Scientists are conducting research on water-saving alternatives to photosynthesis in a climate that is likely to become hotter and drier in the future. The American Society of Plant Biologists reported on the creation of drought resistant crops with the metabolism of red blood acid, also known as photosynthesis of CAM. An article in The Plant Cell magazine reports about the environmental benefits of water conservation in a new model of leaf metabolism.
Drought causes large crop losses in many parts of the world, and climate change threatens to exacerbate the situation in both temperate and arid regions. In a new paper, Dr. Nadine Toepfer of the Leibniz Institute for Plant Genetics and Crop Research, along with colleagues at Oxford University in the UK, analyzed the potential for creating drought-tolerant plants through the introduction of redox metabolism into crops.
BRA metabolism (also known as photosynthesis of CAM) is a carbon sequestration pathway that some plants have developed as a result of adaptation to dry climates.
In plants that use CAM photosynthesis, the mouths on the leaves remain closed during the day to reduce evapotranspiration (in other words, evaporation of water). However, they open at night to collect carbon dioxide, which allows them to diffuse malate (malic acid) into mesophyll cells. At night, CO2 is stored in vacuum as tetracarbon malate and during the day it is transported to chloroplastics where it is again converted to CO2. This carbon dioxide is then used during photosynthesis. The pre-collected CO2 is concentrated around ribuloseobisobisphosphate carboxylase (enzyme RuBisCO). It increases the efficiency of photosynthesis. This mechanism of acid exchange was first discovered in the Crassulaceae family of plants. The most famous type of Crassulaceae in Russia is fatty, which was nicknamed “money tree”.
Scientists have used a complex mathematical approach to modeling to study the effects of the introduction of photosynthesis in different plants.
The leading author, Nadine Toepfer, who performed this work during her tenure as Dr. Marie-Curie in Professor Lee Sweetlove’s group in Oxford, said: “Simulation is a powerful tool for investigating complex systems and it provides insight that can help in laboratory and field research. I believe our results will inspire researchers who are looking to transfer the water-saving properties of CAM plants to other species.
Using simulations over a wide range of temperatures and relative humidity conditions, the authors of the study asked whether CAM photosynthesis or alternative water-saving methods would be more productive under conditions where C3-photosynthesis crops are typically grown.
They found that the vacuum capacity of the sheet is the main factor limiting water efficiency during CAM photosynthesis. They also found that the environmental conditions form the different phases of the CAM cycle. Mathematical modelling revealed an alternative CAM cycle that includes mitochondrial isocitrate dehydrogenase as a potential factor in initial carbon fixation at night.
Their results showed not only that the water-saving potential for photosynthesis of CAM is highly dependent on the environment (with the daytime environment being more important than the night environment). The scientists also noted that alternative metabolic regimes, different from the natural CAM cycle, can be useful under certain conditions. For example, on shorter days with less extreme temperatures. The scientists’ conclusions will help humanity to prepare for growing food crops in increasingly hot and dry climates.