How Leaves Change Angle Due to Hormone Changes in Flooded Tomato Plants

Jim Crocker
5th February, 2024

How Leaves Change Angle Due to Hormone Changes in Flooded Tomato Plants

Image Source: Natural Science News, 2024

Have you ever wondered what happens to plants when their roots are drowning in water? It's a stressful situation for them, much like how you would feel if you were stuck in a room filling up with water. With their roots submerged, plants can't breathe properly—yes, roots need to breathe too! This is known as waterlogging, and as you can imagine, it causes all sorts of trouble below the ground. But it's not just the roots that feel the effects; the whole plant goes into a sort of crisis mode, including the leaves above ground. For instance, when tomato plants are waterlogged, their leaves start to curl downwards—a bit like when people hunch their shoulders in distress. This phenomenon is called leaf epinasty. Now, scientists have been aware for a while that this leaf curling is related to chemicals in the plant called hormones, which are sort of like the plant’s messengers, sending signals to help it adjust to the stress. It's been traditionally believed that this curling was orchestrated by two main hormones, ethylene and auxins. But there's a catch—plants have more messengers than just these two, and they could be passing around crucial information during a flood crisis too! Researchers decided to listen in on the chemical chatter of tomato plants by doing some impressive detective work. They employed a method called hormonomics—that’s a fancy way of saying they closely analyzed the full spectrum of hormones to see what's going on when the plants' 'feet' get wet. In this recent study, they took a close look at different parts of the tomato plant every so often within a 48-hour period of the roots being waterlogged. And guess what? They found out that plants are more like us than we might think. Just as our bodies would react differently based on our age when under stress, so do the hormones in tomato plants. Young and old leaves apparently have their unique ways of dealing with soggy situations, and it turns out there's a whole cast of hormonal characters involved, not just the leading duo of ethylene and auxins. The researchers discovered that right off the bat, within the first 12 hours of being waterlogged, there's a hormone called abscisic acid (ABA for short) that peaks in the stems that connect leaves to the rest of the plant. It's like an emergency flare, signaling that there's trouble afoot—or, should we say, 'aroot'. Interestingly, the substances that usually lead to the production of ABA don’t increase until much later, which suggests that ABA is rushing in from elsewhere in the plant. Meanwhile, another set of hormones known as cytokinins took a nosedive. Their levels dropped drastically when waterlogging occurred, and this happened in all leaves, regardless of age. This freefall likely signals to the plant that it's time to let auxins and ethylene do their thing and cause the leaves to bend in response to the stress. Another interesting discovery was that while ABA showed up early to the crisis scene, auxins (the hormone previously known for their leading role in leaf bending) took their sweet time. They didn't rise significantly in the stems until 48 hours had passed since the roots got flooded. It’s like they decided to wait until they were sure the plant needed to hunker down for a longer haul. The scientists suggest from their hormone profiling that perhaps ethylene and ABA play a buddy-cop role in the early stages following waterlogging to start the process of leaf bending. Down the line, it seems to be a delicate balancing act between auxins and cytokinins that adjusts the growth in the leaf stems—think of it like a tug-of-war where both sides need to be in balance for the proper response. In essence, it's like the tomato plants are coordinating their response to waterlogging through a complex web of hormonal signals, revealing a much more dynamic and intricate hormonal symphony than was previously understood. While it might sound a bit like a Plant Soap Opera, "As the Stem Bends," the knowledge gained from this study could have practical applications. By understanding how tomato plants—and possibly other crops—respond to the stress of waterlogging, we can help farmers and gardeners predict, and perhaps even manage, the survival and yield of their plants better when the weather decides to go all aquatic on them. So, the next time you see a plant in a puddle, know that inside, there's a dramatic hormonal tale unfolding!

BiochemPlant ScienceAgriculture


Main Study

1) Leaf ontogeny modulates epinasty through shifts in hormone dynamics during waterlogging in tomato.

Published 2nd February, 2024

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