The objectives of the study were to determine whether raspberries responded to decreased red to far-red ratio and whether it was more effective at the beginning or end of the dark period. Increased proportions of far-red light increased the internode length when at the beginning of the dark period on the three raspberry cultivars `Lauren',`Reveille', and `Titan'. Cultivars varied in that internode length also increased in ambient daylength compared to short days in `Lauren' and `Reveille', but not in `Titan'. They also responded differently to photoperiod: `Titan' and `Lauren' grew under short days, whereas `Reveille' ceased growth.
Adam Dale and Theo J. Blom
Glenn L. Roberts, M.J. Tsujita and T. Blom
Lilium hybrid `Enchantment' bulbs were grown at a -4C or +4C DIF in growth chambers set at 100 μmolm-2s-1 PPF, with or without one hour red or far-red light extensions to each end of an eight hour photoperiod. Far-red light extensions completely reversed the growth regulating effect of negative DIF temperatures. Negative DIF treated plants given far-red extensions were 43% taller than plants with no light extensions and 15% taller than plants given red light extensions. Prephotoperiod red or far-red extensions did not increase stem elongation over similar plants given no light extension, but postphotoperiod far-red extension stimulated stem elongation up to 52%. Red light extensions caused a less dramatic increase than far-red in some cases. The phenomenon is not photoperiodic since lengthening the photoperiod to ten hours caused no appreciable increase in stem elongation. Total 24 hour accumulated energy also proved not to be involved in the process.
Po-Lung Chia and Chieri Kubota
solar radiation in the greenhouse exceeded 800 W·m −2 . End-of-day far-red light treatments. After 5 to 7 d from seeding, the rootstock seedlings were subject to daily EOD-FR light treatments. EOD treatments were initiated at 1830 hr at varied
Isabel Pimentel and Samuel Contreras
under far-red light at 98% RH for 216 h, Dark = seeds treated at 98% RH in darkness for 24 h, Priming = seeds treated in -1.25 MPa (12.5 bar) solution with fluorescent light for 48 h. All treatments were performed at 20 °C. After each treatment, seeds
Gary R. Bachman and Margaret J. McMahon
`Celebrity White' hybrid petunia plants (Petunia ×hybrida Hort. Vilm-Andr.) were grown either in chambers constructed of CuSO4-filled panels acting as spectral filters removing the far-red light (-FR) or in environmental control chambers under temperature treatments of 24 °C day/18 °C night (+DIF) or 18 °C day/24 °C night (-DIF). Growth responses for plants grown under CuSO4 filter (-FR) or -DIF temperatures were similar in that both treatments resulted in decreased internode length, increased stem diameter, and decreased cell length and cell diameter in epidermal, cortical, and pith tissues. Reduced cortical cell length contributed the largest percentage to internode length reductions compared to epidermal and pith tissue for the -FR treatment while reductions in cell length of all three tissues contributed to internode reduction of -DIF-treated plants. Chlorophyll a increased for plants grown under -FR, but decreased for plants grown in -DIF when compared to the appropriate controls.
Shumin Li, Nihal C. Rajapakse and Ryu Oi
The far-red light intercepting photoselective plastic greenhouse covers have been shown to be effective in producing compact vegetable transplants. However, photoselective films reduce the photosynthetic photon flux (PPF) transmission compared to conventional plastic films because of the dye contained in the film. The low PPF in greenhouses covered with photoselective films may result in decreased plant dry matter production and could especially be a problem in the season with low light level and in northern latitudes. Therefore, this study was conducted to determine if covering at the end of the day (EOD) with photoselective films was effective in controlling height of vegetable seedlings. This will allow growers to maintain a high light level during daytime for optimum growth of plants. Cucumber seedlings were exposed to light transmitted through a photoselective film and a clear control film. Three exposure durations: continuous, exposure to filtered light from 3:00 pm to 9:00 am, and from 5:00 pm - 9:00 am, were evaluated. Results show that, after 15 days of treatment, about 25% of height reduction could be achieved by exposing the plants at the EOD from 3:00 pm to 9:00 am or from 5:00 pm to 9:00 am. Plants grown continuously under filtered light were the shortest. Compared to plants grown in photoselective chamber continuously, EOD exposed plants had greater leaf, stem and shoot dry weights, greater leaf area and thicker stem. Specific leaf and stem dry weights were also greater in EOD exposed plants. Number of leaves was not significantly affected by any exposure periods tested. The results suggested that the EOD use of photoselective film is effective in reducing height of cucumber seedlings. The responses of other crops need to be evaluated to test the feasibility of using photoselective film as a EOD cover on wide range of crops.
Mengzi Zhang and Erik S. Runkle
Chia, P.L. Kubota, C. 2010 End-of-day far-red light quality and dose requirements for tomato rootstock hypocotyl elongation HortScience 45 1501 1506 Clifford, S.C. Runkle, E.S. Langton, F.A. Mead, A. Foster, S.A. Pearson, S. Heins, R.D. 2004 Height
Brent L. Black, Harry J. Swartz, Gerald F. Deitzer, Bryan Butler and Craig K. Chandler
The effect of altered red/far-red light environment on subsequent field performance of strawberry plug plants was tested. Two wavelength-selective plastic films were compared to neutral shade and full-sun control for conditioning `Chandler' strawberry plug plants before transplanting to a winter production system. The following year, plug plants of `Chandler', `Sweet Charlie', and `Allstar' were conditioned under the same treatments, with the addition of a continuous incandescent light and a short-day photoperiod, and plant performance was followed in the winter production system in Florida, a cold-climate annual hill system in Maryland, and in a low-input greenhouse production system. During the first year, the red light-filtering film slightly advanced fruiting in Florida. However, during the second year, the effect of the red light-filtering film was not significant, and a short-day treatment resulted in a greater reduction in runnering and increased early crown and flower development. For June-bearing strawberry plants maintained above 20 °C, altering the red/far-red environment did not consistently advance flowering.
Toshio Shibuya, Ryosuke Endo, Yuki Kitamura, Yoshiaki Kitaya and Nobuaki Hayashi
1. Leaf fresh weight, leaf area, relative chlorophyll content of first leaf, and shoot length in cucumber seedlings grown under fluorescent lamps with high red:far-red light (FL H ) or metal-halide lamps (ML) (Expt. 1). Expt. 2. The
David G. Clark and John W. Kelly
Potted miniature roses (Rosa × hybrida `Confection ' & `Meijikatar') were treated at the end of each 8 hour photoperiod with 30, min of red (R) or far-red (FR) light for 21 days. These light treatments convert phytochrome to the Pfr and Pr forms respectively. Plants were paper sleeved and stored in cardboard boxes at 16°C for 5 days to simulate postharvest shipping conditions. `Meijikatar' plants treated with FR light showed more postharvest leaf chlorosis than plants treated with R light or controls.
`Meijikatar' plants treated at the end of each 12 hour photoperiod with FR light exhibited more postharvest leaf chlorosis than plants treated with R light. There were no differences in postharvest leaf chlorosis between plants treated with FR light followed by R light or plants treated with R light followed by FR light. These results suggest that an avoidance of end-of-day FR light will result in less postharvest leaf chlorosis in potted roses.