Effects of calcium in the nitrogen-fixing symbiosis between actinorhizal <Emphasis Type="Italic">Discaria trinervis</Emphasis> (Rhamnaceae) and <Emphasis Type="Italic">Frankia</Emphasis> |
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Authors: | Claudio Valverde Alejandro Ferrari Luis Gabriel Wall |
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Institution: | 1.Programa de Investigación sobre Interacciones Biológicas, Departamento de Ciencia y Tecnología,Universidad Nacional de Quilmes,Bernal,Argentina |
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Abstract: | We have analysed the growth and symbiotic performance of actinorhizal Discaria trinervis at various Ca supply regimes. We aimed at discriminating between specific, if any, effects on nodulation and general growth
stimulation by Ca. The hypothesis that a high Ca supply would interfere with nodulation by Frankia was also tested. Results showed that plant growth increased with Ca supply. Nodulation was stimulated by moderate levels
of Ca, but inhibited by Ca higher than 0.77 mM. Growth of nodules was less affected by Ca than shoot and root growth. Ca concentration
of symbiotic plants increased with Ca supply, but nitrogen concentration was independent of Ca at concentrations which did
not impair plant growth. All together, these results show that Ca has a positive effect on the establishment and functioning
of the symbiosis between Discaria trinervis and Frankia. However, the positive influence of Ca was more likely due to a promotion of plant growth rather than a direct effect on
nodule growth and nitrogen fixation itself. At high levels of Ca supply nodulation was impaired. Given the intercellular infection
pathway in Discaria trinervis, we suggest that the increment of Ca availability would strengthen its root cell walls, thus decreasing Frankia penetration of the root. |
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