How to create a If statment for dropdown box in python tkinter

I am a beginner to python and I am trying to create an if statement based on the dropdown box and I am not sure how to do it. My idea was if someone selects vertical from the dropdown the vertical_button() function will run and the same for horizontal. I have tried different methods and does not seem to work.

Any help would be much appreciated.

def horizontal_button():
    SVV_bbh = Button(root,text = "Calculate system vapour volume", command=lambda:Horizontal_vessel_calc())
    SVV_bbh.grid(row = 12, column = 1)  
    SVV_th = Label(root,text = "System Vapour Volume [Vg] =")
    SVV_th.grid(row = 14, column = 0)
    SVV_bh = Entry(root,bd=2,textvariable=h1)
    SVV_bh.grid(row = 14, column = 1)

def vertical_button():
    SVV_bbv = Button(root,text = "Calculate system vapour volume", command=lambda:vertical_vessel_calc())
    SVV_bbv.grid(row = 12, column = 1)  
    SVV_tv = Label(root,text = "System Vapour Volume [Vg] =")
    SVV_tv.grid(row = 14, column = 0)
    SVV_bv = Entry(root,bd=2,textvariable=v1)
    SVV_bv.grid(row = 14, column = 1)

clicked = StringVar()
options = ["Vertical","Horizontal"]
clicked.set("Vertical")
Orientation_t = Label(root, text = "Vessel Orientation")
Orientation_t.grid(row = 8, column = 0)
drop = OptionMenu(root,clicked, *options)
drop.grid(row = 8, column = 1)