2014 Plug & Cutting Conference 9/23/2014. Erik Runkle and Roberto Lopez. Presentation Outline. Propagation Environment.

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1 Impact & Management of Light & Temperature Erik S. Runkle Michigan State University Department of Horticulture Roberto G. Lopez Purdue University Department of Horticulture and Landscape Architecture Presentation Outline Understanding light intensity and DLI Supplemental and sole source lighting of plugs and cuttings High-intensity lighting guidelines and options Effects of photoperiod on plugs/liners Managing air and media temperature Propagation Environment To promote rapid root formation of plugs and liners, environmental factors need to be controlled, especially in the first 7-10 days: High relative humidity Minimal air movement Moderate light intensity Warm media temperature The term daily light integral (DLI) describes this cumulative amount of light (photons of light) that an area or location receives during one day. Quantity of Light DLI is the cumulative amount of photosynthetic light received in 1 square meter of area (10.8 sq. ft.) each day, or mol m 2 d 1. Daily Light Integral (DLI) Values from sunlight outdoors vary from 5 (winter in the North) to 60 mol m -2 d -1 (in the Southwest in summer). In a greenhouse, values seldom exceed 30 mol m -2 d -1 because of shading which can reduce light by 40 to 70%. Inside a propagation greenhouse, a target DLI is 8 to 12 mol m -2 d -1. In the Northern 1/3 of the U.S. and in Canada, values are often lower until March. DLI Outdoors 1

2 DLI and Young Plants Plant Responses to Increased DLI Avg. Greenhouse DLI (mol m -2 d-1 ) 6 to 8 8 to to 12 Benefit of Supplemental Lighting Large Moderate Small Leaves (smaller and thicker) Time to flower (faster, due partly to temperature) Branching (increased) Stem diameter (increased) Plant height (reduced) Root growth (increased) Low DLI High DLI (Korczynski et al., 2002) February (Runkle, 2011) Supplemental Lighting during Plug Production (Seedlings) Salvia Vista Red 22 days from seed sow at 73 F Grown under a DLI of: (mol m -2 d -1 ) Supplemental Lighting of Plugs with HPS The seedling stage was divided into thirds, each lasting 9 day (petunia) or 11 days (pansy) Plugs were lighted for 1/3 or 2/3 of the plug stage, not at all, or during the entire period L-L-L H-L-L L-H-L L-L-H H-H-L L-H-H H-H-H 1st 2nd 3rd Low DLI High DLI Pansy Delta Premium Yellow 33 days after seed sow at 68 F = Low-intensity lighting (3 µmol m 2 s 1 ) = High-intensity lighting (90 µmol m 2 s 1 ) Each or represents 11 days Sowing Emergence Transplant 2

3 Petunia Madness Red 27 days after seed sow at 68 F = Low-intensity lighting (3 µmol m 2 s 1 ) = High-intensity lighting (90 µmol m 2 s 1 ) An Increase in DLI During Propagation Can Accelerate Flowering Petunia Madness Red 7-11 mol m 2 d mol m 2 d a a ab bc ab c c a ab abc cd a bcd d Each or represents 9 days The greatest value of supplemental lighting of plugs and liners is during the later production stages 44 0 Days to Flower with Stages of Supplemental Lighting 44 0 Supplemental Lighting of Plugs with LEDs 85% R 15% B HPS Catharanthus roseus Titan Punch Sunlight + HPS 100R 85R:15B 70R:30B 100% R 70% R 30% B 16-h photoperiod with 4 supplemental lighting treatments (100 µmol m -2 s -1 ) 70 F air temperature set point Treatment duration = 28 days Catharanthus roseus Titan Punch HPS 100R 85R:15B 70R:30B Stem length (cm) a b c c Catharanthus roseus Titan Punch HPS 100R 85R:15B 70R:30B a a a a Stem caliper (cm) a a a a Shoot dry mass (mg) a a b ab 0.00 HPS 100R:0B 85R:15B 70R:30B 0.0 HPS 100R:0B 85R:15B 70R:30B Supplemental light Supplemental light 3

4 Petunia hybrida Plush Blue Sunlight + HPS 100R 85R:15B 70R:30B Petunia hybrida Plush Blue HPS 100R 85R:15B 70R:30B Stem length (cm) a b bc c Stem caliper (cm) a a a a HPS 100R:0B 85R:15B 70R:30B Supplemental light Petunia hybrida Plush Blue HPS 100R 85R:15B 70R:30B Shoot dry mass (mg) ab ab a b a ab ab b HPS 100R:0B 85R:15B 70R:30B Supplemental light Light Intensity Supplemental Lighting during Liner Production (Cuttings) Stage 1: stick to callus formation: Initially, provide cuttings with low light levels, between 100 and 200 µmol m -2 s-1 (500 to 1,000 fc) Stage 2: after root initiation: After roots have initiated, more moderate light intensities of 200 to 400 µmol m -2 s-1 (1,000 to 2,000 fc) are generally preferred. Stage 3: after roots fill half the plug: Once roots fill about half of the plug cell, maximum light intensity can be increased to 500 to 800 µmol m -2 s-1 (2,500 to 4,000 fc). 4

