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Registro Completo |
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Biblioteca(s): |
Embrapa Pantanal. |
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Data corrente: |
02/03/1999 |
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Data da última atualização: |
02/03/1999 |
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Autoria: |
SCHJORRING, J. K.; JENSEN, P. |
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Título: |
Phosphorus nutrition of barley, buckwheat and rape seedlings. II. Influx and efflux of phosphorus by intact roots of different P status. |
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Ano de publicação: |
1984 |
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Fonte/Imprenta: |
Physiologia Plantarum, v.61, p.584-590, 1984. |
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Idioma: |
Inglês |
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Conteúdo: |
Seedlings of barley (Hordeum vulgare L. cvs Salka and Zita), buckwheat (Fagopyrum esculentum Moench) and rape (Brassica napus L. ssp. napus cv. Line) were raised at 8 or 10 different external P concentrations in the range 0-2000 uM. Apart from P, the nutrient solutions were complete. Phosphate influx in roots of different P status was determined by use a nutrient solution containing 0.1 mM 32P-labelled phosphate. A double labelling technique was used for simultaneous determination of influx (33P) and efflux (32P) of phosphorus by roots of barley and rape with three selected P levels. Flux determination were also done in presence of a metabolic uncoupler (2,4-dinitrophenol) and a protein synthesis inhibitor (cycloheximide). Influx of phosphate was maximal at a certain optimal P level of the roots and decreased at both lower and higher P levels. Maximum phosphate influxes [umol (g root)-1 h-1] were: rape 4.4, buckwheat 2.2, barley cv. Salka 1.6, barley cv. Zita 1.5. Both Hill plots and plots of the untrasformed decreasing phosphate influx vs root P concentrations above the optimal were linear and had high correlation coefficients. The Hill coefficient varied between -3.1 and -4.2. The decrease of phosphate influx from the maximum to the lowest value at the highest P concentration of the roots was 60-70%. Hence, phosphate influx appeared to be regulated through negative feedback by the internal level of phosphorus in the roots. The regulation mechanism seems basically similar for the three species and may be of an allosteric type. P efflux from roots of low and optimal (with regard to P influx) P status was 15-20% of the simultaneous P influx. Contrary to P influx, P efflux increased at high P status and almost eliminated (barley) or halved (raoe) net P uptake. 2,4-Dinitrophenol reduced both P influx and P efflux by low P roots and gave linearly P efflux with increasing root P status. This indicates that P efflux partly occurred by counter transport and ion exchange at the uptake sites, partly by poassive P efflux along an electrochemical potential gradient. Phosphate influx was not affected by inhibition of barley root growth with cycloheximide, but P efflux increased considerably. MenosSeedlings of barley (Hordeum vulgare L. cvs Salka and Zita), buckwheat (Fagopyrum esculentum Moench) and rape (Brassica napus L. ssp. napus cv. Line) were raised at 8 or 10 different external P concentrations in the range 0-2000 uM. Apart from P, the nutrient solutions were complete. Phosphate influx in roots of different P status was determined by use a nutrient solution containing 0.1 mM 32P-labelled phosphate. A double labelling technique was used for simultaneous determination of influx (33P) and efflux (32P) of phosphorus by roots of barley and rape with three selected P levels. Flux determination were also done in presence of a metabolic uncoupler (2,4-dinitrophenol) and a protein synthesis inhibitor (cycloheximide). Influx of phosphate was maximal at a certain optimal P level of the roots and decreased at both lower and higher P levels. Maximum phosphate influxes [umol (g root)-1 h-1] were: rape 4.4, buckwheat 2.2, barley cv. Salka 1.6, barley cv. Zita 1.5. Both Hill plots and plots of the untrasformed decreasing phosphate influx vs root P concentrations above the optimal were linear and had high correlation coefficients. The Hill coefficient varied between -3.1 and -4.2. The decrease of phosphate influx from the maximum to the lowest value at the highest P concentration of the roots was 60-70%. Hence, phosphate influx appeared to be regulated through negative feedback by the internal level of phosphorus in the roots. The regulation mechanism seems basically similar f... Mostrar Tudo |
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Palavras-Chave: |
Allosteric regulation; Hill coefficient; Plant. |
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Thesagro: |
Cevada; Fósforo; Nutrição; Planta. |
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Thesaurus Nal: |
barley; cycloheximide; nutrition; phosphorus. |
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Categoria do assunto: |
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Marc: |
LEADER 02951naa a2200265 a 4500
001 1793847
005 1999-03-02
008 1984 bl --- 0-- u #d
100 1 $aSCHJORRING, J. K.
