Texas team takes the stress out of rice production


Researchers used time-lapse photography to monitor rice plant growth and development in response to transplanting density and root pruning.
DR. ABDUL RAZACK MOHAMMED, TEXAS A&M AGRILIFE RESEARCH AND EXTENSION CENTER

Researchers in Texas have found new ways to treat stress in rice plants that could significantly increase yields.

Rice plants face stress from a variety of factors from high temperatures to replanting.

"We tend to view these environmental stresses as necessary evils – especially temperature stresses – as if there is little we can do to counter the effect," says Texas A&M plant physiologist Dr. Lee Tarpley.

"We're finding that we can use specific knowledge of how the stress affects the plant to design prevention measures."

Tarpley and Dr. Abdul Razack Mohammed have studied not only the effect of heat but cold, submergence, salinity, wind and drought on rice crops.

One of the specific impacts, they discovered, is high nighttime temperatures.

"High night temperatures do two things to rice plants," Tarpley said. "The rice plant increases its production of a plant stress hormone, and an oxidative-stress response occurs, which injures the plant. Both of these ultimately lead to losses in yield and quality."

Because they were able to track the nighttime heat stress to those two factors, he added, they were able to determine potential management strategies.

"We can spray the crop with a chemical that prevents the stress hormone activity, so that the plant never senses that it is supposed to be in stress," Tarpley said. "Or we can spray the plants with a sort of vaccination, which is like a small dose of 'oxidative stress.' That triggers the plant to build its capacity to be acclimated to future stresses."

Tarpley and Mohammed have also been studying transplanting shock, a condition that affects farms mostly in Asian countries where rice is started in a nursery then transported to a field for planting.

"Transplanting shock can decrease growth and development," Tarpley said. "And one thing we noticed is that a lot of root pruning occurs during the transplanting process. That reduces the production of tillers, which are important since that is where the rice grains develop."

They found that root pruning reduces the photosynthetic rate by reducing the amount of chlorophyll available, which is linked to the production of ethylene, a natural plant hormone that causes fruit to ripen.

The researchers decided to treat some plants with 1-methylcyclopropene, or 1-MCP, a compound that is used to keep plants and produce fresh by blocking ethylene perception in plants.

The idea was to see if 1-MCP would make the rice plants unaware that the roots were pruned, thus slowing the effect of ethylene and maintaining a healthy level of chlorophyll, Tarpley.

"The application of 1-MCP prevented transplanting shock in rice," he said. "The treated plants had more tillers per plant, more root length and greater chlorophyll concentration and net photosynthetic rate."

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