Warmer nights can disrupt a good night’s sleep for humans, but could the biological processes of agricultural crops also be difficult about nighttime temperatures?
Researchers at Kansas State University and North Carolina State University believe so, and there is growing evidence to prove that the rice circadian clock genes – and may -being wheat – go wrong when the nights get hotter.
âWe still don’t know all the details, but we’re limiting the major regulatory players,â said Colleen Doherty, associate professor of biochemistry at North Carolina State University.
Professor Doherty and K-State and crop physiologist Krishna Jagadish began studying the impact of nighttime temperatures seven years ago when Jagadish was working at the International Rice Research Institute in the Philippines.
âEssentially, we found that the warmer nights disrupt the internal clock in the paddy field,â Doherty said.
Jagadish said warm temperatures are causing “hundreds of genes” to be expressed earlier than usual, and hundreds more later than usual. This disrupts key biological processes such as photosynthesis and respiration (a process that uses sugars produced during photosynthesis to create energy for plant growth).
In field trials with rice, Jagadish used artificial heaters under field conditions to keep the experimental plots 2 degrees Celsius above room temperature, and compared samples – taken every three hours for 24 hours – on plots cultivated at room temperature.
Similar studies at K-State have shown a 5% reduction in wheat yield for every one degree Celsius increase in temperature, according to Jagadish. For wheat, he added, “these changes in grain composition on hot nights will impact both the quantity and the quality of the bread.”
âMost people think plants aren’t dynamic, but they are,â Doherty said. âPlants are constantly regulating their biological processes – preparing for photosynthesis just before dawn, shutting it down in the late afternoon, determining precisely how and where to burn their energy resources. The plants are busy, it’s just hard to see all this activity from the outside.
“And what we’ve learned is that the clock responsible for regulating all of this activity goes wrong when the nights get hotter than the days.”
Doherty is currently focusing his work on rice, while Jagadish has studied the impact of nighttime temperatures on rice and wheat. âRice and wheat behave the same as warm nights, so progress made with one crop can benefit the other,â Jagadish said.
The researchers’ goal is to better identify the factors that disrupt the circadian rhythms of plants so that scientists can select strains that perform better in conditions with higher nighttime temperatures.
âIt is the starch-rich grain crops that are most vulnerable to high nighttime temperatures,â Jagadish said. He and his team are currently studying the impact of nighttime temperatures on corn at K-State’s North Farm in Manhattan.
âCorn, for example, has very high levels of starch. We believe that with warmer nights we will lose starch which will negatively impact the quality of the kernels and the amount of biofuel that can be generated from corn. In other words, with the varieties we have now, warmer nights could negatively impact the food and biofuels industry. “
In a 1,200-page report published in 2019, the United Nations linked an increase in global temperatures to increasing pressure on fertile soils, putting global food security at risk. Jagadish and Doherty note that rice, wheat, and other grain crops feed hundreds of millions of people around the world.
â(Our study) is not just an interesting scientific question,â Doherty said. âIt’s a problem of global food security.
The research is supported by the National Institute of Food and Agriculture, USDA. The researchers published an article that discusses their work with. Warm Nights Disrupt Global Transcriptional Rhythms in Field-Grown Rice Panicles appears in the June 2021 Proceedings of the National Academy of Sciences of the United States of America, known as PNAS.