Innovative use of natural and supplemental light for high latitude crop production

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
205	1123	1020	25%
205	1129	1020	25%
205	1430	1020	25%
205	2123	1020	25%

Progress 10/01/00 to 09/30/06

Outputs
In a high pressure sodium (HPS) production system, the red to far-red ratio was decreased from near 2.2 to 1.2 using incandescent (INC) lamps. Rudbeckia hirta flowered 10 to 14 days earlier in the INC amended environment. One hour of red LED light (660 nm) at the beginning or end of the dark in a 16 hour HPS environment resulted in 4 to 5 days earlier flowering. Plants in long days (LD, 16 hours) flowered 12 weeks from seeding while visible buds at continuous short days (SD, 8 hours) failed to develop into flowers. Plants grew 18 cm tall with LD but less than 8 cm in SD. Plants shifted to LD after 3 weeks had slower flower development than continuous LD but overall height decreased. Flowering of sunflower 'Pacino' was also identified at SD and LD. Plants moved to SD after 1 to 3 weeks flowered similar to those at uninterrupted SD. Four initial weeks of LD delayed flowering 7 days while 2 or 3 weeks of SD followed by LD hastened flowering 5 to 10 days. At 48 initial SD, flower buds were minute requiring 14 LD to flower. Plant height was 18 cm in SD and doubled from 20 to 40 cm with one to 4 initial LD weeks. Flower diameter varied from 9.8 to 16.4 cm and increased 0.18 cm for each cm of plant height. Pansy ('Banner') grown in INC or natural light flowered 61 to 66 days from seeding. HPS delayed flowering with 22 to 26 days. In natural or INC light, first flower developed after 5 to 7 nodes. Under HPS, 7 ('Banner Yellow') or 12 ('Banner Blue') nodes appeared before flowering. One week of INC 35 days from seeding was sufficient to hasten flowering without excess stem elongation. The head lettuce Alpha was moved 5 days from seeding to HPS and LED environments. Hypocotyl length was 3 mm shorter following exposure to one daily hour of red LED in the morning or in the evening compared to only HPS. The ratio between root and shoot dry weights increased from 0.13 under HPS to 0.17 for the LED treatments. Pelleted seed of head lettuce was placed on a peat-lite medium and covered with additional medium (5 mm) or perlite (8 mm). A single layer of white or black surfaced plastic film was also evaluated as seed cover. Following a study in February, the experiment was replicated in April and in May. HPS lamps provided light for 16 hours at 10 mol/day and m2 in February. HPS and natural light was adjusted to 16 hour days and 10 mol/day and m2 in April. No supplemental lamps were used in May and light averaged 10.8 mol/day and m2. Temperature was 18C. Media temperature was slightly higher (19.2C) than air at 1 cm depth but did not differ among treatments. After 14 days, white plastic resulted in a hypocotyl significantly shorter (5.2 mm) and black plastic in the longest hypocotyl (11.0 mm). Peat-lite covered seed resulted in hypocotyls of 10.7 mm and perlite at 6.4 mm. Transplant height was similar after 14 days for white plastic, peat-lite and perlite grown seedlings (7.3-7.4 cm). Black plastic resulted in significantly taller seedlings of 9.1 cm. All seedlings had 6 expanded leaves suggesting matching developmental age independent of cover material and light arrangement. White plastic or perlite cover can be recommended for quality transplant production.

Impacts
Light conditions are fundamental to plant growth and crop productivity. Technical, yet simple, modifications to traditional greenhouse and controlled environment production systems can significantly improve and provide for increased crop returns. For instance, combining and adapting long and short days to specific stages of development can produce highly desirable plants and crops. Information generated in this project on expected crop response, development and production efficiency from various types of light sources is implemented in the planning and running of a local geothermally heated and powered greenhouse. On the basis of our findings, perlite is now regularly used including in the Scandinavian countries, to produce short high quality lettuce, tomato and cucumber seedlings intended for greenhouse and field crop production. As rate of development and plant morphology are highly dependent on light, knowing amount and type of available light provides local producers with opportunities to exactly forecast crop progression and schedule crops for timely harvest.

