A sensitive spectrophotometric method for the determination of silver is described. The reaction involves a silver-enhanced reduction of 2,3,5-triphenyl-2H-tetrazolium chloride by semicarbazide hydrochloride to yield a pink-colored product with maximum absorption at 510 nm. Beer's law is obeyed in the concentration range of 0.02-0.34 microg cm(-3) of silver, and the molar absorptivity is 4.51 x...

The testa of higher plant seeds protects the embryo against adverse environmental conditions. Its role is assumed mainly by controlling germination through dormancy imposition and by limiting the detrimental activity of physical and biological agents during seed storage. To analyze the function of the testa in the model plant Arabidopsis, we compared mutants affected in testa pigmentation and/o...

Conditions were assessed which would permit more rapid recognition of bacterial growth than has been previously reported using tetrazolium salts. Microtitration trays were used. 2-(p-Iodophenyl)-3(p-nitrophenyl)-5-phenyltetrazolium chloride is rapidly reduced by respiring cells in tissue homogenates but is more toxic than other tetrazoliums when added to growing bacterial cultures. Phenazine me...