Effects of incubation temperature and oxygen tension on nitrogenase activity of legume root nodules |
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Authors: | P J Dart and J M Day |
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Institution: | (1) Rothamsted Experimental Station, Harpenden, Herts;(2) Luton College of Technology, Luton, Beds, England |
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Abstract: | Summary Acetylene reduction and H2 evolution by legume root nodules from several plant species depended on incubation temperature; some nodules were active
from 2 to 40°C. Acetylene reduction rates differed between plant species, with maximum activity at temperatures between 20
and 30°C forVicia faba, V. sativa, Trifolium pratense, T. subterraneum, Medicago truncatula and soybean, at 35°C forM. sativa and at 40°C for cowpea. OnlyM. sativa and cowpea reduced substantial amounts at 37.5°C. Temperatures from 2 to 10°C only slightly lessened activity ofT. subterraneum andV. sativa nodules. Nitrogenase functioned at temperatures which prevent establishment of other aspects of the symbiosis. The rate of
acetylene reduction was constant for several hours at temperatures below 15°C, and activity continued for several days at
2°C for some species, but declined with time at warmer temperatures. Some nitrogenase was denatured at warmer temperatures,
but the O2 tension in the assay vial also affected activity. In closed assay vessels nodule respiration decreased the pO2 and reduced nitrogenase activity. Activity was restored by adding O2 or regassing assay vials with air or Ar/O2. When the pO2 was maintained, acetylene reduction and H2 evolution by detached soybean nodules continued unchanged for 6 h. |
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