Publications

Fitzgerald, D., H. Rader and M. Karlsson. 2006. Small farm viability. Agroborealis 38:31-33.
Peterson, C.E. 2006. Can lettuce growers profitably use smaller containers for seedlings? AFES Pubblication ST 2006-02:9-12.
Peterson, C.E. 2004. Lettuce seedling growth in flats with different cell size and shape. Senior thesis. School of Natural Resources and Agricultural Sciences, University of Alaska Fairbanks.
Gallagher, J. 2004. Growth and development of Lactuca sativa seedlings under three light treatments. Senior thesis. School of Natural Resources and Agricultural Sciences, University of Alaska Fairbanks.
Kolberg, T. 2002. Morphology and yield of three strawberry types in response to photoperiod. Senior thesis. School of Natural Resources and Agricultural Sciences, University of Alaska Fairbanks.

Progress 01/01/05 to 12/31/05

Outputs
Compact lettuce (Lactuca sativa) transplants with well-developed root systems are desirable for sequential field plantings. Pelleted seed of head lettuce Alpha was placed on a peat-lite medium and covered with additional medium (5 mm) or perlite (8 mm). A single layer of white or black surfaced plastic film was also evaluated. The film covered the 10 cm diameter pot with a 5 mm large opening allowing seedling emergence. Following a study in February, the experiment was replicated in April and early May to accommodate three lighting arrangements. Natural light is limited at our location in February due to low sun angle and less than 8 hours and 59 minutes from sunrise to sunset. High pressure sodium (HPS) lamps provided light for 16 hours during the initial study at 10 mol per day and square meter (175 micromol per square meter and second). HPS lamps and natural light were adjusted to 16 hour days and 10 mol per day and square meter during the April study. In the May study, time between sunrise and sunset increased from 15 hours and 59 minutes to 17 hours and 51 minutes. No supplemental lamps were used and natural light averaged 10.8 plus/minus 3.1 mol per day and square meter. Temperature was maintained at 18 plus/minus 2 degrees C. In addition to air temperature, media temperature was recorded at 1 cm medium depth. Although slightly higher at 19.2 plus/minus 0.8 degrees C than the air, there was no significant difference in media temperature among type of cover. Plant height, cotyledon length and leaf number were similar for the various covering materials under the three lighting arrangements. Lettuce seeded and covered with white plastic had significantly shorter hypocotyl length at 5.2 mm after 14 days. The longest hypocotyl (11.0 mm) was recorded for seeds under black plastic. Peat-lite covered seed resulted in transplants with hypocotyl length at 10.7 mm and perlite at 6.4 mm. After 14 days, overall transplant height was similar for white plastic, peat-lite and perlite grown seedlings at 7.3 to 7.4 cm. Black plastic resulted in significantly taller seedlings of 9.1 cm. Leaf formation was similar with 6 expanded leaves suggesting matching developmental stage independent of seedling morphology, covering material and light arrangement. White plastic or perlite cover is therefore expected to support quality lettuce transplant production. Flowering in response to day length was identified for sunflower 'Pacino Gold'. Plants were placed at long days (LD, 16 hours) or short days (SD, 8 hours), 20 degrees C and 8 mol per day and square meter. At the 48 SD flowering, buds were minute in LD requiring 14 more days to flower. Plants started at LD and moved to SD after 1 to 3 weeks, flowered similar to those at uninterrupted SD. Four initial LD weeks delayed flowering 7 days while 2 or 3 weeks of SD followed by LD hastened flowering 5 to 10 days. Plant height was 18 cm in SD and doubled from 20 to 40 cm with one to 4 initial LD weeks. Flower diameter varied from 9.8 to 16.4 cm and increased 0.18 cm for each cm of plant height. Opportunities producing short plants with large flowers are therefore limited.

Impacts
Light conditions are fundamental to plant growth and crop productivity. During periods with limited or non-existing natural light in protected environments, an understanding of required type, amount and arrangement of supplemental lighting is vital to efficient production. Information generated in this project on expected crop response, development and production efficiency from various types of light sources is implemented in the planning, startup and running of a local geothermal driven greenhouse. Scheduling and timing crops to meet local marketing opportunities and demands necessitate reliable and predictive production throughout the year. As rate of development is highly dependent on light, knowing amount and levels of available production light provides local producers with opportunities to exactly forecast crop progression and harvest.

Publications

Karlsson, M. and J. Werner. 2005. Daylength effects on pot crops. Greenhouse Product News. Scranton Gillette Communications 15(12): 38-40.
Karlsson, M. and J. Werner. 2005. Day length controls flowering and height of sunflower. HortScience 40:1013-1014.
Karlsson, M. and J. Werner. 2005. Lettuce transplant growth in response to media surface color. ISHS 5th International Symposium on Artificial Lighting in Horticulture, Scientific Programme, page 53. Lillehammer, Norway.

