What did Stephen Hales discover about water movement in plants?

Stephen Hales was a pioneer in plant physiology who introduced quantitative measurement techniques to the study of water movement in plants. His key discoveries include:1

• Transpiration: Hales was the first to measure the emission of water vapour from plants, a process known as transpiration. He determined that this water loss occurs primarily through the leaves.12
• Upward Flow: He discovered that transpiration encourages a continuous upward flow of water and dissolved nutrients from the roots.12
• Sap Dynamics: Hales established that sap flows upward in plants. He also conducted measurements of the pressure exerted by roots on sap and measured the rates of growth for shoots and leaves.1

His research, published in Vegetable Staticks (1727), provided foundational insights into how plants manage water, demonstrating that they "imbibe" and "perspire" significant amounts of water compared to animals.12