Units of Freezing of Deep Supercooled Water in Woody Xylem 1
AUTOR(ES)
Hong, Sung-Gak
RESUMO
The low temperature exotherms (LTE) of 1-year-old twigs of Haralson apple (Malus pumila Mill.), shagbark hickory (Carya ovata [Mill.] K. Koch), green ash (Fraxinus pennsylvanica Marsh), honey locust (Gleditsia triacanthos L.), American chestnut (Castanea dentata [Marsh] Borkh.), and red oak (Quercus rubra L.) were determined by differential thermal analysis (DTA). In one type of experiment freezing during a DTA experiment was halted for up to 2.5 hours after part of the supercooled water had frozen at temperatures between −25 and −42 C. Upon resumption of cooling the freezing started within 2 C of the stopping temperature. In a second type of experiment living and dead cells were microscopically observed in the same ray after partial freezing in the DTA apparatus. In another experiment, the LTE persisted even after tangential and radial sectioning of the twig to 0.13 millimeters. In a final experiment the LTE of a single multiseriate ray of red oak had the same shape as the LTE of wood with many uniseriate rays.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=440527Documentos Relacionados
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