The effects of light quality, fertilization, and ethylene on performance of foliage plants in low light environments

Abstract

Ficus benjamina, F. stricta, Dieffenbachia amoena, and Brassaia arboricola were used to determine the effects of light quality and fertility on long-term maintenance in low light. Three light sources, (1) 100% PAR fluorescent, (2) 70% PAR fluorescent + 30% PAR incandescent, and (3) 50% PAR Gro-Lux + 50% PAR Gro-Lux Wide Spectrum, were used to determine the effects of light quality. PAR was equalized between treatments at 14 (mu)Em('-2)s('-1) (104 ft-c). After 1 year in the interior, no significant differences were observed in plant response (height, fresh and dry wt. of plant tops and roots, leaf number, leaf area, chlorophyll, and overall quality). Three fertilizer regimes were used in maintaining the 4 species for 1 year at 12 (mu)Em('-2)s('-1) (89 ft-c) in an interior environment: (1) soluble fertilizer (Peters 20-20-20) added weekly in the irrigation water at 200 ppm N: 88 ppm P: 166 ppm K, (2) slow-release fertilizer (Osmocote, 3 month release formulation) applied as a top dress every 3 months at 4.1g N/6" pot, and (3) an unfertilized control. After 1 year the effects of fertilization under low-light were found to be minimal on the parameters measured. A major problem in studying performance in interior environments is inconsistent leaf drop between replicated experiments. To find a means to consistently induce leaf drop in the interior, 2 current acclimatization methods were studied using F. benjamina and F. stricta. Plants were grown, (1) at 5 light intensities from 1685 to 340 (mu)Em('-2)s('-1) (8610 to 1737 ft-c) and placed directly into an interior environment or, (2) grown at 1685 (mu)Em('-2)s('-1) then acclimatized for 6 weeks at the various light intensities prior to placement indoors. PAR in the interior was set at 10.5 (mu)Em('-2)s('-1) (78 ft-c). Acclimatization reduced leaf drop but neither method proved superior. Full sun treatments, with the exception of 2, exhibited a higher percentage leaf drop than shade grown or acclimatized plants. The effects of ethylene on leaf abscission in the 2 Ficus spp. were also studied. Each proved sensitive to ethylene gas, which induced leaf drop, however, no evolution of ethylene was detected. During the study, depletion of the gas from the environment by soil microbes was detected.