The effect of light quality on ethylene production in leaves of oat seedlings (Avena sativa L.)

Abstract The effect of UV, blue, green, red, far-red and white fluorescent lights at a fluence of 1.5–20 μmol m −2 s −1 photon flux density (PFD) on endogenous and ACC-dependent ethylene production by etiolated and green apical oat-leaf segments was investigated. It was found that endogenous ethylene production in light-irradiated green and etiolated oat leaves depends upon light quality and its fluence. All light of the visible spectrum (400–700 nm) at PFD 5–20 μmol m −2 s −1 reduced conversion of ACC to ethylene in green oat leaves incubated in 10 −3 M ACC. Blue light was most effective in the inhibition of ACC-dependent ethylene production at 5–10 μmol m −2 s −1 PFD, and endogenous ethylene formation at 10 μmol m −2 s −1 PFD. At 20 μmol m −2 s −1 PFD, all visible light wavebands substantially reduced endogenous ethylene production but blue and red light were most effective. In etiolated leaves UV at 1.5 μmol m −2 s −1 PFD, enhanced endogenous ethylene production and other lights at 20 μmol m −2 s −1 PFD decreased evolution of ethylene, whereas ACC-dependent ethylene formation was stimulated by UV, red and far-red wavebands. Growth of 10-day old seedlings was reduced by 40% under continuous blue light irradiation relative to that obtained with white light. Irradiation of etiolated and green leaf segments for 18 hr with blue light reduced ACC oxidase activity when compared to dark-treated ones. The influence of light quality and its fluence rate on the control of ethylene biosynthesis in oat leaves is discussed.