Growth of Impatiens, Petunia, Salvia, and Tomato Seedlings under Blue, Green, and Red Light-emitting Diodes

Abstract

<jats:p>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 (<jats:italic>Impatiens walleriana</jats:italic>), salvia (<jats:italic>Salvia splendens</jats:italic>), petunia (<jats:italic>Petunia ×hybrida</jats:italic>), and tomato (<jats:italic>Solanum lycopersicum</jats:italic>) under six sole-source light-emitting diode (LED) treatments or one cool-white fluorescent treatment that each delivered a photosynthetic photon flux (<jats:italic>PPF</jats:italic>) of 160 µmol·m<jats:sup>−2</jats:sup>·s<jats:sup>–1</jats:sup> for 18 h·d<jats:sup>−1</jats:sup>. 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.</jats:p>

Physiological responses of cucumber seedlings under different blue and red photon flux ratios using LEDs

“…Plant responses to monochromatic R light are species specific. For example, Wollaeger and Runkle (2014) showed that leaf area of tomato, salvia and petunia was 47-130% greater in plants grown under monochromatic R compared to those grown under 25% or more B added to R. Ohashi-Kaneko et al (2007) also reported greater leaf area in leaf lettuce and komatsuna on plants grown under monochromatic R compared to plants grown under the combination of R and B light. In contrast, Brown et al (1995) found 36% greater leaf area in the R:B treatment than the monochromatic R treatment in pepper plants.…”

“…Plant growth rate responses under R compared to the responses under the combination of R and B are species specific. For example, Wollaeger and Runkle (2014) showed that tomato, salvia and petunia had 48-112% greater shoot fresh mass when grown under 100R% light than when grown under 25% or more B light (PPF: 160 mmol m À2 s À1 , photoperiod 18 h). In komatsuna leaves, OhashiKaneko et al (2007) reported 43% greater dry mass under R light than white light (PPF: 300 mmol m À2 s À1 , photoperiod 12 h).…”

“…We postulate that greater leaf area, LMA, leaf Pn and leaf g s increased whole plant photosynthetic rate and consequently growth rate in the 100B:0R% treatment. Few research reports on the growth rate of plants under 100% B light are available (Gu et al, 2012;Hogewoning et al, 2010b;Lian et al, 2002;Liu et al, 2011;Wollaeger and Runkle, 2014). For example, Wollaeger and Runkle (2014) found no differences in shoot fresh mass and shoot dry mass in impatiens, tomato, salvia and petunia under 100B:0R% and under 50B:50R%.…”

“…For example, Nanya et al (2012) showed that tomato dry mass was greater under the 10B:90R% treatment than under 50B:50R% or 30B:70R%. Wollaeger and Runkle (2014) showed greater dry mass in tomato seedlings grown under monochromatic R than those grown under G:R, B:G:R, B:G, B:R and monochromatic B. Liu et al (2011) showed that cherry tomato seedlings grown under monochromatic B LEDs had greater dry mass than plants grown under B:R, B:G:R and R LEDs.…”

“…In vegetable transplants, such as tomato, lettuce, pepper and cucumber, different R:G:B PF ratios have been tested. In tomato, under sole source electrical lighting, studies agree that higher B:R ratios decrease tomato plant height (Liu et al, 2011;Nanya et al, 2012;Wollaeger and Runkle, 2014). However, conflicting results are reported on tomato growth rate.…”