Food security

“Does dew provide water to plants?”

In ancient times, the dew was believed to be a source of vegetative and plant life and considered a great blessing. According to the literature, the accumulation of dew at night on plants can negatively impact vegetation and fruits by creating spongy effects. But some scientists say dew is an important source of moisture or water for plant life. This could be especially true in climates such as the Eastern Mediterranean and some parts of the US Great Basin Desert.

single drop of dew on corn plant leaf
Dew droplet on top of the small corn plant. Dewdrops that form or fall onto the soil surface decrease soil evaporation loss and mitigate soil water tension. Credit: Udayakumar Sekaran

Most arid and semi-arid regions are under dry conditions for half of the year. Therefore, dew is an essential water source from the air. During cool nights, water from the air precipitates on plant leaves. This dew surrounds the plant leaves every morning and helps them grow.

In arid and semi-arid regions, dew is the major water source because dew forms more frequently than rain events. Dew helps plants to accelerate their metabolism and increase plant biomass. Dew also plays an essential role in regulating the inner water of plants and helps them activate photosynthesis rapidly.

drops of dew on watermelon
Dew surrounds the top of a watermelon. Water in the air condenses on plants during cool evenings. Credit: Udayakumar Sekaran

Plants in the arid and semi-arid regions close their stomatal openings in the middle of the day. This is a defense mechanism to conserve moisture within the plant. During this time, a plant cannot perform the photosynthetic activity. However, in these regions, early mornings are the maximum plant growth period because dew drops surround the leaves of the plants and trigger photosynthetic activity.

By regulating transpiration pressure, dew also helps the plant from wilting by creating a higher steady restoration state.

In some context, dew also plays an indirect role in plant health by improving soil moisture condition. Dewdrops on the soil surface decrease soil evaporation loss and mitigate soil water tension.

drops of dew on potted plant leaves
The early morning dew surrounds plant leaves. In arid environments, dew can provide plants with a needed source of water. Credit: Udayakumar Sekaran

Forest ecosystems also receive numerous benefits from dew. Dew deposition on the forest canopy regulates the micro-climate changes and is also connected with the water-heat exchange process.

So, dew can help the plant rapidly activate photosynthetic activity during desiccation and rehydration. It can help some species survive drought conditions. Dew reduces water stress for plants by reducing transpiration. So, dew can be a significant water source in some arid and semi-arid regions.

Answered by Udayakumar Sekaran, Clemson University

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5 replies »

  1. This article gets the physics and biology mostly wrong: photosynthesis–the driver of all dry matter increase (growth) if not physical size increase–only increases as light levels and temperatures increase in the morning, and as leaf surfaces dry off. Water on the leaf surface from dew blocks stomata, so is most valuable if it runs off leaves into the soil for plant uptake.

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