PROTON-PUMPING AND NITROGEN METABOLISM IN RICE UNDER HUMID TROPIC CONDITIONS

Rodrigo Grazinoli Garrido, Fabiola de S.R.G. Garrido, Sonia Regina de Souza, Manlio Silvestre Fernandes

Abstract


In rice plants, it is important to recognize N metabolism efficiency parameters in order to design strategies for improvements, increasing grain protein and enhancing people nutrition quality. Two rice varieties grown under humid tropic conditions were evaluated: Piaui, a landrace adapted to low N availability, and reduced light supply, and IAC-47, an improved variety. The assay was carried out in controlled conditions of 24oC and 12/12 hour light/dark periods (200 µE.m-2.s-1) using a growth chamber, simulating humid tropic environment. Rice plants were grown under 0.1 and 1.0 mM NH4+-N, in a Hoagland & Arnon nutrient solution, pH 5.5, up to 26 days after germination. The activity of PM H+-ATPases in the plasma membrane, vacuole VH+-ATPases, H+-PPases as well as GS, GOGAT, and GDH were determined. PM H+-ATPase presented higher activity in IAC-47 roots. On the other hand, Piaui roots showed an enhanced microsomal protein content and VH+-ATPases activity, which apparently allows this variety to absorb N as well as the improved one. Increases in the cytosolic ammonium would result in high GDH deamination in Piaui variety at 1.0 mM NH4+-N. Meanwhile, GS increases were observed in IAC-47 shoots, together with GOGAT increases at same treatment.

Keywords


Oryza sativa; Ammonium; V-ATPase; P-ATPase; V-PPase; GS; GOGAT; GDH

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URN: http://www.revista.ccba.uady.mx/urn:ISSN:1870-0462-tsaes.v15i3.1211



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