Journal of the American College of Nutrition, Vol. 23, No. 6, 751S-753S (2004)
Published by the American College of Nutrition
Magnesium-Content of Rhizobium Nodules in Different Plants: The Importance of Magnesium in Nitrogen-Fixation of Nodules
Sandor A. Kiss, PhD,
Eva Stefanovits-Bányai, PhD and
Maria Takács-Hájos, PhD
Hungarian Magnesium Society, Szeged (S.A.K.)
Szent István University, Faculty of Food Science, Department of Applied Chemistry, Budapest (E.S.-B.)
Tessedik Sámuel College Agricultural Water and Environment Management Department, Szarvas (M.T.-H.), HUNGARY
Address reprint requests to: Eva Stefanovits-Bányai, PhD, Szent István University, Faculty of Food Science, Department of Applied Chemistry (E.S.-B.), H-1118 Budapest, Villányi str. 29-31, Hungary, HUNGARY. E-mail: eva.banyai{at}uni-corvinus.hu
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ABSTRACT
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Objective: Rhizobium bacteria induce nodules (tumors) in roots of leguminous crops that fix nitrogen (N2) from the atmosphere.
Methods: Trials were carried on in sterile perlite where two species of peas were grown hydroponically, and in two different soil types (brown forest soil and meadow silt soil), in a field where different leguminous plants were chosen for test plants: lupin, soybean, broad-bean, lentil and bean inoculated by Rhizobium bacteria. The Mg-content of the nutrient solution was higher than that of the control, but in the soil tests 1% Mg leaf fertilization was applied after bacterial inoculation. Number, weight and Mg-content of nodules were evaluated using an AAS method compared with the thick and thin hair/roots of the given plant.
Results and Conclusions: Our results clearly show that the Mg nutrition treatment increased the number of Rhizobium nodules and their Mg-content, resulting in increased N2-fixation and yield.
Key words: Rhizobium bacteria, magnesium, nitrogen fixation, leguminous plants
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INTRODUCTION AND BACKGROUND
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In view of the importance of Mg in nitrogen (N2)-fixing nodule development and the need for adequate Mg for metabolism of the Rhizobium bacteria, that produce nodules (tumors) in the roots of leguminous crops, the effect of Mg on nodule development and its Mg content was studied. The nodules fix nitrogen (N2) from the atmosphere. The N2, thus fixed, is used partly for bacterial anabolism and partly for symbiotic transport to the host plant. The bacteria need materials that can supply energy (adenosine triphosphate: ATP), which is present in all cells of living organisms and is derived from the host plant, in the N2-fixing process. Rhizobium strains differ in their N2-fixing ability. Active strains require higher ATP; the N2 fixation of nodules is proportional to the ATP quantity. Macsavariani and Begisvili [1] found that the active clones require more ATP than do inactive clones. ATP must be present as a Mg-complex to promote its linkage to the N2 fixing enzymes. Multiplication of Rhizobium also depends on availability of Mg [2].
N2-fixation can be described as:
A possible means by which ATP is regenerated is another Mg requiring process:
Mg affects plant hormones enzymes; it stimulates their de novo synthesis and changes their activity. For example, since Mg stimulates de novo synthesis of gibberellins [3], more gibberellins were detected in wheat seedlings obtained from wheat seeds treated with Mg than in untreated control [4]. A relatively high quantity of Mg is indispensable in the enzyme processes of N2-fixation, as well as in reductive and energy supplying molecules. Moreover, proteins needed in enzyme synthesis and nodule development are in ribosomes. That process generally requires 10–3 mole Mg-concentration. Considering also that the two enzymes taking part in N2-fixation have a very short half-life of 0.5 and 10 minutes, maintaining adequate Mg is very important [5].
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MATERIALS AND METHODS
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The effect of Mg on nodule development was studied in two pea (Pisum sativum L.) varieties (Rajnai törpe, Debreceni világos) in containers filled with perlite, in normal and Mg-deficient solutions. Seeds were inoculated by Rhizobium bacteria before sowing. Five replications were used. Outdoors in two different soil types (brown forest soil and meadow silt soil) small plot trials leaves were sprayed with Mg (1 liter 1% MgSO4 solution for 4 m2) at two-week intervals. Plant numbers were identical in each plot.
After washing the roots, nodules were removed after short soaking, dried at 80°C and weighed. Nodules of different field crops (lupin, soybean, lentil, broad-bean, bean, pea {Pisum sativum L.} varieties {Budai csemege, Express} were also collected. Dried nodules were placed in porcelain dishes and ashed in an electric oven, Mg was extracted by 10% hydrochloric acid and its quantity evaluated by atomic absorption spectrometry (AAS). The same method was used to evaluate the Mg content of thick and thin roots without nodules. Plant height was also measured.
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RESULTS AND DISCUSSION
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Our results are summarized in four tables. As already observed at sampling, plants treated with Mg had more and larger nodules. When the two pea varieties were grown either hydroponically or in field, there were differences between control and Mg treated samples (Table 1) in the weight of Rhizobium nodules. Their total weight was essentially higher than the average by 196% (Table 1).
Thick roots contained less Mg content than did the nodules, while the Mg content of thin roots varied depending on variety and year (Table 2). This phenomenon is indirect proof of increased biological activity.
When two pea varieties (Budai csemege, Express) were grown in field (brown forest soil) the Mg treatment increased the stem length, pod number of plant and the seed number of pod (Table 3).
Mg-treated plants were taller than Mg-deficient plants, due partly to the stimulating effect of Mg on gibberellin and auxins (hormone) synthesis [4,6]. Early measurements [7] proved that the nodules of Phaseolus lanatus L. also produce gibberellins depending on Rhizobium strains (Table 4).
A large part of gibberellins is transmitted to the host plant and so promote growth. The increase in stem length can be explained by the effect of Mg on gibberellin production. The effect of Mg and gibberellin also depends on pea varieties. Considerable differences can be found in the gibberellin producing capacity of Rhizobium species. Aging of plants (nodules) reduced the gibberellin producing activity. The dependence of stem length on gibberellin is also demonstrated.
Received August 5, 2004.
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REFERENCES
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- Macsavarian MZ, Begisvili CK, Szoohscs AN: Szoderzsanie ATF kletkah Rhizobium leguminosarium. Gruz SzSzr. Tbiliszi74
:453
–455,1974
.
- Norris DO: Rhizobium bacterium. Australian J Agricult Res10
:651
–698,1959
.
- Lang A: Gibberellins: Structure and metabolism. Ann Review Plant Physiol21
:537
,1970
.
- Kiss AS: Magnesium effect on the synthesis of embryiosomal gibberelline. Proc 17th Hung Ann Meet Biochem Kecskemét, pp115
–116,1977
.
- Kondorosi Á: Nitrogén fixálás a Rhizobiumok révén enzimatikus úton. Nitrogen fixation with Rhizobium by enzymatic way. In "Biokémia" (in Hungarian), pp12
–24,1980
.
- Kiss AS: "Magnesium Fertilization, Magnesium in Biology." Budapest: Mez
gazdasági Kiadó (in Hungarian),1983
.
- Evensen KB, Blevins DG: Differences in endogenous level of gibberellin like substance in nodules of Phaseolus lanatus. Plant Physiol68
:195
–198,1951
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TOP
ABSTRACT
INTRODUCTION AND BACKGROUND
