グラジオラス木子の休眠程度と発芽温度との関係

Abstract

In order to examine the relation between the depth of dormancy and temperature for sprouting, gladiolus cormels harvested early in November and stored dry at room temperature were planted at different times in petri dishes containing about 0.6% agar alone as a substratum and placed at constant temperatures of 10, 15, 20, 25 and 30°C.Regardless of temperature, few cormels planted in December sprouted except bare cormels (shell removed) of ‘Professor Goudriaan’, in which sprouting took place at 10 and 20°C. This indicates that cormels are usually in a state of true dormancy about 2 months after harvest.On the other hand, cormels planted in January or later had been exposed to a long term of natural low temperature and were able to sprout at a wider range of temperature than cormels planted earlier. Namely, cormels first became able to sprout at lower temperatures of 10-15°C and then gradually at higher temperatures of 20-25°C. Bare cormels began to sprout at a wide temperature range earlier than intact ones (shell adherent).It may be concluded from these results that about 15°C or 20°C is optimal for the sprouting of cormels which are in a state of postdormancy or out of dormancy, respectively. For any planting date, few cormels sprouted at 30°C and therefore the maximum temperature for sprouting is presumed to be about 30°C.Moreover it was demonstrated that sprouting was promoted by storing cormels dry at room temperature for an extended period of 17 months and planting them in the early spring of the year after next.Cormels which were presumed to be in true dormancy at planting time remained in non-sprouting conditions for a year or longer, as long as they were placed in a wet condition at constant temperature between 10 and 30°C, especially between 20 and 30°C. However they gradually turned to a state of postdormancy during the non-sprouting period.