Effect of boron supply on nitrate concentration and its reduction in roots and leaves of tobacco plants

Shoot and root mass of tobacco plants treated with only 0.05 μM boron was decreased by 25 and 50 %, respectively, when compared to plants sufficiently supplied with B (2 and 5 μM). Leaf B content of 0.05 μM B-treated plants decreased (about 80–90 %) when compared to 2 μM B treated plants; this drop of B content were not as marked (about 25–45 %) in roots. Leaf and root nitrate contents in B-deficient plants were 45–60 % and 35–45 % lower, respectively, than those from 2 and 5 μM B treated plants. It is suggested that B deficiency might decrease nitrate uptake rather than nitrate reductase activity in tobacco plants.     

LEAD TOLERANCE AND ACCUMULATION IN PTERIS VITTATA AND PITYROGRAMMA CALOMELANOS,AND THEIR POTENTIAL FOR PHYTOREMEDIATION OF LEAD-CONTAMINATED SOIL

A field survey was conducted to search for Pb accumulation in fern species at Bo Ngam Pb mine, Thailand. Eleven fern species including Pteris vittata accumulated Pb in the range of 23.3–295.6 mg kg^?1 in the aboveground parts. Hydroponic, pot, and field trial experiments were carried out to investigate Pb-accumulation ability in ferns; including P. vittata and the ornamental species, Pityrogramma calomelanos, Nephrolepis exaltata cv. Gracillimum, and N. exaltata cv. Smirha. In hydroponic experiment, Pi. calomelanos accumulated the highest concentration of Pb (root 14161.1 mg kg^?1, frond 402.7 mg kg^?1). The pot study showed that P. vittata, Pi. calomelanos, and N. exaltata cv. Gracillimum grew well when grown in soil Pb at 92900 mg kg^?1. N. exaltata cv. Gracillimum accumulated the highest Pb concentration in the frond (5074 mg kg^?1) and P. vittata accumulated the highest Pb concentration in the root (16257.5 mg kg^?1). All fern species exhibited TF values less than 1 in both hydroponic and pot experiments. When P. vittata and Pi. calomelanos were grown at mine soils for 6 months, P. vittata tolerated higher soil Pb (94584–101405 mg kg^?1) and accumulated more Pb in frond (4829.6 mg kg^?1) and showed TF > 1 after 2 months of growth. These results indicated that P. vittata can be potentially useful for phytoremediation of Pb-contaminated soil.     

Identifying Environmental Determinants of Diurnal Distribution in Marine Birds and Mammals

Marine birds and mammals move between various habitats during the day as they engage in behaviors related to resting, sleeping, preening, feeding, and breeding. The per capita rates of movement between these habitats, and hence the habitat occupancy dynamics, often are functions of environmental variables such as tide height, solar elevation, wind speed, and temperature. If the system recovers rapidly after disturbance, differential equation models of occupancy dynamics can be reduced to algebraic equations on two time scales. Identification of environmental factors that influence movement between habitats requires time series census data collected in both the absence and presence of disturbance.     

Forest bioenergy climate impact can be improved by allocating forest residue removal

Bioenergy from forest residues can be used to avoid fossil carbon emissions, but removing biomass from forests reduces carbon stock sizes and carbon input to litter and soil. The magnitude and longevity of these carbon stock changes determine how effective measures to utilize bioenergy from forest residues are to reduce greenhouse gas (GHG) emissions from the energy sector and to mitigate climate change. In this study, we estimate the variability of GHG emissions and consequent climate impacts resulting from producing bioenergy from stumps, branches and residual biomass of forest thinning operations in Finland, and the contribution of the variability in key factors, i.e. forest residue diameter, tree species, geographical location of the forest biomass removal site and harvesting method, to the emissions and their climate impact. The GHG emissions and the consequent climate impacts estimated as changes in radiative forcing were comparable to fossil fuels when bioenergy production from forest residues was initiated. The emissions and climate impacts decreased over time because forest residues were predicted to decompose releasing CO₂ even if left in the forest. Both were mainly affected by forest residue diameter and climatic conditions of the forest residue collection site. Tree species and the harvest method of thinning wood (whole tree or stem‐only) had a smaller effect on the magnitude of emissions. The largest reduction in the energy production climate impacts after 20 years, up to 62%, was achieved when coal was replaced by the branches collected from Southern Finland, whereas the smallest reduction 7% was gained by using stumps from Northern Finland instead of natural gas. After 100 years the corresponding values were 77% and 21%. The choice of forest residue biomass collected affects significantly the emissions and climate impacts of forest bioenergy.     

