Definition - What does Transpiration mean?
Transpiration is a biological process that is specific to plant species including grape vines. The process is when moisture/water travels from the roots to small pores on the leaves. The underside leaf pores release the water/moisture, which transforms into vapor where it evaporates into the atmosphere. Transpiration rates have many variables including; temperatures, humidity, precipitation, soil type and saturation level, land slopes, water tables, wind strength and the species of plant. Grapevine transpiration can be controlled by having exact climate conditions, closely controlled irrigation system and measurements on soil saturation.
WineFrog explains Transpiration
All plants transpire and this moisture loss is very important to vineyard crops and grape quality. During the growing season between April and October, the grapevine leaf can transpire its own weight in moisture several times. Even though the plant is releasing moisture, it isn’t visible to the human eye. To monitor transpiration rates, winemakers must take climate variations, like temperature and humidity, into consideration as well as soil and vineyard placement. Higher temperatures and increased wind speeds cause transpiration rates to also increase.
However, high humidity decreases transpiration rates, as the air is saturated with water. Soil moisture should be kept constant, too much moisture and the soil may require cover crops to absorb the excess water and to make sure the vine doesn’t drown. Too little moisture causes less transpiration and a wilting of the vine and berries. Placement close to the water table and different species of vine/hybrids can also cause unstable or unpredictable transpiration rates.