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The strange secrets of seagrasses: How did these underwater plants evolve their bizarre flowers?
Seagrasses are the only flowering plants that grow in marine environments. These underwater plants have about 60 species, each belonging to four families: Posidoniaceae, Zosteraceae, Hydrocharitaceae and Cymodoceaceae, and are classified in the monocotyledonous plant family. Down. Seagrasses originally originated from ground plants and returned to the oceans about 70 to 100 million years ago. Seagrass gets its name from its long, narrow leaves, which look similar to grass.
While growing underwater, seagrasses have evolved a variety of adaptive strategies to survive in the changing marine environment.
Most of these underwater plants are found in shallow coastal waters, and their leaves carry out photosynthesis in underwater photosynthetic zones. It is worth mentioning that seagrasses usually undergo underwater pollination and complete their life cycle in water. Previous studies have assumed that seagrass pollination was driven by currents, but in fact, at least one species, Thalassia testudinum, exhibits a hybrid biotic-abiotic pollination strategy. The plant produces nutrient-rich pollen masses that attract small invertebrates to carry the pollen, which is very different from the way terrestrial plants are pollinated.
The ecological role of seagrass
Dense meadows of seagrasses are considered some of the most productive ecosystems worldwide, serving as important carbon sinks and providing habitat and food for a diverse range of marine life, functions comparable to those of coral reefs. Seagrass habitats not only provide fish habitat, but also support the reproduction and growth of many marine species.
Recent studies show that seagrass is essential for maintaining the stability and diversity of coastal ecosystems, but its survival faces multiple threats.
Seagrass habitats are facing the challenge of global decline as human activities increase. Seagrass species populations are already threatened in North America’s coastal waters, with at least ten species listed as elevated in extinction risk and three labeled endangered. The loss of seagrasses, and the decline in seagrass biodiversity, will have serious impacts on marine biodiversity and the human populations that depend on these resources and ecosystem services.
Evolution
As early as about 140 million years ago, seagrasses evolved from early monocotyledons and underwent a process of adaptation to the ocean. During this process, three independent seagrass systems (Hydrocharitaceae, Cymodoceaceae, and Zosteraceae) evolved from a single monocotyledonous system. Despite the relatively small number of seagrass species, they have managed to establish themselves on the land shelves of all continents except Antarctica.
Genomic studies of seagrasses are revealing how these plants adapted to the marine environment and showing key changes required for the transition from land plants to underwater ecosystems.
Reproductive methods
Seagrasses have a variety of strategies for sexual reproduction, with some short-lived seagrass species producing small seed banks, while long-lived seagrasses have the ability to produce buoyant fruits. These reproductive strategies of seagrasses help them maintain genetic diversity and better adapt to new environments in the face of environmental change and disturbance.
Seagrass microbiome
The interaction between seaweed and microorganisms is very complex. These microorganisms are essential to the growth and health of seagrass, providing it with essential nutrients and defense mechanisms. Seagrass-specific microbial communities can be divided into several types, including microbial communities on the root surface, in the rhizosphere, and within the root system, all of which play important roles in influencing seagrass growth and adaptation.
Conclusion
With global environmental changes and the increase in human activities, the protection of seagrass becomes increasingly important. Understanding the evolutionary history and ecological functions of these underwater plants can help us better protect these precious ecological resources. When we reflect on these beautiful and important underwater plants, what they actually give us is not just a green meadow, but a far-reaching ecosystem. How can we act to protect the future of these ecosystems? ?
