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].
Conclusion Though antioxidants are undoubtedly found in natural species of Ocimum , it is safer if plant that produces those chemicals is subjected to the in vitro culture. In this manner, the cleanliness or asepsis could be possibly controlled. For further experiment, 2,4-D should be replaced with weaker auxin, for instance, NAA to initiate callus and direct induction for synthesis of antioxidant compounds from lemon basil callus is attractive too.