Why is there a difference in using method ".plot()" between jupyter notebook and pycharm?

Question

I'm following pandas tutorial1 with pycharm.

Tutorial describes how to use method '.plot()' with jupyter-notebook as enter image description here

But if I write this code in pycharm, nothing is shown. if I change code as below, it works same with image

    import pandas as pd
    import matplotlib.pyplot as plt

    air_quality = pd.read_csv("air_quality_no2.csv", index_col=0, 
    parse_dates=True)

    plt.plot(air_quality)
    plt.show()

Why is there a difference in using method ".plot()" between jupyter notebook and pycharm?

Thanks.