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SUMMARY: Maize plastid terminal oxidase1 (ZmPTOX1) plays a pivotal role in seed development by upholding redox balance within seed plastids. This study focuses on characterizing the white kernel mutant 3735 (wk3735) mutant, which yields pale‐yellow seeds characterized by heightened protein but reduced carotenoid levels, along with delayed germination compared to wild‐type (WT) seeds. We successfully cloned and identified the target gene ZmPTOX1, responsible for encoding maize PTOX—a versatile plastoquinol oxidase and redox sensor located in plastid membranes. While PTOX's established role involves regulating redox states and participating in carotenoid metabolism in Arabidopsis leaves and tomato fruits, our investigation marks the first exploration of its function in storage organs lacking a photosynthetic system. Through our research, we validated the existence of plastid‐localized ZmPTOX1, existing as a homomultimer, and established its interaction with ferredoxin‐NADP+ oxidoreductase 1 (ZmFNR1), a crucial component of the electron transport chain (ETC). This interaction contributes to the maintenance of redox equilibrium within plastids. Our findings indicate a propensity for excessive accumulation of reactive oxygen species (ROS) in wk3735 seeds. Beyond its known role in carotenoids' antioxidant properties, ZmPTOX1 also impacts ROS homeostasis owing to its oxidizing function. Altogether, our results underscore the critical involvement of ZmPTOX1 in governing seed development and germination by preserving redox balance within the seed plastids. Significance Statement: Aside from its established role as a vital regulator of redox states and its involvement in carotenoid metabolism, as observed in Arabidopsis leaves and tomato fruits, this study marks the inaugural exploration into PTOX's function within storage organs lacking a photosynthetic system. Our findings elucidate how ZmPTOX1 significantly impacts protein and starch accumulation in seeds, along with the pace of seed germination. Moreover, it actively maintains redox equilibrium across various stages of seed development and germination. [ABSTRACT FROM AUTHOR]