Journal of Energy Bioscience 2025, Vol.16, No.2, 64-74 http://bioscipublisher.com/index.php/jeb 69 regulate the response of cells around the stomata while maintaining a balance in ROS levels (Postiglione and Muday, 2020; Li et al., 2022). SA and JA have opposite effects on ROS. SA enhances the signal of ROS, while JA inhibits it. They have a bit of "opposite" effects on each other. It is this balance that allows plants to respond appropriately to different stresses (Lukan and Coll, 2022; Myers et al., 2022). 4.3 Cross-talk between ROS and other signaling pathways in potato stress responses When facing stress, ROS is not only a signaling molecule, it also interacts with other signaling pathways in the potato body to jointly regulate the plant's response. It affects a signaling pathway called TOR. TOR was originally a key system for regulating cell growth and autophagy, but when there is stress, ROS will participate in regulating this pathway to help potatoes improve their disease resistance, such as fighting late blight (Luo et al., 2021). ROS also often works in conjunction with calcium signals. These two signaling systems form a network that together transmit "stress information" in the environment to different parts of the plant. Certain key proteins can connect ROS and calcium signals, allowing plants to quickly sense stress and respond (Ravi et al., 2023). This "cooperative combat" approach is an important guarantee for potatoes to adapt to external changes. 5 Antioxidant Defense Mechanisms in Potatoes 5.1 Enzymatic antioxidants in potatoes Potatoes rely on some enzymes to remove excess reactive oxygen species (ROS) in the body, which can reduce oxidative damage. These enzymes mainly include superoxide dismutase (SOD), catalase (CAT) and peroxidase (PRXs). SOD converts superoxide radicals into hydrogen peroxide, and then CAT and PRXs decompose hydrogen peroxide into water and oxygen to help cells avoid injury (Fan, 2014; Koubaa et al., 2021). The activity of these enzymes will also change under different stress conditions. For example, under hypoxia or when oxygen is just restored, the activity of SOD, CAT and APX enzymes in the mitochondria of potato tubers will decrease at first, and then increase again. This shows that they will adjust according to the amount of ROS (Fan, 2014). In particular, class III peroxidases are also important in removing ROS. For example, a gene called IbPRX17 functions under the regulation of a transcription factor called IbBBX24. It can enhance the activity of peroxidase and reduce the accumulation of hydrogen peroxide, thereby improving the tolerance of potatoes to salinity and drought (Zhang et al., 2021). This also shows that transcriptional regulation is also critical in the potato antioxidant system. 5.2 Non-enzymatic antioxidants in potatoes In addition to enzymes, there are some non-enzymatic substances in potatoes that fight ROS, mainly including ascorbic acid, glutathione and flavonoids, which can directly remove ROS and play a role in supplementing defense in cells. Among them, ascorbic acid and glutathione are an important part of the ascorbic acid-glutathione cycle. They help detoxify hydrogen peroxide and maintain the balance of redox in cells. The content of these substances usually increases when facing environmental stress. Some potato varieties with stronger resistance have higher levels of these antioxidants in their bodies (Sahoo et al., 2021; Li and Huang, 2024), especially glutathione, which plays a vital role in potato's response to biological stress such as viruses. Glutathione can reduce oxidative damage and regulate defense responses. When potatoes interact with viruses, glutathione levels will increase, and its content will increase more in resistance reactions. This change is also related to the reduction of viruses and the decrease of ROS (Otulak-Kozieł et al., 2022). 5.3 Dynamic balance between ROS production and scavenging in potatoes under stress Under stress, the generation and removal of ROS in potatoes must maintain a dynamic balance. ROS is a byproduct of plant metabolism and a stress signal molecule. If there are too many ROS, it may damage cells. Therefore, the scavenging system in plants must be strong enough to control the dynamic balance of ROS (Fan, 2014; Sahoo et al., 2021). This balance is mainly achieved by the two sets of enzymatic and non-enzymatic antioxidant systems. Together, they can reduce the damage caused by ROS to the plant itself. Under the osmotic stress caused by polyethylene glycol, the ability of potatoes to remove ROS will increase. This includes both the enhanced activity of scavenging enzymes and the increased content of non-enzymatic antioxidants, which work
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