Suppose you could magically remove 5 percent of the leaves from all the plants in your soybean fields? Would it be detrimental to plant development and yield?
To the contrary, say scientists at the University of Illinois College of Agricultural, Consumer, and Environmental Sciences, it could result in a yield increase of as much as 8 percent.
In replicated trials, they deliberately snipped off new leaflets to reduce soybean leaf area by 5 percent, and got an 8 percent increase in seed yield.
As reported in Science Daily, computer model simulations have projected that modern soybean plants grow many more leaves than they actually need, which can be a detriment to yield, a situation that’s worsened by increasing levels of atmospheric carbon dioxide.
The yield increase from leaf removal is attributed to increased photosynthesis, decreased respiration, and diversion of water and nutrients that go to producing more leaves than seeds.
“The reduction in leaves allows more sunlight to penetrate through the canopy, making the whole plant more productive, and it also reduces crop water demand,” says project leader Praveen Kumar, Lovell Professor of Civil and Environmental Engineering at ACES.
“Soybeans are one of the four major staple crops, and also the most important vegetable protein source in the world,” says first author and post-doctoral researcher Venkatraman Srinivasan. “If we can increase the yield of soybeans, we can solve the problems of protein demand and food production at the same time.”
Currently, only about a 1 percent increase in yield is due to crop improvements, which have slowed over the past decade, says Steve Long, project co-leader, and Gutgsell Endowed Professor of Plant Biology and Crop Sciences at the Carl R. Woese Institute for Genomic Biology. “This rate is insufficient to fulfill the needs for global food security, where we need to produce 70 percent to 100 percent more food by 2050 to feed an estimated 9.7 billion people.”
Published in Global Change Biology, their study found that many of the leaves on a soybean plant are shaded and inefficient, thereby wasting resources like water, carbon, and nitrogen. The computer model shows “by investing less in leaves, the plant can produce more seeds,” Srinivasan says.
The model predicted that a 30 percent to 40 percent reduction in leaf area would boost yield by 8 percent to 10 percent.
“The experiment indicates that our model is conservative,” Srinivasan says. “We hypothesize that plants with fewer leaves need less water, which requires fewer roots. Cutting down on roots could produce additional carbon savings that the plant can invest toward boosting yield. Alternatively, plants with fewer leaves are more water-efficient, and thus may be potentially drought-tolerant.”
The researchers will now bioengineer plants, or search for varieties that naturally have fewer leaves, to test their findings on a larger scale. And they’ll continue exploring other ways to optimize the soybean canopy, such as the distribution and angle of leaves, with the aim of designing better soybean plants that yield more while using less water and other resources.