Effect of Far-red Light on Saffron (<i>Crocus sativus</i> L.) Growth and Crocin Yields

Abstract

This study investigated the effect of the red (R) to far-red (FR) photon flux density ratio on the growth and crocin yields of 64 saffron (Crocus sativus L.) corms that were hydroponically cultivated in closed chambers. The life cycle of saffron can be divided into four stages: formation of the flower buds, flowering, formation of the daughter corms (FD) and development of the daughter corms (DD). During the DD stage, the saffron corms were cultivated under the same environmental conditions except for the light quality, which was applied at an R/FR ratio of 15.8 (FL treatment) or 1.8 (FR treatment). There was no significant difference between treatments in the shoot length, or the maximum diameter, weight and stigma weight of the daughter corms. However, there was a significant difference in the absorbance of crocin solutions. Although the cause of FR-induced increase in crocin was not elucidated, it was presumed that a low R/FR ratio during the DD stage accelerates the translocation of photosynthetic products from the leaves to the corms to generate carbohydrate-enriched corms. This might result from increased sink strength, which is associated with phytochrome equilibrium.

Monochromatic blue light enhances crocin and picrocrocin content by upregulating the expression of underlying biosynthetic pathway genes in saffron (Crocus sativus L.)

“…However, there are few studies on the effect of light on saffron secondary metabolites. In a study on the effect of the R:FR ratio on crocin production, a positive effect of FR was reported (Kajikawa et al, 2018). In the current study, a positive effect of B light was detected in crocin production in saffron plants.…”

“…Corms were incubated at 17 • C under different light conditions provided by blue (B, 400-500 nm), red (R, 600-700 nm), combinations of B and R light including 100%B (monochromatic B light), 75%B (75%B + 25%R), 50%B (50%B + 50%R), 25%B (25%B + 75%R), 0% (monochromatic R light), and white (W) provided by LED modules (24 W, OPPEL, China) at a photosynthetic photon flux density (PPFD) of 150 ± 10 µmol m −2 s −1 . Following this, the temperature was set to 15/6 • C (light/dark) with an 11/13 h photoperiod for induction of corms since previous studies showed that the highest sink capacity of corms occurs in this condition (Miyagawa et al, 2015;Kajikawa et al, 2018).…”

“…Despite many studies on many other environmental factors, the effect of light on the production of secondary metabolites of saffron has mostly slipped the scientific attention. To date, just one study has mentioned the positive effect of far-red (FR) light on the crocin production of saffron stigma (Kajikawa et al, 2018).…”

Blue Light Improves Photosynthetic Performance and Biomass Partitioning toward Harvestable Organs in Saffron (Crocus sativus L.)

“…To induce the emergence of flowers, corms were incubated at 17 • C under light conditions provided by blue (B, 400-500 nm), red (R, 600-700 nm), a combination of B and R light, and white (W) LEDs at a photon flux density of 150 µmol m −2 s −1 . Following flowering, the temperature was set to 15/6 • C (light/dark) with 11/13 h photoperiod for induction of corms, since previous studies showed that the highest sink capacity of corms occurs in this condition [23,24].…”

Structural and Spectroscopic Characterization of Saffron Starches at Different Growth Stages

“…Saffron bulbs were obtained from a farmer in Taketa City, Oita Prefecture, Japan, and cultivated as described in the previous study. [ 20 ] The bulbs were stored at 25 °C in darkness for 97 days to induce bud formation. Subsequently, the germinated saffron bulbs were further hydroponically cultivated with half‐strength Otsuka‐A prescription at 17 °C for 59–70 days, relative humidity of 85%, and 400 ppm CO 2 conditions.…”