ISSN:
1573-5036
Keywords:
actinorhizal
;
Alnus glutinosa
;
acetylene reduction
;
carbon dioxide
;
Frankia
;
nitrogen fixation
;
nodules
;
roots
Source:
Springer Online Journal Archives 1860-2000
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Abstract The effects of aeration of the N-free rooting medium with elevated CO2 on (a) acetylene reduction by perlite-grown plants and (b) N2-fixation and long-term growth of nutrient solution-grown plants were determined for nodulatedAlnus glutinosa (L.) Gaertn. In the former experiments, roots of intact plants were incubated in acetylene in air in darkened glass jars for 3 hr, followed by a further 3 hr incubation period in air enriched with CO2 (0–5%). During incubation, the CO2 content of the jars increased by 0.17% per hour due to respiration of the root system, so that the CO2 content at 3 hr was 0.5%. Additional enrichment of the rooting medium gas-phase with CO2 equivalent to 1.1% and 1.75% CO2 of the gas volume significantly increased nitrogenase activity (ethylene production) by 55% and 50% respectively, while enrichment with greater than 2.5% CO2 decreased activity. In contrast, ethylene production by control plants, where CO2 was not added to the assay jars, decreased by 8% over the assay period. In long-term growth experiments, nodulated roots of intactAlnus glutinosa plants were sealed into jars containing N-free nutrient solution (pH 6.3) and aerated with air, or air containing elevated levels of CO2 (1.5% and 5%). Comparison of the appearance of CO2-treated with air treated plants suggested that 1.5% CO2 stimulated plant growth. However, at harvest after 5 or 6 weeks variability between plants masked the significance of differences in plant dry weight. A significant increase of 33% in total nitrogen of plants aerated with 1.5% CO2, compared with air-treated plants, was demonstrated, broadly in line with the short-term increase in acetylene reducing activity observed following incubations with similar CO2 concentrations. Shoot dry weight was not affected significantly by long-term exposure to 5% CO2, the main effect on growth being a 20% reduction in dry weight of the root system, possibly through inhibition of root system respiration. However, in contrast to the inhibitory effects of high CO2 on acetylene reduction there was no significant effect on the amounts of N2 fixed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01347705
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