence on the natural abundance of ¹⁸O in soils.     

Modelling the long-term impacts of selective logging on genetic diversity and demographic structure of four tropical tree species in the Amazon forest

In the last three decades, Amazon tropical forests have experienced high rates of deforestation, both by clearing for agriculture and by logging. In this study, we use computer simulations to examine the potential effects of forest logging on genetic diversity and demographic recovery (basal area development) of four neotropical tree species over a time frame reflecting multiple logging events. The study species, Bagassa guianensis Aubl., Hymenaea courbaril L., Manilkara huberi (Ducke) Chevalier, and Symphonia globulifera L.f., are all taxa which are commonly exploited for timber in the Brazilian Amazon. The simulations were parameterized using empirical data from field studies in the Tapajós National Forest, Pará State, Brazil, including genotypes at microsatellite loci, demography, ecology and growth for each species. Eight scenarios, combining two different cutting cycles and two minimum cutting diameters, were examined for each of the four species. The scenarios represent the actual forest practices used in Brazil and French Guiana (cutting diameter 45 and 60 cm, and cutting cycle of 30 and 65 years, respectively). Logging scenarios were applied for six cutting cycles, and final genetic and demographic data were compared to baseline data from corresponding control scenarios. At the end of the simulated period the basal area was strongly reduced under all conditions in B. guianensis, H. courbaril, and M. huberi. In only two scenarios was a species able to recover its basal area following logging (S. globulifera with both 45- and 60-cm cutting diameters under a 65-year cutting cycle). In the logging scenarios, all species showed a loss of alleles and genotypes and an increased genetic distance (calculated between each population at the start and the end of the simulations). These effects were higher under the most intensive logging cycles (30 years, 45 cm). However, effective number of alleles, expected and observed heterozygosities, and the fixation index were little affected by the logging simulations. Over all, we conclude that, even under very optimistic conditions for growth and recruitment, current logging practices are not sustainable in terms of basal area. Our simulations show that different species respond differently to logging, both demographically and genetically. No single set of logging parameters can be applied to the forest as a whole. Rather, forest management practices must be species-specific, taking into account not only growth parameters but also ecological and reproductive variables, in order to move toward long-term forest sustainability.     

Pear decline resistance in progenies of <Emphasis Type="Italic">Pyrus</Emphasis> taxa used as rootstocks

Progenies of 39 open-pollinated genotypes belonging to 26 Pyrus taxa were examined for pear decline resistance and pomological traits when used as rootstocks. Following graft inoculation and observation over 18 years, considerable differences in pear decline resistance between and within the progenies were observed. Not affected or little affected and moderately to severely affected trees were observed in all progenies. However, great quantitative differences among them were observed. In the progenies of about one third of the pollinated trees most of the individuals showed a high level of resistance to grafted trees. Significantly different from this group was another third of the progenies that mostly showed high susceptibility in grafted trees. Between these two groups there were progenies that statistically neither differed from the resistant nor from the susceptible group. These progenies were defined as moderately resistant. Significant differences in resistance were also observed between progenies of genotypes of the same species that originated from different locations. These data indicate segregation of the resistance trait and show that seedling progenies are unsuitable as rootstocks in commercial pear growing. Instead, careful selection of suitable genotypes for propagation is required. Great differences between and within the progenies examined were also observed in vigour and yield efficiency.     

Water deficit and cold stress on the evening primrose seed quality

Evening primrose is a valuable oilseed crop with pharmaceutical and nutritional supplementation. Due to presence of valuable and rare gamma linolenic fatty acid, research on this plant has been started since 1970s by German and Britain scientists. Information about evening primrose cultivation is going to rise. Following to pervious studies the goal of this experiment was to clarify the effect of water and temperature stresses on seed yield and seed quality. Results showed that seed yield was significantly influenced by low temperature and water deficit. Plants grown under cold stress during rosette stage produced a lower seed yield than controls. The lowest seed yield was observed in the plants grown under permanent stress. Although the oil content of seeds was not influenced by low temperature stress, water stress strongly influenced the oil content and water stress stimulates oil accumulation. Like oil content, the GLA production seems to be increased under water stress conditions.     

