Public Release: 

Respiration rate of sorghum may indicate cold tolerance

Texas A&M AgriLife Communications

CANYON - The respiration rate of sorghum may tell researchers what varieties will be more cold tolerant than others, according to Texas Agricultural Experiment Station and West Texas A&M University researchers.

Because sorghum is a tropical plant originally from Africa, temperatures in the Great Plains are sub-optimal for it during germination, emergence and early seedling growth, said Dr. Bill Payne, Experiment Station crop stress physiology researcher.

Increased seedling cold tolerance has a number of benefits for farmers, includng earlier planting, faster and more uniform emergence and a crop that develops and matures faster, Payne said.

Respiration is a metabolic process essential to plant growth, he said. The specialized organelle in plant cells responsible for respiration is the mitochondria.

Dr. Maria Balota, an Experiment Station research associate at Bushland who works with Payne, is extracting mitochondria from sorghum plants to pinpoint the basic physiologic processes that could lead to improved performance of sorghum plants under cool conditions.

For the past few years, Balota and Payne have grown 50 varieties of sorghum from different regions of the world to test for germination and emergence in a cold environment.

"The next step is to identify cold tolerance mechanisms in sorghum," Balota said. "The breeders can use this information to extend sorghum production into the northern regions of the United States and into other regions of the world."

A mitochondria extraction lab has been set up by Balota and Payne in cooperation with Dr. Bob Stewart, distinguished professor of agriculture and director of West Texas A&M's Dryland Agriculture Institute, and his graduate student, Srinivas Veeragoni, in the plant soil and environmental science department.

"We suspect the membrane of the mitochondria are responsible for the differences among genotypes for cold tolerance," Balota said.

Experiment Station equipment, including a centrifuge, spectophotometer, respiration oxygraph system and incubator, were put together with an oven and refrigerator from West Texas A&M to create a lab equipped for extracting mitochondria and taking respiration measurements.

"Where this really helps both of us is, we can't begin to have all the equipment and expertise that ARS (Agricultural Research Service) and TAES has," Stewart said. "When we partner, there is a whole world of opportunity. And with Srinivas, Maria is getting a young mind to stimulate the work."

Balota said not many labs are set up to concentrate on basic plant physiology research. If the researchers can successfully extract mitochondria, "we can do other work with organelles. It is an essential link between genetics and whole plant or crop physiology."

In the lab, Veeragoni grows seedlings for two days and measures the fresh weight, as well as the rate of respiration, and then dries plants before weighing them. He also allows plants to grow for an additional week for mitochondria extraction and respiration rate measurements.

"Eventually we want to compare respiration of seedlings with that of mitochondria and with the rate of growth," Balota said.

Mitochondria extraction is still in the experimental phase, she said.

Balota and Veeragoni are working with a variety of solutions and buffers that will allow the mitochondria to be centrifuged and separated, but remain alive and intact for respiration monitoring. Once the mitochondria are extracted, Veeragoni will measure the respiration rate.

A long-term goal of Payne and Balota is to determine if fatty acid saturation within the mitochondrial membranes makes the difference between cold-tolerant and intolerant sorghum varieties.

"At that point, we can go to the enzymes and genes that are responsible and hopefully identify molecular markers that can indicate genes for cold tolerance," Balota said. "Then we should be able to rapidly screen many varieties to help breeders' efforts to develop cold-tolerant sorghum."


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