Relative Efficiency of High- and Low-pressure Sodium and Incandescent Filament Lamps Used to Supplement Natural Winter Light in Greenhouses1

Abstract

The relative efficiencies of high-pressure (HPS) and low-pressure sodium (LPS) lamps for plant growth were determined for 32 species of foliage and flowering plants in greenhouse under winter conditions at 37°N latitude. HPS with a relatively wide spectral emission peaking at 589 nm, and low-pressure sodium (LPS) with a monochromatic line at 589 nm were compared at 42 W/m2 irradiance in the 400–700 nm region for various lengths of time at various times of day. Although radiation in the far-red region (700–800 nm) differed, HPS and LPS equally accelerated rates of increase in fresh weights, and heights, and flowering of most herbaceous and tropical foliage plants evaluated. High-pressure sodium and LPS were ineffective, however, in promoting growth of deciduous trees and some woody plants and had no more effect than exposure of the plants to natural winter days with 0.9 W/m2 from incandescent lamps for 8 hrs (2000-0400) night interruption (long day controls). After 16 hours, about half the species showed photomorphogical differences between plants grown at intensities of 21 and plants grown at 42 W/m2 from LPS. All showed significantly better growth characteristics (fresh weight, height, early flowering) than the long day controls. Lighting during the day or night (42 W/m2 from 0800–1600 or from 2000–0400) was equally effective in promoting growth responses with 15 of the 32 species evaluated. Night lighting was more effective than day lighting with 10 of the 32 species tested. The majority of the species grew equally well when lighted 16 hours daily (0800-2400) with 21 W/m2 or 8 hours daily (2000–0400) with 42 W/m2. Effectiveness of the lighting was generally unrelated to the photoperiodic requirements of the plants. Many of the plants, which were previously classified as day-neutral (DN), flowered as if they were long day plants. Such day-neutral plants apparently required adequate light (intensity and duration) for photosynthesis. Increased daylength alone, without regard to intensity, was not sufficient to accelerate growth and early flowering of day-neutral plants. Since HPS and LPS were equally effective on most species tested, we concluded that light quality was less important than total irradiation (energy) for the growth and early flowering of many herbaceous plants.

Influence of Intensity and Duration of Cool White Fluorescent Lighting and Fertilizer on Growth and Quality of Foliage Plants1

“…The effect of this treatment on new root growth after planting and its subsequent effect on the root/shoot ratio of different rootstocks/scion combinations has not been studied in detail. In earlier reports, it was shown that moderate shoot pruning at planting increased new shoot production and decreased new root growth while maintaining a constant root/shoot ratio (6,10). Preston (11) found that pruning the leader and lateral shoots at planting decreased total root weight compared to pruning only the leader or no pruning.…”

“…More recently, Epel (14) found that continuous fluorescent light inhibited division of green algae, but did not appear to influence photosynthetic growth. Cathey et al (4,5,6) have conducted extensive research on artificial lighting of woody and herbaceous plants, but their work '…”

Long‐term effects of artificial nighttime lighting and trophic complexity on plant biomass and foliar carbon and nitrogen in a grassland community

“…Through a promotive effect on the activity of plant photoreceptors, the white LED treatment could have stimulated plant growth of some species in winter, when most plant species are dormant. Supplemental lighting that comes from light sources that emit red light (e.g., HPS lighting) has been shown to promote plant growth in winter (Cathey & Campbell, 1979 ; Grimstad, 1987 ). This suggests that cool white LED lighting might have increased plant competition for nutrients through a higher nutrient uptake required to sustain continuous plant growth (e.g., growth in the cold season).…”

Acclimatization of ex Vitro Strawberry Plantlets in CO2-enriched Environments and Supplementary Lighting

“…He also showed that root development was improved by high irradiance (18). In the greenhouse industry, highpressure sodium (HPS) SL is used to increase yield and quality of crops (5). However, there is no study on the effects of HPS SL on the acclimatization of ex vitro plantlets.…”