A bstract. Soybean, Glycine max L., and elodea, Elodea canadensis Michx, leaves were exposed to sublethal and lethal temperatures and examined by light microscopy. Loss

Two field experiments were conducted to assess peach (Prurus persica L.) cultivar susceptibility to the three Botryosphaeria spp. that cause peach tree fungal gummosis. Inoculated trees were evaluated for disease severity by rating gum exudation, vascular discoloration, and fungal colonization. Each severity measurement yielded a different rank ordering of cultivars for susceptibility. However, in a greenhouse study, these same measurements gave consistent rankings for aggressiveness of the fungal species on `Blake'. Despite large differences in disease severity in the greenhouse study, none of the severity measures were correlated with tree growth after inoculation. The only factor significantly correlated with growth rate of the trees after inoculation was growth rate before inoculation.

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Mature peach trees (Prunus persica (L.) Batsch. cv. Southland) were treated with 0, 1.73, 2.42, and 3.11 Mmoles/1 of (2-chlorethyl)phosphonic acid (ethephon) and ethylene evolution was measured up to 9 days after treatment. Ethephon caused a marked increase in ethylene evolution, a sharp decrease in the breaking force of fruit abscission, and a pronounced increase in leaf abscission. Ethylene evolution was higher in leaves than fruits. In general, ethylene from tissue explants containing the abscission zone of fruits was higher than that of explants from the side of fruits from treated trees. However, it was postulated that ethylene has an overall affect on all tissue with subsequent abscission rather than a direct effect on the abscission zone of leaves and fruits of peaches.

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