The rate of permafrost carbon release under aerobic and anaerobic conditions and its potential effects on climate

Recent observations suggest that permafrost thaw may create two completely different soil environments: aerobic in relatively well‐drained uplands and anaerobic in poorly drained wetlands. The soil oxygen availability will dictate the rate of permafrost carbon release as carbon dioxide (CO₂) and as methane (CH₄), and the overall effects of these emitted greenhouse gases on climate. The objective of this study was to quantify CO₂ and CH₄ release over a 500‐day period from permafrost soil under aerobic and anaerobic conditions in the laboratory and to compare the potential effects of these emissions on future climate by estimating their relative climate forcing. We used permafrost soils collected from Alaska and Siberia with varying organic matter characteristics and simultaneously incubated them under aerobic and anaerobic conditions to determine rates of CO₂ and CH₄ production. Over 500 days of soil incubation at 15 °C, we observed that carbon released under aerobic conditions was 3.9–10.0 times greater than anaerobic conditions. When scaled by greenhouse warming potential to account for differences between CO₂ and CH₄, relative climate forcing ranged between 1.5 and 7.1. Carbon release in organic soils was nearly 20 times greater than mineral soils on a per gram soil basis, but when compared on a per gram carbon basis, deep permafrost mineral soils showed carbon release rates similar to organic soils for some soil types. This suggests that permafrost carbon may be very labile, but that there are significant differences across soil types depending on the processes that controlled initial permafrost carbon accumulation within a particular landscape. Overall, our study showed that, independent of soil type, permafrost carbon in a relatively aerobic upland ecosystems may have a greater effect on climate when compared with a similar amount of permafrost carbon thawing in an anaerobic environment, despite the release of CH₄ that occurs in anaerobic conditions.     

镉诱导萝卜幼苗活性氧产生、脂质过氧化和抗氧化酶活性的变化

通过水培试验,研究Cd2+胁迫对萝卜幼苗活性氧的产生、脂质过氧化和抗氧化酶活性的影响。超氧 阴离子(O 2)的产生速率和丙二醛(MDA)的含量与对照相比有不同程度的增加,表明Cd2+胁迫能导致萝卜体 内的氧化胁迫;超氧化物歧化酶(SOD)的活性,随着Cd2+浓度提高,首先明显上升,然后逐渐下降,甚至低于 对照,叶片过氧化氢酶(CAT)的活性明显增加,根系CAT活性则减少,根系以及较高浓度Cd2+处理后期叶片 谷胱甘肽还原酶(GR)的活性均显著增加。推测:胁迫初期可能主要由SOD和CAT发挥抗氧化作用;后期由 于抗坏血酸—谷胱甘肽(AsA GsH)循环途径的激活,以及还原型谷胱甘肽(GSH)和植物络合素(Phytochela tins,PCs)的合成,可能在清除活性氧或者直接鏊合Cd2+中起作用。     

The Frasnian-Famennian mass extinction: insights from high-resolution sequence stratigraphy and cyclostratigraphy in South China