Progress 01/01/04 to 12/31/04

Outputs
A lettuce transplant suitable for mechanical transplanting, handling and field establishment is compact with a well-developed root system and short hypocotyl. Pelleted seed of the head lettuce cultivar Alpha was placed directly on the surface of a moist peatlite medium and covered with a thin layer of additional peat-lite medium (5 mm) or perlite (8 mm). As a comparison, seed was also covered with a single layer of white or black surfaced plastic NFT (nutrient film technique) film. The film was cut to cover the 10 cm diameter pot with a 5 mm large opening in the center to allow seedling emergence. At the time of seeding, the pots were placed in a greenhouse environment of 16 plus/minus 2 degrees C. High pressure sodium lamps provided 16 hours at 10 mol per day and square meter (approximately 175 micromol per square meter and second). Lettuce seeded and covered with perlite had after 12 days the shortest hypocotyl (root/shoot junction to cotyledons) at 7.6 mm. The longest hypocotyl (18.3 mm) was recorded for seeds protected with peat medium. Seedlings grown from seeds shielded with black plastic were similar to those of peat covered seeds at 17.0 mm hypocotyl length. The white plastic resulted in transplants with 12.1 mm hypocotyl. Overall transplant height, after 12 days, was also shortest for the perlite grown seedlings at 4 cm. Transplants were 4.8 cm with peat or white plastic while black plastic resulted in the tallest seedlings of 5.9 cm. These results suggest perlite or white plastic mulch could aid production of compact lettuce transplants. A high red to far-red reflected ratio may explain the shorter transplants using perlite or white plastic cover. The Rudbeckia hirta cultivar Toto Gold was grown at 8 or 16 hours day length. To study the effects of alternating short and long day conditions, some plants were shifted to the opposite day length after 3 weeks. Long days resulted in flowering 12 weeks from seeding while initiated visible buds at continuous short days failed to develop into flower. Plants grew 18 cm tall with long days but less than 8 cm in short days. Although 3 initial weeks of short days slightly slowed flower development compared to continuous long days, overall height was reduced resulting in high quality flowering plants using 21 initial short days. Rudbeckia Toto Gold and the compact sunflower Pacino Gold were grown at 16 degree centigrade using five day and night temperature combinations. The day length was 12 hours at 6 mol per day and square meter. Different day and night temperatures promoted growth and flowering compared to a steady daily temperature. Even a large difference between day (12 degrees C) and night (20 degrees C) resulted in fast growth, uniform flowering and high quality plant features for Pacino Gold. The 12 hour day length resulted in flowering at the rosette stage without stem extension independent of temperature conditions for Toto Gold.

Impacts
Daily light duration, type and amount control performance and production time of crops in greenhouse and protected environments. Understanding the environmental cues and relationships is essential as, for instance, day lengths too short for some crops result in unmarketable rosette flowering plants. Combining and adapting long and short days to specific stages of development however, produce highly desirable, well branched flowering plants at premium market value. Light sources for exclusively lighted environments or to supplement daylight require appropriately balanced spectra for crop production. Using lamps with high ratios of red to far-red wavelengths is less efficient for flower induction while highly satisfactory for leafy crops. Scheduling and timing crops to meet market opportunities and demands necessitate predictive production times. As rate of development is highly dependent on light, knowing amount and levels of production light provides possibilities to exactly forecast crop progression and harvest.

Publications

Karlsson, M. 2004. Culture profile: flowering poppy anemone. The Cut Flower Quarterly 16(3):6-8.
Karlsson, M. and J. Werner. 2004. Enhanced development and flowering of Rudbeckia hirta in far-red amended environments. HortScience 39:834.
Werner, J. and M. Karlsson. 2004. Media surface color alters lettuce transplant growth. International controlled environment meeting. Australasian controlled environment working, UK environmental working group and the NCR-101 committee on use and technology in controlled environments. Brisbane, Australia.

