Plant growth is regulated by hormones such as auxins, cytokinins (CKs), and abscisic acid (ABA). The hormones affect the plant, the microbes inside the plant and possibly even the creatures (such as humans) that eat the plant tissue.
Researchers have hypothesized a link between dietary intake of plant hormones and various human illnesses, including diabetes, inflammatory bowel disease, certain types of cancer and depression. The string connecting all the dots is made up of microorganisms. “Plant and human microbiota affect host fitness by mediating nutrient assimilation, stress responses and hormone production,” write Chanclud and Lacombe.
Chemicals, including hormones, in plants are similar to those in mammals. In humans, for example, the neurotransmitter serotonin is synthesized from the essential amino acid tryptophan. In plants, auxin is made from tryptophan and related to serotonin. Auxin levels may have the potential to affect depression. Gibberellic acids are plant hormones produced by microbes. They have an anti-inflammatory properties. In contrast, abscisic acid which is produced during drought conditions triggers inflammation.
Does this mean that a diet of stressed plants is less healthy than a diet of pampered plants? The relationships between plant hormones, plant microbes, human gut microbes and human hormones is complicated and poorly understood. But in the future, maybe your doctor will give a prescription of laid-back lettuce to treat depression or contented carrots to help with diabetes.
Plant Hormones: Key Players in Gut Microbiota and Human Diseases? Emilie Chanclud, Benoît Lacombe. Trends in Plant Science, September 2017, Volume 22, Issue 9, p754–758.
- Janet Wallace