5 Light Intensity Diffuse, indirect light is best. White wash or exterior shade in combination with retractable shade curtains can provide a good system for light modulation, especially in the spring and summer. Retractable shade curtains alone can be the most effective way to modulate light transmission. Avoid excessive shading during winter months or during cloudy weather. New Guinea impatiens Harmony White Photo taken after 16 d of propagation DLI (mol m -2 d-1 ) Sunlight Sun light + HPS Argyranthemum Madiera Cherry Red Photo taken after 21 d of propagation DLI (mol m -2 d-1 ) Sunlight Sun light + HPS Petunia Tiny Tunia Violet Ice Cuttings Photo Taken after 16 d of propagation DLI (mol) HPS 100R:0B 85R:15B 70R:30B Impatiens Celebrette Frost Shoot dry mass increases with DLI 300 Argyranthemum, R 2 = 0.45 *** 250 Angelonia, R 2 = 0.42 *** Petunia Suncatcher Midnight Blue Shoot dry mass (mg) DLI (mol m -2 d ) Daily light integral (mol m -2 d-1 ) 5

6 Stem caliper increases with DLI Root biomass increases with DLI Argyranthemum, R 2 = 0.51*** Angelonia, R 2 = 0.31 *** 80 Angelonia, R 2 = 0.70 *** Argyranthemum, r 2 = 0.70 *** Diascia, r 2 = 0.65 *** Stem caliper (mm) Daily light integral (mol m -2 d-1 ) Daily light integral (mol m Daily light integral (mol m -2 d -1 ) d -1 ) Supplemental Lighting Guidelines The high-pressure sodium lamp is the most economical lamp type for many seasonal greenhouse applications Lamps should turn on/off automatically by an environmental control computer based on light conditions, for example: On: Light intensity less than 200 µmol m 2 s 1 for more than 5 minutes Off: Light intensity more than 400 µmol m 2 s 1 for more than 10 minutes Supplemental Lighting Guidelines Light intensity and duration are both important Common recommendation is to provide 50 to 75 μmol m -2 s-1 of photosynthetic light (PAR) at plant level, which adds 0.18 to 0.27 mol m -2 each hour lamps are on. For example: Hours per PAR intensity (μmol m -2 s-1 ) day mol 2.2 mol 2.9 mol mol 3.2 mol 4.3 mol mol 4.3 mol 5.8 mol mol 5.4 mol 7.2 mol From October to March (North) Greatest Benefit from Supplemental Lighting From November to February (South) During non-sunny conditions (during the night and on cloudy days) 6

7 Supplemental Lighting Guidelines Choose lamps based on: Efficiency: Photons per watt (µmol/w) Greenhouse dimensions, especially hanging height Reliability: Use trusted brands with warrantees Purchase and installation costs and return on investment Light spectrum for desired plant responses High-Intensity Lighting Efficiency For LEDs, the efficiencies are rapidly improving PPF efficiency Lamp type (µmol/w) HPS, magnetic, 400 W 0.94 HPS, magnetic, 1000 W 1.16 HPS, electronic, 1000 W 1.30 HPS, electronic, 1000 W, double ended 1.70 Ceramic metal halide, 315 W Red + Blue LED fixtures Source: Nelson J.A. and B. Bugbee Economic analysis of greenhouse lighting: Light emitting diodes vs. high intensity discharge fixtures. PLoS ONE 9(6):e Using Sole Source LEDs in Young Plant Production Experimental objective: To quantify how seedlings of popular annual crops acclimate to blue, green, and red light Produce compact ornamentals that are consistent, uniform, and have desirable growth characteristics Relative leaf area Seedling Acclimation to Light Quality Impatiens Tomato Salvia Light quality treatment Photo: OSRAM Opto Semiconductors Seedling Acclimation to Light Quality Seedling Acclimation to Light Quality Impatiens Tomato Salvia Impatiens Tomato Salvia Relative height Relative shoot dry weight Light quality treatment Light quality treatment 7

