Effect of far-red light on saffron (crocus sativus 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.