For decades, the basics of plant growth have been taught in grade-school: Plants make their food out of water from the soil, light from the sun and carbon dioxide from the air in a process called photosynthesis.

What gets less attention is that plants release some of that carbon dioxide back into the air in a parallel process called photorespiration. Most scientists think this parallel process is a waste of the plant’s energy, consuming 30 percent or more overall. Millions of dollars have been spent on research trying to eliminate photorespiration, with the aim of redirecting that “wasted” energy to boost crop production. So far, progress has been slow.

But, “plants are not stupid,” said Arnold Bloom, a distinguished professor in the UC Davis Department of Plant Sciences. For more than three decades, he has studied photorespiration and is convinced: “Plants would not have evolved over billions of years and have kept a wasteful process.”

Bloom has proposed a previously unrecognized biochemical pathway that is part of photorespiration. This pathway – let’s call it the Bloom cycle -- takes nitrogen the plant has absorbed from the soil and converts it into compounds essential for life, such as proteins, DNA and chemicals that deter insects and disease. An article explaining this process was published Jan. 29 in the journal Plant, Cell and Environment.

Value of photorespiration

This presents a new perspective, Bloom said. This cycle reveals a strategy for developing crop plants that are productive, yet are also nutritious and resist pests. 

“To meet those goals, you have to understand the value of photorespiration. Instead, we’ve made assumptions that may be misleading.”

The Bloom cycle coordinates many processes, including storing energy in the form of sugars and organic acids, moving energy around the plant, regenerating chemicals needed for photosynthesis, and creating other compounds plants use to protect themselves.

In addition, the Bloom cycle explains the critical role of the element manganese, which maintains the balance between crop yields on the one hand, and nutritional quality and pest resistance on the other. The link to manganese also explains how plants will respond as temperatures warm and carbon dioxide levels in the air increase.

“We’ve been missing a significant part of what’s going on,” Bloom said.

Read more here: Why Plants Are Not Stupid: Introducing the “Bloom Cycle" (Department of Plant Sciences)