Study: Mesophyll Conductance Doubles in Soybean Domestication, Providing Opportunity to be Enhanced Through Selective Breeding

Oct 29, 2024

In a new study conducted by the Realizing Increased Photosynthetic Efficiency (RIPE) project, researchers at the University of Illinois Urbana-Champaign looked back in time at soybean growth and discovered that modern plants have increased mesophyll conductance. This means that carbon dioxide travels faster from inside the leaf to the carbon-fixing enzyme Rubisco and consequently increases photosynthesis without loss of additional water.

This discovery was recently published in Plant, Cell and Environment.

“We thought it would be really intriguing to look at some ancestral cultivars of soybean and compare them to a modern cultivar, this gives us an insight into whether there is natural variability to assist direct breeding selection for increased productivity and water-use efficiency” said Elena Pelech, a postdoctoral researcher in the Long Lab.

“I grew a high-yielding soybean cultivar called LD11 (Glycine max), which was bred here in the Midwest, and then I selected four ancestral cultivars (Glycine soja) discovered from the northeast provinces of China, the assumed area of domestication,” said Pelech.

This study involved growing both modern and ancestral soybeans from seeds in a greenhouse and measuring mesophyll conductance following shade-to-sun transitions using concurrent measurements of gas exchange and carbon isotope discrimination.

“The ancestors of domesticated soybean are a vining plant that would have escaped much shade compared today’s dense soybean canopies where shade-to-sun transitions are frequent, and the speed mesophyll conductance can increase following these transitions affects photosynthesis.”

Most published data have focused on steady-state conditions meaning the plants are kept under a steady light, temperature, or CO₂ condition. With the concurrent gas exchange and carbon isotope discrimination method, the researchers were able to change those conditions—specifically the light variable—to measure the dynamic response of the mesophyll conductance. The results led to the research team discovering that following shade-to-sun transitions, mesophyll conductance was a significant limitation to soybean photosynthesis, but mesophyll conductance for the modern cultivar was two times higher which corresponded to a substantial increase in photosynthesis and water-use efficiency.

“This data is telling a story,” said Pelech. “There is evidence that we have indirectly increased mesophyll conductance by a 2-fold, suggesting a strong limitation on photosynthesis which has decreased through selection and subsequent breeding.”

Now, armed with this knowledge, scientists can tap into the unexplored potential within soybean breeding to deliver further sustainable yield improvements without more water, a strategy among many to supplement breeding efforts to increase crop production on existing land for agriculture.

Source : illinois.edu

Video: Spring 2026 weather outlook for Wisconsin; What an early-arriving El Niño could mean

Northeast Wisconsin is a small corner of the world, but our weather is still affected by what happens across the globe.

That includes in the equatorial Pacific, where changes between El Niño and La Niña play a role in the weather here -- and boy, have there been some abrupt changes as of late.

El Niño and La Niña are the two phases of what is collectively known as the El Niño Southern Oscillation, or ENSO for short. These are the swings back and forth from unusually warm to unusually cold sea surface temperatures in the Pacific Ocean along the equator.

Since this past September, we have been in a weak La Niña, which means water temperatures near the Eastern Pacific equator have been cooler than usual. That's where we're at right now.

Even last fall, the long-term outlook suggested a return to neutral conditions by spring and potentially El Niño conditions by summer.

But there are some signs this may be happening faster than usual, which could accelerate the onset of El Niño.

Over the last few weeks, unusually strong bursts of westerly winds farther west in the Pacific -- where sea surface temperatures are warmer than average -- have been observed. There is a chance that this could accelerate the warming of those eastern Pacific waters and potentially push us into El Niño sooner than usual.

If we do enter El Nino by spring -- which we'll define as the period of March, April and May -- there are some long-term correlations with our weather here in Northeast Wisconsin.

Looking at a map of anomalously warm weather, most of the upper Great Lakes doesn't show a strong correlation, but in general, the northern tiers of the United States do tend to lean to that direction.

The stronger correlation is with precipitation. El Niño conditions in spring have historically come with a higher risk of very dry weather over that time frame, so this will definitely be a transition we'll have to watch closely as we move out of winter.