The key reason for this increased growth rate could have been the photo-sterilization and photo-generation of ‘‘active oxygen like superoxide and hydroxide anions’’ by nano-TiO2 that enhanced seed stress resistance and encouraged capsule penetration for intakes of water and oxygen needed for quick germination (Khot et al., 2012). Zheng et al. (2005) reported that nanosized TiO2 contributed to water absorption by spinach seeds and as result accelerated seed germination.