Role of diurnal light spectrum on flowering in Chrysanthemum morifolium

MSc-thesis abstract (submitted 4 September 2017): Chrysanthemum morifolium is an important ornamental crop grown worldwide as pot plant and as cut flower. Its flowering process can be regulated by parameters as light (photoperiod, spectrum and intensity) and temperature.
The present research aims to get a better insight on flowering in chrysanthemum in different light spectrum treatments, from flowering induction to bud formation along with plant morphology.

Rooted cuttings from C.morifolium ‘Baltica’ and ‘Radost’ were used. The experiment consisted in six different light treatments, SD and long days (LD) conditions:
White Deep Red (WDR) and Red(R) + Blue(B) during 11h (SD); R+B(11h)_+B(4h) and WDR(11h)_+B(4h)_(LD) and another two LD treatments: R+B+FR(11h)_+B(4h) and WDR+FR(11h)_+B(4h).

Time until flower induction and number of visible buds were equal under R+B(SD) and under R+B;B(LD). Broader light spectrums
(WDR and WDR;B) induced earlier flowering with a higher final developmental bud stage without difference in final number of buds comparing with the dichromatic spectrums (R+B_and_R+B;B).
Treatments with lower Phytochrome Stationary Stage_(PSS) values stimulated significantly higher plant elongation, from which plants under R+B+FR;B(LD) formed less number of leaves and internodes compared to other light treatments and ultimately inhibited flowering.
Plants under WDR+FR;B treatment caused partial flowering inhibition (30%-50%).

The experiment results suggest that the day extension with B light is not repressing flowering whenever it is anteceded by a main light period with high R:FR_ratio.

Keywords: Chrysanthemum morifolium, flower induction, LEDs, light spectrum, photoperiod