AXILLARY BUD PROLIFERATION AND ETHYLENE PRODUCTION AS CONTROLLED BY RADIATION OF DIFFERENT SPECTRAL COMPOSITION AND EXOGENOUS PHYTOHORMONES

The effect of radiation of different spectral composition on axillary proliferation of lavandin (Lavandula officinalis Chaix x Lavandula lat ifolia Villars cv. Grosso) was studied in combination with application of exogenous benzyladenine (BA) and putrescine (Put) and endogenous e thylene production. The effect of BA was predominant over the radiatio n. Continuous far-red showed a fluence rate-dependent promotion of sho ot proliferation in the presence of BA. On BA-free medium, shoot numbe r was enhanced under blue, white, and red radiation, at low photon flu ence rates. BA, however, could reduce the inhibiting effect of blue an d ultraviolet radiation, at high photon fluence rates. Exogenous Put s timulated axillary bud proliferation under some radiation treatments i n the presence of Ba. Moreover, Put, analogously to BA, could overcome the detrimental effect of ultraviolet radiation. A positive correlati on between biotic ethylene production and shoot formation was evidence d under far-red at high photon fluence rate in the presence of BA, and under white, red and blue radiation at low photon fluence rate in the BA-free medium. However, when abiotic ethylene (released from the aga rized medium) was stimulated by UV, no improvement of shoot formation was observed.