Answer:
Leftward; after-tax wage rate falls
Step-by-step explanation:
A labor supply curve is a graphical representation of labor supply at an organisation or at work where the hypothetical wage rates are shown at the vertical ordinate while the will to supply the labor at that particular wage rate is plotted at the horizontal abscissa.
If there is any change in anything that impacts or affects the labor demand or supply, for example any change in government tax or regulation, changes in the production process or output process, it causes a shift in the labor supply curve.
So when there is any increase in the taxes on labor income, the labor supply curve shifts towards the left and the after tax wage rate falls immediately.
Thus the answer is ---
Leftward; after-tax wage rate falls