Energy Status and Functioning of Phosphorus-Deficient Soybean Nodules

Abstract

Characterization of the effects of long-term P deficiency and of onset and recovery from P deficiency on bacteroid mass and number per unit nodule mass and energy status of soybean (Glycine max L. Meff.) nodules was used to investigate the mechanisms by which P deficiency decreases symbiotic N2 fixation. The continuous P deficiency treatment (0.05 millimolar P) significantly decreased the whole plant dry mass, P, and N by 62, 90, and 78%, respectively, relative to the P-sufficient control (1.0 millimolar) at 44 days after transplanting. Specific nitrogenase activity was decreased an average of 28% over a 16-day experimental period by P deficiency. Whole nodules of P-deficient controls contained 70 to 75% lower ATP concentrations than nodules of P-sufficient controls. Energy charge and ATP concentrations in the bacteroid fraction of nodules were not significantly affected by P treatment. However, ATP and total adenylate concentrations and energy charge in the plant cell fraction of nodules were significantly decreased 91, 62, and 50%, respectively, by the P deficiency treatment. Specific nitrogenase activity, energy charge, and ATP concentration in the plant cell fraction increased to the levels of nonstressed controls within 2, 2, and 4 days, respectively, after alleviafion of extemal P limitation, whereas bacteroid mass per unit nodule mass and bacteroid N concentration did not increase to the level of nonstressed controls until 7 days after alleviation of external P limitation. All of these parameters except bacteroid mass per unit nodule mass decreased to the levels of the P-deficient controls by 11 days after onset of extemal P limitation. Concentration of ATP in the bacteroid fraction was not significantly affected by alteration in the extemal P supply. Energy charge in the bacteroid fraction from plants recovering from P deficiency was decreased to a small (10%) but significant extent (P < 0.05) at two sampling dates relative to Psufficient controls. These ATP concentration and energy charge measurements indicate that P deficiency impaired oxidative phosphorylation in the plant cell fraction of nodules to a much greater extent than in the bacteroids. The concurrence of significant changes in specific nitrogenase activity (2 days) and in the energy charge (2 days) and ATP concentration (4 days) in the plant cell fraction during recovery from extemal P limitation is consistent with the conclusion that P deficiency decreases the specific nitrogenase activity by inhibiting an energy-dependent reaction(s) in the plant cell fraction of the nodules.An improvement in P status of several legumes solely dependent on symbiotic N2 fixation has been reported to increase tissue N concentrations as well as overall host plant growth (1,14,27). This response results from symbiotic N2 fixation being stimulated to a greater degree by improvement in P nutrition than by host plant growth. Greater stimulation of symbiotic N2 fixation than of host plant growth with improvement in P nutrition is associated with an enhance...

Routes of pyruvate synthesis in phosphorus‐deficient lupin roots and nodules

“…In this study the effects of P deficiency are reported for plants grown at 2 µM P, which was lower than reported concentrations (50 µM) used for P starvation studies in soybeans (Sa & Israel, 1991). The 2 mM P levels used as a HP control also compares favourably with previous work using a 1.75 mM P control treatment to P starvation (Rychter & Mikulska, 1990;Rychter et al, 1992;Rychter & Randall, 1994;Ciereszko et al, 1999;Juszczuk et al, 2001).…”

“…physiological studies (Sa & Israel, 1991;Al-Niemi et al, 1997;Al-Niemi et al, 1998) it is apparent that bacteroids in the nodule almost always operate at low P concentrations and that bacteroids can fulfil their P requirements by scavenging from the host cells (Al-Niemi et al, 1997Colebatch et al, 2004).…”

Seedling treatments and phosphorus solution concentrations affect nodulation and nodule functions in soybean (Glycine max L.)

“…In soybean, P deficiency-decreased nitrogenase activity was suggested to result from inhibited energy-dependent reactions in nodules (Tang et al 2001), decreased Lb concentration in nodules or decreased bacteroid biomass (Sa and Israel 1991). In our experiment, low P in seedlings decreased Lb concentration per plant irrespective of P level, which may be caused by the fact that Lb is an oxygen-carrying heme protein in nodules, capable of binding oxygen to produce an oxygenated form only in active reduced state (Shleev et al 2001).…”

“…It is known that P regulation of photosynthesis and carbohydrate metabolism in leaves was one of the major factors limiting the plant growth (Marschner 1986). Moreover, P has stimulating effects on nodule growth and nitrogenase activity in nodules of legumes (Jakobsen 1985, Israel 1987, Hart 1989, Tang et al 2001); on the contrary its deficiency decreased nodule mass (Singleton et al 1985, Israel 1987, Ribet and Drevon 1995, Drevon and Hartwig 1997, nodule number ( Jakobsen 1985, Tang et al 2001) and nitrogenase activity (Sa and Israel 1991).…”

Soil microbe mediated zinc uptake in soy bean: A review

“…Soils with high concentration of P are deficient in available zinc, application of high amounts of P can induce Zn deficiency in plants and the availability of Zn is highest below pH 7 [35,36]. As pH increases, the availability of Zn decreases.…”