観賞樹木の生育に及ぼす温周性と光周性の相互影響 (第4報)

Abstract

Interrelated effects of daylength and winter chilling on the growth and dormancy of several woody plants were studied for two consecutive years.1. The shoot growth of Japanese holly (Ilex crenata Thunb.) cuttings remained linear throughout most of the test period at 16hr or more daylengths, though under daylengths less than 16hr the shoot of Japanese holly cuttings ceased to elongate after a certain period of growth. Shoot growth of Japanese black pine (Pinus thunbergii Parl. ) seedlings seemed daylength-independent.2. The shoot of Japanese holly cuttings did not respond to winter chilling, though they showed active growth under long day conditions. Contrary to Japanese holly cuttings, the shoot of trident maple (Acer buergerianum Miq.) seedlings became dormant even under long day conditions and eventually died unless it had previously been exposed to winter chilling. When trident maple seedlings were subjected to winter chilling, however, their shoots continued to grow vigorously even under short day conditions, that is, the shoot growth of trident maple seedlings was typically chilling-dependent. The shoot growth of Japanese privet (Ligustrum japonicum Thunb.) seedlings was facultative-long-day-dependent. The winter chilling treatment did not affect the shoot growth of sweet viburnum (Viburnum awabuki K. Koch) cuttings and Japanese black pine seedlings showed facultative-chilling-dependent responses along with facultative-long-day-dependent behavior, whereas that of sawleaf zelkova (Zelkova serrata (Thunb.) Makino) seedlings was facultative-chilling-dependent and daylength-independent.3. The seedlings of Japanese privet and Japanese black pine which were not exposed to winter chilling produced much fewer numbers of lateral shoots under both long and short day conditions than those exposed. No matter what daylengths Japanese privet seedlings and Japanese holly cuttings received, more than half of them bloomed when they were exposed previously to winter chilling, whereas those that were not subjected to winter chilling never bloomed.