INFLUENCE OF SUPPLEMENTAL LIGHTING ON FRESH AND DRY MATTER ACCUMULATION OF ORIENTAL LILIES DURING FORCING

Quality of oriental lilies during winter forcing is often reduced as the result of insufficient light level. The effect of supplemental lighting on fresh and dry matter distribution of two oriental lily cultivars: ‘Star Gazer’ and ‘Laura Lee’ were investigated and compared with plants grown at ambient light conditions. At two weeks intervals plants were harvested and their fresh and dry weight of organs such as bulbs, stems, leaves and flowers were determined. The fresh and dry weights of lily bulbs (mother and daughter portion) decreased sharply during the initial six weeks of growth, namely about 70 % in both varieties. The depletion of bulb weight in plants grown at ambient light level was observed until flowering. The progressive increase in fresh and dry weight of bulbs of plants grown with supplemental lighting was observed from the tenth week till flowering, due to daughter bulbs enlargement. The rate of fresh and dry matter accumulation in leaves and stems increased with light level. Since the eight weeks of growth, the fresh and dry weights of these organs increased only in plants grown with additional lighting. Supplemental lighting throughout the forcing period strongly increased flower bud fresh and dry weights in both cultivars. At flowering the fresh weight of flower buds was 3 and 1.4 times higher in ‘Laura Lee’ and ‘Star Gazer’, respectively, compared to plants grown at ambient light conditions. Supplemental lighting significantly increased stem sturdiness expressed as the ratio of FW and DW of stem to plant height.

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