THE EFFECT OF PHOTOPERIOD, TEMPERATURE AND PHOTON FLUX-DENSITY ON FLOWERING IN PIMELEA-CILIATA

A range of photoperiods were investigated to determine their effect on newer induction in Pimelea ciliata. Temperatures and photon flux dens ities were also investigated to determine their effect on modifying th e response to photoperiod. Pimelea ciliata developed flowers on all pl ants after exposure to at least 4 weeks of an 8 h photo- and thermoper iod at a high photon flux density. As the time under the 8 h photo- an d thermoperiod increased, the total number of flowers produced and the percentage of buds which were floral on each flowering plant increase d. Plants gown under a 16 or 10 h photoperiod for up to 8 weeks did no t produce any flowers. Under a 12 h photoperiod, only two plants out o f 36 flowered, and they produced a low number of flowers. Under the co nditions tested, temperature had no apparent effect on the number of p lants which flowered or the number of flowers on each flowering plant. However, a vernalisation response may be increasing the rate of flowe ring. The flowering response was reduced when plants were grown under a low photon flux density. Few plants produced flowers, and the percen tage of shoots that were floral was also reduced under low light.