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Effect of Salinity on the Functional Components of the Soybean‐ Rhizobium japonicum Symbiosis 1
Author(s) -
Singleton P. W.,
Bohlool B. B.
Publication year - 1983
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci1983.0011183x002300050003x
Subject(s) - shoot , biology , salinity , nitrogenase , nitrogen fixation , symbiosis , root system , root nodule , rhizobium , horticulture , sowing , glycine , botany , agronomy , inoculation , ecology , genetics , bacteria , biochemistry , amino acid
A split‐root solution culture system was used to partition the effects of salinity on the functional components of the soybean [ Glycine max (L.) Merr] ‐ Rhizobium japonicum symbiosis. Nodules were confined to half of the root system. After nodules were well developed (40 days from planting), 120 m M NaCl was applied to the half‐root systems in the following combinations: 1)unstressed, no salt to either half‐root system; 2) partially stressed shoot and unstressed nodules, salt to only the nonnodulated halfroot system; 3) partially stressed shoot and stressed nodules, salt to only the nodulated half‐root system; and 4) stressed shoot and nodules, salt to both half‐root systems. Leaf osmotic potentials (ψs) for the four treatments were: 1) −1.02; 2) −1.12; 3) −1.23; and 4) −1.83 MPa. Nodule ψs for the treatments were: 1) −0.70; 2) −0.72; 3) −1.12; and 4) −1.21 MPa. While total and specific nitrogenase activity as well as shoot N content were suppressed in treatment 3, the greatest decrease in activity and shoot N was observed when the plant was stressed by having both half‐root systems in salt (treatment 4). The rate of leaf expansion in treatment 4 was half the rate observed in the other treatments. We conclude that reduced N 2 fixation by nodulated soybeans growing in saline environments was more a result of the effect of salt on leaf ψs and expansion, than the direct action of salt on the functional processes of the nitrogenase system.