Text and photo by Francisco Javier Jiménez López
When we talk about global change, we usually think about rising temperatures, but other less obvious environmental factors are also changing, such as ultraviolet (UV) radiation. In recent decades, Spain and the Mediterranean region have recorded a sustained increase in this type of radiation, associated with changes in the atmosphere, such as variations in aerosols and cloud cover. This increase can have significant effects on plants, especially during reproduction, a key stage for the survival of species.
Flowers not only serve to attract pollinators, but they also protect highly sensitive structures, such as pollen and ovules, from adverse environmental conditions. Many plants possess pigments and floral patterns that absorb UV radiation, invisible to the human eye but perceptible to insects. These traits can act as a protective barrier against excessive radiation and, at the same time, influence the relationship between plants and pollinators.
To better understand how plants respond to increased UV radiation, an experiment was conducted with two common annual species in Mediterranean environments, Lysimachia arvensis and L. loeflingii. The study included nearly 900 plants from various natural populations, which were exposed to different levels of UV radiation under controlled conditions. Throughout the experiment, changes in plant growth, flower size and shape, fruit and seed production, and the presence of protective pigments in leaves and flowers were analyzed.
The results show a clear pattern: when UV radiation increases, plants grow less and produce less biomass. Furthermore, they tend to flower earlier, especially L. loeflingii, which could be interpreted as a strategy to complete their life cycle quickly in a more stressful environment. The flowers are also affected, becoming smaller and producing fewer fruits and seeds. This is compounded by a reduction in pollinator visits, suggesting that UV-induced changes do not enhance flower attractiveness but may actually hinder plant-pollinator interactions.
In response to these negative effects, plants activate defense mechanisms, such as increasing the production of pigments capable of absorbing UV radiation. These compounds help protect the most sensitive reproductive tissues, but, at least in these species and under the experimental conditions, they do not fully compensate for the loss of growth and reproductive success.
This work was made possible by a grant for postdoctoral researchers funded by the Global Change Research Institute (IICG) at Rey Juan Carlos University, which has allowed us to advance our understanding of how Mediterranean plants may respond to current and future environmental changes. Understanding these processes is fundamental to anticipating how global change could affect biodiversity and ecosystem functioning in the coming years.