Amazing stuff!
"Watching grass grow gets a bad name—studying how grass grows is anything but boring. Grasses include many of our most critical food sources including wheat, rice, and corn. And until recently, nobody was quite sure what factors caused these plants to grow tall.
In a new study, a team of researchers revealed that temperature, not light, determines when grass stems harden, allowing for vertical growth.
To monitor growth, the scientists merged a gene important for the development of the secondary cell wall—the structure that causes grass stems to become rigid—with the gene that makes fireflies glow.
Then, they exposed the plant to a variety of light and temperature conditions and watched how they responded with a time-lapse camera. ...
Neither daylight nor any sort of internal clock had an impact on grass growth. But when the biologists varied the temperature, their grasses responded. In cooler conditions, plants started slowly before rapidly growing; in the heat, grass growth initially spiked but soon dropped to a slower pace.
In addition, pulses of warmth in cool temperatures prompted the greatest growth rates, while cold blasts in the heat ground growth to nearly a halt.
What the study might mean for crop growth, including in the context of climate change, remains unknown. Nevertheless, the findings present new insights into the unexpectedly fascinating process of how grass grows. ..."
From the highlights and abstract:
"Highlights
• Thermocycles, not light or the circadian clock, drive CESA8 rhythms
• CESA8 expression increases during cool nights and declines during warm days
• Secondary-wall gene expression is coordinated with stem elongation
• Warm and cold pulses trigger opposing responses, explained by an incoherent feedforward loop model
Summary
Secondary cell wall thickening is essential for plant structural development, providing the mechanical strength and rigidity required for upright growth. However, direct observation of this process in its endogenous developmental context within living plants has remained limited.
Cellulose, the predominant component of secondary walls and the most abundant biopolymer on Earth, is synthesized at the plasma membrane by complexes containing CELLULOSE SYNTHASE A (CESA) proteins.
Despite its central role, the precise timing and regulation of cellulose deposition during plant development remain unclear.
To address this gap, we developed a real-time bioluminescence imaging system in the model grass Brachypodium distachyon using a luciferase transcriptional reporter driven by the CESA8 cis-regulatory region.
Bioluminescence imaging revealed a consistent spatial pattern of CESA8 expression within elongating internodes, coinciding with regions undergoing secondary wall deposition and progressive increases in cellulose crystallinity. Time-lapse imaging showed that expression follows a robust daily rhythm driven by temperature cycles, independent of light or endogenous circadian signals. Temperature-pulse experiments uncovered rapid, transient inverse responses that were accurately predicted by a mathematical model based on an incoherent feedforward loop.
CESA8 expression correlated strongly with stem elongation, linking structural reinforcement with temperature-driven shoot growth in grasses."
ScienceAdviser
Graphical abstract
