Using maize green - and white - leaf tissues, we have examined the effect of various chemicals on cytoplasmic leakage with respect to the light requirement or chloroplast targeting for their activities.
Oxyfluorfen, oxadiazon, diuron, and paraquat, which are known as representative herbicides acting on plant chloroplasts, caused the electrolyte leakage only in the green tissues, whereas 2, 4-dinitrophenol, rose bengal (singlet oxygen producing chemical) and methyl-jasmoante (senescence-stimulating chemical) play a role both in green- and white - tissues.
Benzoyl(a) pyrene, generating superoxide radical upon light illumination, functions only in white tissues.
Tralkoxydim, metsulfuron-methyl and norflurazon showed no effect in two tested plant samples. In terms of light requirement in electrolyte leakage activity, diuron, oxyfluorfen, oxadiazon, rose bengal, and benzoyl(a) pyrene absolutely require the light for their functions, but other chemicals did not.
Based on these results, we could classify into four different response types according to whether chemicals require light or chloroplasts for their action.
This classification is likely to be applied to simply and rapidly identify the requirement of light and chloroplasts for the actions of chemicals, thereby it makes easy to characterize many new herbicides that their action mechanisms are unclear, and to elucidate the mode of action of them.