Although thermogenesis, a process by which organisms generate heat internally that occurs in some plants, cannot be directly preserved in the fossil record, scientists can infer its presence in ancient plants by studying similar anatomical structures today. A new study led by the Barcelona Botanical Institute (IBB-CSIC-CMCNB), a joint center of the Higher Council for Scientific Research (CSIC) and the Consorci Museu Ciències Naturals de Barcelona (CMCNB), has examined the characteristics of current thermogenic plants , those that have the ability to produce their own heat from internal metabolic processes, and has compared them to fossil plant lineages. The work, which is published in Nature Plants, has been carried out in collaboration with the Complutense University of Madrid and institutions such as the Geological and Mining Institute of Spain (IGME–CSIC), the Smithsonian Institution, the University of Barcelona and the Botanical Gardens of Sydney.
Thermogenesis is usually associated with animals, but some plants have also developed this ability. This metabolic process allows certain parts of the plant, such as flowers and inflorescences (groups of flowers), to raise their temperature above that of the environment. The heat they generate helps volatilize and disperse floral fragrances and other chemical compounds that attract insects such as beetles, flies and thrips to the plants, facilitating their pollination. Furthermore, thermogenesis stabilizes the development of reproductive organs in cold climates and facilitates the growth of pollen tubes.
“Our findings suggest that thermogenesis in plants is an older phenomenon than previously thought,” explains David Peris, IBB researcher and first author of the study. «200 million years ago, the diversification of angiosperms, flowering plants, had not yet occurred. “Therefore, thermogenesis could have been a crucial factor in the evolutionary success of seed plants in general, and flowering plants in particular, and also in that of their pollinators.”
Evolutionary implications
In thermogenic plants, female structures mature before male structures to avoid self-fertilization. This characteristic is identified in the most primitive current groups of angiosperms, where the stamens and carpels (the male and female reproductive parts respectively) were closed separately in small chambers. Furthermore, the fact that some fossil plants had reproductive chambers that could have trapped pollinating insects suggests that this feature already existed in plants before the appearance of flowers.
Large reproductive structures, such as perianths or cones, could also indicate thermogenesis, as they retain heat better. This study has allowed scientists to identify which fossil plant lineages could have had thermogenic activity, suggesting that thermogenesis has been present in seed plants for longer than previously thought.
According to the research, the ability to generate heat may have given certain Mesozoic plants, more than 200 million years ago, a competitive advantage over non-thermogenic plants by attracting pollinating insects more efficiently, thus contributing to their reproductive success. This pollinator attraction strategy could have preceded others, such as the striking colors of flowers, and been influenced by past climate changes. Furthermore, thermogenesis is closely linked to the emission of fragrances, another crucial factor in insect attraction.
This study opens new avenues to explore how these interactions influenced the diversification of plants and their pollinators throughout evolutionary history. «Thermogenesis in plants is not only a botanical curiosity,» says Iván Pérez-Lorenzo, IBB researcher and also a participant in the study, «but it is an important factor that has contributed to the success of the two most important groups of organisms. diverse today: insects and angiosperms, and has key implications for understanding the evolution of pollination strategies.
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