EVALUATION OF THE LOWER RESPIRATORY TRACT IN PSITTACINES USING RADIOLOGY AND COMPUTED TOMOGRAPHY

In the last 2¹/₂ years, 288 grey parrot and amazon species with symptoms of respiratory disease clinically were presented to the clinic for avian medicine at the Justus-Liebig-University in Giessen. Ventro-dorsal and latero-lateral radiographs were taken from all birds; radiologic signs of lower respiratory tract disease were noted. Radiographs were normal in 55 of the birds. The results of the radiographic examination for the remaining 233 birds were compared with the necropsy results of terminally ill parrots, with the results of laboratory examinations/endoscopy/and/or with an examination by computed tomography. Thoracic radiographs were evaluated for occurring radiological abnormalities pertaining to the respiratory tract. The frequency of these lesions and their association with a disease process and/or specific etiology was noted.     

The importance of the soil skeleton for plant-available nutrients in sites of the Southern Black Forest,Germany

The skeletal fraction of forest soils in the Southern Black Forest has a cation exchange capacity (CEC) within the same order of magnitude as fine earth. As the base saturation in the skeleton is much higher than in the fine earth, stones provide a physiologically more favourable environment for nutrient uptake by plants. The fact that 70% of the skeleton grains showed adherent rhizomorphae and/or fine roots suggests that this potential is widely used by nutrient-adsorbing tissues. Therefore the ecological importance of this additional and, until now, unconsidered ion pool available to plants is probably higher than what is reflected by simple ion quantities. The effective CEC of the coarse fraction in forest sites with crystalline bedrock is reasonably predictable considering the water vapour adsorption of the 105°C dried skeleton at a suction of pF 4.6 (vapour pressure equilibrium with an oversaturated K₂SO₄ solution). The content of exchangeable base cations in the coarse fraction can be estimated using the content of exchangeable Mg in the fine earth. These stochastic relations are causally plausible. The regressions are a first approach to identify pedo-transfer functions predicting the skeletons nutrient potential with the aid of easily measurable site parameters.     

渭北刺槐和油松人工林林分质量初步研究

林木质量等级组成和期望成材类型的蓄积量被作为表达渭北黄土高原刺槐和油松人工林的林分质量的数量指标。结果表明，没有利用价值的林木占总林木株数的50%以上；龄级间各期望成材类型的蓄积均值趋于随着龄级的增长而增加，但波动较大，特别是在好的立地条件下生长的刺槐乔林；油松和刺槐矮林在好的立地条件下，期望成材的蓄积量高于其在并的立地条件下的值，对刺槐乔林来说则截然相反；在相同龄级内刺槐乔林的期望成材蓄积量高于刺槐矮林和油松林；由于林分间变异系数太大，因而龄级和好坏立地条件之间各期望成材类型的蓄积量差异并不显著，仅有个别龄级在好和差的立地条件下可见微小的差异；这是由无规则的抚育间代利用造成的，立地越好，采伐强度越大。     

Isolation, structure determination, and sensory activity of mouth-drying and astringent nitrogen-containing phytochemicals isolated from red currants (Ribes rubrum)

Application of chromatographic separation and taste dilution analyses recently revealed, besides a series of flavon-3-ol glycosides and (E)/(Z)-aconitic acid, four nitrogen-containing phytochemicals as the key astringent and mouth-drying compounds in red currants (Ribes rubrum). The isolation and structure determination of the astringent indoles 3-carboxymethyl-indole-1-N-beta-D-glucopyranoside (1) and 3-methylcarboxymethyl-indole-1-N-beta-D-glucopyranoside (2), as well as the astringent, noncyanogenic nitriles 2-(4-hydroxybenzoyloxymethyl)-4-beta-D-glucopyranosyloxy-2(E)-butenenitrile (3) and 2-(4-hydroxy-3-methoxybenzoyloxymethyl)-4-beta-D-glucopyranosyloxy-2(E)-butenenitrile (4) by means of 1D/2D NMR, LC-MS/MS, and UV-vis spectroscopy are reported. The structures of compounds 1 and 2 were confirmed by synthesis. Using the recently developed half-tongue test, human recognition thresholds for the astringent and mouth-drying nitrogen compounds were determined to be between 0.0003 and 5.9 micromol/L (water). In particular, the extraordinarily low threshold of 0.0003 micromol/L evaluated for the indole 1 represents the lowest recognition threshold of any astringent phytochemical reported to date.