Progress 01/01/03 to 12/31/03

Outputs
Head lettuce of the cultivar Alpha was seeded in 200-cell black or white plug flats using a peatlite medium (Premier Pro-Mix BX). The pelleted seed was placed directly on the surface of the medium and covered with a thin layer of additional medium or perlite. As a comparison, seed was also placed uncovered on the media or on a thin layer of perlite. There were no significant differences in hypocotyl length or plant height for seedlings grown in black or white flats after 18 days. The hypocotyl length was 9.5 mm for seed covered with perlite compared to 11.4 mm for seed placed on top of perlite. There was no difference (17.3 mm) in hypocotyl length for seed on the surface or covered with medium. Overall seedling height was largest at 7.9 cm for seeds covered with medium. Seed covered with or on top of perlite produced 7 cm tall seedlings. The height of seedlings from uncovered seeds was 7.3 cm. Average expanded leaves was 4 independent of seed placement. These results suggest perlite is beneficial for producing compact lettuce transplants. Lettuce (Alpha) transplant development was observed in 200 and 72-cell flats. In addition, flats with cells of round or square shape were compared. Individual cell volume was approximately 10 ml for the 200 cell flats and 50 ml for the 72-cell flats. Five weeks from seeding, transplants in 200-cell flats were 13.5 cm in height and had developed 8 leaves. The 72-cell plants had 10 developed leaves at a height of 15 cm. Although seedlings in 72-cell flats averaged 0.078 gram root dry weight and 0.380 gram top dry weight compared to 0.025 gram root dry weight and 0.146 gram top dry weight for seedlings in 200-cell flats, the root to shoot ratios were not statistically different. No differences were detected between transplants in round or square plug cells of 72 or 200 cell flats. Pansy Banner Clear Blue and Banner Clear Yellow flowered one week faster in an incandescent environment while high pressure sodium delayed flowering for one week compared to natural light. Exposing plans to one week of incandescent light 35 days from seeding and then returned to daylight was sufficient to hasten development compared to a continuous high pressure sodium or daylight environment. These results suggest opportunities for improved development without excess stem elongation using limited exposure to incandescent irradiance. Attempts to improve flower and fruit set of greenhouse strawberry production using fertilizer high in phosphorus (Blossom Booster 10-30-20) or potassium (Hydrosol 5-11-26) at 150 mg per liter nitrogen were compared to a balanced fertilizer (Peters 15-16-17). The day-neutral cultivars Aromas, Diamante, Hecker and Selva were grown in a peatlite bag culture system. Increasing phosphorus and potassium did not increase strawberry yield in this study. Changing fertilizer ratio during the production cycle may be more beneficial than the use of one fertilizer type throughout the cropping cycle.

Impacts
Technical, yet simple, modifications to traditional greenhouse and controlled environment production systems can significantly improve and provide for increased crop returns. Adding incandescent lamps to improve the spectral distribution of high irradiance discharge lamps results in more rapid production and increased profits. Opportunities for year-round controlled environment production of perishable high quality produce and ornamentals will be greatly increased if recommendations for optimal amount, daily duration and quality of light are known and utilized.

Publications

Karlsson, M. and J. Werner. 2003. Cold requirements for flowering of forget-me-not. International Society of Horticultural Science. Acta Horticulturae 624:223-227.
Karlsson, M. and J. Werner. 2003. German primrose has a fresh new look. Greenhouse Product News 13(12): 68, 70-72.
Karlsson, M. and J. Werner. 2003. Lighting effects on black-eyed Susan. Greenhouse Product News 13(9): 36, 38, 40.
Karlsson, M. 2003. Flowering poppy anemones. Greenhouse Product News 13(3): 36, 38, 40-42.
Karlsson, M. 2003. Producing ravishing ranunculus. Greenhouse Product News 13(1): 44, 46-48.
Karlsson, M. and J. Werner. 2003. Flowering of Myosotis in response to irradiance and photoperiod. HortScience 38:752. (Abstr.)

