Fig. 3. A. Electronic image of DNA from rice seedlings exposed to 0.9, 1.8, 2.7, 3.6, and 0 kJ/m² of UVB radiation. Samples are paired; the first (-) was incubated with buffer alone, while the companion sample (+) was incubated with UV endonuclease. Molecular length standard DNAs are bacteriophages G (750 kb) and T4 (170 kb); marker Lane M contains and a HindIII digest of . B. Cyclobutyl pyrimidine dimer induction in DNA in rice seedlings as a function of exposure to broad spectrum UV radiation from an FS–20 lamp. Data were obtained from gels such as in Panel A. Small symbols, individual samples (electrophoresed on replicate independent gels, data from each gel shown as one symbol—filled circles, filled triangles, filled diamond, or filled inverted triangles) from the same plant material; large symbols, averages; error bars, standard errors. In some cases the standard error is less than the size of the symbol for the average