VPO is the pinch off voltage for VGS = 0 in an FET. When

V_PO is the pinch off voltage for V_GS = 0 in an FET. When the gate is reverse biased by V_{G S} the pinch off voltage—

1. Will be less than V
2. Will be more than V
3. Will be the same as V
4. Does not depend on V

Will be less than VPO, because when gate is reverse biased depletion width increases, which decreases the pinch-off voltage.