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The intriguing balance of photosynthesis: How do plants adjust light to stay healthy?
In the biological world, photosynthesis is not only a basic survival requirement for plants, but also a key process in maintaining the ecological balance of the earth. However, too much light can actually be harmful to some plants. How vegetation protects itself from excessive light has become a hot topic of scientific discussion.
Plants and other photosynthetic organisms have developed a range of photoprotection mechanisms to combat molecular damage caused by sunlight.
In organisms that perform oxygenic photosynthesis, excessive light exposure can lead to photoinhibition, a reaction that does not necessarily involve chemical damage. When photosynthetic antenna pigments such as carotenoids become excited by light absorption, non-productive reactions may occur, leading to the generation of reactive oxygen species, which are particularly dangerous during the generation of O2.
Because factors such as high light intensity, variable light environments, and malnutrition can exacerbate this threat, photosynthetic organisms have developed a variety of mechanisms to mitigate these potential threats. In eukaryotic photosynthetic organisms, these mechanisms include non-photochemical quenching mechanisms such as the xanthophyll cycle, changes in structural arrangement, and the use of antioxidant molecules.
Although plants need light to grow, too much light can cause physiological damage to them. Therefore, plants need to maintain a balance of light to ensure their optimal growth.
When plants are exposed to high light intensities, they activate their photoprotection mechanisms, such as adjusting the arrangement of their leaves to reduce direct exposure to light. In addition, plants produce essential enzymes to assist in photoprotection, such as anthocyanin-synthesizing enzymes. In this regard, plants lacking photoprotective enzymes are more susceptible to light damage than plants with functional photoprotective enzymes.
In addition to basic photoprotective enzymes, plants also produce a variety of secondary metabolites that aid in their survival. These substances not only provide photoprotection for plants, but also play an important role in certain human sunscreen products and medicines. Plants use pigments and compounds as a form of UV photoprotection. For example, green moss in Antarctica is naturally shaded by rocks or other physical obstacles, while red moss is common in areas that receive direct sunlight, a color change that reflects the difference in light intensity.
In-depth research on this phenomenon has attracted the attention of scientists. An experiment conducted by Shuiman et al. analyzed the photoprotective properties of ultraviolet absorbing compounds (UVACs) and their red pigments in Antarctic mosses. The results showed that higher concentrations of UVACs and red pigments in the cell walls compared with those inside the moss can effectively improve the survival ability of moss in high-intensity light environments.
Plants upregulate production of UVAC and red pigments under high light intensity, a process thought to be part of long-term photoprotection.
As global temperatures continue to rise, many plants are becoming more sensitive to damage from light. Water shortage, soil nutrient richness and changes in ambient temperature can affect the plant's photoprotection mechanism.
Photoprotection may become an absolute priority in the field of plant biology in the future. Humans have also developed effective photoprotection mechanisms during the process of evolution to defend against damage caused by ultraviolet rays. For example, melanin inside the skin plays an important role in protecting the skin from light damage. This internal conversion photoprotection mechanism effectively reduces direct and indirect DNA damage.
As digital technology and human health become increasingly intertwined, plant photoprotection mechanisms can help us understand how organisms cope with changing environmental challenges and resource constraints. As science advances, can we gain new inspiration from the survival wisdom of plants to improve our own light protection strategies?
