As part of our study of the phenotypes of disease lesion mimics (see Hoisington et al., 1982, Devel. Biol. 98:381; Walbot et al., 1983, in: Genetic Engineering of Plants, ed. T. Kosuge et al.) we measure the spread of lesions on individual leaves. The leaves are numbered using a marking pen. Inadvertently, we discovered that the MARKSALOT brand of pen induced dramatic lesion formation in Les1 and Les*-1451 leaves, which at the time had not yet made lesions. Normal sibs showed no lesions. Several other Les mutants show some lesions along pen marks. The effect occurs within 24 hr--the edge of the pen mark is covered with lesions. All colors of MARKSALOT cause this effect, suggesting that the dye is not causing the lesions. No other brand of marking pen tested causes lesions, suggesting that there is a specific chemical found in this brand of pen. From a list supplied by the manufacturer of chemicals in MARKSALOT, the "active" ingredient was shown to be n-propanol. Isopropanol, n-butanol, ethanol and methanol have no effect. The propanol works in a 5% aqueous solution; n-propanol or a contaminant may be a toxic "trigger" to plants with certain Les mutations.
Query: Has anyone ever noticed tissue damage from marking pens?
Nigel Ray and Virginia Walbot
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