Journal of Energy Bioscience 2025, Vol.16, No.2, 64-74 http://bioscipublisher.com/index.php/jeb 65 stress. They are like signal "couriers" and play a role in many physiological activities (Fan, 2014; Zhang et al., 2021; Ma et al., 2021b). The amount of ROS needs to be balanced. Too many can harm cells, such as destroying fats, proteins, and DNA, but if the amount is right, they are important for the normal functioning of cells, such as helping growth, development, and resisting pathogens (Luo et al., 2021; Ma et al., 2021a; Sahoo et al., 2021). 2.1 Types of ROS relevant to potato physiology The common types of ROS in potatoes are mainly superoxide anions (O2 -) and hydrogen peroxide (H2O2). Superoxide anions are mostly generated during electron transfer in mitochondria and chloroplasts during photosynthesis or respiration. It is not very stable and is quickly converted into hydrogen peroxide by an enzyme called superoxide dismutase (SOD) (Fan, 2014; Koubaa et al., 2021). Hydrogen peroxide is more stable than superoxide anions. It can also pass through cell membranes and regulate plant development and response to stress like a signal (Ma et al., 2021b; Sahoo et al., 2021). There is also a type of ROS called hydroxyl radical (•OH), which is generated from hydrogen peroxide through a process called Fenton reaction. This molecule is particularly reactive and can cause great damage to cells. But cells control its production very strictly to prevent it from causing serious damage (Hua et al., 2020; Ma et al., 2021a). 2.2 Cellular sources of ROS in potatoes In potato cells, ROS mainly come from three places: chloroplasts, mitochondria and plasma membrane. Chloroplasts are where plants carry out photosynthesis, and in this process, electrons accidentally run to oxygen to form superoxide anions (Fan, 2014; Koubaa et al., 2021). Mitochondria are also a source of ROS, especially when they are under stress and the respiratory chain is affected, ROS are more likely to appear (Huang et al., 2016). There is also the plasma membrane, where NADPH oxidase can directly generate superoxide anions. These enzymes are important for plants because the ROS they produce can be used as signals to activate a series of defense responses (Luo et al., 2021; Ma et al., 2021b). 2.3 Dual role of ROS: essential signaling molecules vs. oxidative stress agents ROS has two different roles in potatoes. On the one hand, it is an essential signaling molecule that can regulate many important processes, such as plant growth, development, and response to various stresses. It can also affect the expression of some genes, allowing plants to better fight pathogens (Ma et al., 2021a; Zhang et al., 2021; Otulak-Kozieł et al., 2022). On the other hand, if too much ROS accumulates, it will cause oxidative stress, damage various cell structures, and make cells malfunction. If the plant's antioxidant system is not strong, for example, the enzymes that remove ROS (such as catalase and peroxidase) are not active enough, then the cells are easily damaged or even die (Hua et al., 2020; Koubaa et al., 2021; Sahoo et al., 2021) (Figure 1). 3 ROS Production in Potatoes Under Stress 3.1 Abiotic stress 3.1.1 Drought-induced ROS production and effects on photosynthesis in potatoes When potatoes encounter drought, more reactive oxygen species (ROS) are produced in their bodies. Most of these ROS are produced in chloroplasts during photosynthesis. Once ROS increases, it may interfere with photosynthesis, reduce efficiency, and may also damage cells (You and Chan, 2015; Miller et al., 2021). However, the accumulation of ROS under drought also has benefits. It can serve as a signal to initiate some responses to stress and help potatoes adapt to the environment. But if there are too many ROS and they are not removed in time, it is easy to cause cell damage (Czarnocka and Karpiński, 2018; Panda et al., 2024). In order to reduce the damage caused by ROS, potatoes will activate some protective mechanisms. These include enzymes such as superoxide dismutase (SOD) and catalase (CAT), as well as some non-enzymatic antioxidants (ascorbic acid and glutathione), which work together to remove excess ROS and protect cells from damage (Das and Roychoudhury, 2014; Hasanuzzaman et al., 2020). Whether the generation and removal of ROS can be balanced is important for cell health and plant drought resistance (Mahalingam and Fedoroff, 2003; Jajić et al., 2015).
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