FIGURE 6.

Superoxide detection in quiona (a,b) and seed-borne microorganisms (c,d). (a) Quinoa seeds were imbibed in water containing 0.2 mM NBT for 12 h, arranged according to their developmental stage and photographed. Note the lack of superoxide generation in non-germinating individuals (top; 1 representative shown). (b) NBT stainings of 4-days-old seedlings grown on damp filter paper. Experiments were repeated at least three times; one representative is shown. (c) Quinoa seedlings heavily colonized by endogenous microbes were incubated in NBT solution for 10 min. The seeds had been germinated on filter paper under high-humidity conditions for three (top) or four (bottom) days. (d) Microbial colonies proliferating on YPD agar were stained in NBT solution and photographed after 2 min. Note that color intensity is particularly high at the border, i.e., growing zone. Scale bar: 1 cm.