As high temperatures become more common in citrus-growing regions, researchers are searching for ways to help trees better tolerate heat. A new study suggests that two naturally occurring plant hormones — abscisic acid (ABA) and brassinosteroids (BR) — may strengthen citrus trees’ defenses against heat stress.
The research was published in the journal Horticulturae by Longfei Jin, Yueting Sun, Yanmei Wu, Feng Liu and Peng Wang with the Institute of Citrus Research, Zhejiang Academy of Agricultural Sciences in Taizhou, China; and Penghui Wang with Yangtze University in Jingzhou, China.
Researchers sprayed young citrus trees with either ABA or BR before exposing them to temperatures of 107.6 degrees Fahrenheit. Compared to untreated plants, the hormone-treated trees accumulated more soluble sugars and proline, compounds that help protect plant cells during stress. They also showed higher activity of antioxidant enzymes that reduce damage caused by heat. In addition, the treatments increased activity in several heat shock protein genes, which help plants protect proteins and recover from stressful conditions.
The research team also examined thousands of genes to better understand how citrus responds at the molecular level. They found that ABA and BR activated pathways involved in plant hormones, stress signaling and cellular protection, providing new insight into the biological processes that help citrus tolerate extreme heat.
For citrus growers, the study highlights the growing potential of plant growth regulators as tools for improving heat tolerance. While the results are encouraging, they were obtained using young trees under controlled environmental conditions rather than mature trees in commercial groves. The researchers note that additional studies are needed to determine whether these hormone treatments improve tree survival, photosynthesis, recovery, growth and yield under real-world field conditions before they can be recommended for commercial use.
See the full article, Physiological and Transcriptomic Response of Exogenous Abscisic Acid and Brassinosteroid on Citrus Under Heat Stress.
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