Nighttime carbon absorption helps tropical trees bypass daytime dehydration

Plants typically open their stomata during the day to absorb carbon dioxide for photosynthesis, a process that risks rapid dehydration in arid climates. To bypass this, some species employ Crassulacean Acid Metabolism (CAM), closing pores during the heat of the day and absorbing CO2 at night, storing it as malic acid for later use. This metabolic shift acts as a biological survival mechanism against water loss.

Research from the University of Vienna suggests that this adaptation in the tropical Clusia genus did not emerge as a static trait, but through a dynamic genetic overhaul. These trees are the only known woody representatives of CAM plants, and within the genus, different species exhibit varying degrees of this metabolic flexibility.

The genomic analysis of Clusia rosea, Clusia minor, and Clusia major reveals that their adaptation was driven by polyploidization—a process where the genome is duplicated. This duplication provided a genetic surplus, allowing the plants to lose unnecessary copies or repurpose others for new functions. This plasticity created a spectrum of survival strategies rather than a single evolutionary solution.

The three species demonstrate distinct operational models:

• Clusia rosea maintains a stable, committed CAM-photosynthesis regime.
• Clusia minor remains facultative, switching to the night-mode only under severe stress and utilizing the standard C3 pathway when water is abundant.
• Clusia major employs a hybrid strategy, blending both methods.

These differences indicate that CAM-photosynthesis emerged through repeated genomic reorganizations, with each species tailoring its mechanism to a specific ecological niche. The distinction between a fixed trait and a conditional response highlights how genetic redundancy allows for precise environmental tuning.

Identifying the specific genes responsible for nighttime carbon storage provides a blueprint for agricultural engineering. The goal is to transpose these mechanisms into crop varieties, potentially creating plants capable of thriving in extreme heat and drought with minimal water consumption.