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This article in CS

  1. Vol. 26 No. 4, p. 756-760
    Received: June 3, 1985

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Evaluation of Chlorophyll Fluorescence Parameters for an Intact-Plant Herbicide Bioassay1

  1. D. R. Shaw,
  2. T. F. Peeper and
  3. D. L. Nofziger2



The correlations between various chlorophyll fluorescence induction curve parameters and metribuzin [4-Amino-6-(1,1-dimethyl-ethyl)-3-(methylthio)-1,2,4-triazin-5(4/H)-one], diuron [3-(3,4-Dichlorophenyl)-1,1-dimethylurea], and atrazine (2-chloro-4-ethylamino-6- isopropylamino-S-triazine) concentrations were compared in laboratory studies. The ratio of the initial inflection point (I) to the initial peak (P) was the most precise indicator of photosynthetic inhibition over time intervals of 4 to 48 h after an oat (Avena sativa L. ‘Chilocco’) plant was transplanted into herbicide-treated soil. The height of the initial inflection point (I), the peak level (P), and the fluorescence level 30 s after the onset of illumination (T) were also useful at 4 and 8 h after transplanting, but correlated poorly with herbicide concentration at later time intervals. Other variables examined included the slopes from I to P and P to S, the percent decay from P to T, and the complementary area. These parameters did not correlate to herbicide concentration as well, and had a much higher degree of variability associated with them.

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