Study: Trees That "Breathe" at Night to Survive Drought

Nature continues to offer valuable lessons. Three tropical tree species of the genus • Clusia• employ different forms of a strategy to absorb carbon dioxide at night, when water loss is minimized. Researchers discovered that this adaptation stems from genetic changes that occurred over millions of years. The study was published in the journal • Nature Communications• . While most plants absorb carbon dioxide during the day-when light enables photosynthesis-some • Clusia• species have found a different solution: they open their stomata (microscopic leaf pores) at night to take in carbon dioxide. During the day, when temperatures are higher and water evaporation is more intense, the stomata remain closed. This strategy allows the trees to reduce water loss and better withstand periods of drought.

• Three species, three strategies

According to researchers from the University of Vienna, who led the study, the three analyzed species-• Clusia rosea• , • Clusia minor• , and • Clusia major• -do not utilize this mechanism in the same way. • Clusia rosea• employs a robust form of CAM photosynthesis, storing significant amounts of carbon dioxide as malic acid during the night. • Clusia minor• can activate this mechanism more intensely when subjected to water-deficit stress. In contrast, • Clusia major• uses an intermediate strategy, combining standard C3 photosynthesis with CAM photosynthesis. CAM photosynthesis-short for "Crassulacean Acid Metabolism"-has long been known to science. It is found primarily in plants adapted to water-scarce environments, such as cacti and other succulents. However, the • Clusia• genus is unique because it includes trees capable of employing this strategy. The Smithsonian Tropical Research Institute notes that some • Clusia• species can even switch from standard photosynthesis to nocturnal photosynthesis depending on the season and the amount of water available in the soil.

• A mechanism shaped over millions of years

Researchers analyzed the genomes of three species and found that they all resulted from ancient genome duplication events, followed by long periods of genetic material reorganization. Over time, some gene copies were lost, others were deactivated, and some acquired new functions. The genes involved in the nocturnal storage of carbon dioxide underwent similar transformations. The result is surprising diversity within a single genus: related trees that have come to use different mechanisms to cope with environmental conditions. Researchers studied the plants under conditions mimicking their natural habitat, varying water availability while simultaneously analyzing physiological activity, gene expression, proteins, and metabolic products.

• A potential lesson for agriculture

Interest in this strategy extends beyond academia. Plants that utilize CAM photosynthesis can use water more efficiently than plants that rely exclusively on standard photosynthesis. According to the University of Vienna, genetic information obtained from studying • Clusia• species could help researchers better understand the mechanisms enabling efficient carbon dioxide fixation and low water usage. In the long run, this knowledge could contribute to the development of drought-resistant crops. For now, however, • Clusia• does not offer a ready-made solution for agriculture. Instead, the research highlights the complexity of plant adaptation to water scarcity and shows how genetic changes accumulated over millions of years have enabled certain tropical trees to shift part of their photosynthetic activity to the night.