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  • Author or Editor: Heidi Marie Wollaeger x
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Light-emitting diodes (LEDs) are of increasing interest in controlled environment plant production because of their increasing energy efficiency, long lifetime, and colors can be combined to elicit desirable plant responses. Red light (600–700 nm) is considered the most efficient wavelength for photosynthesis, but little research has compared growth responses under different wavelengths of red. We grew seedlings of impatiens (Impatiens walleriana), petunia (Petunia ×hybrida), tomato (Solanum lycopersicum), and marigold (Tagetes patula) or salvia (Salvia splendens) at 20 °C under six sole-source LED lighting treatments. In the first experiment, a photosynthetic photon flux (PPF) of 160 μmol·m−2·s–1 was provided for 18 h·d−1 by 10% blue (B; peak = 446 nm) and 10% green (G; peak = 516 nm) lights, with the remaining percentages consisting of orange (O; peak = 596 nm)–red (R; peak = 634 nm)–hyper red (HR; peak = 664 nm) of 20–30–30, 0–80–0, 0–60–20, 0–40–40, 0–20–60, and 0–0–80, respectively. There were no consistent effects of lighting treatment across species on any of the growth characteristics measured including leaf area, plant height, or shoot fresh weight. In a second experiment, seedlings were grown under two light intensities (low, 125 μmol·m−2·s–1 and high, 250 μmol·m−2·s–1) consisting of 10% B and 10% G light and the following percentages of R–HR: 0–80, 40–40, 80–0. Shoot fresh weight was similar in all light treatments, whereas shoot dry weight was often greater under the higher light intensity, especially under the 40–40 treatments. Leaf chlorophyll concentration under 40–40low, 80–0low, or both was often greater than that in plants under the high light treatments, indicating that plants acclimated to the lower light intensity to better use photons available for photosynthesis. We conclude that O, R, and HR light have generally similar effects on plant growth at the intensities tested when background G and B lights are provided and thus, selection of red LEDs for horticultural applications could be based on other factors such as economics and durability.

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Plant growth and architecture are regulated in part by light quality. We performed experiments to better understand how young plants acclimate to blue (B), green (G), and red (R) light and how those responses can be used to produce plants with desirable morphological characteristics. We grew seedlings of impatiens (Impatiens walleriana), salvia (Salvia splendens), petunia (Petunia ×hybrida), and tomato (Solanum lycopersicum) under six sole-source light-emitting diode (LED) treatments or one cool-white fluorescent treatment that each delivered a photosynthetic photon flux (PPF) of 160 µmol·m−2·s–1 for 18 h·d−1. Leaf number was similar among treatments, but plants grown under 25% or greater B light were 41% to 57% shorter than those under only R light. Plants under R light had 47% to 130% greater leaf area and 48% to 112% greater fresh shoot weight than plants grown under treatments with 25% or greater B. Plants grown under only R had a fresh shoot weight similar to that of those grown under fluorescent light for all species except tomato. In impatiens, flower bud number at harvest generally increased with B light, whereas in tomato, the number of leaflets with intumescences decreased with B light. This research discusses how light quality can be manipulated for desired growth characteristics of young plants, which is important in the production of specialty crops such as ornamentals, herbs, and microgreens.

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Declining bee populations has garnered media attention, which has pressured plant retailers to ask or demand the reduction or elimination of neonicotinoid insecticide use in greenhouse production. This study investigated consumer perspectives on eco-friendly ornamental plant production practices in combination with a variety of insect management practices. Data from an online study were collected from 1555 Americans in May 2015. Over half (55%), nearly half (48.2%), and more than 30% of the participants felt that “bees are not harmed,” “better for the environment,” or “plants that attract bees,” respectively, was a characteristic of bee-friendly insect management practices. The latter group erroneously confused bee-friendly insect management practices with plants that are a potential food source for bees. When asked to rate various insect management plant production practices on a five-point Likert scale, consumer mean scores were positive (defined here as 3.5 to 5.0) for “plants grown using bee-friendly insect management practices,” “plants grown using insect management strategies that are safe for pollinators,” “plants grown using best insect management practices to protect pollinators,” and “plants grown using insect management practices that leaves no insecticide residue on the plant.” Plant species accounted for 31.6% of the decision to purchase the plant, followed by price (25.1%), insect management strategy (23.3%), and eco-friendly practices (20.1%) that was similar to prior published findings. Analyses showed that plants labeled as “grown using bee-friendly insect management practices” were worth $0.26, $0.26, $0.89, and $1.15 more than plants labeled as “grown in a sustainably produced potting soil/mix,” “grown using recycled/recaptured water,” “grown using protective neonicotinoid insecticides,” and “grown using traditional insect management practices,” respectively. In addition, plants labeled as “grown using best insect management practices to protect pollinators” were worth $0.10, $0.10, $0.73, and $0.99 more than plants labeled as “grown in a sustainably produced potting soil/mix,” “grown using recycled/recaptured water,” “grown using protective neonicotinoid insecticides,” and “grown using traditional insect management practices,” respectively. Thus, selected insect management strategies were valued more, on average, than eco-friendly production practices.

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