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  • Author or Editor: W. T. Liu x
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Fumigation with 1 mg·L-1 of thymol vapor retarded mycelial growth of Monilinia fructicola (G. Wint.) Honey. Mean colony diameter was reduced from 49 mm in the control to 13 mm when the conidia were cultured on potato dextrose agar. Fumigation of apricots (Prunus armeniaca L.) with 2 mg·L-1 of thymol vapor reduced the germination of M. fructicola conidia to 2% compared with 98% on untreated fruit. Microscopic observations showed that the spores fumigated with thymol were shrunken and had collapsed protoplasts. In in vivo experiments, surface-sterilized apricots and plums (Prunus salicina L.) were inoculated with conidia of M. fructicola by applying 20 μL of a spore suspension to wounds on the fruit, and then were fumigated with thymol or acetic acid. The incidence of brown rot was reduced to 3% and 32% when `Manch' apricots were fumigated with thymol or acetic acid at 5 mg·L-1, respectively, compared with 64% incidence in untreated fruit. Fumigation of `Violette' plums with thymol or acetic acid at 8 mg·L-1 reduced brown rot from 88% in the control to 24% and 25%, respectively. Fumigation of `Veeblue' plums with thymol at 4 mg·L-1 reduced brown rot from 56% in the control to 14%. Fumigation of apricots with thymol resulted in firmer fruit and higher surface browning, but total soluble solids and titratable acidity were not affected. Fumigation of plum with thymol resulted in higher total soluble solids, but firmness and titratable acidity were not affected. Thymol fumigation caused phytotoxicity on apricots but not on plums.

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Leaf water potentials did not limit stomatal opening of Vitis labruscana Bailey cv. Concord during the summers of 1972 and 1973 in a New York vineyard. Midday leaf-water potentials ranged from −8 to −16 bars and were closely related to individual leaf irradiance. The diurnal variation of leaf, stem, and fruit cluster water potentials on a typical clear day were about 5, 11, and 6 bars, respectively. Water potential gradients at midday across the root, shoot, and petiole-leaf systems averaged about 10, 1 and 3 bars, respectively. The gradient across the root consistently increased throughout the day relative to plant transpiration rate. Minimum stomatal resistance on days after cold nights (less than 10°C) was 2.7 ± 1.1 s cm-1, while the mean resistance on all other days was 1.0 ± 0.5 s cm-1. Cool night temperatures inhibited stomatal opening and closing independently of leaf water potential.

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