A recent study revealed that extreme heat severely affects the process of photosynthesis in plants, including agricultural crops, which humans rely on as a main part of their daily diet, posing a threat to global food security.

Plants are at the first level of the food chain, and thus they represent one of the producer organisms; they can—through a series of chemical reactions—utilize sunlight and carbon dioxide to produce food and oxygen in a process known as photosynthesis, thereby contributing to supporting the life of all living organisms on Earth.

Therefore, scientists are keen to study them thoroughly and provide the necessary information and data to understand their nature. It was essential to consider the impact of rising temperatures in light of climate changes.

A research group from the University of California, San Diego, in the United States, has focused on studying the mechanisms that these plants follow in response to heat. They published their study in the journal "New Phytologist" on October 1, 2024.

Regulating gateway

The stomata present on the surface of the leaves act as a regulating gateway for heat and the process of photosynthesis; they control the plant's ability to consume carbon dioxide or release water vapor. Thus, the stomata contribute to the plants' sensing of changes occurring in their surrounding environment and determining the appropriate mechanisms to deal with those changes, which helps them survive.

With the rise in temperatures, plants respond by opening their stomata, allowing water to evaporate outward—a process known as transpiration, which is similar to sweating in humans when they stay in a place with high temperatures. Scientists have understood this mechanism in plants for decades, but the biggest challenge is understanding the molecular basis behind it.

Complications

There were many complexities surrounding the mechanisms of stomatal opening, and scientists have spent decades trying to decode them, but to no avail. This is due to some challenges in measuring the "vapor pressure difference," which refers to the difference between the vapor pressure inside the leaf and the vapor pressure outside it. Prior to the emergence of this research, it was unclear how plants react to stomatal openings on their leaves during temperature increases and during periods of intense heat.

The authors of the study developed a new approach to adjust the vapor pressure difference of the leaves to understand the effects of temperature on the process of stomatal opening. They studied two different types of plants: Arabidopsis thaliana, a weed, and Brachypodium distachyon, a flowering plant commonly found in cereal crops like rice, corn, and wheat.

Researchers found that with rising temperatures, photosynthesis increases, meaning that plants benefit from carbon dioxide. However, extreme heat stresses photosynthesis and reduces the plant's ability to manage water, negatively affecting our reliance on crops like rice, corn, and wheat.