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.

This research aimed to develop regression models that estimate starch concentration in saffron (Crocus sativus L.) corms from hyperspectral light scattering images. Light scattering images were captured from corms at wavelengths from 650 nm to 1,000 nm in 5 nm intervals. Light decay curves were measured, and the integrated value of the curve at each wavelength (S l ) was calculated by image processing algorithms. The starch concentration in each captured corm was also measured using the phenol sulfuric acid colorimetric method for validation. A principal component regression method was applied to develop regression models in order to estimate the starch concentration from the S l spectra. The results indicated that the estimation accuracy was high, and this model had practical use based on the ratio of performance to deviation (RPD) criterion (R cal 2 ϭ 0.913, standard error of calibration (SEC) ϭ 1.33 w.b., R val ϭ 0.932, standard error of validation (SEP) ϭ 1.54 w.b., RPD ϭ 2.81). The S l was found to be negatively correlated with starch concentration since light scattering increased considerably as starch concentration increased.