INFLUENCE OF SPECTRAL FILTERS ON GROWTH AND POSTHARVEST QUALITY OF POTTED MINIATURE ROSES

The role of light quality on growth and postharvest characteristics of potted miniature roses (Rosa X hybrida cultivar 'Meijikatar') was evaluated using 6% CuSO4 and water (control) as spectral filters. The CuSO4 spectral filters reduced R and FR wavelengths and increased the R:FR, B:FR and B:R ratios (R=600-700 nm; FR=700-800 nm; B=400-500 nm) and 0 of transmitted light compared with control filter. Light transmitted through the CuSO4 filter significantly reduced plant height and internode length and increased the number of lateral shoots compared with control plants. However, the degree of response varied with growing season. CuSO4 filters slightly accelerated flowering in early spring-grown plants but slightly delayed flowering in late spring and summer. Total number of flowers was not affected by spectral filter but plants grown under control filter had larger flowers than those grown under the CuSO4 filter. Light transmitted through CuSO4 filter reduced leaf sucrose and starch concentration by 40% and 65%, respectively. Leaf glucose and fructose concentrations were not affected by light quality. Postharvest quality of plants grown under CuSO4 and control filters was reduced and leaf yellowing increased as the shipping temperature increased. Light quality in the growing environment did not significantly reduce the overall appearance of plants shipped at 4 degrees C or 15 degrees C. However, plants grown under CuSO4 filter had slightly higher percentage of yellow leaves than the corresponding control plants after shipping at any temperature. Alteration of light quality in the greenhouse can be used to control height of rose plants but extended shipping at high temperatures could result in leaf yellowing possibly because of reduced carbohydrate status.