What did the first plants on Earth look like?

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.

1. Oxygen production: Through the process of photosynthesis, plants convert sunlight, carbon dioxide, and water into oxygen and glucose. The oxygen they release is vital for the survival of aerobic organisms, including humans and other animals.
2. Carbon sequestration: Plants absorb carbon dioxide from the atmosphere, using it for photosynthesis and storing it in their tissues. This process, known as carbon sequestration, helps to mitigate the effects of climate change by reducing the amount of carbon dioxide in the atmosphere.
3. Food source: Plants form the basis of the food chain, providing energy and nutrients for herbivores, which in turn are consumed by carnivores and omnivores. Without plants, the entire food chain would collapse, causing a massive loss of biodiversity and ecological imbalance.
4. Habitat provision: Plants create habitats for various organisms, including insects, birds, and mammals. These habitats offer shelter, protection from predators, and breeding grounds for countless species.
5. Soil formation and preservation: Plant roots help to bind and stabilize the soil, reducing erosion and promoting the formation of new soil. Decomposing plant material also contributes to the formation of nutrient-rich humus, which is essential for the growth of other plants and the overall health of the ecosystem.
6. Nutrient cycling: Plants play a crucial role in nutrient cycling, taking up nutrients from the soil and incorporating them into their tissues. When plants die and decompose, these nutrients are released back into the soil, making them available for use by other organisms.
7. Water cycle regulation: Plants help regulate the water cycle by absorbing water from the soil and releasing it into the atmosphere through transpiration. This process contributes to the formation of clouds and precipitation, ensuring a continuous supply of water for the ecosystem.
8. Climate regulation: Plants influence local and global climate through the processes of evapotranspiration, carbon sequestration, and albedo (the reflection of solar radiation). By affecting temperature, humidity, and other climatic factors, plants play a crucial role in maintaining the balance of the Earth’s ecosystems.
9. Medicinal resources: Many plants have medicinal properties and are used to treat various health conditions. They are an essential source of pharmaceutical compounds and play a significant role in the development of new medicines.
10. Aesthetic and cultural value: Plants contribute to the aesthetic beauty of our environment and have significant cultural value in many societies. They have inspired art, literature, and countless human traditions and beliefs throughout history.

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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