Nitrogenase activity is required for the activation of iron‐stress response in iron‐inefficient T203 soybean

Abstract

Iron (Fe)-stress response and symbiotic nitrogen (N 2 ) fixation are chemical reduction processes within the roots which interact to the extent that nodulated, Fe-stressed, Fe-inefficient soybean initiates Fe-stress response, but similar nonnodulated soybean does not. The objective of this study was to examine the relationship between nitrogenase activity and Fe-stress response in the Fe-inefficient T203 soybean by inoculating plants with effective or ineffective strains of Bradyrhizobium japonicum on either side of split-root systems. Half the roots of each plant were either inoculated with effective or ineffective strains or left uninoculated. Nodules formed on roots inoculated with the ineffective B. japonicum strain, SM5, were similar in number and shape to those on roots inoculated with the effective strain, 61A209, but roots inoculated with SM5 were free of nitrogenase activity. Hydrogen ion and reductant were not released from uninoculated roots or roots inoculated with SM5, but were released from active, effective nodules and the roots below the active nodule clusters of roots inoculated with effective B. japonicum. Plants with effective and ineffective strains inoculated on either half of the roots exhibited Fe-stress response only on the half with nitrogenase activity. Plants inoculated with both effective and ineffective strains, but provided nitrate to inhibit nitrogenase activity, lacked Fe-stress response and became severely Fe chlorotic. Iron reduction and hydrogen (H + ) release around nodules and roots of inoculated Fe-inefficient T203 soybean is keyed to nitrogenase activity.

The Effect of Ferrous Nano-oxide Particles on Physiological Traits and Nutritional Compounds of Soybean ( Glycine max L.) Seed

“…The iron usage in soils that have defect of this element can cause to increasing in soybean seed yield. Iron defection in soybean can also cause to negative effect on nitrogen fixation activity (Chonkar and Chandel 1991, Terry and Jolley 1994, Burke et al 2015.…”

Interpreting Relationships between Soil Variables and Soybean Iron Deficiency using Factor Analysis

“…2008). Under conditions of Fe chlorosis, biological N fi xation is oft en arrested (Chonkar and Chandel, 1991;Terry and Jolley, 1994), creating potential N defi ciency. In this case, the lack of addition of N fertilizer, found to be benefi cial to improving early soybean growth and yield (Azfa et al, 1987;Starling et al, 1998), could contribute to soil N being benefi cial under low N conditions.…”

Nutritional and management related interactions with iron-deficiency stress response mechanisms

“…Similarly, plants inoculated with effective or ineffective strains, but provided with nitrate in the growth media to inhibit nitrogenase activity, lacked Fe-stress response and became severely Fe chlorotic. These experiments clearly illustrate that Fe reduction and release of H+ and reductants around nodules and roots of inoculated Fe-inefficient T203 soybean are keyed to nitrogenase activity (Terry and Jolley 1994).…”

“…However, in the absence of both N and Fe, T203 roots inoculated with Bradyrhizobium japonicum responded to Fe-deficiency stress by exuding both H+ and reductants and reducing Fe (Table 4). Iron reduction activity was exhibited just below the nodule clusters and H+ was released in association with active nodules (Terry et al 1991;Terry and Jolley 1994). In split-root experiments (Terry et al 1991), soybeans were nodulated by B. japonicum only on one half of the root system and H+ and reductant release appeared only on the nodulated side of T203 split-root systems.…”

“…In split-root experiments (Terry et al 1991), soybeans were nodulated by B. japonicum only on one half of the root system and H+ and reductant release appeared only on the nodulated side of T203 split-root systems. In another split-root experiment, T203 soybean was inoculated with combinations of effective or ineffective strains of B. japonicum (Terry and Jolley 1994). Root nodules formed with the ineffective B. japonicum strain were similar in number and shape to those on roots inoculated with the effective strain, but hydrogen ion and reductant were not released.…”