Progress 01/01/02 to 12/31/02

Outputs
High pressure sodium lamps are used extensively to provide supplemental lighting in high latitude greenhouse and controlled environment production. Compared to natural light, the proportion far-red wavelengths of the spectral energy distribution is limited in high pressure sodium irradiance. The far-red spectral energy component and the red (660 nm) to far-red (730 nm) ratio are known critical for determining morphology and flowering. The importance of far-red was evaluated for the development of Rudbeckia hirta. In a high pressure sodium production system, a limited number of incandescent lamps were added. The red to far-red ratio decreased through the addition of incandescent lighting from approximately 2.2 of high pressure sodium to 1.2. The dwarf R. hirta cultivars Toto Gold, Toto Lemon and Toto Rustic, suitable as container or bedding plants, were transplanted into 10 cm containers one month after seeding and the experiment was initiated 3 weeks later. At this time, the plants had 7 to 8 leaves and were 3 to 4 cm in height. Flowering time decreased with 10 to 14 days for the R. hirta cultivars in the incandescent amended environment compared to exclusive high pressure sodium. The natural day length from sunrise to sunset decreased from 8 hours and 34 minutes to 3 hours and 42 minutes at winter solstice to 4 hours and 38 minutes at the termination of the experiment. Daily duration and timing of changes in spectral energy distribution similar to those naturally occurring during twilight periods, are known significant for controlling plant growth and development. Limited exposure to a red enriched environment at the end or beginning of the daily dark period may produce desired plant morphology and faster flowering. To study the effects of controlled daily red light exposure, combinations of red light emitting diodes (LED, peak emission at 660 nm) and high pressure sodium lamps were used. Environments with 16 hours of high pressure sodium were supplemented with one hour exclusively of LED at the end of the dark period or one hour of LED in combination with the first daily hour of high pressure sodium. The additional daily irradiance from the hour of exposure to LED was limited. R. hirta `Toto Lemon' flowered 4 to 5 days earlier with exposure to one daily hour of LED exclusively or in combination with high pressure sodium. Head lettuce of the cultivar Alpha was seeded in plug flats and moved at germination (5 days from seeding) to the three high pressure sodium and LED environments. The limited daily exposure to LED resulted in altered morphology. The ratio between root and shoot dry weights increased from 0.13 in the high pressure sodium environment to 0.17 for the LED treatments. The hypocotyl length was 3 mm shorter following exposure to one daily hour of red LED exclusively or in combination with high pressure sodium compared to only high pressure sodium irradiance.

Impacts
Traditional greenhouse and controlled environment production systems can have significant crop improvements through technical, yet simple, modifications. Adding incandescent lamps to improve the spectral distribution of high irradiance discharge lamps results in more rapid production and increased profits. Opportunities for year-round controlled environment production of perishable high quality produce and ornamentals will be greatly increased if recommendations for optimal amount, daily duration and quality of light are known and utilized.

Publications

Karlsson, M. 2003. Ranunculus with flower colors from white to purple is a more and more appealing bedding plant. Greenhouse Product News 13(1):(in press).
Karlsson, M. and J. Werner. 2003. Requirements for flowering of Forget-me-not. International Society of Horticultural Science. Acta Horticulturae 610: (in press).
Karlsson, M.G. and J.W. Werner. 2002. Flowering of Primula malacoides in response to photoperiod and temperature. Scientia Horticulturae 95:351-356.
Karlsson, M.G. 2002. Flower formation in Primula vulgaris is affected by temperature, photoperiod and daily light integral. Scientia Horticulturae 95:99-110.
Karlsson, M.G. and J.W. Werner. 2002. Photoperiod and temperature affect flowering in German primrose. HortTechnology 12(2):217-219.
Karlsson, M. and J. Werner. 2002. Requirements for flowering of forget-me-not. XXVI International Horticultural Congress & Exhibition and the American Society for Horticultural Science Annual Conference, Ontario, Canada. Abstract number 482:S19-P-46. (Abstr.)
Karlsson, M. and J. Werner. 2002. Raspberries: a new greenhouse crop opportunity. Greenhouse Product News 12(10):36, 38-41.
Karlsson, M. 2002. Primula, an all time favorite. Greenhouse Product News 12(8):34, 36, 38, 40, 42-43.
Karlsson, M. 2002. Forget-me-not as a potted plant. Greenhouse Product News 12(5):32, 34, 35.

