Increased tropospheric ozone (O₃) concentrations in boreal forests affect the emission of biogenic volatile organic compounds (BVOCs), which play crucial roles in biosphere-atmosphere feedbacks. Although it has been well documented that BVOC emissions are altered in response to elevated O₃, consequent effects on the carbon budget have been largely unexplored. Here, we studied the effects of elevated O₃ (80 nmol mol⁻¹) on diurnal variation of BVOC emissions and gas exchange of CO₂ from above- and belowground parts of Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) and further investigated effects on the carbon budget. In spring, elevated O₃ decreased BVOC emissions and net photosynthesis rate (Pn) from above-ground parts of both species. As BVOC emissions have a causal relationship with dormancy recovery, O₃-induced decreases in BVOC emissions indicated the inhibition of dormancy recovery. Contrary to the spring results, in summer BVOC emissions from aboveground parts were increased in response to elevated O₃ in both species. Decreases in Pn indicated O₃ stress. O₃-induced monoterpene emissions from aboveground were the main volatile defense response. Elevated O₃ had little effect on BVOC emissions from belowground parts of either species in spring or summer. In spring, elevated O₃ decreased the proportion of carbon emitted as BVOCs relative to that assimilated by photosynthesis (the proportion of BVOC-C loss) at the soil-plant system levels in both species. In summer, elevated O₃ resulted in a net CO₂–C loss at the soil-plant system level of Scots pine. During this process, O₃-induced BVOC-C loss can represent a significant fraction of carbon exchange between the atmosphere and Scots pine. In Norway spruce, the effects of O₃ were less pronounced. The current results highlight the need for prediction of BVOC emissions and their contributions to the carbon budget in boreal forests under O₃ stress.

Reuse of sewage sludge is a general trend and land application is an essential way to reuse sludge. The outbreak of coronavirus disease has raised concerns about human pathogens and their serious threat to public health. The risk of pathogenic bacterial contamination from land application of municipal sludge has not been well assessed. The purpose of this study was to investigate the presence of pathogenic bacteria in municipal sewage sludge and to examine the survival potential of certain multidrug-resistant enteroaggregative Escherichia coli (EAEC) strain isolated from sewage sludge during heat treatment. The sewage sludge produced in the two wastewater treatment plants contained pathogenic bacteria such as pathogenic E. coli, Shigella flexneri, and Citrobacter freundii. The environmental strain of EAEC isolated from the sludge was resistant to eight types of antibiotics. It could also enter the dormant state after 4.5 h of treatment at 55 °C and regrow at 37 °C, while maintaining its antibiotic resistance. Our results indicate that the dormancy of EAEC might be why it is heat-resistant and could not be killed completely during the sludge heat treatment process. Owing to the regrowth of the dormant pathogenic bacteria, it is risky to apply the sludge to land even if the sludge is heat-treated, and there is also a risk of spreading antibiotic resistance.

Climate change will have a considerable impact upon the processes that moderate weed invasion, in particular to that of parthenium weed (Parthenium hysterophorus L.). This study evaluated the performance of two Australian biotypes of parthenium weed under a range of environmental conditions including soil moisture (100 and 50% of field capacity), atmospheric carbon dioxide (CO₂) concentration (390 and 550 ppm), and temperature (35/20 and 30/15 °C/day/night). Measurements were taken upon growth, reproductive output, seed biology (fill, viability and dormancy) and soil seed longevity. Parthenium weed growth and seed output were significantly increased under the elevated CO₂ concentration (550 ppm) and in the cooler (30/15 °C) and wetter (field capacity) conditions. However, elevated CO₂ concentration could not promote growth or seed output when the plants were grown under the warmer (35/20 °C) and wetter conditions. Warm temperatures accelerated the growth of parthenium weed, producing plants with greater height biomass but with a shorter life span. Warm temperatures also affected the reproductive output by promoting both seed production and fill, and promoting seed longevity. Dryer soil conditions (50% of field capacity) also promoted the reproductive output, but did not retain high seed fill or promote seed longevity. Therefore, the rising temperatures, the increased atmospheric CO₂ concentration and the longer periods of drought predicted under climate change scenarios are likely to substantially enhance the growth and reproductive output of these two Australian parthenium weed biotypes. This may facilitate the further invasion of this noxious weed in tropical and sub-tropical natural and agro-ecosystems.

This study explored the effects of two hydro- and osmo-priming durations (8 and 16 h) on growth and yield components of sunflowers (Helianthus annuus L.) under water stress. The pot experiment, performed under a rain shelter, consisted of 9 treatments replicated five times: unprimed seeds as control (C), hydro-primed seeds (T0), osmo-primed seeds in 10, 20, and 30% PEG-6000 (T1, T2, and T3, respectively). Severe water stress was applied for 12 days to all treatments at the beginning of the flowering stage. Statistical analysis revealed a very highly significant positive effect (p < 0.01) by all treatments on sunflower seed germination compared with the control. Moreover, primed seeds improved significantly for all growth parameters and yield components, but no significant differences were observed according to either priming technique or duration. The highest value of germination capacity, for fresh and dry biomasses, was obtained with PEG-primed seeds at 10% for 16 h. The grain number per anthodium and grain yield per plant from primed seeds were higher than those in the control (1.9- to 2.5-fold and 2.8- to 3.3-fold respectively). Under conditions of water stress, the proline content in primed plants was significantly higher than that in unprimed ones, with the exception of T3 treatment primed for 8 h. Soluble sugars and chlorophyll contents increased significantly with all applied treatments compared with the control. The study showed that the applied priming treatments improved germination characteristics in particular and increased growth and yield components for sunflowers under drought stress conditions.

Air pollution is considered to be one of the main causes of forest decline. The cambium is responsible for increase in tree girth, and its functioning is determined by environmental pressures. This study compared cambium histology of Ceiba speciosa (A. St.-Hil.) Ravenna (Malvaceae) in polluted and preserved sites in the Atlantic Rainforest domain. Samples were obtained during periods of cambial activity and dormancy and were processed and examined according to standard light microscopy techniques. In addition to differences typically observed in cambium during periods of activity and dormancy, the fusiform initials were shorter in trees of the polluted site. Furthermore, cambial rays were shorter, but larger, in the polluted site. It should be noted that all parameters related to cambial rays showed significant differences between the study sites. This is the first report of the effects of pollution on cambial activity in a South American species. The results suggest a tolerance of C. speciosa to pollution and reveal this species to be an important biomarker for environmental monitoring studies.

The quantification of oxygen release by plants in different stages of wetland plant life cycle was made in this study. Results obtained from 1 year measurement in subsurface wetland microcosms demonstrated that oxygen release from Phragmites australis varied from 108.89 to 404.44 mg O₂/m²/d during the different periods from budding to dormancy. Plant species, substrate types, and culture solutions had a significant effect on the capacity of oxygen release of wetland plants. Oxygen supply by wetland plants was estimated to potentially support a removal of 300.37 mg COD/m²/d or 55.87 mg NH₄-N/m²/d. According to oxygen balance analysis, oxygen release by plants could provide 0.43–1.12 % of biochemical oxygen demand in typical subsurface-flow constructed wetlands (CWs). This demonstrates that oxygen release of plants may be a potential source for pollutants removal especially in low-loaded CWs. The results make it possible to quantify the role of plants in wastewater purification.