Effects of photoperiod extension via red–blue light-emitting diodes and high-pressure sodium lamps on the growth and photosynthetic characteristics in Paeonia lactiflora

Abstract

Herbaceous peony (Paeonia lactiflora) is a flowering species of tremendous commercial potential. Forcing in the greenhouse is used to overcome the problem of the limited flowering period of this species. However, peony growth is constrained by weak light in indoor facilities under winter forcing cultivation. In this study, we used high-pressure sodium (HPS) lamps and light-emitting diodes (LEDs, red: blue = 9:5) as supplemental light sources for the peony cultivar ‘Da Fugui’. This supplemental lighting at an intensity of 200–220 μmol m−2 s−1 provided an additional 5 h of light per day (from 5:00 to 8:00 and from 17:00 to 19:00). The growth and bloom characteristics as well as photosynthesis parameters and products of the peony plants were measured. The results showed that LED treatment increased the net photosynthetic rate (PN) and stomatal conductance (Gs) of leaves at different periods, compared with HPS treatment. By prolonging the photoperiod, both types of light sources significantly increased the flower number, blooming rate, flower diameter and florescence, and improvements were greater with LEDs than with HPS lamps. The findings indicate that LEDs are more suitable for winter supplemental lighting of ‘Da Fugui’ than are HPS lamps.