Genotypic difference in the short-term response of nitrogenase activity (C2H2 reduction) to salinity and oxygen in the common bean

摘要

Four genotypes of common bean (Phaseolus vulgaris L.) differing in seed color, were grown hydroponically in a growth chamber to study the short-term effects of 0.1 M NaCl on their symbiotic acetylene reducing activity (ARA). For all genotypes, the ARA was reduced dramatically during the first hour following NaCl application. This was followed by a slower decrease during the next 5 h during which genotypical differences in response to salinity were found. When expressed as percent of the control, the red-seed genotype was significantly less inhibited by NaCl than the three others. For all genotypes, the increase in ARA after raising rhizosphere pO(2) was affected by the NaCl treatment. With NaCl the red-seed genotype showed the highest stimulation by pO(2), which was associated with its higher tolerance to NaCl application. However for all genotypes, raising pO(2) did not allow a complete recovery from the NaCl effect. It is concluded that nitrogenase inhibition by NaCl application in common bean varies among genotypes, and is associated with a short-term nodule limitation by O-2 diffusion, although other mechanisms may also be involved in nodule inhibition by NaCl.