Tropospheric ozone-induced structural changes in leaf mesophyll cell walls in grapevine plants

The structural changes in leaves of grapevine plants (Vitis vinifera L.) exposed to different ozone concentrations were investigated. Ozone fumigations were performed in open-top chambers at four different ozone levels (charcoal-filtered air (F), ambient air (N), ambient air + 25 mm³m⁻³ ozone (O-25) and ambient air + 50 mm³m⁻³ ozone (O-50)). The leaves of plants from chambers with increased ozone concentrations (O-25 and O-50) were significantly thicker than the controls (F), owing to increased thickness of the mesophyll layer. Observing O-50 leaves, it was found that the mesophyll cell wall displayed structural changes. In some places cell wall thickness increased up to 1 μm. We found callose deposits on the inner side of the cell walls of mesophyll cells. These data are in accord with the concept that the mesophyll cell wall acts as a barrier against the penetration of tropospheric ozone into the cells.     

Fumigant activity of essential oils and their components from Eucalyptus codonocarpa and E. dives against Tetranychus urticae (Acari: Tetranychidae) at three temperatures

Essential oils derived from eighteen species of the Myrtaceae family native to Australia, and major constituents of two oils selected from these oils were tested for their fumigant activity against adult females and eggs of Tetranychus urticae Koch (Acari: Tetranychidae) at 5, 15 and 25°C. Essential oils of Eucalyptus codonocarpa and Eucalyptus dives showed the highest fumigant activity against female adults at 10 μl/l at 15 and 25°C. Among major constituents of the two essential oils, piperitone was the most effective against female adults, followed by terpinene‐4‐ol at 10 μl/l at all three temperatures. The two essential oils and these two constituents lowered egg hatchability at 10 μl/l at 25°C. Our results suggest that piperitone should be further investigated as a potential fumigant against T. urticae.     

Increased mercury in forest soils under elevated carbon dioxide

Fossil fuel combustion is the primary anthropogenic source of both CO₂ and Hg to the atmosphere. On a global scale, most Hg that enters ecosystems is derived from atmospheric Hg that deposits onto the land surface. Increasing concentrations of atmospheric CO₂ may affect Hg deposition to terrestrial systems and storage in soils through CO₂-mediated changes in plant and soil properties. We show, using free-air CO₂ enrichment (FACE) experiments, that soil Hg concentrations are almost 30% greater under elevated atmospheric CO₂ in two temperate forests. There were no direct CO₂ effects, however, on litterfall, throughfall or stemflow Hg inputs. Soil Hg was positively correlated with percent soil organic matter (SOM), suggesting that CO₂-mediated changes in SOM have influenced soil Hg concentrations. Through its impacts on SOM, elevated atmospheric CO₂ may increase the Hg storage capacity of soils and modulate the movement of Hg through the biosphere. Such effects of rising CO₂, ones that transcend the typically studied effects on C and nutrient cycling, are an important next phase for research on global environmental change.     

农田冬小麦生长和产量对臭氧动态暴露的响应

 评估臭氧(O₃)污染对农田冬小麦生长和产量的影响是污染生态学和生理生态学研究的重要内容之一。该研究运用开顶式气室(OTC),对冬小麦‘ 嘉403’(Triticum aestivum cv. Jia 403)进行了O₃动态暴露的田间原位试验。实验设置过滤空气组(CF)、自然大气组(NF)和两个不同浓度的 O₃动态暴露组(DO100和DO150)。结果表明：1) O₃浓度增加,一方面可以改变灌浆期冬小麦叶片气体交换参数的日变化规律;另一方面引起表观 光量子产额、光饱和点和光补偿点等光响应参数的显著降低。这表明灌浆期叶片光合能力的下降是气孔因素和非气孔因素共同作用的结果。2) O₃暴露可以改变小麦形态特征,如植株变矮、叶片衰老加速、 叶面积变小,并最终导致产量大幅下降。     

Characterization of Gaseous Ozone Decomposition in Soil

Laboratory scale batch experiments were performed to investigate the decomposition characteristics of gaseous ozone in porous media. The decomposition rates of gaseous ozone in several solid media were determined, and the relationship of moisture content with sorbed ozone molecules was evaluated. Ozone decomposition in control and glass beads packed columns followed second-order reaction kinetics, while ozone consumption in a sand-packed column demonstrated first-order kinetics with a rate constant of 0.0109 min^?1 and half-life of 1.0 h. The presence of typical metal oxides in the soil resulted in ozone consumption rates in the following order: hematite (Fe₂O₃) > silica-alumina (SiO₂Al₂O₃) > alumina (Al₂O₃) > silica (SiO₂). Ozone decomposition was highly dependent upon soil moisture content. Over 90% of the total ozone mass decomposed in the field soil with moisture content at less than 1 wt%, whereas as low as 5–15% of the total ozone mass degraded with moisture content at more than 2 wt%. In conclusion, ozone decomposition in soils was primarily controlled not only by soil organic matter but also by reactive metal oxides on the soil surface. These two factors were shown to be highly dependent upon soil moisture content.     

