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Plant Physiology 45:390-394 (1970) © 1970 American Society of Plant Biologists The Environmental Control of Cold Acclimation in Apple 1a Department of Horticultural Science, University of Minnesota, St. Paul, Minnesota 55101
The role of photoperiod and temperature in the cold acclimation of living Haralson apple (Pyrus malus L.) bark was studied in the autumn under field conditions in Minnesota. Whole trees, or different parts of the same tree, were exposed to either natural conditions, artifically lengthened days, or artificially warmed nights, or they were subjected to manual leaf removal. The results indicate that acclimation occurs in two stages which are induced by short days and frost (or low temperature), respectively. Leaves were stimulated by short days to produce translocatable substance(s) which promoted cold acclimation of the living bark. Leaves of plants grown under long days were the source of a translocatable substance(s) which inhibited acclimation. The second stage of hardiness, induced by frost (or low temperature), did not involve translocatable factors. Inductive short days could overcome the effect of high temperatures, and low temperatures could overcome the effect of noninductive long days in promoting the first stage of acclimation to 30 C. Frost was necessary for maximum hardiness to 55 C. Plants grown in a greenhouse, in the autumn, under long days and high temperatures acclimated slightly in spite of the noninductive conditions. Short days and frost (or low temperatures) appeared to regulate different and independent endogenous acclimation processes.
2 Present address: Department of Horticulture, Michigan State University, East Lansing, Michigan 48912. 1 Scientific Journal Series Paper 6937 of the Minnesota Agricultural Experiment Station. This article has been cited by other articles:
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