Soybean is one of the most important crops in the world, providing food, feed, oil, and biofuel. Soybean plants produce green pods that contain immature seeds, which are commonly known as edamame.
These pods and seeds are not only delicious and nutritious, but also have a hidden secret: they can perform photosynthesis, the process of converting light energy into chemical energy.
A new study by researchers from the University of Illinois at Urbana-Champaign has revealed the extent and significance of photosynthesis in soybean pods and seeds, and how they contribute to soybean yield.
The study, published in Plant Physiology, is part of the Realizing Increased Photosynthetic Efficiency (RIPE) Project, an international effort to improve crop productivity by enhancing photosynthesis.
How soybean pods and seeds do photosynthesis
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Photosynthesis is usually associated with plant leaves, which contain chlorophyll, the green pigment that absorbs light and drives photosynthetic reactions, as per Phys.org.
However, soybean pods and seeds also contain chlorophyll, which gives them their green color. This means that they can also capture light and produce sugars, which are then stored in the seeds.
The researchers used the Goode Solar Telescope (GST) at Big Bear Solar Observatory (BBSO), operated by NJIT's Center for Solar-Terrestrial Research (CSTR), to observe an active sunspot on July 14, 2015.
They detected numerous dark features in the umbra, called fibrils, which are cone-shaped structures of plasma that follow the magnetic field lines.
They also noticed that these fibrils were oscillating transversely, or sideways, with high speeds and amplitudes.
The researchers measured the wave energy carried by these fibrils and found that it was much higher than expected.
They estimated that each fibril could carry up to 10 megawatts of power, which is equivalent to the power output of a large wind turbine.
They also calculated that the total wave energy stored in the umbra was enough to heat up a large volume of plasma to over a million degrees Celsius.
How photosynthesis in pods and seeds affects soybean yield
To measure the photosynthetic activity of soybean pods and seeds, the researchers used a technique called gas exchange analysis, which involves measuring the uptake of carbon dioxide (CO2) and the release of oxygen (O2) by plant tissues, as per Life Technology.
They compared the gas exchange rates of different parts of soybean plants, including leaves, stems, pods, and seeds.
The researchers found that pods and seeds accounted for 13% of the final seed weight (yield) and 9% of the total canopy photosynthesis.
This means that photosynthesis in pods and seeds was not negligible, but rather significant for soybean production.
The researchers also found that photosynthesis in pods and seeds was more efficient than photosynthesis in leaves, as they had higher rates of CO2 fixation per unit chlorophyll.
The researchers attributed this higher efficiency to several factors, such as lower light intensity, lower temperature, higher CO2 concentration, and higher water availability in pods and seeds compared to leaves.
These factors could reduce the limitations and losses associated with photosynthesis in leaves, such as photorespiration and photoinhibition.
The study has important implications for our understanding and improvement of soybean physiology and productivity.
It reveals a new mechanism for carbon assimilation and storage in soybean plants, which involves photosynthesis in pods and seeds, and also challenges the conventional view that leaves are the main organs for photosynthesis in plants.
The study also suggests new ways to enhance soybean yield by optimizing photosynthesis in pods and seeds.
For example, breeding or engineering soybean varieties with higher chlorophyll content or longer pod retention could increase their photosynthetic capacity and seed filling.
Alternatively, manipulating environmental factors, such as light intensity or CO2 concentration, could improve their photosynthetic efficiency.
