Vapour pressure deficit VPD is an indicator for air dryness which defined as the amount of moisture in the air and how much moisture the air can hold when it is saturated Extreme temperatures can dire

The vapour pressure deficit (VPD) is a measure of air dryness that reflects the amount of moisture present in the air and its capacity to hold moisture when saturated. Extreme temperatures can have a direct impact on crop tissue, resulting in reduced yield potential. Furthermore, they can also lead to moisture stress by increasing the VPD.