Data/hora: 19/06/2024 17:53:47

Biblioteca(s): 	Embrapa Agrobiologia.	
Data corrente: 	02/08/2004	
Data da última atualização: 	02/08/2004	
Autoria: 	ARAÚJO, A. P.; TEIXEIRA, M. G.	
Título: 	Ontogenetic variations on absorption and utilization of phosphorus in common bean cultivars under biological nitrogen fixation.	
Ano de publicação: 	2000	
Fonte/Imprenta: 	Plant and Soil, Dordrecht, v. 225, p. 1-10, 2000.	
Idioma: 	Inglês	
Conteúdo: 	An experiment was conducted to evaluate the effect of plant ontogeny on traits associated with absorption and utilization of P by common bean (Phaseolus vulgaris L.) cultivars under biological N2 fixation through plant growth analysis. Eigth cultivars were grown in pots at two levels of applied P (20 and 80 mg P kg-¹ soil) and harvested at three growth stages (third trifoliate expanded, plentiful flowering, pod setting). The development of nodulation differed among cultivars and depended on P supply; some cultivars showed an intense decline in nodule number after flowering. There were different patterns of root growth: some cultivars increased root area after flowering mainly by increasing root mass, whereas others by decreasing root radius. Despite the overall drift of reducing P influx into roots over time, some cultivars maintained P influx almost stable after flowering. Cultivars with greater root area had lower influx, whereas cultivars with smaller root area had higher influx, denoting a compensatory mechanism between root growth and P influx, such mechanism presenting ontogenetic variations associated to patterns of root area production. The cultivars differed in specific P utilization rate at low but not at high soil P level; hence P utilization seems an important physiological component for screening bean genotypes under limited P supply. High correlation between net assimilation rate and specific P utilization rate suggests that P utilization is strongly related to photosynthetic activity. Despite, the wide variation among cultivars on root growth, nodulation and rates of P absorption and utilization, the genotypic variability for total dry mass and P content was narrow by pod setting. Owing to growth constraints caused by a possible inefficient symbiosis, the concomitant selection of bean genotypes for tolerance to low P and high N2 fixation activity should prioritize traits related to the root system and to  N2 fixation over total dry matter. The ontogenetic variations of traits associated with P adsorption and utilization in common bean cultivars require evaluations at different plant growth stages.	
Palavras-Chave: 	Biological nitrogen fixation; BNF; Common bean; FBN; Fixação biológica de nitrogênio; Genotypes; P; Root nodulation.	
Thesagro: 	Feijão; Fósforo; Genética; Genótipo; Nodulação; Phaseolus Vulgaris.	
Thesaurus Nal: 	genetics; phosphorus.	
Categoria do assunto: 	--	
Registro original: 	Embrapa Agrobiologia (CNPAB)	
Exemplares: 	CNPAB - (30402-1) - UPC - SP - -- -  -  - 0022741 - DIS