福岡県農業総合試験場研究報告22(2003) pp 85 - 89
ヒマワリの４月出し栽培における奇形花発生と低温遭遇
黒柳直彦・國武利浩・坂井康弘・谷川孝弘１）
（園芸研究所）
福岡県のヒマワリの４月出し無加温栽培において、茎先端に複数の花が着く「複数花」、あるいは頂花と側花が癒着する「癒着花」等の奇形花が発生し問題となっている。
品種‘サンリッチオレンジ’を用いて、この奇形花発生と、窒素施用量および土壌水分ならびに花芽発達段階の低温遭遇の関係について検討した。その結果、生育中の窒素施用量と土壌水分の影響は認められなかったが、花芽発達時に氷点下低温に遭遇した12月播種で、すべて奇形花となり、花芽分化後、低温に遭遇しなかった１月播種で、奇形花が発生しなかった。このことから、花芽発達期間中の氷点下の低温遭遇が、奇形花発生の要因として推定された。そこで、人為的に低温遭遇（−３℃）させた結果、花芽未分化時では奇形花は発生せず、生長点膨大期以降では奇形花が発生し、その発生率は、低温遭遇時間が長く、遭遇日数が多いほど高くなる傾向が認められた。
［キ−ワ−ド：ヒマワリ，奇形花，低温遭遇、花芽発達期］
1)現福岡県農政部農業技術課
Generation of Malformed Flowers and Low-temperature Exposure in Cropping Type Sunflowers Harvested in April. KUROYANAGI Naohiko, Toshihiro KUNITAKE, Yasuhiro SAKAI and Takahiro TANIGAWA. Fukuoka Agricultural Research Center, Chikushino, Fukuoka 818-8549, JAPAN) Bull. Fukuoka Agric. Cent., 22: 85 - 89 (2003)
In unheated cultivation sunflowers of Fukuoka Prefecture harvested in April, malformed flowers have developed causing problems in cultivation. Two of the major malformations were "multiple flower", where more than one flower bloomed at the stem tip, and "stack flowers", where the terminal flower and side flowers adhered to each other.
Using the 'Sunrich orange' variety, the relation between this malformed flower generation and the rate of nitrogen fertilizer application, level of soil moisture, and low-temperature exposure at the developmental stage of flower buds was examined. As a result of the examination, the rate of nitrogen fertilizer application and the level of soil moisture were found not to contribute to the generation of malformed flowers. However, all flowers became malformed when seeded in December, having been exposed to low temperature below the freezing point in the developmental stage of flower buds. Also, none of the flowers became malformed when seeded in January having not been exposed to low temperatures after flower-bud initiation. This fact suggests that low temperature exposure below the freezing point during the developmental stage of flower bud was the main factor inducing generation of malformed flowers. When low-temperature exposure (-3℃) was artificially staged, malformed flowers did not develop in the vegetative stage, while they developed after the growing point enlarged stage. The generation of malformed flowers tended to increase as the low-temperature exposure hours increased, and as the number of exposure days increased.
[Keyword: Sunflower, malformed flower, low-temperature exposure, flower bud development]
第１図（jpg. 77KB） 第２図（jpg. 80KB） 第４図（jpg. 104KB） 第５図（jpg. 154KB）
