H. Okubo
Changes in endogenous plant hormone levels and growth response of Iris, Hyacinthus, Lilium and Hippeastrum to different environmental conditions were investigated.

Induction of nonbulb forming aspects in bulbous iris plants from 3–4 g bulbs which were stored at 20°C and grown at 25°C enabled the comparison of IAA and ABA levels in the bulb-forming and nonbulb-forming plants. Then, using scaling technique, seasonal changes of bulblet development and subsequent leaf growth and changes of endogenous plant hormones in the parent bulbs were investigated in Hyacinthus, Lilium and Hippeastrum.

The results were that low temperature, 20°C for storage and 15°C for growth, induced bulb formation in iris, that the level of ABA increased only in the bulb-forming iris plants, that the induction of dormancy in Hyacinthus and Lilium was caused by low temperature, that bulbous iris did not enter dormancy without bulb formation and that ABA increased when Iris, Hyacinthus and Lilium received low temperature. Even in Hippeastrum, a tropical origin, internal periodicity of growth and changes in ABA were found.

Taking into consideration of these results together with the reports by other researchers such that bulb formation of many fall planting bulbous plants are induced by low temperature, that dormant bulbous iris contains high levels of ABA, that ABA declines at the time of dormancy release, etc., the author proposes a concept of dormancy that the induction of bulb formation and that of bulb dormancy are the same process, or that the induction of bulb formation is the start of dormancy induction.

Applicability of the concept of dormancy to the phenomenon of organ differentiation in other plants such as induction of corms, tubers, rhizomes, rosette in perennial plants, heading in cabbage, runner in strawberry, etc. is also discussed.

Okubo, H. (1992). DORMANCY IN BULBOUS PLANTS. Acta Hortic. 325, 35-42
DOI: 10.17660/ActaHortic.1992.325.2

Acta Horticulturae