The use of post‐luminescence decay and fluorescence emission to detect initial herbicide toxicity.

Abstract

Summary: The influence of pyrazon. norflurazon and glyphosate on post‐luminescence decay and fluorescence emission was studied. Pyrazon and norflurazon significantly increased post‐luminescence decay in wheat (Triticum vulgare L) and cuckoo flower (Cardamine pratensis L.). Pyrazon was much more active than norflurazon m this respect, No influence of’glyphosate on post‐luminescence and the emission ol” fluorescence was observed. Measurements of post‐luminescence decay and fluorescence emission can serve to define some aspects of herbicidal pbyto‐toxicity and provide information on the initial action of those compounds that inhibit photosynthesis.

Influence of Buthidazole, Diuron, and Atrazine on Some Light Reactions of Photosynthesis

“…As in previous studies with simazine, norflurazon, and pyrazon (5,19), data collected in this study on the influence of buthidazole, diuron, and atrazine on fluorescence and postluminescence indicate that measurements of this kind can serve to define some aspects of herbicidal phytotoxicity. and provide information on the initial action of those compounds that inhibit photosynthesis.…”

“…It is apparent from this study and others (2,5,6,10,19), that herbicides that block photosynthetic electron transport also enhance fluorescence and inhibit postluminescence. The two phenomena affected by herbicides that function in this manner could be expressed as the ratio C = relative fluorescence relative postluminescence to give a numerical value (C) for the phytotoxicity of the herbicide to a given plant species.…”

“…A number of herbicides have been developed that inhibit photosynthesis, and laboratory screening of new herbicides almost always includes observations of their effect on photosynthesis. Recently, Murkowski (19) and Devlin et ala (5) demonstrated that some of the light reactions (fluorescence and postluminescence) of photosynthesis could be used for very rapid detection of herbicide phytotoxicity.…”

“…Postluminescence most likely involves recombination of electrons and "holes" generated at the reaction centers (1,4). Changes in postluminescence were observed in plants treated with simazine [2-chloro-4,6-bis(ethylamino)-s-triazine] , norflurazon [4-chloro-5-(methylamino)-2-(a,a,atrifluoro-m-tolyl)-3(2H)-pyridazinone], and pyrazon [5amino-4-chloro-2-phenyl-3(2H)-pyridazinone] (5,19). All three herbicides interfere with photosynthetic electron transport (8,13,17).…”

“…However, preemergence control with DCPA varied from inconsistent results in the Southeast (7) to effective control in the Northeast (3). Posternergence applications of glyphosate and paraquat will control many winter annuals, but the bermudagrass must be completely dormant when treatments are applied in order to prevent injury (5,12)…”