scholarly journals 506 PB 248 DETERMINING THE EFFECT OF CLOUD CONDITIONS ON THE VARIATION IN DAYLENGTH PERCEIVED BY PLANTS

HortScience ◽  
1994 ◽  
Vol 29 (5) ◽  
pp. 504a-504
Author(s):  
James E. Faust ◽  
Royal D. Heins
Keyword(s):  
Dark Period ◽  
Extended Period ◽  
Canopy Height ◽  
Photon Flux ◽  
Flower Initiation ◽  
Plant Canopy ◽  
Maximum Difference ◽  
Photosynthetic Photon Flux ◽  
Naval Observatory ◽  
Actual Difference

Quantum sensors were placed at plant canopy height inside and outside a glass greenhouse. Photosynthetic photon flux (PPF) was measured during September for a 3-hour period near sunrise and sunset, which were determined from US Naval Observatory Circular #171. Under clear skies, the PPF at the canopy exceeded 0.25 μmol·m-2·s-1 for nearly 20 minutes before sunrise through 20 minutes after sunset. Under heavy overcast, the duration was only 5 minutes before sunrise through 5 minutes after sunset. The PPF at the canopy reached 0.25 μmol·m-2·s-1 approximately 12 minutes later in the morning and 12 minutes earlier in the evening than it did outside the greenhouse. The length of the dark period perceived by plants in a greenhouse on September 21st (assuming plants perceive light at 0.25 μmol·m-2·s-1) can range from 11:37 (hr:min) during cloudy conditions to 11:15 during clear ones, a difference of 22 minutes. At 43°N latitude, the maximum difference in date of flower initiation because of an extended period of heavily overcast versus clear weather on a crop such as poinsettias would be one week since the night length during September increases by 3 minutes per day. The actual difference from year to year is probably less because a seven-day duration of heavily overcast weather is unlikely.

scholarly journals Vernalization Duration and Light Intensity Influence Flowering of Three Hybrid Nobile Dendrobium Cultivars

HortScience ◽  
2011 ◽  
Vol 46 (3) ◽  
pp. 406-410 ◽  
Author(s):  
Min Lin ◽  
Terri W. Starman ◽  
Yin-Tung Wang ◽  
Genhua Niu
Keyword(s):  
Light Intensity ◽  
Flowering Time ◽  
Photon Flux ◽  
Flower Initiation ◽  
Flower Longevity ◽  
Photosynthetic Photon Flux ◽  
Flower Diameter ◽  
Flower Quality ◽  
Delayed Flowering

The flowering time and flower quality of three hybrid Dendrobium nobile cultivars in relation to light intensity during cooling and duration of vernalization were studied in the first experiment. Mature Dendrobium Red Emperor ‘Prince’, Den. Sea Mary ‘Snow King’, and Den. Love Memory ‘Fizz’ plants were vernalized at 10 °C under 300 to 350 μmol·m−2·s−1 photosynthetic photon flux (PPF) (12-h photoperiod) or darkness, each with four cooling durations (2, 4, 6, or 8 weeks). Plants were forced in a greenhouse after vernalization. At least 4 weeks of 10 °C cooling in light was needed for complete flower initiation of Den. Red Emperor ‘Prince’, whereas Den. Sea Mary ‘Snow King’ and Den. Love Memory ‘Fizz’ only needed 2 weeks of 10 °C cooling regardless of light. For all three cultivars, darkness during vernalization slightly delayed flowering and resulted in fewer but larger flowers. Longer cooling duration delayed flowering, decreased flower longevity, and produced more and larger flowers. In a second experiment, Den. Love Memory ‘Fizz’ plants were vernalized at 15 °C for 4 weeks under a 12-h photoperiod and PPF of 0, 50, 100, or 200 μmol·m−2·s−1. Compared with 200 μmol·m−2·s−1, low PPF at 50 or 100 μmol·m−2·s−1 did not affect flowering time or flower qualities; however, darkness delayed flowering and reduced flower qualities except flower diameter.

scholarly journals Effects of Light Intensity and Paclobutrazol on Growth and Interior Performance of Pachira aquatica Aubl.