Progress 01/01/01 to 12/31/01

Outputs
Artificial lighting is essential for high latitude greenhouse and controlled environment crop production. High pressure sodium (HPS) lamps are used extensively to provide supplemental lighting for efficient plant growth and development. Compared to natural light, the proportion farred (FR) wavelengths of the spectral energy distribution (SED) is limited in HPS irradiance. For plants adapted to high latitudes and natural long days, the FR SED component and the red (R, 660 nm) to FR (730 nm) ratio are known to be critical for morphology and flowering. The importance of FR for the development of Rudbeckia hirta 'Toto', a dwarf cultivar suitable as a container or bedding plant, was determined. Seedlings were transplanted one month after seeding and the experiment initiated 3 weeks later. At this time, the plants had 7 to 8 leaves and were 3 to 4 cm in height. In a polycarbonate greenhouse at 15 C, plants were grown in environments with exclusively HPS, exclusively incandescent irradiance (INC), or natural light with no supplemental lighting. Day length was 16 hours for HPS and INC. The natural day length increased from 12 hours and 58 minutes at the start of the experiment to 19 hours and 44 minutes by termination in May. The light integral for HPS and INC treatments averaged 8.5 mol/(day and m2). Since flowering has been correlated to the elongation of the stem in some plants, the growth regulator ProGibb (gibberellic acid, GA, Abbott Laboratories, North Chicago) was used at 1.9 mg active ingredient per plant to promote stem elongation. Height at flowering was, as expected, greater for plants treated with GA although not significantly different from the plants under INC. Natural light produced the shortest averaging 23 cm and HPS with GA the tallest plants (43 cm). The first observed open flower averaged 96 to 109 days from seeding. GA significantly decreased flowering time at HPS and natural light, but did not affect flowering time under INC. All plants treated with GA flowered at a similar time (96 to 97 days). The number of flower buds per plant was equal under HPS and INC. GA treatment had no effect at HPS, significantly decreased at natural light, and at INC increased the flower bud number from 6 to 32. The effects of SED on flowering of pansy 'Accord Clear Blue' and 'Accord Clear Yellow' were similar to the results observed in rudbeckia. There was no significant difference in flowering time between pansy grown under INC and natural light averaging 61 days from seeding for 'Yellow' and 66 days for 'Blue'. HPS delayed flowering with 22 days in 'Yellow' and 26 days in 'Blue'. The number of nodes below the first flower was 5 for 'Yellow' grown at natural or INC and 7 for 'Blue'. Under HPS, nodes below the first developed flower increased to 7 in 'Yellow' and 12 in 'Blue'. To study SED with various proportions of R and FR, HPS combined with INC may be used. R. hirta 'Toto' grown at a mixture of HPS and INC resulting in R/FR of approximately 0.9, flowered 95 days from seeding. In the same experiment, rudbeckia under HPS (R/FR 2.2) flowered 13 days later and at INC (R/FR 0.75) 5 days earlier than in the 0.9 R/FR environment.

Impacts
A high latitude location provides unique opportunities to study seasonal and daily effects of natural light on plant growth and development in comparison to artificial means of providing irradiance. Documenting the significance of the light type or quality, amount and daily duration on plant morphology is essential to improve greenhouse and controlled environments for efficient crop production. Uncovering the environmental factors governing plant adaptations to various natural conditions, locations and climates is expected to advance the discipline and knowledge of plant physiology.

Publications

Karlsson, M.G. 2001. Primula culture and production. HortTechnology 11(4):627-635.
Karlsson, M.G. and J.W. Werner. 2001. Temperature affects leaf unfolding rate and flowering in cyclamen. HortScience 36:292-294.
Karlsson, M.G. and J.W. Werner. 2001. Temperature after flower initiation affects morphology and flowering of cyclamen. Scientia Horticulturae 91(3-4):357-363.
Karlsson, M. and J. Werner. 2001. More uniform development and height with growth regulators in Rudbeckia hirta 'Toto'. HortScience 36:592. (Abstr.)
Karlsson, M. and J. Werner. 2001. Temperature affects leaf unfolding rate and flowering of cyclamen. HortTechnology 11:488. (Abstr.)
Karlsson, M. 2001. Recent findings may make you rethink cyclamen. Greenhouse Product News 11(3):22-24.
Karlsson, M. 2001. From boutonnieres to bedding plants, production of seed-propagated dwarf carnations. Greenhouse Product News 11(4):52-55.
Karlsson, M. 2001. New types and selections make cyclamen a versatile cool season crop. Ohio Florists' Association Bulletin Number 862:13-15.
Karlsson, M. 2001. Black-eyed susan: a novelty potted plant. Greenhouse Product News 11(12):30, 32, 34, 36.
Karlsson, M. 2001. Primula is still a cool crop. Ohio Florists' Association Bulletin Number 863:8-9.

Progress 10/01/00 to 12/31/00

Outputs
Plants originating from high latitudes are adapted to higher proportions of farred in the spectral distribution for determining the length of the day. The farred component is especially important for controlling flowering of long day plants. In June, the sun is lower than 10 degrees on the horizon from 21:00 to 05:00 in Fairbanks. During these low sun angles, light is naturally enriched in farred. Studies are under way to determine the possibility of controlling plant and flower development by altering the red to farred ratio of natural light at critical periods of the day.

Impacts
A high latitude location provides unique opportunities to study the seasonal and daily effects of natural light conditions on plant growth and development. Uncovering the controlling factors for plant growth and adaptations to natural conditions is expected to improve crop efficiency and advance the understanding of plant physiology.

Publications

No publications reported this period