Ecological impact on the photochemical apparatus is alleviated by increased cyclic electron flow around photosystem in restinga plants following Brazil's largest environmental disaster

Title : Ecological impact on the photochemical apparatus is alleviated by increased cyclic electron flow around photosystem in restinga plants following Brazil's largest environmental disaster

Abstract:

The collapse of the Fundão dam, the biggest environmental disaster in the mineral sector worldwide, released millions of cubic meters of iron ore waste into the environment, causing chronic environmental impacts on several ecosystems. In this study, herbaceous plants from the coastal Restinga ecosystem (Canavalia rosea, Ipomoea imperati and Ipomoea pes caprae) were monitored in situ for three years (january 2021 to march 2023) to reveal the photoprotective functions of cyclic electron flow (CEF) in these species. CEF in photosystem I (PSI) can protect and maintain the stability of electron transport chain (ETC) and photosystem II (PSII), but its physiological mechanism under in situ conditions is poorly understood. Therefore, the main objective of this study was to identify a photochemical pattern capable of reflecting the contamination dynamics present in the ecosystem, using chlorophyll fluorescence emission as a tool to determine biophysical parameters related to plant vitality. The results indicate that during periods of greater precipitation there is a tendency for metals to bioaccumulate in the leaves, correlated with restrictions in the photosynthetic electron transport between PSII and PSI, observed by increased fluorescence intensity in OJIP curves, especially in the H band, which reflects the redox conditions of the plastoquinone (PQ) pool. The increase in variable fluorescence at point I and the quinone turnover number also indicate higher redox activity of PQ. Thus, the alteration in electron transport flow revealed an adequate partition of electron flows on the acceptor side of PSI, alleviating the damage caused by reactive oxygen species (ROS) through the Mehler reaction, diverting electrons from PSI directly to ROS (superoxide anion) prodution, forming less reactive ROS (hydrogen peroxide), which can then be are quickly neutralized by antioxidants in the chloroplasts. In conclusion, CEF alleviated the excitation pressure on the ETC in the leaves of Restinga plants, increasing heat dissipation in PSII, reducing oxidative stress, and maintaining PQ stability to accommodate the photosynthetic electron flow. Additionally, the impact assessment method used in this study can be applied to determine the contamination effects of tailings in other Restinga areas, based on OJIP transients and JIP test, significantly reducing the cost, labor, and time required for laboratory analysis.

Audience Take Away Notes:

• Environmental Consequences: Understanding the impact of Brazil's largest environmental disaster on local ecosystems, specifically focusing on restinga plants
• Photocellular Processes: Explanation of the role of the photochemical apparatus in plants and how it is affected by environmental stressors
• Cyclic Electron Flow: Exploring the concept of cyclic electron flow around Photosystem I and its significance in plant physiology
• Alleviation of Ecological Impact: Discussing how restinga plants exhibit a mitigation of ecological damage through increased cyclic electron flow post-disaster
• Implications for Conservation: Examining the broader implications for environmental conservation efforts, particularly in response to large-scale environmental crises

Biography:

Diolina Moura Silva completed her doctorate in Plant Physiology at the Federal University of Vicosa (UFV) in 1998. She is currently a Full Professor at the Federal University of Espírito Santo. She is also professor-advisor of the Graduate Program in Plant Biology and the Graduate Program in Biotechnology at the Federal University of Espírito Santo. She was the Coordinator of the Graduate Program in Plant Biology from its creation in 2003 until 2007. She works in the area of Plant Physiology and Biotechnology. She is the coordinator of the Photosynthesis Research Center, developing projects focused on the Photosynthesis of cultivated plants and particularly on the ecophysiology of fruit trees. In the context of her scientific and technological production, transient fluorescence of chlorophyll a, Photochemical efficiency, Photosynthesis.