夏秋ギク'岩の白扇'における花芽発達段階別の低温および高温が開花に及ぼす影響(発育制御)  [in Japanese] The Stages of Flower Bud Development Sensitive to Low and High Temperatures for Flowering of Summer-to-Autumn Flowering-Type 'Iwa-no-hakusen' Chrysanthemum (Chrysanthemum morifolium Ramat.)(Growth Regulation)  [in Japanese]

夏秋ギク'岩の白扇'の開花に関する温度感応性が高い時期を明らかにするため,花芽発達段階ごとの生育温度が開花時期や花序形態に及ぼす影響を検討した.ビニルハウスで電照栽培した株を,消灯日から5日おきに5回にわたり人工気象室へ搬入し,10日間の温度処理を行った.人工気象室での温度処理条件は,対照区を25/20℃(昼/夜温)として,低温および高温区をそれぞれ2005年には20/15℃および30/25℃,2006年には17/12℃および33/28℃とした.開花時期に関する温度感応性は,花弁形成期から処理を終了した発蕾後約12日目までの花芽発達段階において高く,この時期の高温遭遇は発蕾以降の発達を抑制し,開花時期を遅らせた.遭遇する低温および高温条件の程度が著しくなると,早い花芽発達段階の温度も開花時期に影響を及ぼした.また,総苞形成後期から小花形成後期の高温により,花序の重さおよび小花数の増加や管状花率の低下など品質が向上する傾向がみられた.以上より,東北地域における夏秋ギク'岩の白扇'の8月開花の作型で問題となる開花時期の不安定性は,温度に対する感応性が高い花弁形成期から発蕾期における気温の年次変動の大きさが原因となっていると考えられた.

Effects of temperature at various stages during flower bud development on flowering time and cut flower quality were investigated in summer-to-autumn flowering-type 'Iwa-no-hakusen' chrysanthemum. Plants grown in a plastic green house were transferred to artificial climate rooms at 0, 5, 10, 15 and 20 days after the start of short days, and were grown under control, low or high temperature for 10 days. The artificial climate rooms were maintained at 25/20℃ (day/night) for control temperature, and 20/15℃ or 30/25℃ in 2005 and 17/12℃ or 33/28℃ in 2006 for low or high temperature regimens, respectively. The stage that was most sensitive to temperature for anthesis was during petal formation and flower budding in 2005. The development of flower bud after flower budding was delayed by high temperature at this stage, and the number of days to anthesis was increased. In 2006, this stage was extended by a more severe low or high temperature regimen before petal formation compared to that in 2005. High temperature during the late stage of involucre formation and late stage of floret formation increased the weight of inflorescence and number of florets, and decreased the percentage of disk florets, resulting in preferable cut flower quality. In conclusion, unstable temperature during petal formation and flower budding contributes to the annual fluctuation in the flowering time of 'Iwa-no-hakusen' chrysanthemum.