Growth and Photomorphogenesis of Pepper Plants under Red Light-emitting Diodes with Supplemental Blue or Far-red Lighting

Abstract

<jats:p>Light-emitting diodes (LEDs) are a potential irradiation source for intensive plant culture systems and photobiological research. They have small size, low mass, a long functional life, and narrow spectral output. In this study, we measured the growth and dry matter partitioning of `Hungarian Wax' pepper <jats:italic>(Capsicum annum</jats:italic> L.) plants grown under red LEDs compared with similar plants grown under red LEDs with supplemental blue or far-red radiation or under broad spectrum metal halide (MH) lamps. Additionally, we describe the thermal and spectra1 characteristics of these sources. The LEDs used in this study had a narrow bandwidth at half peak height (25 nm) and a focused maximum spectral output at 660 nm for the red and 735 nm for the far-red. Near infrared radiation (800 to 3000 nm) was below detection and thermal infrared radiation (3000 to 50,000 nm) was lower in the LEDs compared to the MH source. Although the red to far-red ratio varied considerably, the calculated phytochrome photostationary state (φ) was only slightly different between the radiation sources. Plant biomass was reduced when peppers were grown under red LEDs in the absence of blue wavelengths compared to plants grown under supplemental blue fluorescent lamps or MH lamps. The addition of far-red radiation resulted in taller plants with greater stem mass than red LEDs alone. There were fewer leaves under red or red plus far-red radiation than with lamps producing blue wavelengths. These results indicate that red LEDs may be suitable, in proper combination with other wavelengths of light, for the culture of plants in tightly controlled environments such as space-based plant culture systems.</jats:p>

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

“…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. In spinach and cherry tomato no leaf area differences were found between plants in the monochromatic R treatment and plants in the R:B treatment (Liu et al, 2011;Ohashi-Kaneko et al, 2007).…”

“…The decrease of stem extension in vegetable transplants caused by the increase of B PF to a dominant R PF spectrum has been reported Liu et al, 2011;Nanya et al, 2012;Wollaeger and Runkle, 2013). For example, Brown et al (1995) showed greater stem length in pepper seedlings under the 0B:100R% treatment than under the 10B:90R% treatment (PPF: 300 mmol m À2 s À1 , photoperiod 12 h). Liu et al (2011) In the present study, plants under the 100B:0R% treatment had greater plant height, hypocotyl, and epicotyl length than plants under all other treatments (P < 0.0001) (Figs.…”

“…For example, Yorio et al (1998) summarized work done by NASA life support program on blue light requirements of lettuce, potato, radish, spinach, and wheat, and concluded that a minimum of 35 mmol m À2 s À1 of B light (in an otherwise R light regime) is necessary for normal plant growth and development. Also, Brown et al (1995) showed that pepper seedlings, when grown under 100R% light (660 nm peak wavelength), had longer stem length and lower plant dry mass than when grown under the combination of R LED and B fluorescent light (PPF: high intensity LEDs, research continued to focus on plant growth and morphological responses to B, green (G) and R PF ratios (Massa et al, 2008). In vegetable transplants, such as tomato, lettuce, pepper and cucumber, different R:G:B PF ratios have been tested.…”

Acclimations to light quality on plant and leaf level affect the vulnerability of pepper (Capsicum annuum L.) to water deficit

“…The sensitivity of pepper to water deficit is demonstrated in a large number of publications dealing with physiological responses as well as plant growth and biomass production (Delfine et al 2001;De Pascale et al 2003;González-Dugo et al 2007;Ferrara et al 2011;Kulkarni and Phalke 2009;Sezen et al 2006;Smittle et al 1994;Sziderics et al 2010). In addition, findings demonstrate the sensitivity of pepper plants to light quality, including light-induced alterations in plant growth, dry matter partitioning and anatomical features of leaves and stems (Brown et al 1995;Schuerger et al 1997). In the present study, pepper plants were cultivated either under a wide-band light spectrum provided by CFL, or under LEDs offering narrow band spectra with dominant peaks at 445 and 665 nm.…”

“…In the last decades, a significant number of publications provided precise information on the effect of light quality on plant growth, morphogenesis and photosynthetic responses (Abidi et al 2012;Brown et al 1995;Hogewoning et al 2010a, b;Murakami et al 2014;Muraoka et al 2002;Schuerger et al 1997;Terfa et al 2013). In controlled (climate chamber) and semi-controlled (greenhouse) environments, compact fluorescence lamps (CFL) and high pressure sodium lamps are commonly used to provide photosynthetic active radiation (PAR) to the plants.…”