Activity Changes in Selected Enzymes from Soybean Leaves Following Ozone Exposure

Soybeans [Glycine max(L.) Merr.] were harvested at various time periods after a 2-h exposure to either 0 or 0.5 μ1/1 ozone to determine the effects of ozone on selected enzymes. Carbohydrate metabolism was modified by a depression of glyceraldehyde 3-phaosphate dehydrogenase and an activation of glucose 6-phosphate dehydrogenase. Ozone did not alter the levels of RNase, protease, acid phosphatase or esterase as might be expected if ozone enhanced leaf senescence. The activities of phenylalanine ammonia lyase, polyphenol oxidase and peroxidase were initially depressed and then stimulated following the ozone exposure. The reactions of soybeans to an acute ozone stress were more nearly akin to those elicited in response to other stresses than to the process of senescence.     

The importance of pre-thicket conifer plantations for nesting Hen Harriers Circus cyaneus in Ireland

Hen Harriers Circus cyaneus are threatened across much of their range and their conservation requires appropriate habitat management. The locations of 148 Hen Harrier nests found in the Republic of Ireland during national breeding surveys in 2000 and 2005 were used to assess nest-site selection. The distribution of these nests was compared to distributions of randomly located points to investigate selection at the scale of the nest-site and landscape. The main nesting habitats selected were pre-thicket stage of first and, particularly, second rotation plantations, mostly of exotic conifers. There was no evidence that the area of post-closure plantations negatively affected Hen Harrier nest distribution. There was a positive correlation across study areas between changes in numbers of Hen Harrier nests between 2000 and 2005 and changes in the area of pre-thicket second rotation plantations over the same period. The overall effect of plantation forests on breeding Hen Harriers in Ireland therefore appears to be positive. However, this study did not consider the effects of plantation habitats on breeding success. Improved grassland was strongly avoided as a nesting habitat. Furthermore, after controlling for the influence of nesting habitat on nest location, landscapes with a high percentage cover of improved grassland were also avoided. Further agricultural intensification of grassland in areas where Hen Harriers breed is likely to have a negative impact on this species. These results are required for the development of management strategies for the conservation of this species.     

Changes in species richness and composition in European acidic grasslands over the past 70 years: the contribution of cumulative atmospheric nitrogen deposition

Our study investigates the negative impact of nitrogen (N) deposition on species richness in acidic grasslands, based on a temporal comparison of vegetation data spanning a period of almost 70 years. We compiled a large data base of plots assigned to the Violion caninae grassland type, composed of managed, but unfertilized semi-natural grasslands on nutrient-poor, acidic soils. In total 1114 plots, mainly from Great Britain, the Netherlands and Germany, were compiled, dating back to 1939. Environmental site information included geographical and soil (mean Ellenberg values) variables as well as estimates of cumulative N and sulphur (S) deposition since 1939. Statistical analyses were carried out separately for the data subsets from the three regions. In all regions, the vegetation differentiation was mainly related to soil acidity and nutrient availability, as well as to the year of sampling and the cumulative amounts of N and S deposition. Plot-species richness of vascular plants and bryophytes (analysed for Great Britain only) decreased with time and analyses suggest these are affected by various factors, notably soil pH, but also latitude and cumulative N deposition. The latter explained more of the variation in species number than the year of sampling and cumulative S deposition, which supports the interpretation that the decline in species richness is mainly caused by increasing N availability and less by altered management and soil acidification. For Great Britain and Germany, cumulative N deposition showed a strong negative relationship with several biodiversity measures, especially the proportion of dicots, whereas it was positively related to the proportion of grass species. In general, our results give temporal evidence for the negative effect of N deposition on species richness in semi-natural vegetation.     

