生育温度がグラジオラス及びオキザリス (<i>Oxalis bowieana</i> Lodd.) のけん引根及び子球の形成•肥大に及ぼす影響

Abstract

1. Day/night temperatures of 30/24°C markedly promoted the growth of aboveground parts in both gladiolus and oxalis (Oxalis bowieana Lodd.), and especially in oxalis, continued unfolding of leaves and development of axillary inflorescences were without formation of daughter bulbs. Low temperatures of 17/12°C, however, depressed the growth of aboveground parts, and especially in oxalis, there occurred no increase in the number of leaves and leaf area and no development of inflorescences. While at 24/17°C, the growth was much favoured in both of the aboveground parts and the underground parts. Moreover, when root temperature was controlled independent of air temperature in gladiolus, the growth of aboveground parts was better at lower root temperatures, and such effect of root temperature was greater at the medium than high air temperatures.2. In both gladiolus and oxalis, the number of contractile roots was not affected by air and root temperatures. The elongation and thickening growth of contractile roots, however, were promoted at lower temperatures. The maximal weight of contractile roots and its decrease following contraction were greater in order of low, medium, and high temperatures. Especially in oxalis, there occurred no thickening growth and in gladiolus, not a few contractile roots deteriorated, at the high temperatures of 30/24°C. The formation and thickening growth of daughter corm or bulbs were depressed at higher temperatures, and in oxalis no daughter bulbs were produced. The above-mentioned effects of temperature seemed to be mostly due to the root temperature, at least in gladiolus, according to the experiment in which air and root temperatures were controlled separately.3. The contribution rates of contractile root(s) to the thickining growth of daughter corm or bulbs were calculated as in the previous report (2). In oxalis, the values as high as 56-59% were obtained and they did not vary with growing temperatures. While in gladiolus, they were markedly low and differed with growing temperatures, being comparatively higher at lower temperatures.