Light Emitting Diodes as an Alternative to Cool White Fluorescents for Healing of Grafted Tomato Transplants

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1 Light Emitting Diodes as an lternative to Cool White Fluorescents for Healing of Grafted Tomato Transplants Jimmy Byrtus² Christian Collado¹, Gregory Sheets¹, Melanie Yelton², and Ricardo Hernández¹ ¹Department of Horticultural Sciences, North Carolina State University, Raleigh, NC ²LumiGrow Inc., Emeryville, C Introduction Grafted tomato seedlings propagation must be optimized to increase production efficiencies. Grafting has several steps that include growing, grafting, healing, and acclimation. Healing is considered the most critical step. Healing is the joining of cambium between rootstock and scion to form vascular tissue and is commonly done under modified greenhouse conditions or inside healing chambers. Previous work determined that light during the healing period influences morphology and quality of grafted tomatoes. Cool white fluorescent (CWF) at a photosynthetic photon flux of 100 µmol m-2 s-1 is recommended for healing chambers. Light emitting diodes (LED) make possible optimizing the spectral requirements for healing LumiGrow, Inc. ll right reserved.

2 Materials and Methods The Treatments: CWF 100: Cool White Fluorescent 100 µmol m-2 s-1 Cultivars: Root Stock, Scion: Trust CWF 75: Cool White Fluorescent 75 µmol m-2 s-1 Greenhouse planting density : 1,000 plants m-2 B4:G5:R89: LumiGrow LED top lighting fixture emitting 4% blue, 5% green and 89% red photon flux, 75 µmol m-2 s-1 B30:G2:R68: LumiGrow LED top lighting fixture emitting 30% blue, 2% Green and 67% red photon flux, 75 µmol m-2 s-1 B50:R50: LumiGrow LED top lighting fixture emitting 50% blue, and 50% red photon flux, 75 µmol m-2 s-1 B76:R24: : LumiGrow LED top lighting fixture emitting 76% blue, and 24% red photon flux, 75 µmol m-2 s-1 Healing Box Planting Density: 500 plants m-2 Experimental Time: 2 Repetitions, 13 to 15 days starting June 22nd and ending July 21st Healing Box Growth Time: 6 Days Greenhouse Fertilization: Sub irrigated as needed with Hydroponic Solution Pre Graft Measurements: Height, Stem Diameter, Leaf rea, Leaf Number Post Graft Measurements: Height, Fresh Mass, Dry Mass, Leaf Number, Leaf rea, Stem Diameter, Calculated Plant Compactness LumiGrow, Inc. ll right reserved.

3 Greenhouse Environmental Conditions Measurement Units Rep 1 Rep 2 Specifications verage DLI mol m-2 d One Location at Canopy Height verage Photoperiod Hours verage day length over 14 days, No Supplemental Lighting was used One location in the center of the Greenhouse Greenhouse ir Temperature C Day 25.3± ± 1.6 C Night 25.5± ± 1.8 Day 85.1 ± 7.5 Night 81.8 ± ± ± 6.3 Greenhouse Relative Humidity Greenhouse Vapor Pressure kpa Deficit kpa tmospheric CO2 One Location calculations based on ir and Humidity Data Day 0.49 ± ± 0.2 Night 0.61 ± ± 0.28 mbient mmol mol-1 Nutrient Solution ph Nutrient Solution Electrical Conductivity Same Location as the Greenhouse ir Temperature ds m-1 mbient Natural Ventilation 6.29 ± ± 0.09 Data captured for each fertigation 1.79 ± ± 0.08 Data captured for each fertigation Temperature C 30B:2G:68R 76B:24R 4B:5G:89R 50B:50R CWF 75 CWF 100 Rep ± ± ± ± ± ± 0.28 Rep ± ± ± ± ± ± LumiGrow, Inc. ll right reserved.

4 Mean Initial Stem Diameter (mm) Mean Initial Leaf rea (mm²) Height (mm) 1650 Stem Diameter (mm) Mean Initial Ht (mm) Leaf rea (mm²) Results Mean Plant Compactness (g/mm) 84 Mean % Difference in Leaf rea % 50% C BC BC B BC % Difference in Leaf rea Plant Compactness (g/mm) Mean % Difference in Height Mean Final Dry Mass (g) 30% 25% % Difference in Height Dry Mass (g) 20% 0% B B B B B 20% 15% 10% 5% 0% % 10% % B30:G2:R68 B4:G5:R89 B50:R50 B76:R24 CWF LumiGrow, Inc. ll right reserved. CWF 75

5 Conclusions Light treatment had no effect on percent difference for leaf area (mm²). Plant compactness (g/mm) calculation showed that treatments of CWF 100 significantly more compact, 22%, than both B4:G5:R89 and 30B:G2:R68 treatments and similar to 50B:50R, 76B:24R, and CWF 75. B4:G5:R89 treatment has a 31% increase in % difference in height. This was significantly different from all other treatments. Based on pre graft data collected, initial height, initial stem diameter, and initial leaf area showed no differences between treatments. Based on the results LED lighting can heal grafted tomatoes as well as Cool White Fluorescent lighting in a sole source lighting scenario. CWF 100 was significantly different from B30:G2:R68 for mean final dry mass resulting in a 21% increase in final dry mass Can t Get Enough Research? Visit our website. (800) sales@lumigrow.com LumiGrow, Inc. ll right reserved.