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J Plant Physiol ; 168(10): 1009-15, 2011 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-21371777

RESUMO

The widespread use of NO(3)(-) fertilization has had a major ecological impact. NH(4)(+) nutrition may help to reduce this impact, although high NH(4)(+) concentrations are toxic for most plants. The underlying tolerance mechanisms are not yet fully understood, although they are thought to include the limitation of C, the disruption of ion homeostasis, and a wasteful NH(4)(+) influx/efflux cycle that carries an extra energetic cost for root cells. In this study, high irradiance (HI) was found to induce a notable tolerance to NH(4)(+) in the range 2.5-10mM in pea plants by inducing higher C availability, as shown by carbohydrate content. This capacity was accompanied by a general lower relative N content, indicating that tolerance is not achieved through higher net N assimilation on C-skeletons, and it was also not attributable to increased GS content or activity in roots or leaves. Moreover, HI plants showed higher ATP content and respiration rates. This extra energy availability is related to the internal NH(4)(+) content regulation (probably NH(4)(+) influx/efflux) and to an improvement of the cell ionic balance. The limited C availability at lower irradiance (LI) and high NH(4)(+) resulted in a series of metabolic imbalances, as reflected in a much higher organic acid content, thereby suggesting that the origin of the toxicity in plants cultured at high NH(4)(+) and LI is related to their inability to avoid large-scale accumulation of the NH(4)(+) ion.


Assuntos
Adaptação Fisiológica/efeitos dos fármacos , Trifosfato de Adenosina/metabolismo , Sulfato de Amônio/farmacologia , Carbono/metabolismo , Pisum sativum/metabolismo , Estresse Fisiológico/efeitos dos fármacos , Adaptação Fisiológica/efeitos da radiação , Trifosfato de Adenosina/análise , Sulfato de Amônio/análise , Sulfato de Amônio/metabolismo , Carboidratos/análise , Carbono/análise , Glutamato-Amônia Ligase/metabolismo , Nitratos/análise , Nitratos/metabolismo , Nitrogênio/análise , Nitrogênio/metabolismo , Pisum sativum/efeitos dos fármacos , Pisum sativum/efeitos da radiação , Fótons , Fotossíntese/efeitos dos fármacos , Folhas de Planta/enzimologia , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/metabolismo , Raízes de Plantas/enzimologia , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/metabolismo , Estresse Fisiológico/efeitos da radiação
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