Low temperature exotherms of winter buds of hardy conifers

概要

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Differential thermal analysis (DTA) of winter buds and the excised primordial shoots of sub-alpine or sub-cold firs revealed that these buds had all low temperature exotherms around -30℃. However, no low temperature exotherm below -15℃ was detected in the spring buds. In the winter bud of Abies firma, a temperate fir native to Japan, a low temperature exotherm was detected around -20℃, which is higher by 10℃ than that of sub-alpine or sub-cold firs. The low temperature exotherms of these firs occurred at nearly the same temperatures that result in the death of these primordial shoots. On the other hand, little or no low temperature exotherm was detected in the winter buds of sub-cold spruces. In larch winter buds, numerous small exotherms were observed, which are probably due to the many leaf primordia in the buds. Unlike many temperate deciduous broad-leaved trees, no low temperature exotherm was detected below -15℃ in winter twig xylem of conifers such as Abies, Picea, Pinus, Larix and Pseudotsuga. Thus, very hardy coniferous twigs can tolerate extracellular freezing to -70℃.
日本植物生理学会の論文
1978-12-00