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The Glycine‐Glomus‐Bradyhizobium symbiosis. VIII. Phosphorususe efficiency of CO 2 and N 2 fixation in mycorrhizal soybean
Author(s) -
Brown Milford S.,
Thamsurakul Supaporn,
Bethlenfalvay Gabor J.
Publication year - 1988
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1988.tb04957.x
Subject(s) - nitrogenase , biology , symbiosis , glomus , nitrogen fixation , dry weight , nodule (geology) , photosynthesis , glycine , botany , bradyrhizobium japonicum , mycorrhiza , fungus , horticulture , legume , inoculation , rhizobiaceae , bacteria , biochemistry , amino acid , paleontology , genetics
Soybean [ Glycine max (L.) Merr. cv. Hobbit] plants nodulated by Bradyhizobium japonicum strain USDA 110 were grown in pot cultures in severely P‐ and N‐deficient soil and either colonized by the vesicular‐arbuscular mycorrhizal (VAM) fungus Glomus mosseae (Nicol. & Gerd.) Gerd. and Trappe or fertilized with a high (HP) or low (LP) level of KH 2 PO 4 (0.6 or 0.3 m M , respectively), After 7 weeks of growth, nodule and chloroplast activities (C 2 H 2 reduction and CO 2 exchange rate) were determined. Photosynthetic P‐use efficiency of CO 2 fixation was significantly higher in VAM than in HP plants, while that of nitrogenase activity was lower. The LP plants were intermediate in both respects. The ratio of nodule to chloroplast activity [mol C 2 H 2 reduced (mol CO 2 fixed) −1 ] was highest in HP and lowest in VAM plants. Root colonization by the VAM fungus significantly increased nodule number and dry weight and reduced nodule specific mass and activity in comparison to HP plants. In spite of lower nodule activity, VAM plants were significantly larger and had higher N concentrations than the HP plants. The results suggest nonnutritional. VAM‐elicited and host‐mediated effects on the symbiotic functions of the legume association.