紅龍果光周性與萌芽物候期

Abstract

紅龍果屬長日植物，在北半球每年5-10月間可以萌生數批花苞，產期集中於夏季。其臨界日長約為12小時，因此春、秋分為營養生長與生殖生長之轉折。甫成熟的紅龍果枝條進入春分，開始感應長日訊息進入生殖生長，依次完成花芽誘導、呼喚及分化而萌生花苞。未成熟的幼嫩枝條無感應日長的 能力。在台灣南部，甫成熟的枝條在春分後9週完成花芽呼喚萌生花苞。肉質莖上雖具有很多刺座，除遠軸端萌花的刺座外，其餘刺座雖完成花芽誘導、甚至呼喚後受頂芽優勢抑制，處於靜止狀態。進入秋分後，刺座若未即時完成花芽呼喚並且萌出花苞，則持續靜止至春分以後才恢復芽體生長並萌花 ，部分芽體也可能受低溫影響而死亡。秋分過後，在台灣南部11月中旬前給予暗中斷，遠軸端芽體可以恢復發育、萌生花苞。早春肇因於溫度太低產期調節常常失敗，建議在夜溫回升至高於15℃或者提高夜溫，暗中斷處理的效果才會穩定。 Pitaya is a long-day plant, which owers in several ushes between May and October and produces fruits mainly in summer in the Northern Hemisphere. The critical day length of red pitaya was observed to be approximately 12 h, suggesting that the two switches between inductive and noninductive periods for red pitaya occur at the vernal and autumnal equinoxes, respectively. The immature shoots are not competent to response to the stimulus of long day length. In southern Taiwan, the newly matured shootsturn into reproductive phase through oral induction, evocation, di erentiation and nally emerge oral buds about 9 weeksafter vernal equinox. Because of apical dormancy, numerous other areoles, except those that owered, rested despite having already been exposed to adequate long-day length.After the autumnal equinox, the rested buds were unable to emerge as oral buds before the subsequent vernal equinox, and some of them did not survive the cold season. The induced but rested buds at the distal end may develop into oral buds if the NB treatment is applied in before middle November.According to the data of bud transformation and temperature variation in a winter trial in Southern Taiwan, a night temperature lower than 15 °C may limit bud development. Therefore, we concluded that NB treatment should be applied after mid-February in Southern Taiwan, when the minimum temperature seldom drops lower than 15 °C.