The effects of gamma irradiation on secondary metabolite production in callus cultures derived from four doses of gamma irradiated seedlings on Andrographis paniculata were studied. The effects of lower doses of gamma irradiation on secondary metabolite production in callus cultures were also examined in Andrographis echiodes, since the seedlings of these species were highly sensitive to higher doses of gamma irradiation. The results of this study indicated that gamma irradiation positively influencedandrographolide production in A.paniculata from the callus cultures. The significant impact...