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The effect of bacterial strain and temperature changes on the nitrogenase activity of Lotus pedunculatus root nodules
Author(s) -
Pankhurst C. E.,
Layzell D. B.
Publication year - 1984
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.1399-3054.1984.tb04593.x
Subject(s) - nitrogenase , symbiosis , lotus , dry weight , biology , nitrogen fixation , strain (injury) , nodule (geology) , bradyrhizobium , rhizobium , inoculation , root nodule , botany , bradyrhizobium japonicum , lotus japonicus , horticulture , rhizobiaceae , bacteria , paleontology , anatomy , genetics
After 40 days of growth at 25°C, Lotus pedunculatus cav., cv. Maku plants infected with Rhizobium loti strain NZP2037 displayed similar relative growth rates but had twice the nodule mass and only one third the whole plant dry weight of plants infected with Bradyrhizobium sp. ( Lotus ) strain CC814s. In the NZP2037 symbiosis, the rate of CO 2 evolution (per g dry weight of nodulated root) was 1.6 times as high as that in the CC814s symbiosis while the rate of C 2 H 2 reduction (per g dry weight of nodule) was only 48% of that in the CC814s symbiosis. Studies of the effect of short term temperature changes on the gas exchange characteristics (CO 2 and H 2 evolution, C 2 H 2 reduction) of these symbioses revealed wide differences in the optima for C 2 H 2 reduction. Nodules infected with NZP2037 displayed maximal C 2 H 2 reduction rates [157 μmol (g dry weight nodule) −1 h −1 ] at 12°C, whereas nodules infected with CC814s were optimal at 30°C [208 μmol (g dry weight nodule) −1 h −1 ]. These short term studies suggested that differences in temperature optima for N 2 may have partially accounted for the poorer effectivity, at 25°C, of strain NZP2037 when compared with strain CC‐814s. The relative efficiency [RE = 1 – (H 2 evolution/C 2 H 2 reduction)] of N 2 fixation varied widely with temperature in the two symbioses, but there was a general trend toward higher RE with lower temperatures. The ratio of CO 2 evolution: C 2 H 2 reduction (mol/mol) in nodulated roots infected with CC814s was constant (ca 10 CO 2 /C 2 H 2 ) between 5°C and 30°C, whereas in plants infected with NZP2037 it reached a minimal value of 3.3 CO 2 /C 2 H 2 at 10°C and was 19 CO 2 /C 2 H 2 at the growing temperature (25°C).