報告書番号

U03033

タイトル（和文）

夜間の短時間補光によるホウレンソウの成長促進 --低照度条件下の栽培における適用の可能性--

タイトル（英文）

Acceleration of growth in spinach induced by brief exposures to supplemental lights during the night: Possibility of applying the lights to cultivation under low daylight irradiance

概要 （図表や脚注は「報告書全文」に掲載しております）

光不足によるホウレンソウの成長不良を改善するため，夜の終了時に青色光を照射するか，夜の開始時に赤色光を照射すると，30分間の短時間補光でも成長促進が認められる。そこで，昼間の光不足条件が，夜間の短時間補光による成長促進に影響を及ぼすかどうかを調べた。昼間のPPFDが400μmol m-2 s-1以下では，青色や赤色の補光により草丈や全乾物重が増加した。全乾物重の増加割合はPPFDが低下すると増大し，200μmol m-2 s-1において最大（青色光で36%，赤色光で46%）であった。成長促進の効果は，昼間が10時間以下の短日条件下でも起こり，日長延長にともなう反応でないことが明らかになった。また，青色と赤色の補光を併用すると成長促進の効果を高めることが可能で，PPFDが200μmol m-2 s-1では全乾物重は51～53％増加した。重要な栄養成分であるβ-カロテンやアスコルビン酸の含有濃度には影響が認められなかった。

概要 （英文）

To improve the insufficient growth of spinach due to lack of solar radiation, the effects of quality and lighting period of supplemental light on growth was investigated in our previous study through experiments using artificial light in growth chambers. It was found that even a brief exposure of 30 minutes to either blue light at the end of the night or red light at the beginning of the night induced acceleration of growth.This study sought to clarify whether the levels of photosynthetic photon flux density (PPFD) and daylength during the daytime affects the acceleration of spinach growth induced by a brief exposure to supplemental blue or red light during the night. When the level of PPFD during the daytime was less than 400μmol m-2 s-1, plant height and total dry weight increased by exposure to supplemental blue and red light. In addition, increase rate of total dry weight became greater as PPFD reduced, and the rate was greatest when PPFD was 200μmol m-2 s-1 ; 36% with blue light and 46% with red light. The accelerative effect of growth occurred under obvious short-day conditions when daylength was less than 10 hours, indicating that it was not due to physiological response to day extension.Furthermore, spinach was briefly exposed to both supplemental blue light at the end of the night and red light at the beginning of the night in order to enhance the accelerative effect of growth, resulting in increase of total dry weight by 51% to 53% at 200μmol m-2 s-1 of PPFD. On the other hand, there was no influence of using both blue and red supplemental lights on the content of the important nutritious elements β-carotene and ascorbic acid.

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