Warmer Night Temperatures Alter Rice Plants’ Circadian Rhythm Leading to Curbing Crop Yields

According to a study done by a team of international researchers, warmer nighttime temperatures are altering the circadian rhythm of rice plants. 

The rising evening temperatures are curbing crop yields for rice. Colleen Doherty, an associate professor of biochemistry at North Carolina State University, stated, “Essentially, we found that warmer nights throw the rice plant’s internal clock out of whack.” 

She continued, “Most people think plants aren’t dynamic, but they are. Plants are constantly regulating their biological processes — gearing up for photosynthesis just before dawn, winding that down in the late afternoon, determining precisely how and where to burn their energy resources. Plants are busy, it’s just difficult to observe all that activity from the outside.”

The increase in temperatures globally is an effect of climate change. According to Doherty, the nighttime temperatures also rise faster than daytime temperatures. 

Doherty and a team of international researchers, namely Krishna Jagadish of Kansas State University and Lovely Lawas of the International Rice Research Institute, initiated the study on why warm evenings are bad for rice plants. 

The team established two study sites in the Philippines, with temperatures being manipulated in different areas of each study site using ceramic heaters or heat tents.

Jagadish’s team maintained experimental plots made use of ceramic heaters at 2 degrees Celsius above ambient temperature and took samples of rice plants every three hours for 24 hours. Controlled plots were not heated but were also sampled during the same 24-hour period. 

In Doherty’s team, they had found that more than a thousand genes in rice plants were being “expressed” at a wrong time when nighttime temperatures were high. Hotter nights resulted in hundreds of genes that became active later in the day. On the other hand, hundreds of other genes became active much earlier in the evening than normal. 

“It’s not clear what all of these genes do, but it is clear that these conflicting schedule shifts are not good for the plant,” added Doherty. The rice plants’ finely tuned biological clock assured optimal yield and with these disruptions found in the study, yield of rice crops have curbed.

“We need to do additional work to figure out exactly what’s happening here, so that we can begin breeding rice that’s resilient against warmer nights. Rice is an important food crop. And other staple crops are also affected by hotter nights — including wheat. This isn’t just an interesting scientific question, it’s a global food security issue,” Doherty added.