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TypeII, singlet oxygenmediated photosensitized damage has already been shown to occur in epicotyls of darkgerminated pea (Pisum sativum L.) seedlings upon illumination, resulting in fast turgor loss and wilting. In this study we show evidence that the palette of reactive oxygen species (ROS) is more complex. Hydrogen peroxide, superoxide and hydroxyl radicals are also formed, suggesting the occurrence of typeI reactions as well. Moreover, hydrogen peroxide injection into the epicotyls in the dark was able to provoke wilting directly. Formation of hydroxyl radicals could also be triggered by the addition of hydrogen peroxide in the dark, preferentially in the midsections where wilting occurs, showing that potential mediators of a Fenton reaction are present in the epicotyls, but unevenly distributed. Localization of lightinducible ROS formation fully (hydrogen peroxide) or partially (superoxide radicals …