Plants don't actually cry like humans do. The 'tears' you might see on leaf edges, especially in the morning, are actually water droplets released through a process called guttation. This phenomenon often occurs at night or early morning when conditions are humid and soil moisture is high.
Understanding Guttation
Guttation is the excretion of water droplets from the tips or edges of leaves of some vascular plants. This happens when transpiration, the process where plants release water vapor through pores called stomata, is suppressed or very low. Stomata are typically closed at night to conserve water.
Why Guttation Happens, Especially at Night
With stomata closed, water intake by the roots can exceed the plant's need for water and the rate at which it can be transpired. This builds up root pressure, forcing water up through the plant. The excess water is then pushed out through specialized pores called hydathodes, located on the leaf margins.
Based on the reference, guttation is commonly triggered by specific conditions:
- Excessive Watering: As the reference states, guttation most often occurs when we water the plant too abundantly. This means there is ample water available for the roots to absorb.
- High Humidity: The reference notes it can also happen under other circumstances, such as when the surrounding area is too humid. High humidity reduces the evaporation rate of water from the leaves, lowering transpiration.
- Mineral Salt Concentration: According to the reference, it can also occur "when there are a lot of mineral salts in the soil." High salt concentration can increase the osmotic potential in the soil, but within the plant, root pressure builds, pushing out excess water and salts.
Here's a quick look at the main triggers for guttation:
| Condition | Impact on Plant Water Balance |
|---|---|
| Excessive Water | Roots absorb more water than the plant needs or can transpire. |
| High Humidity | Lowers transpiration rate, causing water buildup inside the plant. |
| High Mineral Salts | Contributes to internal root pressure forcing water out. |
These conditions, combined with the reduced transpiration rate that occurs when stomata close at night, create the perfect environment for guttation to happen. The plant is essentially managing its internal water pressure by expelling excess water.
So, while it looks like the plant is crying, it's simply regulating its water balance under certain environmental conditions, particularly when transpiration is low or soil moisture/salt levels are high.
