Spectral effects of LEDs on chlorophyll fluorescence and pigmentation in Phalaenopsis 'Vivien' and 'Purple Star'

摘要

We examined the effect of light emitting diode (LED) lighting in greenhouse facilities on growth, chlorophyll fluorescence and pigmentation in Phalaenopsis Vivien' and Purple Star' under purpose-built LED arrays yielding c. 200 mu molm(-2)s(-1) at plant height for 14h per day and 24/18 degrees Cdayight temperature, respectively, from January to April 2013. The light treatments were (1) 40% blue in 60% red (40% B/R), (2) 0% blue in 100% red (0% B/R) and (3) white LEDs with 32% blue in white (32% B/W, control), with background daylight under shade screens. The plants were harvested twice for leaf growth and pigmentation. There was no clear pattern in the spectral effect on growth since the order of leaf size differed between harvests in March and April. F-v/F-m was in the range of 0.52-0.72, but overall slightly higher in the control, which indicated a permanent downregulation of PSII in the colored treatments. The fluorescence quenching showed no acclimation to color in Purple Star', while Vivien' had lower ETR and higher NPQ in the 40% B/R, resembling low light acclimation. The pigmentation showed corresponding spectral response with increasing concentration of lutein while increasing the fraction of blue light, which increased the light absorption in the green/yellow part of the spectrum. The permanent downregulation of PSII moved a substantial part of the thermal dissipation from the light regulated NPQ to non-regulated energy losses estimated by phi(NPQ) and phi(NO) and the difference found in the balance between phi(PSII) and phi(NPQ) in Vivien' disappeared when phi(NO) was included in the thermal dissipation.