Nakamura et al. [25] reported that rice callus arising on medium consisted of 2,4-D
under light condition was typically ivory yellow and proplastids rather than chloroplasts were
found in those cells. Nevertheless, when the callus was moved to the medium
supplemented with low concentration of auxin and high level of cytokinin, chloroplast
started developing and green callus was finally obtained. Herbicidal effect of high amounts
of 2,4-D also took place in radish seedling (Raphanus sativus L.) because a lesser amount of
chlorophyll was found in 2,4-D-treated plants when compared to the controls [26]-[27].