Light and temperature collaborate to boost plant growth

For centuries, scientists have noticed that plants lengthen and bend to secure access to sunlight. However, the precise mechanisms behind this phenomenon are not yet clearly understood. 

Now, a research team led by the Salk Institute for Biological Research in San Diego, California has discovered that two plant factors – the protein PIF7 and the growth hormone auxin – are the main triggers which accelerate growth when plants are shaded by canopy and exposed to warm temperatures simultaneously. These findings may help scientists predict how plants will respond to climate change, and possibly increase crop productivity despite the detrimental effects of global warming.

“Right now, we grow crops in certain densities, but our findings indicate that we will need to lower these densities to optimize growth as our climate changes,” said study senior author Joanne Chory, an expert in Plant Molecular and Cellular Biology at the Salk Institute. “Understanding the molecular basis of how plants respond to light and temperature will allow us to fine-tune crop density in a specific way that leads to the best yields.”

During sprouting, seedlings quickly elongate their stems to break through the soil and get access to sunlight as soon as possible. While the stem usually slows down its growth after being exposed to sunlight, it can lengthen rapidly again if the plant is competing with surrounding plants for light, or in response to warming temperature in order to increase the distance between the leaves and the hot ground. Although both canopy shade and warm temperatures induce stem growth, they reduce yield.

By using the model plant Arabidopsis thaliana, tomato plants, and a close relative to tobacco, the researchers investigated the factors leading to plant growth under canopy shade and in warm temperatures – a condition mimicking high crop density during climate change. They found that across all three species, the plants grew taller when trying to avoid the canopy shade created by neighboring plants, while being exposed to high temperatures.

Molecular analyses revealed that the transcription factor PIF7 – a protein playing a fundamental role in activating and deactivating certain genes – was the dominant factor driving the increased growth. Moreover, when crops detected neighboring plants, the growth hormone auxin also increased, fostering rapid growth in response to simultaneous warmer temperatures. Thus, the synergistic PIF7-auxin pathway is what allows plants to respond to environmental stressors and adapt to search for the best growing conditions.

“Global temperatures are increasing, so we need food crops that can thrive in these new conditions. We’ve identified key factors that regulate plant growth during warm temperatures, which will help us to develop better-performing crops to feed future generations,” Professor Chory concluded.

The study is published in the journal Nature Communications.

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By Andrei Ionescu, Earth.com Staff Writer