FLOWER ORIENTATION INFLUENCES OVARY TEMPERATURE DURING FROST IN PEACH

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  • 1 Department of Horticulture, University of Georgia, Athens GA 30602

Ovary temperatures of upward and downward facing flowers of `Junegold' Peach (Prunus persica (L.) Batsch) were measured on 5 nights in March 1991 to determine whether differential survival of ovaries following frost was related to flower orientation. Flowering twigs were removed from mature trees and positioned horizontally ≈ 1.5 m above ground level prior to occurrence of low temperatures (0-5C). Thermocouples were inserted through the hypanthium to contact ovaries of 10 upward and 10 downward facing flowers, and temperature and meteorological data were logged every five minutes. Under clear, calm conditions, temperature of upward facing flowers averaged 0.33C lower than that of downward facing flowers during the coldest period of the night, with maximal differences of 0.77C. Under cloudy, calm conditions, temperature differences between upward and downward facing flowers were less frequently observed and lower in magnitude (0.08 - 0.15C). Under windy conditions (>2.5 m/s), no temperature difference between upward and downward facing flowers occurred, despite strongly negative net radiation. Based on known values of ovary cold tolerance, it is concluded that differences in survival of Up to 38% could occur due to flower orientation when air temperature reaches critical values.

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