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THE EFFECT OF CO 2 ENRICHMENT ON ROOT NODULE DEVELOPMENT AND SYMBIOTIC N 2 REDUCTION IN PISUM SATIVUM L.
Author(s) -
Phillips Donald A.,
Newell Keith D.,
Hassell Shirley A.,
Felling Charles E.
Publication year - 1976
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1976.tb11822.x
Subject(s) - sativum , biology , nitrogenase , nodule (geology) , pisum , rhizobium leguminosarum , dry weight , root nodule , horticulture , symbiosis , botany , nitrogen fixation , zoology , rhizobiaceae , bacteria , paleontology , genetics
A very significant increase in N 2 (C 2 H 2 ) reduction by Visum sativum L. infected with Rhizobium leguminosarum occurred when plants were grown in the light with 6 hr of CO 2 enrichment (0.00120 atm). Plants grown for 4 wk under 0.00120 atm CO 2 showed significant increases over control plants at 0.00032 atm CO 2 in plant dry weight, N content, root nodule mass, number of nodules, and mean nodule dry weight. Acetylene‐reduction assays, however, revealed no reproducible increase in nitrogenase activity/mg nodule in plants subjected to long‐term CO 2 enrichment. Both control and CO 2 ‐enriched plants optimized the sink/source ratio between the mass of nodules and the extranodular plant mass. The optimum ratio for N 2 reduction by 4‐week‐old peas was 0.05. Long‐term CO 2 enrichment did not promote root nodule formation to a greater degree than total plant development, and increases in N content were directly proportional to increases in nodule mass. Morphological data revealed significantly greater deposits of starch in root nodules of plants grown under CO 2 ‐enriched conditions. The results are interpreted as showing that short‐term increases in CO 2 levels promote N 2 reduction by affecting root nodule functioning, whereas long‐term CO 2 enrichment promotes N 2 reduction by increasing total plant and root nodule development.