The purpose of this study was to measure the auxin content on the basal parts of young leaves and the growing point of pineapple plants under the condition of particular weather or different period by using bioassay method and also measure the respiratory changes between day and night time and to find the relation between the condition of pineapple plant and the effect of flower-inducing by treating calcium carbide and NAA as the base of improving flower-inducing method to raise the yield of pineapple. The results were summarized as follows; 1 The IAA content of the growing point of pineapple stem was the highest at 3 am, and the lowest 9 am. The IAA content of basal parts of young leaves was also the highest at 3 am, and the lowest at 3 am. However the inhibitor of stem growing point and basal part of young leaves was more in night than daytime, especially the highest at 3 am. 2 The auxin contents both in the basal parts of young leaves and the growing point of pineapple stems were hi her during the period of June to November, and lower during the period of December to May, especially the highest in August to October and the lowest in March. 3 The auxin content of basal part of young leaves and the growing point of stem would be increased gradually after applying fertilizer on pineapple plants and would reach the highest on 15-20th day after fertilizer application and then decreased radually. 4 The weather conditions would directly affect the auxin content of pineapple plant. Usually the dail changes between day and night time of auxin content were re ualr and higher in daytime than night on fine day little change on cloudy day and irregular on rainyday. 5 The effect of calcium carbide was greater in night time than day time treatment. The treatment at 3 am was the most effective because of found between and larger fruit. However, no significant difference was found between the effect of NAA treatment and time of treatmet. 6 The effect of NAA treatment was good and stable during February to May, however, the effect was poor and unstable during August to November. 7 After calcium carbide treatment the growing substances at the stem growing point of pineapple plant would be decreased and the inhibitor would be rapidly increased. Hence, the decrement of growing substances and increment of inhibitor might be a major reason for inducing pineapple flower differentiation. 8 Based on the result, the auxin contents around the growing point of pineapple plant seemed to be associated with inducing flower differentiation by calcium carbide treatment especially, the content of inhibitor seemed to be more important than IAA content. 9 Although the respiration rates of various parts of pineapple leafblade were different, the respiration rate at night were greater than in daytime. This might be associated with the opening of stomata and the effect of calcium carbide carbide treatment.