Effects of shading on biological nitrogen fixation in bean plants

• Autor(a) principal: Hungria, Mariangela
• Data de Publicação: 2014
• Outros Autores: Thomas, Richard J., Döbereiner, Johanna
• Tipo de documento: Artigo
• Idioma: por
• Título da fonte: Pesquisa Agropecuária Brasileira (Online)
• Texto Completo: https://seer.sct.embrapa.br/index.php/pab/article/view/16260
• topic: Phaseolus vulgaris; Rhizobium; N2 fixation; nitrogenase activity; nodulation; leaf area; transport of N in the xylem sap; shading; light; temperature; Phaseolus vulgaris; Rhizobium; fixação do N2; atividade da nitrogenase; nodulação; área foliar; transporte de N na seiva do xilema; sombreamento; luz; temperatura

Two experiments were performed to investigate the effect of decreasing luminosity and temperature caused by shading on biological nitrogen fixation of common beans (Phaseolus vulgaris L.). When the shading was at 25% level, there was an increase, in relation to full light, of the dry weight, nitrogenase activity, total nitrogen in xylem sap, rate of N as ureides and total nitrogen in shoots. At this level of shading, an increase in nodular efficiency compensated for the decrease in nodule weight. The favourable effect of reducing 25% of the luminosity was caused by the decrease in maximal diurnal temperature in the shaded pots and the decrease of solar energy was compensated by and increase in leaf area. At 40% shading, there was a decrease in the rhizosphere temperature and an increase in leaf area but this was not enough to compensate for the lower photosynthetic activity. Generally the high temperature did not affect the infection process and the growth of the nodules, but altered nodule metabolism, decreasing nitrogenase activity and total nitrogen in shoots.