A groundbreaking study conducted by researchers at the University of Bristol has led to a significant shift in our understanding of the origins of plant branching. By investigating the mechanisms responsible for this process, the scientists have uncovered insights into the appearance of Earth’s first land plants millions of years ago.
The research, which focused on vascular plants, has identified a common mechanism for branching despite the fact that these plants exhibit fundamentally different growth patterns.
“Diverse shapes abound in the dominant flowering plant group, and gardeners will be familiar with ‘pinching out’ plants’ shoot tips to stimulate side branch growth, leading to a bushier overall form. However, unlike flowering plants, other vascular plants branch by splitting the shoot apex into two during growth, a process known as ‘dichotomy,'” said Dr. Jill Harrison from Bristol’s School of Biological Sciences.
The team examined lycophytes, an ancient vascular plant lineage that formed coal seams during the Carboniferous era, as they preserve the ancestral pattern of dichotomous branching. Through a series of surgical experiments on a lycophyte specimen, the researchers discovered that dichotomy is regulated by short-range auxin transport and coordinated in different parts of the plant by long-range auxin transport.
These findings, published in the journal Development, reveal that both flowering and lycophyte branching are regulated by auxin transport. This suggests that similar mechanisms were present in the earliest vascular plants around 420 million years ago.
By combining this new knowledge with discoveries made in the non-vascular, non-branching moss group, the researchers were able to infer the appearance of the first land plants about 480 million years ago.
In a previous study, Dr. Harrison’s lab disrupted auxin transport in a moss, causing it to branch in a manner akin to the earliest branching fossils. The combination of these studies implies that the earliest land plants were branched and that branching was lost during the evolution of non-vascular mosses.
Dr. Harrison emphasized the importance of this discovery: “The greening of the land by plants paved the way for all terrestrial life to evolve as it provided food for animals and oxygen to breathe, and branching was a key innovation in the radiation of land plants. Our work implies that branching evolved earlier than thought, which is an important evolutionary conclusion.”
Moreover, the revelation that distantly related plants use the same genetic mechanisms to regulate branching offers significant potential for future applications. “The fact that we have shown that plants that are so distantly related use the same genetic mechanisms to regulate branching brings great potential to transfer knowledge in engineering plant shape to improve future productivity and yield,” said Dr. Harrison.
Plants play a critical role in maintaining Earth’s ecosystems and are essential for the survival of countless organisms, including humans. Here are some of the reasons why plants are so important to the Earth’s ecosystems, and why determining exactly how plants evolved is vital to science as we strive to protect them during this period of climate change.
In summary, plants are indispensable for maintaining the balance and functioning of Earth’s ecosystems. They provide oxygen, food, shelter, and countless other benefits that are essential for the survival of organisms and the health of the planet.
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