Two sequences (SFr, SFa), each 1-1.2 Myr in duration, are recognised in the strata across the Frasnian-Famennian (F-F) transition both in carbonate platform and interplatform basinal successions in South China. The sequence boundary between the two sequences is placed a little below the top of the Frasnian. The sequences are basically composed of coarsening-upward/bed-thickness increasing-upward cycles and shallowing-upward cycles (parasequences) in basinal and platform deposits respectively, which stack into cycle-sets (typically six to eight cycles). 10 and 12 cycle-sets are identified in sequences SFr and SFa respectively. These cycle-sets can be further grouped into larger-scale composite cycle-sets (herein termed mesocycle- and megacycle-sets with two and four cycle-sets respectively). This vertical cycle-stacking pattern and the hierarchy of cyclicity suggest a Milankovitch style of forcing such that the cycles and cycle-sets were formed in response to the orbital perturbations of precession (16-18 kyr) and eccentricity (∼100 kyr in duration), respectively. In the basinal cycles, smaller-scale rhythmic stratification beds (typically six to eight beds in a cycle) are extensive, and were likely caused by millennial-scale climatic forcing. In the lower sequence, SFr, the latest highstand deposits consist of calciturbidites and debrites in deep-water strata and fenestral limestones in shallow-water strata, representing a major (third-order) sea-level fall. Within these deposits, four cycle-sets are further identified in both coeval deep-water and platform successions. Succeeding deeper-water organic-rich facies, within which three cycles occur, are the transgressive deposits of the overlying Famennian sequence (SFa). These cycles represent three higher-frequency (16-18 kyr) sea-level fluctuations and accompanying anoxia, superimposed on a major third-order sea-level rise. The F-F boundary is placed at the top of the first cycle, based on conodont data. Thus, a major sea-level fall and then a rise occurred in the F-F transitional period. Faunal and sedimentological data reveal a massive biotic decline in concert with the major sea-level fall, and a further biotic demise coinciding with the major sea-level rise and its three superimposed higher-frequency sea-level fluctuations and accompanying anoxia. The F-F biotic crisis was therefore characterised by two episodes of step-down extinction. On the basis of Milankovitch orbital rhythms, the first major biotic extinction took place over ∼400 kyr, and the subsequent event was ∼50 kyr in duration, i.e. ∼450 kyr for the entire event. At the same time as the massive decline of normal-marine fossils during the latest Frasnian sea-level fall, there was widespread cyanobacterial growth and a thriving of planktonic calcispheres, suggesting eutrophic conditions. This situation could have caused a severe biotic loss, as a result of the deterioration of surface water clarity and formation of anoxic bottom waters due to over-consumption of oxygen through respiratory demands and decomposition by the cyanobacteria and phytoplankton. The subsequent rapid sea-level rise with superimposed higher-frequency sea-level fluctuations and accompanying anoxia could have caused rapid elevation of anoxic bottom waters and expansion of eutrophic surface waters over shallow-water platforms due to enhanced upwelling ocean currents and improved ocean circulation. This situation would have exerted further stresses upon the already-weakened biota, leading to a further biotic demise. However, a small number of organisms such as pelagic tentaculitids, small mud-adapted brachiopods and gastropods did survive into the Famennian, although with very low diversity.     

Predicting insect pest status under climate change scenarios: combining experimental data and population dynamics modelling

Climate change could profoundly affect the status of agricultural insect pests. Several approaches have been used to predict how the temperature and precipitation changes could modify the abundances, distributions or status of insect pests. In this article it is demonstrated how the use of simple models, such as Ricker’s classic equation, including a mechanistic representation of the influence of exogenous forces may improve our predictive capacity of the dynamic behaviour of insect populations. Using data from classical experiments in population ecology, we evaluate how temperature and humidity influence the density of two stored grain insect pest, Tribolium confusum and Callosobruchus chinensis, and then, using the A2 and B2 scenarios proposed by the Intergovernmental Panel on Climate Change and the previous modelling, we develop predictions over the future pest status of T. confusum along South America austral region, and specifically for eight cities in the continental Chilean territory. Tribolium confusum and C. chinensis show qualitatively different responses to the exogenous forcing of temperature and humidity, respectively. Our simulations predict a change in the equilibrium density of T. confusum from 10 to 14% under the moderate B2 scenario and 12 to 22% under the extreme A2 scenario to the period, 2071–2100. Both results imply a severe change in the pest status of this species in the southern region. This study illustrates how the use of theoretically based models may improve our predictive capacity. This approach provides an opportunity to examine the link between invasive species and climate change and how new suitable habitat may become available for species whose niche space is limited in some degree by climatic conditions. The use of different scenarios allows us to examine the sensitivity of the predictions, and to improve the communication with the general public and decision‐makers; a key aspect in integrated pest management.     

Cadmium and copper uptake and translocation in five willow (Salix L.) species

The efficacy for phytoremediation of five willow species was tested by experimental copper and cadmium uptake in a greenhouse hydroponic system. Five treatments included two concentrations (5 and 25 microM for each metal) and a control. Metal concentrations in solution as well as solution uptake were monitored. Metal resistance was assessed through effects on the dry weight of roots and shoots. The willow species tested were generally resistant of increased Cu and Cd content. Metal accumulation was found in all plant organs of all species. Growth and transpiration were not decreased by 5 microM of copper and 25 microM of cadmium in the solution for most species. 25 microM copper caused injury and reduced the dry weight for all species after 21 d. Salix nigra was highly resistant of both Cu and Cd and accumulated more metals than other species. Future field study should be conducted to confirm the findings and feasibility of the phytoremediation technology using those species.