Time-course Pattern of Electrolyte Leakage from Tuberous Roots of Sweetpotato (Ipomoea batatas (L.) Lam.) after Short-term High Temperature

Sweetpotato (Ipomoea batatas (L.) Lam.) plants which are surface-irrigated periodically, i.e., twice a week on root media, show greater -tocopherol content in their tuberous roots with no apparent change in either tuberous root development or oxygen concentration around the roots as compared to sub-irrigated plants (Eguchi et al., 2012). We speculated that surface irrigation might temporarily cover the tuberous root surface with water and inhibit oxygen movement into the roots, thereby increasing the antioxidant -tocopherol content as a coping mechanism for the slight oxidative stress, i.e. hypoxia, occurring within the roots. Therefore, we performed instantaneous flooding, which completely covered the entire root surface of sweetpotato plants with water (Eguchi et al., 2015) and demonstrated that electrolyte leakage from the tuberous root flesh cells showed a temporal increase with flooding treatment and is an indicator of cellular responses to various stress factors (Demidchik et al., 2014). Rise in temperature activates respiration within the heated plant part; in a similar way, high-temperature treatment applied to the tuberous root can also cause slight oxidative stress within the root similar to that caused by instantaneous flooding. We therefore investigated electrolyte leakage from tuberous roots subjected to high temperature for short durations.