A fly has flown onto the leaves of the butterwort – and is now stuck. Their movements trigger the release of digestive enzymes that slowly break down the insect.
The leaves of the butterwort shine in the sun. A fly has flown onto the surface of the plant – and is now stuck. The water-based mucus that tiny glandular hairs secrete holds them in place. Their movements trigger the release of digestive enzymes that slowly break down the insect. This is how the carnivorous butterwort “Pinguicula” obtains nutrients from its prey. It grows on dry rocky soils in the mountainous regions of Mexico – where cacti and agaves otherwise thrive.
A research team led by Gudrun Kadereit from the LMU Munich has now investigated how butterwort saves water in this dry environment. Until now, it was unclear how the fatty herbs could compensate for the lack of water and still provide enough liquid for the trapped slime. The team exposed the plants to complete drought in climate chambers to recreate the extreme conditions of their natural environment. They analyzed their metabolic processes.
The result: The fatty herbs use the same water-saving metabolic pathway as cacti, the so-called CAM photosynthesis (CAM = Crassulacean Acid Metabolism). The stomata in the leaves remain closed during the day, so that no CO2 is absorbed for photosynthesis, but the plants do not lose any water through evaporation during this dry, hot time. Only at night do the stomata open and the plant “breathes” in CO2, which is stored. During the day, this carbon reserve from the night is used.
“We did not expect these results. Until now, we did not know about the CAM photosynthesis pathway in carnivorous plants, nor among the bladderwort plants, to which butterworts belong,” says Kadereit.
The genus “Pinguicula” is therefore another example of a group of plants in which CAM photosynthesis has developed independently. In total, the metabolic pathway is now known in 39 plant families.
The discovery shows how versatile plants can be in the course of evolution. The Mexican butterworts have evolved from moisture-loving swamp plants into species that can survive even extremely dry periods. In view of climate change, which will change habitats, they could represent an interesting study group for further investigation.