Vapour-pressure deficit the plant may dry out and die. For this reason the ideal range for VPD in a greenhouse is from 0.45 kPa to 1.25 kPa, ideally sitting at around 0.85 kPa. As a general rule, most plants grow well at VPDs of between 0.8 and 0.95 kPa. In ecology, it is the difference between the actual water vapour pressure and the saturation water vapour pressure at a particular temperature. Unlike relative humidity, vapour-pressure deficit has a simple nearly straight-line relationship to the rate of evapotranspiration and other measures of evaporation. To compute the VPD, we need the ambient (greenhouse) air
High-water mark of the Confederacy High-water mark of the Confederacy The high-water mark of the Confederacy refers to an area on Cemetery Ridge near Gettysburg, Pennsylvania, marking the farthest point reached by Confederate forces during Pickett's Charge on July 3, 1863. Similar to a high water mark of water, the term is a reference to arguably the Confederate Army's best chance of achieving victory in the war. The line of advance was east of "The Angle" stone wall at various distances, e.g., the Virginians pushed the Union line back. This designation was invented by government historian John B. Bachelder after the war when the monuments