TBPBB optical signals were used to monitor the fluctuating ROS level during the early stages of pea seeds' germination, providing a comprehensive understanding of the redox dynamics . As the germination time prolonged, the seed cells gradually swelled, allowing them to absorb more TBPBB, which was measured using the UV-vis absorption spectra through a subtraction method after soaking. The amount of TBPBB absorbed by the germinated seeds reached saturation after 72 hours (Fig. ).