Saffron (Crocus sativus L.) is an herb with outstanding medicinal functions and commercial value. Light is an important factor in plant growth, and the sensitivity of plant photosynthesis to light quality can be characterized by photosynthetic spectral response curves. This study aims to measure the spectral response curves of saffron leaves so as to provide theoretical guidance for a supplemental lighting spectrum to increase saffron production. The measurement results show the peaks of spectral response curves of saffron leaves are at 480 nm and 660 nm, which provides a reference for the peak wavelengths of supplemental lighting spectrum. Full-spectrum white light with low color temperature or red light mixed with a little blue light might be most beneficial for saffron biomass accumulation.

Present indoor cultivation of saffron (Crocus sativus L.) only depends on artificial planting experience, so that flower number and stigma yield are seriously affected in case of cloudy or rainy days and temperature changes. In this study, a luminaire was used at 10-h photoperiod combined 450 nm blue LEDs with 660 nm broad-band red LEDs, which respectively had full width at half maximum (FWHM) of 15 nm and 85 nm, in a ratio of blue: red: far-red light = 20%: 62%: 18%. The influence of total daily light integral (TDLI) was evaluated on flowering characteristics, stigma quality, as well as leaf morphological characteristics. The results showed that flower number, daily flowering proportion, stigma dry weight and crocetin esters content were significantly correlated with TDLI (P < 0.01). The increasing TDLI could slightly promote leaf width and leaf area beyond buds, but had no significant effect on bud length and leaf length. Both the average flower number per corm and dried stigma yield was the highest under the 150 mol m−2 TDLI treatment, up to 3.63 and 24.19 mg respectively. The former was 0.7 more than that under original natural light treatment, while the later was 50% higher. Totaling, combining blue LEDs with a broad-band red LEDs of the 150 mol m−2 TDLI was the most favorable condition for flower number and stigma quality of saffron in this study.