Aerobic and anaerobic nonmicrobial methane emissions from plant material.

Methane (CH(4)) may be generated via microbial and nonmicrobial mechanisms. Nonmicrobial CH(4) is also ubiquitous in nature, such as in biomass burning, the Earth's crust, plants, and animals. Relative to microbial CH(4), nonmicrobial CH(4) is less understood. Using fresh (living) and dried (dead) leaves and commercial structural compounds (dead) of plants, a series of laboratory experiments have been conducted to investigate CH(4) emissions under aerobic and anaerobic conditions. CH(4) emissions from fresh leaves incubated at ambient temperatures were nonmicrobial and enhanced by anaerobic conditions. CH(4) emissions from dried leaves incubated at rising temperature ruled out a microbial-mediated formation pathway and were plant-species-dependent with three categories of response to oxygen levels: enhanced by aerobic conditions, similar under aerobic and anaerobic conditions, and enhanced by anaerobic conditions. CH(4) emissions in plant structural compounds may help to fully understand nonmicrobial CH(4) formation in plant leaves. Experiments of reactive oxygen species (ROS) generator and scavengers indicate that ROS had a significant role in nonmicrobial CH(4) formation in plant material under aerobic and anaerobic conditions. However, the detailed mechanisms of the ROS were uncertain.

Dissolved methane in groundwater of domestic wells and its potential emissions in arid and semi-arid regions of Inner Mongolia, China.

Methane (CH4) is widely present in groundwater. Dissolved CH4 in groundwater is less understood when compared with that in wetlands. In this study, the concentrations and origin of dissolved CH4 in groundwater were investigated and the potential importance of groundwater CH4 emissions in arid and semi-arid regions of Inner Mongolia was discussed. Groundwater was extracted from domestic wells using a submersible pump or manual power and was analyzed for CH4 concentrations, δ13C-CH4, and physico-chemical variables. The results show that the concentrations of dissolved CH4 in groundwater had large spatial variability, ranging from 0 to 0.10 mg L-1 with a mean of 0.01 mg L-1 in Xilingol and from 0 to 8.99 mg L-1 with a mean of 1.44 mg L-1 in Xingan-Tongliao. Substantial CH4 concentrations of about 2.5-5.5 mg L-1 were found in central areas of Xingan-Tongliao in the winter and the summer. The δ13C-CH4 of about -85‰ was highly depleted while CH4 concentration was significantly negatively correlated with SO42- concentration, indicating that dissolved CH4 in groundwater was microbial in origin. This study suggests that groundwater as a source of CH4 might have great implications in arid and semi-arid regions worldwide and should deserve more research.

Effects of Ge-132 and GeO2 on seed germination and seedling growth of Oenothera biennis L. under NaCl stress.

To investigate the effects of ß-carboxyethyl germanium sequioxide (Ge-132) and germanium dioxide (GeO2) on improving salt tolerance of evening primrose (Oenothera biennis L.), seed germination, seedling growth, antioxidase and malondialdehyde (MDA) were observed under treatments of various concentrations (0, 5, 10, 20, 30 µM) of Ge in normal condition and in 50 mM NaCl solution. The results showed that both Ge-132 and GeO2 treatments significantly increased seed germination percentage and shoot length in dose-dependent concentrations but inhibited early root elongation growth. 5-30 µM Ge-132 and 10, 20 µM GeO2 treatments could significantly mitigate even eliminate harmful influence of salt, representing increased percentage of seed germination, root length, ratio between length of root and shoot, and decreased shoot length. These treatments also significantly decreased peroxidase (POD) and catalase (CAT) activities and MDA content. The mechanism is likely that Ge scavenges reactive oxygen species - especially hydrogen peroxide (H2O2) - by its electron configuration 4S24P2 so as to reduce lipid peroxidation. This is the first report about the comparison of bioactivity effect of Ge-132 and GeO2 on seed germination and seedling growth under salt stress. We conclude that Ge-132 is better than GeO2 on promoting salt tolerance of seed and seedling.

The effects of exogenous antioxidant germanium (Ge) on seed germination and growth of Lycium ruthenicum Murr subjected to NaCl stress.

In this paper, we present the results of a study on the effects of exogenous antioxidant germanium (Ge) on seed germination and seedling growth, and its role as a radical scavenger that regulates related enzymes, including superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), under salt stress. Seeds were incubated in 0, 50, 100, 150, 200, 250 and 300 mM NaCl to determine the salt tolerance of the Lycium ruthenicum Murr seedlings and from the results, the critical and ultimate salt concentrations were chosen for the next experiment. Subsequently, two treatments (seeds soaked in Ge and Ge added to salt) with four concentrations of GeO2 (0, 5, 10 and 20 µM) were used with the critical (150 mM) and ultimate salt concentrations (250 mM). The results demonstrated that salt alone inhibited seed germination significantly (≥150 mM) and reduced seedling growth (≥200 mM). The addition of exogenous Ge to the salt solution, as well as soaking the seeds in Ge, attenuated the salt stress effects in a manner dependent on the dose of Ge, as indicated by the increased percentage of seeds that germinated and improved seedling growth. The addition of Ge also showed a significant reversal of salt stress on the activities of antioxidant enzymes, with a decrease in SOD and POD activity, but an increase in CAT activity with 150 mM NaCl, and enhancement of SOD, POD and CAT with 250 mM NaCl. Correspondingly, the level of malondialdehyde was decreased significantly by each Ge treatment under salt stress. Further, for L. ruthenicum, adding 10 Ge and seeds soaked in 5 Ge were the most effective treatments. To our knowledge, this is the first report to show the protective effects of exogenous Ge against salt-induced oxidative damage in L. ruthenicum seed germination and seedling growth. Thus, L. ruthenicum can be used in areas with salty soil and Ge can promote the plants' salt tolerance.