The effect of light on the emission of floral scent in Phalaenopsis orchids

• Main Authors: Ming-ChiLee, 李名綺
• Other Authors: Hong-Hwa Chen
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/47059963069190087184

碩士 === 國立成功大學 === 生命科學系 === 103 === ABSTRACT Phalaenopsis bellina is a scented Phalaenopsis species. The main scent components of P. bellina are monoterpenes including linalool and geraniol with the maximal emission on day 5 post anthesis (D+5). The key enzyme gene for monoterpene biosynthesis in P. bellina is geranyl diphosphate synthase small subunit (PbGDPS_SSU), whose expression is concomitant with the maximal emission of floral scent. Previously, the floral scent production was detected mainly from 10 am to 4 pm for P. bellina. It is possible that the floral scent emission was either light or temperature regulated. We have analyzed whether the scent emission is circadian rhythm or light regulated by either under long-day (16 h/8 h light/dark) or continuous darkness conditions for 4 days since D+4. We found that the emission of orchid floral scent is light-regulated rather than circadian rhythm regulated. In addition, transcriptomic analysis of P. bellina flowers at consecutive stages (from the blooming day to D+7) showed that several photoreceptor genes displayed concurrent expression patterns as that of PbGDPS_SSU, including phytochrome (PHY), cryptochrome (CRY), phototropin (PHOT), and UVBR. Transcription of these unigenes was then verified by using quantitative real-time RT-PCR. Two blue light photoreceptors, PbCRY3 and PbPHOT1, showed similar expression patterns with PbGDPS_SSU. To investigate the role of blue light on floral scent emission in Phalaenopsis, the scent metabolic profiles of two native Phalaenopsis species and two commercial cultivars were analyzed by treating plants with various light factors. The emission levels of linalool and geraniol were higher in these plants under long day condition (white light 100 μmol m-2s-1, 16 h/8 h L/D) than those under far-red light or darkness. In addition, high intensity of blue light (270 μmol m-2s-1) showed a negative effect on the emission of linalool and geraniol in two native species, with more effect on linalool than geraniol. Taken together, these results indicate that light has played a positive effect on orchid floral scent emission, and the effect of light regulation on linalool and geraniol emission might be different.