本試驗探討成熟台灣原生白花蝴蝶蘭(Phalaenopsis aphrodite subsp. formosana)生長於28/20℃(日/夜溫)六週，在不同的日光積值下改變蘭苗還原2, 3, 5-triphenyltetrazolium chloride(TTC)的能力、代謝碳水化合物和有機酸的日韻律變化程度與抽梗情形。日光積值的下降，降低夜間累積蘋果酸及白天堆積澱粉的程度，也降低還原TTC能力，顯示粒線體活力下降。當日光積值降至0.72 mole/m2，澱粉與蘋果酸的日韻律現象消失，而且在黎明時的蘋果酸與蔗糖濃度，以及在黎明與黃昏時的澱粉濃度，皆顯著低於日光積值5.04 mole/m2的控制組，造成花梗無法抽出。在可溶性醣中，蔗糖的平均濃度與日光積值的下降呈現正相關。因此，在低日光積值時，蔗糖濃度的下降可能在抑制台灣原生白花蝴蝶蘭抽梗上扮演重要角色。

This study examined the variation in the daily light integral (DLI) levels altering the capacity of 2, 3, 5-triphenyltetrazolium chloride (TTC) reduction, the amplitude of diurnal changes in carbohydrate and organic acid concentrations and flower stalk emergence of mature Phalaenopsis aphrodite subsp. formosana plants grown under 28/20oC (day/night temperature) for six weeks. The decrease of DLI levels decreased the amplitudes of nocturnal malate accumulation and diurnal starch deposition, and TTC reduction capacity, which indicates the decrease of the mitochondria viability. Once the level of DLI decreased to 0.72 mole/ m2, the diurnal fluctuation of starch and malate was abolished, and the concentrations of malate and sucrose at dawn, and starch at dawn and at dusk were substantially lowered than those of the control plants receiving 5.04 mole/m2 DLI, resulting in the inhibition of flower stalk emergence. Among the soluble sugars, the average sucrose concentration appeared to be positively correlated to the level of DLI. It seems that lowering of sucrose concentration plays a key role in the flower stalk inhibition of Phalaenopsis aphrodite subjected to low DLI.