Ethylene and carbon dioxide concentrations of soils as influenced by rhizosphere of crops under field and pot conditions

Abstract

A method for collecting low volumes of soil gas from a small region, and a technique for determining small concentrations of ethylene using an enrichment process are described. Using these methods, it was found that ethylene and carbon dioxide (CO2) concentrations of soils varied considerably depending on the presence or absence of a rhizosphere. Ethylene was much higher (31-375 nL L-l; mean: 207) in non-cropped areas (i.e., soils without rhizosphere) than in the rhizosphere region (8-136nL L-l; mean: 38) of a field in which maize or soybean were grown. On the other hand, CO 2 concentrations were higher in rhizosphere than in non-rhizosphere soil, especially in pot experiments. The rate of ethylene decomposition was, however, much greater in rhizosphere soil (55 nL g-i day-l) than in non-rhizosphere soil (34 nL g-I day-i). Higher microbial activity was presumed to result in the decrease of ethylene concentration and the increase in CO 2 in rhizosphere regions. The implications of these results in relation to the influence of ethylene in rhizosphere on plant growth, and the role of soil microbes on decomposition of ethylene is discussed.

Effect of soil wetness on air composition and nitrous oxide emission in a loam soil

“…In contrast, no C 2 H 4 was found in soil air in the present study. In other investigations low concentrations (0.5 µl l -1 or less) have been measured in aerobic soils (Otani & Ae 1993), but sometimes also in wet soils (Meek et al 1986). Taken together the results suggest that C 2 H 4 is not a sensitive indicator of hypoxia in soil.…”

Interactions of arbuscular mycorrhizal fungi with other soil organisms

“…The concentration of ethylene in soil air varies within the range of approximately 0.008 -0.4 ppm. Lower concentrations are found in rhizosphere than in non-rhizosphere soil, probably because of the different balance between production and biodegradation by microorganisms (81 ), and may thus stimulate the growth of hyphae of AM fungi.…”

Growth, denitrification and nitrate ammonification of the rhizobial strain TNAU 14 in presence and absence of C2H4 and C2H2

“…The solubility of C 2 H 4 is about 10 times lower than that of C 2 H 2 (Grollman, 1929;Breitbarth et al, 2004). Soil-rhizosphere waterfilms with their specific solubilities may act as barriers for C 2 H 4 or C 2 H 2 and intercellular concentrations of ethylene could be much higher than those of about 2 µl C 2 H 4 l -1 measured in the soil air (Abeles et al, 1993;Otani and Ae, 1993). The comparable relatively low solubility of C 2 H 4 and the favoured C 2 H 4 -release under water saturated conditions (Arshad and Frankenberger, 1990) may not only influence the growth of the N 2 -fixing strain TNAU 14 but also that of many other rhizosphere organisms involved in the global nitrogen cycle.…”

“…If N 2 -fixing bacteria have the potential to denitrify or to dissipate excess reducing equivalents by converting nitrate into ammonium they could remove NO 3 -and bacteroidal N 2 -fixation could continue despite moderate N-fertilisation (Zumpft, 1997;Richardson et al, 2001;Benckiser et al, 2005). Cropping systems exposed to anaerobic conditions or infection stress switch not only to denitrification but also release C 2 H 4 in concentrations between 0.2 to 2 µl l -1 soil air (Abeles et al, 1993;Otani and Ae, 1993;Crossman and Thompson, 2006). C 2 H 4 -concentrations are especially high in presence of nitrate (Shaharoona et al, 2006).…”