8 Impatiens SuperElfin XP Red Seedlings grown at 20 C for 4 weeks under LEDs for 18 h d -1 at PAR=160 µmol m -2 s -1 consisting of (%): B 0 G 0 B 0 G 50 B 25 G 25 B 50 G 50 B 50 G 0 B 100 G 0 R 50 HR 50 R 25 HR 25 R 25 HR 25 R 0 HR 0 R 25 HR 25 R 0 HR 0 Salvia Vista Red Seedlings grown at 20 C for 4 weeks under LEDs for 18 h d -1 at PAR=160 µmol m -2 s -1 consisting of (%): B 0 G 0 B 0 G 50 B 25 G 25 B 50 G 50 B 50 G 0 B 100 G 0 R 50 HR 50 R 25 HR 25 R 25 HR 25 R 0 HR 0 R 25 HR 25 R 0 HR 0 B=blue, 446 nm; G=green, 516 nm; R=red, 634 nm; HR=hyper red, 664 nm B=blue, 446 nm; G=green, 516 nm; R=red, 634 nm; HR=hyper red, 664 nm Plasma Sole source LED 88:12 Sole source LED 70:30 Petunia Dreams Midnight LEDs (Red:Blue) PL HPS SS88:12 LED 88:12 High-pressure sodium Petunia Dreams Midnight Amb PL HPS LEDs (Red:Blue) SS88:12 Height (cm) c b c d d a Amb HPS SS88:12 PL Light Source c b b a a ab Petunia Dreams Midnight Amb PL HPS LEDs (Red:Blue) SS88:12 Leaf area (cm 2 ) SPAD (chlorophyll content) c b bc a ad ba c ba ab b a bc a ab Amb HPS SS88:12 PL Light Source 8

9 Petunia Dreams Midnight Amb PL HPS 20 LEDs (Red:Blue) SS88:12 Shoot dry mass (mg) c b b a a ab b a ab a a a 0 Amb HPS SS88:12 PL Light Source Many bedding plants can be induced to flower during the plug/liner stage Common Bedding Plant Responses to Photoperiod (varies by cultivar) Short-day plants: By providing 7-10 short days (long nights) once mature (often 2-4 leafs) Long-day plants: By providing 2-3 weeks of long days (short nights) once mature (often 4-6 leafs) Day-neutral plants: Some (such as seed impatiens) flower earlier with high light intensity 288-cell 72-cell Short-day plants African marigold Celosia Cosmos Dahlia French marigold Gomphrena Mina vine Moon flower Morning glory Salvia Signet marigold Zinnia (some) Common Bedding Plant Responses to Photoperiod (varies by cultivar) Short-day plants African marigold Celosia Cosmos Dahlia French marigold Gomphrena Mina vine Moon flower Morning glory Salvia Signet marigold Zinnia (some) Long-day plants Facultative Ageratum African daisy Blue salvia Calibrachoa Calendula Dianthus Fuchsia (most) Mexican sunflower Pansy Petunia (most) Salvia Snapdragon Statice Sunflower Verbena Obligate Bachelor s buttons Blue lobelia China aster Fuchsia (some) Gazania Lobelia Monkey flower Nierembergia Petunia (some: Wave) Rudbeckia Strawflower Sweet pea Tuberous begonia SD-Treated Marigold Taishan Yellow Plugs Finished under LD Days to flower from sow SD 7SD 10SD 14SD Number of short days Sonali Padhye, PanAmerican Seed 9

10 SD-Treated Celosia First Flame Orange Plugs Finished under LD 0SD 7SD 10SD 14SD Sonali Padhye, PanAmerican Seed Managing Temperature Monitor media temperature, not just air temperature. For most crops, the media should be 73 to 77 F (it s often colder in the winter) and the air temperature should be 5 to 8 F cooler Factors that influence media temperature: o Air temperature o Water temperature o Light o Media and tray color o Glazing temperature Tagetes Bonanza Yellow Average daily light integral: 10 mol m-2 d-1 15 days from seed sow at: ( F) Estimated days to finished 128-cell plug Average daily light integral: 10 mol m-2 d-1 57 Celosia Gloria Mix 23 days from seed sow at: ( F) Get the Heat to Where it Counts! Estimated days to finished 128-cell plug 10

11 Celosia Sun + LEDs Glow Pink Sun + HPS 100R:0B 90R:10B 80R:20B Catharanthus Titan Icy Pink Sun + HPS 100R:0B 90R:10B 80R:20B Ambient Ambient + 5 F Root zone heating + 5 F Root zone heating + 10 F Root zone heating + 10 F Root zone heating For More Information Acknowledgments We thank former graduate student research assistants and technicians who have performed experiments to generate this information We also thank private horticulture and lighting companies that financially support MSU and Purdue floriculture research including: 11