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A recent study by Los Alamos National Laboratory scientists shows that increased water availability can make some types of plants significantly less responsive to subsequent drought conditions than previously thought.

"This was one of those surprise findings that you encounter by accident while looking for an answer to another problem," said Turin Dickman, scientist at Los Alamos and corresponding author of the study in Scientific Reports. "By putting the pieces together from a number of incidental findings, we came up with a new way to think about an old concept."

The paper analyzed drought responses of two tree species: pi帽on pine and juniper. These two species are very common across the Southwestern United States, and represent alternate strategies for how a plant manages its water levels.

Anisohydric plants, like juniper, tend to respond to conditions such as drought more readily than isohydric plants, like pine, as demonstrated by their ability to adjust their operational leaf water potential. Scientists previously believed that isohydric plants maintain a relatively constant minimum water leaf potential no matter the environmental conditions.

This research found that isohydric plants can be more adaptive than expected, especially regarding increasing water abundance. This causes them to act more closely to anisohydric plants.

The implications of these findings are important for scientists' understanding of how plants respond to varying water availability from drought to abundance, especially in the arid and semi-arid environments of New Mexico.

"Based on our results, the equations that govern stomatal closure may be revised to account for changes in stomatal closure points (SCP) with increased water availability at different timescales," Dickman said.

SCP is the functional tipping point that determines when plants should stop photosynthesis in order to preserve water. Previously, scientists considered SCP to be a relatively static factor in isohydric plants.

These findings will impact scientists' understanding of how plants conduct photosynthesis and handle water loss, which ultimately will help researchers update models that include plant responses to environmental stress. As this work continues, the team will examine additional plant species that may exhibit similar characteristics.

As drought conditions evolve, understanding how plants react to different water availability will help increase ecosystem resilience and aid scientists in understanding how species might adapt to future conditions.