Interaction of root nodule size and oxygen pressure on the rate of nitrogen fixation by cowpea and peanut
Size and anatomical features of nodules influence the rate of O/sub 2/ diffusion into nodules. Availability of oxygen can be a limiting factor in nitrogen fixation. Larger nodules have thicker cortices and low surface to volume ratio leading to lower rates of gaseous diffusion. Increased oxygen pressure in the environment alters the rate of nitrogen fixation but the rate of change may depend on the nodule size. This was investigated by measuring /sup 15/N/sub 2/ incorporation into nodules. Root nodules from 38 day old cowpea and peanut plants were collected and sorted into size groups having diameters of >3 mm, 2-3 mm, and just below 2 mm. Samples of each size group were enclosed in tubes and exposed to various combination of oxygen (8-28%) and /sup 15/N/sub 2/. With higher O/sub 2/ pressure all nodules showed increased N/sub 2/ fixation but the largest nodules showed the maximum increase. Specific activity of larger nodules was higher for N/sub 2/ fixation. For the sizes of nodules examined the largest nodules did not reflect any of the disadvantages of the large size but the benefits of higher rates of O/sub 2/ entry was evident.
- Research Organization:
- Texas A and M Univ., College Station
- OSTI ID:
- 6027924
- Report Number(s):
- CONF-8707108-; TRN: 87-037228
- Journal Information:
- Plant Physiol., Suppl.; (United States), Vol. 83:4; Conference: Annual meeting of the American Society of Plant Physiologists, St. Louis, MO, USA, 19 Jul 1987
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
NITROGEN FIXATION
BIOCHEMICAL REACTION KINETICS
OXYGEN
BIOLOGICAL EFFECTS
ROOTS
MORPHOLOGY
DIFFUSION
LEGUMINOSAE
NITROGEN 15
TRACER TECHNIQUES
BACTERIA
ELEMENTS
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGHT NUCLEI
MICROORGANISMS
NITROGEN ISOTOPES
NONMETALS
NUCLEI
ODD-EVEN NUCLEI
PLANTS
REACTION KINETICS
RHIZOBIUM
STABLE ISOTOPES
550201* - Biochemistry- Tracer Techniques
551001 - Physiological Systems- Tracer Techniques