HortScience ◽  
2009 ◽  
Vol 44 (5) ◽  
pp. 1291-1295 ◽  
Author(s):  
Qiansheng Li ◽  
Min Deng ◽  
Jianjun Chen ◽  
Richard J. Henny
Keyword(s):  
Light Intensity ◽  
Growth Form ◽  
Foliar Application ◽  
Canopy Height ◽  
Internode Length ◽  
Compensation Point ◽  
Photon Flux ◽  
Plant Canopy ◽  
Light Compensation Point ◽  
Compact Growth

Pachira aquatica Aubl. has recently been introduced as an ornamental foliage plant and is widely used for interiorscaping. Its growth and use under low light conditions, however, have two problems: leaf abscission and accelerated internode elongation. This study was undertaken to determine if production light intensity and foliar application of paclobutrazol [β-(4-chlorophenyl)methyl-α-(1,1-dimethylethyl)-1H- 1,2,4- triazole-1-ethanol] improved plant growth and subsequent interior performance. Two-year-old P. aquatica trunks were planted in 15-cm diameter plastic pots using a peat-based medium and were grown in a shaded greenhouse under three daily maximum photosynthetic photon flux densities (PPFD) of 285, 350, and 550 μmol·m−2·s−1. Plant canopy heights, average widths, and internode lengths were recorded monthly over a 1-year production period. Two months after planting, the plant canopy was sprayed once with paclobutrazol solutions at concentrations of 0, 50, and 150 mg·L−1, ≈15 mL per plant. Before the plants were placed indoors under a PPFD of 18 μmol·m−2·s−1 for 6 months, net photosynthetic rates, quantum yield, and light saturation and compensation points were determined. Results showed that lowering production light levels did not significantly affect canopy height, width, or internode length but affected the photosynthetic light response curve and reduced the light compensation point. Foliar application of paclobutrazol reduced internode length, thereby resulting in plants with reduced canopy height and width and more compact growth form. Paclobutrazol application also reduced the light compensation point of plants grown under 550 μmol·m−2·s−1. Plants with the compact growth form did not grow substantially, dropped fewer leaflets, and thus maintained their aesthetic appearance after placement indoors for 6 months. These results indicated that the ornamental value and interior performance of P. aquatica plants can be significantly improved by producing them under a PPFD range between 285 and 350 μmol·m−2·s−1 and foliar spraying of paclobutrazol once at a concentration between 50 and 150 mg·L−1.

scholarly journals Transplant Quality as Affected by Temperature, Light Intensity, and Photoperiod during Storage

HortScience ◽  
1997 ◽  
Vol 32 (3) ◽  
pp. 481C-481
Author(s):  
C. Kubota ◽  
S. Seiyama ◽  
K. Sakami ◽  
T. Kozai
Keyword(s):  
Dark Period ◽  
Solanum Melongena ◽  
Dry Weight ◽  
Continuous Illumination ◽  
Photon Flux ◽  
Photosynthetic Photon Flux ◽  
Successful Management ◽  
Percent Survival ◽  
Different Temperatures ◽  
Plug Seedling

Storage techniques to hold the seedlings for several weeks prior to shipping/transplanting have been required for the successful management in plug seedling production. During storage, it is required to suppress growth and development of the seedlings as well as to preserve their transplant quality. Illumination during storage has been shown to be important for storage of high-quality transplants. In the present experiments, eggplant (Solanum melongena L.) plug seedlings, which were ready for transplanting after 3 weeks of growth under 28/20C photo-/dark period temperature, 330 μmol·m–2·s–1 photosynthetic photon flux (PPF), and 16-hr photoperiod per day, were stored for 3 to 4 weeks under combinations of different temperatures, PPF, and photoperiods. Storage air temperature affected elongation of the seedlings during 3 weeks of storage. Continuous illumination at a PPF close to the light compensation point maintained dry weight of the seedlings unchanged during storage and kept the high percent survival after storage. Storage in darkness reduced the dry weight during storage and, thus, the percent survival after storage. PPF and photoperiod were shown to be important factors in the preservation of transplant quality and suppression of growth of the seedlings during storage.

scholarly journals GAS EXCHANGE RATES BY A STAND OF SOYBEANS GROWN IN A TIGHTLY SEALED CHAMBER

