A new phytohormone was isolated as a metabolite of anthranilate photobiotransformation by Rhodobacter sphaeroides OU5. It was identified by MS and NMR (H-1, C-13) as an indole terpenoid ester [(2E, 4E, 6E, 8E, 10E, 12E, 14E, 16E, 18E) 24-hydroxy-2,6,10,14,19 pentamethyl tetrecosa-2,4,6,8,10,12,14,16,18 nonenyl-2(hydroxy methyl)-1H-indole-3-carboxylate] and is named as rhodestrin. Rhodestrin at 50 nM gave positive test in auxin bioassay and initiated more profuse and early rooting in tissue-cultured plants than other auxins at 5 mu M.