Transgenerational phenotypic plasticity under future atmospheric conditions

Organisms often exhibit transgenerational phenotypic changes in response to an increased risk of parasitism or predation. Shifts in global atmospheric composition could modify these phenotypic effects through changes in either nutrient quantity/quality or altered interactions with higher trophic levels. Here we show that future atmospheric conditions alter a natural enemy‐induced wing polyphenism in aphids. Winged offspring production by Uroleucon nigrotuberculatum aphids on goldenrod (Solidago canadensis var. scabra) does not differ in enriched CO₂ and/or O₃ atmospheres. However, proportionally more winged offspring are produced in response to search cues from both coccinellid predators (Coccinella septempunctata) and hymenopteran parasitoids (Aphidius polygonaphis) relative to plants not searched by natural enemies. Moreover, the magnitude of this response differs under enriched CO₂ and O₃ environments. Aphids produce more winged offspring in response to predators under elevated CO₂, but produce more winged offspring in response to parasitoids under elevated O₃. Thus, global atmospheric changes influence natural enemy‐mediated phenotypic expression, with potentially far‐reaching consequences for trophic dynamics.     

稻米品质性状对开放式空气二氧化碳浓度增高的响应

利用开放式空气CO2浓度增高(FACE)系统平台。研究大田栽培条件下粳稻武香粳14号稻米品质性状对CO2浓度增高200μmol·mol^-1的响应。结果表明．FACE处理稻谷的出糙率平均比CK高1．4个百分点,整精米率平均比CK低12．3个百分点,较低的供N水平有利于提高FACE条件下的出糙率．较高的供N水平有利于提高FACE条件下的整精米率;FACE处理的稻米垩白略有增加。垩白粒率平均比CK高11．9个百分点,垩白度平均比CK平均高2．8个百分点,较高的供N和供P水平有利于降低FACE条件下垩白大小、垩白粒率和垩白度;FACE处理稻米糊化温度平均比CK平均高0．52℃,胶稠度有提高的趋势,但对稻米直链淀粉含量影响较小,较高的供N和供P水平有利于降低FACE条件下稻米的直链淀粉含量,较低的供N和较高的供P水平有利于降低FACE条件下稻米胶稠度,较低的供N水平有利于降低FACE条件下稻米糊化温度;FACE处理使稻米蛋白质含量比CK平均低0．6个百分点,较低的供N和供P水平有利于降低FACE条件下稻米蛋白质含量。     

Foliar physiology of yellow-poplar ( Liriodendron tulipifera L.) exposed to O3 and elevated CO2 over five seasons.

The chronic effects of ozone (O₃) alone or combined with elevated carbon dioxide (CO₂) on the foliar physiology of unfertilized field-grown yellow-poplar ( Liriodendron tulipifera L.) seedlings were studied from 1992 to 1996. Within open-top chambers, juvenile trees were exposed to the following: charcoal-filtered air (CF); 1× ambient ozone (1XO₃); 1.5× ambient ozone (1.5XO₃); 1.5× ambient ozone plus 700 ppm carbon dioxide (1.5XO₃+CO₂); or chamberless open-air (OA). Seasonal 24-h mean ambient O₃ concentrations ranged from 32 to 46 ppm over the five seasons. Averaged over 5 years, midseason net photosynthesis at saturating light ( A _sat) was reduced by 14% ( P =0.029) and stomatal conductance ( g _s) was reduced, albeit non-significant, by 13% ( P =0.096) in upper canopy foliage exposed to 1.5XO₃-air relative to CF controls. There were no significant differences over the 5 years in A _sat and g _s between trees grown in 1XO₃- and 1.5XO₃-air. Our results support the hypothesis that the magnitude of O₃ effects on A _sat and g _s decreases as saplings age. When averaged over the five seasons of exposure, total chlorophyll concentration ( chl) was not significantly affected by exposure to elevated O₃; however, in 1.5XO₃+CO₂-air, foliar chl was reduced by 33% relative to all others ( P <0.001). In 1.5XO₃+CO₂-air, A _sat was 1.4–1.9 times higher ( P <0.001) and g _s was 0.7 times lower ( P =0.022) than all others. O₃ uptake in juvenile trees exposed to elevated O₃ plus elevated CO₂ (1.5XO₃+CO₂-air) was most comparable to trees exposed to ambient air (1XO₃) throughout the study. These findings suggest that elevated CO₂ may minimize the negative effects of O₃ by reducing O₃ uptake through decreased stomatal conductance.