HortScience ◽  
1990 ◽  
Vol 25 (9) ◽  
pp. 1151c-1151
Author(s):  
R.M. Wheeler ◽  
K.A. Corey ◽  
J.C. Sager ◽  
C. L. Mackowiak ◽  
W.M. Knott
Keyword(s):  
Glycine Max ◽  
Life Cycle ◽  
Exchange Rates ◽  
Dark Period ◽  
Photon Flux ◽  
Canopy Closure ◽  
Photosynthetic Photon Flux ◽  
Respiration Rates ◽  
Soybean Plants ◽  
Photosynthesis And Respiration

Soybean plants [Glycine max (L.) Merr. cv. McCall] were grown from seed to harvest (90 days) in NASA's Biomass Production Chamber. The chamber provides approximately 20 m2 of growing area with an atmospheric volume of 113 m3. Photosynthesis and respiration rates of the stand were tracked by monitoring CO2 increase during the 12-h dark period and the subsequent drawdown to controlled set point (1000 ppm) when the lamps were turned on each day. Stand photosynthesis [under 875 μmol m-2 s-1 photosynthetic photon flux (PPF)] peaked at 35 μmol m-2 s-1 at 30 to 35 days after planting (DAP) and averaged 22 μmol m-2 s-1 throughout the life cycle. Dark period respiration peaked near 8 μmol m-2 s-1 at 30 to 35 DAP and averaged nearly 5 μmol m-2 s-1 throughout the life cycle. Prior to full canopy closure near 30 DAP, the light compensation point (LCP) for stand photosynthesis was lass than 100 μmol m-2 s-1 PPF; by 54 DAP the LCP had increasad to 175 μmol m-2 s-1. Stand transpiration rates peaked at 8.2 L m-2 day-1 at 40 to 45 DAP and averaged 4.3 L m-2 day-1 throughout growth.

scholarly journals Light Emitting Diodes (LEDs) as Agricultural Lighting: Impact and Its Potential on Improving Physiology, Flowering, and Secondary Metabolites of Crops

2021 ◽  
Vol 13 (4) ◽  
pp. 1985
Author(s):  
Musa Al Murad ◽  
Kaukab Razi ◽  
Byoung Ryong Jeong ◽  
Prakash Muthu Arjuna Samy ◽  
Sowbiya Muneer
Keyword(s):  
Crop Production ◽  
Morphological Changes ◽  
Light Emitting Diode ◽  
Crop Productivity ◽  
Photon Flux ◽  
Flower Initiation ◽  
Nutrient Metabolism ◽  
Light Emitting ◽  
Cultivation Systems ◽  
Lighting Systems

A reduction in crop productivity in cultivable land and challenging environmental factors have directed advancement in indoor cultivation systems, such that the yield parameters are higher in outdoor cultivation systems. In wake of this situation, light emitting diode (LED) lighting has proved to be promising in the field of agricultural lighting. Properties such as energy efficiency, long lifetime, photon flux efficacy and flexibility in application make LEDs better suited for future agricultural lighting systems over traditional lighting systems. Different LED spectrums have varied effects on the morphogenesis and photosynthetic responses in plants. LEDs have a profound effect on plant growth and development and also control key physiological processes such as phototropism, the immigration of chloroplasts, day/night period control and the opening/closing of stomata. Moreover, the synthesis of bioactive compounds and antioxidants on exposure to LED spectrum also provides information on the possible regulation of antioxidative defense genes to protect the cells from oxidative damage. Similarly, LEDs are also seen to escalate the nutrient metabolism in plants and flower initiation, thus improving the quality of the crops as well. However, the complete management of the irradiance and wavelength is the key to maximize the economic efficacy of crop production, quality, and the nutrition potential of plants grown in controlled environments. This review aims to summarize the various advancements made in the area of LED technology in agriculture, focusing on key processes such as morphological changes, photosynthetic activity, nutrient metabolism, antioxidant capacity and flowering in plants. Emphasis is also made on the variation in activities of different LED spectra between different plant species. In addition, research gaps and future perspectives are also discussed of this emerging multidisciplinary field of research and its development.

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