PHOTOCONTROL OF SOMATIC EMBRYOGENESIS AND POLYAMINE CONTENT IN ARAUJIA-SERICIFERA PETALS

The effects of photoperiod and end-of-day phytochrome control on somat ic embryogenesis and polyamine (PA) content in Araujia sericifera peta ls have been studied. Petals from immature flowers were cultured under 16- and 8-h photoperiods. Far red (FR), red (R) and FR followed by R light treatments were applied at the end of the photoperiods for three weeks. The number of somatic embryos, callus weight and the levels of free and bound PAs in the cultured petal explants were determined 40 days after the beginning of light treatments. Long day (LD) promoted s omatic embryogenesis but did not have any significant effect on PA con tent. Short day (SD) reduced somatic embryogenesis and enhanced total PAs, mainly in the form of bound spermidine. End-of-day FR treatment i ncreased PA content and inhibited somatic embryogensis under LD but ha d no significant effect under SD. This effect of FR on PA levels was c ancelled by R and was independent of the presence of silver thiosulpha te in the medium. End-of-day R treatment reduced the total PA content under SD. However, end-of-day R increased or reduced somatic embryogen esis under SD depending on the presence or absence of silver in the me dium. The results suggest a photoperiodic control of somatic embryogen esis and PA content in A. sericifera. The effects of end-of-day R and FR treatments depend on the length of the photoperiod This finding and the FR/R photoreversibility of end-of-day treatments indicate that ph ytochrome may be involved in both somatic embryogenesis and accumulati on of PA.