IN INOCULANTS Nodulaid - 17th International Nitrogen Fixation ...

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17 th International Congress on Nitrogen Fixation Fremantle, Western Australia 27 November – 1 December 2011 Session Details: Thursday 1 December 2011 Concurrent Session 18 – P Nutrition & Symbioses 1100 - 1230 Authors: Sipho Maseko 1 and Felix D. Dakora 2 1 Department of Crop Science, and 2 Department of Chemistry, Tshwane University of Technology, 175 Nelson Mandela Drive, Private Bag X680, Pretoria 0001, South Africa Presentation Title: Phosphorus nutrition in symbiotic Cyclopia and Aspalathus species from the Cape fynbos of South Africa Presentation Time: 1140 – 1200 Nitrogen and phosphorus are the most limiting nutrients affecting plant growth in the Cape fynbos. In this study, acid and alkaline phosphatase (APase) activity of rhizosphere soils from Cyclopia genistoides, C. subternata, Aspalathus caledonensis and A. aspalathoides were assayed as indicators of P nutrition in these legumes. The results showed a significantly (p≤ 0.05) higher APase activity in rhizosphere soils of the four legumes and the non-legumes Leucadendron strictum, Eleiga thyrsoidea and Mimetes cucullatus relative to bulk soil. Furthermore, rhizosphere P and shoot P concentrations closely mirrored the phosphatase-enzyme activity in the rhizosphere of each species, suggesting that rhizosphere enzyme activity can serve as a good indicator of P nutrition in Cyclopia and Aspalathus species in the Cape fynbos. The relationship between APase activity in organs and P concentration of those organs in three Cyclopia and two Aspalathus species was also assessed at the same sites in the fynbos. At all three sites, APase activity was greater in organs of the legumes compared to the nonlegume Leucadendron strictum. At Koksrivier, leaf APase activity was highest in Cyclopia genistoides, followed by Aspalathus caledonensis, and least in A. aspalathoides. At Kleinberg and Kanetberg, Cyclopia subternata and C. longifolia also showed highest APase activity in leaves, followed by stems, and lowest in roots. The P concentration of each organ closely mirrored its APase activity, and APase activity was positively correlated with P concentration in leaves, stems and roots of C. genistoides, C. subternata, and C. longifolia. This indicates that in the Cape fynbos, APase activity can be used as a good indicator of P nutrition in Cyclopia and to, some extent, Aspalathus species. 110 2011
17 th International Congress on Nitrogen Fixation Fremantle, Western Australia 27 November – 1 December 2011 Session Details: Thursday 1 December 2011 Concurrent Session 18 – P Nutrition & Symbioses 1100 – 1230 Authors: Bargaz Adnane 1,2 , Faghire Mustapha 1 , Mandri Btissam 1 , Farissi Mohamed 1 , Jean Jacques Drevon 2 , and Ghoulam Cherki 1 1 Equipe de Biotechnologie Végétale et Agrophysiologie des Symbioses, Faculté des Sciences et Techniques Guéliz-Marrakech, BP 549, 40000, Marrakech, Morocco. 2 INRA-IRD-SupAgro, UMR Eco&Sols - Ecologie Fonctionnelle & Biogéochimie des Sols & Agroécosystèmes 2 Place Viala, F34060, Montpellier, France. Presentation Title: Phosphorus deficiency affected conductance to O2 and ascorbate peroxydase gene expression in nodules of Phaseolus vulgaris-rhizobia symbiosis Presentation Time: 1200 – 1220 Although recent studies have addressed the effects of phosphorus (P) deficiency on nodule respiration and oxidative stress, little attention has been given to elucidate the relationships between nodule permeability, nodule P status, and antioxidative responses. To study these traits, two recombinant inbred lines, namely RILs L115 and L147 were inoculated with Rhizobium tropici CIAT899, and grown in hydroaeroponic culture under P-sufficiency (250) versus P-deficiency (75 µmol P plant -1 week -1 ) conditions. At the flowering stage, plants and nodules biomasses, P contents and localization of nodule ascorbate peroxidase (APX) transcripts were determined after measuring O2 uptake by nodulated roots and nodule conductance to O2 diffusion (gn). The results showed that Pdeficiency significantly decreased plant growth and nodulation, with differences between bean genotypes. Pdeficiency also induced a decrease in nodule P content (31%) in the sensitive L147 and tolerant line L115, a 42 and 27% reduction in shoots of sensitive and tolerant lines, respectively. Under P-deficiency, gn increased more for the sensitive (39%) than for the tolerant lines (27%). This increase was linked to a rise both in the P levels in nodules and shoots, as well as in the efficiency of symbiotic nitrogen fixation as determined by nodule-dependent biomass production for the sensitive lines. Furthermore, positive correlations were found between O2 permeability, gn and P content both in nodules and shoots (r 2 = 0.94** and r 2 = 0.96**). Additionally, P-deficiency increased electrolyte leakage, the oxidative stress and the transcripts for ascorbate peroxidase gene in nodules. The later was more abundant in the inner cortex and the infected cells close to inner cortex. We conclude that gn increased with increases in both nodule P content and antioxidative responses. 111 2011
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PrinciPal SPonSor: SPonSorS: Progra
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INVENTING THE FUTURE IN INOCULANTS
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IN INOCULANTS Nodulaid - 17th International Nitrogen Fixation ...

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