Callose formation was observed in the pollens during flower development and pollen tube grown in the pistil of A. thaliana. The accumulation of callose occurred in the tetrad in the flower bud and pollen tube. Therefore, the activity of β-glucan synthetase Ⅱ (GS Ⅱ), which is responsible for synthesizing the callose, was measured in the flowers on the same developmental stages. The enzyme activity was increased by about 10% while the level of callose contents was increased by about 70% in tetrads. Then, callose accumulation was increased during pollen tube growth by about 30% higher than the other stages and enzyme activity was detected, 30% more too. These results suggest that callose plays an important role in the growth of pollen and pollen tube by increasing GS Ⅱ activity.