Exposing plants to certain chemicals while they are still seeds to "prime" them can affect their later growth. Researchers found that treating seeds with ethylene gas improved their growth and stress resistance. The discovery involves enhancing photosynthesis and carbohydrate production in plants, offering a potential breakthrough to increase crop yields and protect against environmental stresses.
Just like other living things, plants can be stressed. Typically, conditions such as heat and drought cause this stress, and when they are stressed, plants may not grow as large or produce as much. This is a problem for farmers, so many scientists are trying to genetically modify plants to make them more resistant to stress.
However, plants engineered to increase crop yields tend to be less stress tolerant because they spend more of their energy growing rather than resisting stress. Likewise, increasing a plant's ability to survive stress often results in lower plant yields because they spend more of their energy protecting rather than growing. This conundrum makes it difficult to increase crop yields.
I have been studying how the plant hormone ethylene regulates plant growth and stress responses. In a study published in July 2023, my laboratory discovered an unexpected and exciting phenomenon. We found that when seeds germinate in the dark (usually underground), adding ethylene improves seed growth and stress resistance.
Plants cannot move and therefore cannot avoid stressful environmental conditions such as heat and drought. They receive various signals from their environment, such as light and temperature, which determine how they grow, develop and respond to stressful conditions. As part of this regulation, plants make various hormones that are part of the regulatory network that allows them to adapt to environmental conditions.
Ethylene was first discovered as a gaseous plant hormone more than 100 years ago. Research since then has shown that all land plants studied produce ethylene. In addition to controlling growth and coping with stress, ethylene is involved in other processes, such as causing leaves to change color in autumn and promoting fruit ripening.
My lab studies how plants and bacteria sense ethylene and how ethylene interacts with other hormonal pathways to regulate plant growth and development. While conducting this study, my research team made an unexpected discovery.
We have been conducting an experiment where we germinate seeds in a dark room. Seed germination is a critical period in a plant's life when, under favorable conditions, the seed transforms from a dormant state into a seedling.
In this experiment, we exposed seeds to ethylene gas for several days to see what effects it had. Then we remove the ethylene. Usually, the experiment ends there. However, after collecting data on these seedlings, we transferred them to a light cart. This is not something we would normally do, but we wanted to get these plants to adulthood so we could get seeds for future experiments.
After exposing the seedlings to light for several days, some lab members discovered something surprising and unexpected: The plants that were briefly exposed to ethylene gas were much larger. They have larger leaves and longer, more complex root systems than plants not exposed to ethylene. These plants grow at a faster rate throughout their life cycle.
My colleagues and I wanted to know whether exposure to ethylene during seed germination stimulates the growth of different plant species. We found the answer is yes. We tested the effect of short-term ethylene treatment on tomato, cucumber, wheat and arugula seed germination - all seeds grew.
But what makes us unusual and exciting is that brief ethylene treatment also enhances tolerance to various stresses such as salt stress, high temperature and low oxygen.
The long-term effects of brief stimulation on growth and stress resistance are often referred to as primer effects. You can think of this like priming a pump, the priming process helps make the pump easier and faster to prime. Studies have examined growth of plants after priming at different ages and stages of development. But priming seeds with various chemicals and pressures is probably the most studied because it's easy to implement and, if the experiment is successful, farmers can use it.
Since that first experiment, my experimental group has been trying to figure out what mechanisms allow these plants exposed to ethylene to grow larger and withstand more stress. We found several possible explanations.
One is that ethylene inducement increases photosynthesis, the process by which plants use light to make sugar. Part of photosynthesis involves what's called carbon fixation, where plants absorb carbon dioxide from the atmosphere and use the carbon dioxide molecules as building blocks to make sugar.
During photosynthesis and carbon fixation, plants absorb sunlight and convert it into sugars, which they use for growth. The experimental team found that the amount of carbon fixed by plants increased significantly, which means that plants absorbed more CO₂ from the atmosphere.
Associated with the increase in photosynthesis is a substantial increase in the carbohydrate content of the entire plant. This includes massive increases in starch, the plant's energy storage molecule, and sucrose and glucose, two sugars that provide plants with quick energy.
Increases in these molecules in plants are associated with faster plant growth and better ability to withstand stress.
Research shows that environmental conditions during germination can have profound and long-lasting effects on plants, increasing both their size and stress resistance. Understanding this mechanism is more important than ever to help increase crop yields and feed the world's population.
By Brad Binder, professor of biochemistry and cell and molecular biology at the University of Tennessee Adapted from an article originally published in The Conversation.
Compiled source: ScitechDaily