Infrared heater arrays for warming ecosystem field plots

There is a need for methodology to warm open‐field plots in order to study the likely effects of global warming on ecosystems in the future. Herein, we describe the development of arrays of more powerful and efficient infrared heaters with ceramic heating elements. By tilting the heaters at 45° from horizontal and combining six of them in a hexagonal array, good uniformity of warming was achieved across 3‐m‐diameter plots. Moreover, there do not appear to be obstacles (other than financial) to scaling to larger plots. The efficiency [η_h (%); thermal radiation out per electrical energy in] of these heaters was higher than that of the heaters used in most previous infrared heater experiments and can be described by: η_h= 10 + 25exp(? 0.17 u), where u is wind speed at 2 m height (m s^{? 1}). Graphs are presented to estimate operating costs from degrees of warming, two types of plant canopy, and site windiness. Four such arrays were deployed over plots of grass at Haibei, Qinghai, China and another at Cheyenne, Wyoming, USA, along with corresponding reference plots with dummy heaters. Proportional integral derivative systems with infrared thermometers to sense canopy temperatures of the heated and reference plots were used to control the heater outputs. Over month‐long periods at both sites, about 75% of canopy temperature observations were within 0.5 °C of the set‐point temperature differences between heated and reference plots. Electrical power consumption per 3‐m‐diameter plot averaged 58 and 80 kW h day^{? 1} for Haibei and Cheyenne, respectively. However, the desired temperature differences were set lower at Haibei (1.2 °C daytime, 1.7 °C night) than Cheyenne (1.5 °C daytime, 3.0 °C night), and Cheyenne is a windier site. Thus, we conclude that these hexagonal arrays of ceramic infrared heaters can be a successful temperature free‐air‐controlled enhancement (T‐FACE) system for warming ecosystem field plots.     

Detection and validation of EST‐derived SNPs for poplar leaf rust Melampsora medusae f. sp. deltoidae

We report the discovery, characterization and validation of 118 single nucleotide polymorphisms (SNPs) for poplar leaf rust Melampsora medusae f. sp. deltoidae identified using a gene‐targeted approach in an expressed sequence tag (EST) library. We developed a genotyping assay using the iPLEX? primer extension method for two multiplex assays of 28 and 22 SNPs.     

Differential responses of UK upland plants to nitrogen deposition

Native upland species, Nardus stricta , Eriophorum vaginatum , Erica cinerea and Vaccinium vitis-idaea were given 3 or 60 kg N ha⁻¹ yr⁻¹, over 2 yr, applied as a mist (NH₄NO₃). The high N treatment increased above-ground biomass in all four species, but only significantly in E. cinerea , E. vaginatum and N. stricta . Biomass increases in E. vaginatum and N. stricta resulted from enhanced tiller production rather than shoot elongation. Root growth increased in N. stricta , so that root:shoot ratio in this species was unchanged by N. Root growth in E. vaginatum , E. cinerea and V. vitis-idaea did not respond to N and their root:shoot ratios decreased. Tissue N concentrations increased in both shoots and roots of all species in response to N. The accumulated foliar N did not increase the proportion of N allocated to Rubisco and the photosynthetic capacities of N. stricta , E. vaginatum and V. vitis-idaea were unchanged. Thus growth responses to N were due to altered allocation rather than increased rate of photosynthesis per unit leaf area. The high N treatment increased flower production significantly in E. cinerea but not in the other species. Although in this experiment dwarf shrubs were more responsive than graminoids to N, in the field at current N inputs the enhanced tillering of the graminoids may be more competitively advantageous, especially where gaps develop in the canopy. Thus increasing N deposition may lead to increased grassiness of upland heath, and in particular, a spread of N. stricta .     

The Distribution of Na+, K+ and Glycinebetaine in Salicornia bigelovii

Stems of young actively growing Salicornia bigelovii were dissectedinto the three major tissue layers: vascular, spongy mesophylland palisade. Each layer was analysed for chlorophyll, ash (salt),protein and glycinebetaine content. When glycinebetaine contentwas based on protein content, the vascular and spongy mesophylllayers had nearly identical values. Correction for probableRuBP carboxylase content in the palisade layer gave a glycinebetaine/proteinratio similar to that of the other tissues. All three tissuelayers were found to contain significant amounts of salt. Key words: Salicornia bigelovii, Salt distribution     

Wandering behaviour and pupariation in tsetse larvae

Abstract .Following parturition, the third instar larva of Glossina morsitans morsitans West begins a wandering period in which it crawls to the site of pupariation. The duration of wandering can be drastically shortened by pinching or by denying the larva physical contact with the substrate. Contact with water increases the wandering period. Duration of subsequent activities appears to be rigidly fixed. At the end of the wandering period, the larva quickly progresses through a stereotypic sequence of behaviours that include immobilization and excretion of a liquid from the anus, retraction of the anterior segments, cuticular shrinkage, and tanning. Muscular activity and mechanical changes in the cuticle are reflected in changes of haemocoelic pressure. Muscular contractions produce pressure pulses that gradually increase in frequency and intensity, reaching a peak during retraction of the anterior segments. Changes in the mechanical properties of the cuticle cause a more gradual elevation of baseline pressure as the cuticle shrinks and loses its plasticity. As tanning begins, muscular activity ceases and haemocoelic pressure gradually decreases. In spite of its unusual early development within the confines of the female's uterus, the free-living larva shows the full behavioural repertoire observed in other cyclor-rhaphous Diptera at pupariation.