245 $aPhosphorus nutrition of barley, buckwheat and rape seedlings. II. Influx and efflux of phosphorus by intact roots of different P status.
260 $c1984
520 $aSeedlings of barley (Hordeum vulgare L. cvs Salka and Zita), buckwheat (Fagopyrum esculentum Moench) and rape (Brassica napus L. ssp. napus cv. Line) were raised at 8 or 10 different external P concentrations in the range 0-2000 uM. Apart from P, the nutrient solutions were complete. Phosphate influx in roots of different P status was determined by use a nutrient solution containing 0.1 mM 32P-labelled phosphate. A double labelling technique was used for simultaneous determination of influx (33P) and efflux (32P) of phosphorus by roots of barley and rape with three selected P levels. Flux determination were also done in presence of a metabolic uncoupler (2,4-dinitrophenol) and a protein synthesis inhibitor (cycloheximide). Influx of phosphate was maximal at a certain optimal P level of the roots and decreased at both lower and higher P levels. Maximum phosphate influxes [umol (g root)-1 h-1] were: rape 4.4, buckwheat 2.2, barley cv. Salka 1.6, barley cv. Zita 1.5. Both Hill plots and plots of the untrasformed decreasing phosphate influx vs root P concentrations above the optimal were linear and had high correlation coefficients. The Hill coefficient varied between -3.1 and -4.2. The decrease of phosphate influx from the maximum to the lowest value at the highest P concentration of the roots was 60-70%. Hence, phosphate influx appeared to be regulated through negative feedback by the internal level of phosphorus in the roots. The regulation mechanism seems basically similar for the three species and may be of an allosteric type. P efflux from roots of low and optimal (with regard to P influx) P status was 15-20% of the simultaneous P influx. Contrary to P influx, P efflux increased at high P status and almost eliminated (barley) or halved (raoe) net P uptake. 2,4-Dinitrophenol reduced both P influx and P efflux by low P roots and gave linearly P efflux with increasing root P status. This indicates that P efflux partly occurred by counter transport and ion exchange at the uptake sites, partly by poassive P efflux along an electrochemical potential gradient. Phosphate influx was not affected by inhibition of barley root growth with cycloheximide, but P efflux increased considerably.
650 $abarley
650 $acycloheximide
650 $anutrition
650 $aphosphorus
650 $aCevada
650 $aFósforo
650 $aNutrição
650 $aPlanta
653 $aAllosteric regulation
653 $aHill coefficient
653 $aPlant
700 1 $aJENSEN, P.
773 $tPhysiologia Plantarum$gv.61, p.584-590, 1984.
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Embrapa Pantanal (CPAP) |
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| 1. |  | BARTZ, M. L. C.; PASINI, A.; BROWN, G. G.; MELLO, I.; BORTOLUZZI, J.; TAMIOZZO, T.; PILECCO, O. P.; LUTZ, R. A. de T. Minhocas como bioindicadores de qualidade do sistema plantio direto na palha. In: ENCONTRO LATINO-AMERICANO DE ECOLOGIA E TAXONOMIA DE OLIGOQUETAS, 4., 2010, Curitiba. Minhocas como bioindicadoras ambientais: princípios e práticas: anais. Colombo: Embrapa Florestas, 2010. 1 CD-ROM. (Embrapa Florestas. Documentos, 199). ELAETAO 4. 1 CD-ROM.| Tipo: Artigo em Anais de Congresso |
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