As major changes continue for our planet's climate, scientists are concerned about how plants will grow and adapt.
Researchers in the MSU-DOE Plant Research Laboratory , or PRL, Sharkey lab are studying changes in plant metabolism that occur when plants are grown in high light, high CO2 (HLHC) conditions.
They found that under these conditions, plants photosynthesize more, which can lead to larger plants, and potentially larger crop yields. However, there are tradeoffs; scientists also found that plants lose carbon under these conditions, which they need to make food. This study was published in Scientific Reports.
Environmental conditions are predicted to continue changing in two major ways. First, atmospheric carbon dioxide is projected to continue increasing. Second, a phenomenon known as global brightening is changing light levels as more solar radiation makes its way to the ground than in previous decades.
Scientists predict these conditions will impact plant metabolism, or the internal mechanisms in plants that allow them to live and grow.
"Our work demonstrates that it's very important to study photosynthesis and the carbon metabolism in plants," said Yuan Xu , postdoctoral researcher in the Sharkey lab and first author on the study. "Especially when we think about conditions for the future based on predictions. If you want to do bioengineering in the future, to make a plant that can better adapt to these future conditions, you need to focus on these areas."
This study revealed two major findings: under these future conditions, plants increase their rate of photosynthesis, but their rate of respiration in the light remains consistent with current conditions.
Increasing the rate of photosynthesis means the plant can make more sucrose and starch, the food it needs to survive.
"Most carbon fixed in photosynthesis becomes either starch [to use later] – like putting money in your bank account – or sucrose (table sugar) to use now – like buying an ice cream cone," said Thomas D. Sharkey, University Distinguished Professor in the PRL. "The most surprising observation was that extra carbon at high light and high carbon dioxide went much more to starch (76% increase) rather than sucrose (41% increase). This may help plants become more resilient because they will have extra carbon for growth or defense." Sharkey is also in the Department of Biochemistry & Molecular Biology and the Plant Resilience Institute .
Increased rates of photosynthesis may also lead to larger plants, as the plant is making more food for itself. This can potentially lead to larger yields of the crops we eat.
But a remaining issue is that plants also lose some carbon during photosynthesis – carbon which the plant could be using to make food. During a process known as respiration in light, or RL, CO2 is released by the plant.
This study found that RL remains constant in current and future conditions. What this means is the rate at which CO2 is released by the plant through the RL pathway is the same, despite the increase in photosynthesis.
Innovative methods
The researchers used a unique technique to measure RL. Typically, RL is measured using gas exchange methods such as the Laisk or Kok methods. However, these methods only work in low light conditions.
"That's why this study is unique," Xu explained. "We used a new approach to measure the RL in the high light condition that cannot be measured using the old method."
Xu used a method known as isotopically nonstationary metabolic flux analysis, or INST-MFA, to look at gas exchange in HLHC conditions. This method is tried and true in bacteria and fungi studies but has only been used in a handful of plant studies over the past decade.
The Sharkey lab will continue to use innovative research methods to study respiration in the light. Understanding this process will allow a better understanding of carbon dioxide uptake and release in the future.
"We know from this study that many things are changed [under future conditions] including photosynthesis, photorespiration and respiration in the light," Xu said. "This gave a hint for future work."
This work was funded by the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences at the U.S. Department of Energy , under Grants DE-FOA-0001650 and DE-FG02-91ER20021, and MSU AgBioResearch .
By Kara Headley
