Regulation of nitrogen assimilation by sulfur in bean
2005
Ruiz, J.M. | Rivero, R.M. | Romero, L.
The objective of the present work was to determine the impact of sulfur(s) deficiency or toxicity on NO3(-) metabolism in bean plants (Phaseolus vulgaris cv. 'Strike'). Sulfur was applied to the nutrient solution for 30 d at three dosages: 0 mM (S0), considered deficient; 1.875 mM (S1), considered optimal; and 18.75 mM (S2), considered toxic. The results indicated that the bean plants were comparatively much more sensitive to the deficient than to the toxic S application. The S deficiency translated as decreased assimilation of NO3(-), with the lowest activities in S0 of the enzymes involved in this process (nitrate reductase, nitrite reductase, glutamine synthase, and glutamate synthase) and a notable decline in biomass production. Finally, the application of high rates of S in our experiment also reduced NO3(-) assimilation, possibly due to an antagonism between SO4(=) and NO3(-).
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