Influence of photoperiod on the accumulation of allantoin in comfrey plants

in order to evaluate the influence of photoperiod on the accumulation of allantoin in comfrey (symphytum officinale l.), a well known medicinal plant, an experiment was conducted during july and august, 1998. cuttings obtained from 90 day old plants were submitted to four photoperiods (8, 12, 16 and 20 hours). after 60 days, allantoin content in roots and rhizomes was evaluated. the results showed that increases in photoperiod promoted an increment in the average content of allantoin in roots (0.06%, 0.303%, 1.213% and 4.78%). on the other hand, in rhizomes, allantoin accumulation decreased (9.65%, 7.14%, 0.55%) when the photoperiod was increased from 8 to 12 and 16 hours, respectively, stabilizing on a 20-hour photoperiod (0.53%). plants cultivated under field conditions presented 2.55% and 2.63% allantoin content in rhizomes and roots, respectively. based on the fact that in comfrey the roots are considered to be sites of allantoin synthesis, the results demonstrated that photoperiod could influence both the synthesis of allantoin in these organs as well as its accumulation in the rhizomes.