フレンチマリーゴールド (Tagetes patula, 'Bonanza Yellow') が昼夜間温度差(DIF)に反応しない理由 : 明暗期における伸長量の解析 Reasons for inefficacy of DIF on French marigold (Tagetes patula, 'Bonanza Yellow') : Analysis of hypocotyls elongation in the light and dark periods
フレンチマリーゴールドを対象として, +10 DIF(明期25°C/暗期15°C), 0 DIF(20°C/20°C), -10 DIF(15°C/25°C)における下胚軸の伸長成長量を画像計測し, 定量的に解析を行なった. その結果, マリーゴールドはDIF値が変化しても伸長成長量には有意な差が認められず, DIFに反応しない品目であることが明らかとなった. この原因を探るため明期および暗期における伸長成長量を調べたところ, 本研究で設定した平均気温20°CのDIF条件のうち, 0および+10 DIFではいずれも明暗期ともほぼ同程度の伸長成長量となり, 一方-10 DIFでは明暗期に伸長成長量の差があるものの一日の伸長成長量は0および+10 DIFの場合と同程度となるため, 昼夜間の温度差であるDIFを指標として整理しても明確な関係が得られないことが明らかとなった.
Hypocotyl elongation of French marigold (<I>Tagetes patula</I>, 'Bonanza Yellow') under three DIF (difference between day and night temperature) conditions (day temperature(DT): 25°C/night tempereature (NT):15°C, 20/20, 15/25) was analyzed using image processing. Experiments were conducted in growth chambers with a photosynthetic photon flux (PPF) of 150μmol s<sup>-1</sup> m<sup>-2</sup> on the canopy level and a 12 h photoperiod provided by fluorescent lamps. Images of ten plants were acquired every 10 minutes for 7 days and stored for later evaluation. The stored images were analyzed using software developed in-house and applied subpixel estimation to an area-based pattern-matching algorithm. Hypocotyl elongation over 7 days under three DIF conditions (25/15, 20/20, 15/25) ranged from 5.7 to 6.1 mm. There were no significant differences among the conditions, clearly indicating that DIF was not effective for enhancing marigold culture. ANOVA test on hypoctyl elongation during the light period of the second and third day demonstrated a significant difference. However, in the dark period, ANOVA test did not show a significant difference under DIF treatments. Then multiple comparison tests were performed on hypocotyl elongation during the light period,and that under the -10 DIF condition was significantly lower than that during the light period under other DIF conditions. However, since elongation during the dark period of -10 DIF was relatively higher, the daily elongation under the -10 DIF condition was similar to that under the other DIF conditions. It was clearly shown that the cause of not reacting to DIF was almost constant elongation through a single day under 0 and +10 DIF conditions,while under the -10 DIF condition, elongation was decreased during the light period but increased during the dark. Therefore, the daily elongation was almost the same under all DIF conditions.
植物環境工学 20(1), 26-30, 2008-03-01