Response of conifer species from three latitudinal populations to light spectra generated by light-emitting diodes and high-pressure sodium lamps

Abstract

Light-emitting diode (LED) technology shows promise for supplementing photosynthetically active radiation (PAR) in forest nurseries because of the potential reduction in energy consumption and an ability to supply discrete wavelengths to optimize seedling growth. Our objective was to examine the effects of light spectra supplied by LED and traditional high-pressure sodium (HPS) lamps on growth and physiology of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and Engelmann spruce (Picea engelmannii Parry ex Engelm.) seedlings. We used three latitudinal sources for each species: British Columbia (BC), Idaho (ID), and New Mexico (NM). Container seedlings were grown for 17 weeks in the greenhouse under an 18 h photoperiod of ambient solar light supplemented with light delivered from HPS or LED. In general, seedlings grown under LED had significantly greater growth, gas exchange rates, and chlorophyll contents than those seedlings grown under HPS. The growth and physiological responses to supplemental lighting varied greatly among species and seed sources. Generally, LED-grown seedlings from BC had the greatest growth and tissue dry mass followed by ID and NM populations. Compared with HPS, the significant increase in seedling growth and concomitant energy savings with LED (29% energy consumption relative to HPS) demonstrates the promise of using LED as PAR supplemental lighting for container seedling production.

Nutrient Uptake and Utilization by Fragrant Rosewood (Dalbergia odorifera) Seedlings Cultured with Oligosaccharide Addition under Different Lighting Spectra

“…In other species, leaf biomass was promoted by the LED lighting in Norway spruce seedlings [25] compared to HPS lighting. Leaf biomass was unaffected or negatively impacted by LED lighting relative to the HPS lighting in Scots pine, Douglas-fir, and Engelmann spruce seedlings [20,24]. In our study, neither stem biomass nor root biomass responded to the treatments, indicating that treatments did not drive biomass allocation.…”

“…Most of the current studies did not find any response of RCD to the light spectra between HPS and LED lightings [19,20,24,25]. In studies on highly valued slowly-growing seedlings, there was also a rare RCD response found for the HPS lighting relative to the control [5,6].…”

“…This suggests a hint that starch was metabolized by hydrolyzing into sugars mostly for elevated respiration to counter stress exerted by improper illumination [40]. In our study, the lighting intensity under HPS and LED lightings was measured to be about 72-73 µmol m −2 s −1 , which fell in the range between 70 and 80 µmol m −2 s −1 [24], being sufficient for seedling growth and unlikely to drive stress. Therefore, the increase of sugars and the decrease of starch in the stem under the HPS lighting may have resulted from the spectrum under the lamps.…”

“…However, the response of seedling height to different lighting spectra between LED and HPS lightings seemed to vary to a great extent. For example, Apostol et al [24] reported that compared to seedlings under the HPS lighting, Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) seedlings only responded with a greater height from the Idaho source under the LED lighting, where Engelmann spruce (Picea engelmannii Parry ex Engelm.)…”

“…It is which can be evaluated by the criteria of sturdiness and shoot-to-root ratio (i.e., biomass of shoot divided by biomass of root) [31]. In tree seedlings, height was mostly responsive to different light spectra with little changes in diameter growth [19,24]. However, the faster growth of height relative to diameter would result in a higher sturdiness, which may be an indicator of the depressed seedling quality [25].…”