Effects of Red-light Intensity during Long-day Treatment on Flowering and Cut Flower Quality in Eustoma grandiflorum Cultivars for Early-autumn Shipment

Abstract

Long-day treatment by pre-dawn lighting (6 h) was applied to Eustoma grandiflorum cultivars to investigate flowering responses and cut flower qualities for early-autumn shipment. Seedlings were irradiated by using bulb-type red-light fluorescent lamps, that R : FR ratio was 8.8, with photon flux density (PFD) of red-light (660 ± 30 nm) of 0.1, 0.2 or 0.5 µmol・m −2 ・s −1 .Control plants were grown under ambient day conditions of 14-15 h without long-day treatment. The times from planting to flower budding under long-day treatments were significantly longer than that of the controls. However, there was no significant difference among the times from planting to flower budding in each treatment. Long-day treatment with the highest red-light intensity showed the greatest increase in the number of nodes on the main stem at anthesis of the first floret. The stem lengths of plants grown under long-day treatment with red-light intensities above 0.2 µmol ・m −2 ・s −1 were significantly longer than that of the control. Long-day treatment using bulb-type red-light fluorescent lamps was applied to 11 Eustoma cultivars. Compared with those of control plants, the times from planting to flower budding under long-day treatment were longer in 9 cultivars and the number of nodes on the main stem at anthesis of the first floret was increased to a maximum of 2.4 in 10 cultivars. Moreover, cut flower length under the long-day treatment was 11.3 cm longer at maximum and cut flower weights were increased in 9 cultivars at harvest (at anthesis of the third floret) compared with those of the controls. The increase in the number of nodes on the main stem under long-day treatment was significantly correlated with the days to flowering in the controls. Key Words：cut

Growth and Flowering Responses of Petunia to Various Artificial Light Sources with Different Light Qualities

“…This observation is consistent with the finding that using INC (with low R:FR ratio) as a light source for NI hastens flowering in petunia and Coreopsis grandiflora (Runkle et al, 2012). Sato et al (2009) and Yamada et al (2009aYamada et al ( , 2009b also showed that flowering in Eustoma is promoted when the R:FR ratio of the NI light source is low. In the current study, regression analysis between days to first flower and spectral factors (Table 4) We observed the flowering responses of petunia to growth under artificial light sources for 10 weeks (Table 3), finding that all plants grown under all light sources flowered, except FL tube, which induced flowering in only 20% of petunia plants.…”

“…Light conditions in which relatively high levels of FR are provided by HL are highly similar to shade produced by a plant canopy, which increases apical dominance and suppresses branching (Smith and Whitelam, 1997;Tucker, 1975). In the current study, the number of lateral branches also increased under the light source with the highest ratio of R:FR (Table 1 and Table 2), which is similar to the findings of Yamada et al (2009b), who showed that the number of branches in E. grandiflorum increased with increasing R ratio.…”

“…NI lighting is used to create long days from autumn to spring by supplementing plants with low intensity (photosynthetic photon flux density, PPFD) 1-2 µmol·m -2 ·s -1 light during the middle of the night, such as 4-h NI treatment, i.e., providing light from 10 p.m. to 2 a.m. For some long-day plants (LDPs) such as petunia, the use of bulb-type FL (compact FL) for NI treatment delays flowering compared to INC because the ratio of red light to far-red light (R:FR ratio) in FL (approximately 8.46) is higher than that of INC (approximately 0.60) (Runkle et al, 2012). For Eustoma grandiflorum, an LDP, flowering is inversely proportional to the R:FR ratio of FL under NI (Sato et al, 2009), and the flower bud formation period is reduced under NI using a light source with a low R:FR ratio (Yamada et al, 2009a(Yamada et al, , 2009b. In addition, the bolting of spinach, another LDP, is promoted under NI treatment with high FR light (Hamamoto et al, 2004), and the use of lights with a low R:FR ratio promotes flowering in Matthiola incana (Yoshimura et al, 2002).…”

Survey of How Hanging Baskets Influence the Light Environment at Lower Crop Level in Ornamental Greenhouses in Ontario, Canada

“…There is no agreed-upon convention in the scientific community for measuring and reporting R:FR. In particular, there are wide variations in specific wave bands and the units of measure used to calculate the ratio (Blom and Kerec, 2003;Capers and Chazdon, 2004;Clifford et al, 2004;Erwin et al, 2006;Feldhake and Glenn, 1997;Mata and Botto, 2009;Pecot et al, 2005;Turnbull and Yates, 1993;Yamada et al, 2009;Yang et al, 2012). When discussing this issue with various delegates at the 2012 International Symposium on Horticultural Lighting, it became clear that there is a need for consensus among researchers in order for direct comparisons to be made in the literature.…”

“…Since plants readily absorb red light (used in photosynthesis) but transmit or reflect far red light, the R:FR decreases within dense canopies or below an upper layer of foliage (e.g., a forest understory). The R:FR of ambient sunlight is generally between 1.0 and 1.2, although this varies considerably in the literature depending on location and how the ratio is calculated (Blom and Kerec, 2003;Clifford et al, 2004;Erwin et al, 2006;Feldhake and Glenn, 1997;Mata and Botto, 2009;Smith, 1982;Turnbull and Yates, 1993;Yamada et al, 2009;Yang et al, 2012). When exposed to subambient R:FR, many common floriculture plants will shift their morphological development toward growing taller in an effort to access direct light.…”