PARTITIONING OF CARBOHYDRATES IN THE BULB OF ORIENTAL LILY 'STARGAZER' IS INFLUENCED BY SUPPLEMENTAL LIGHTING DURING FORCING

Following lily planting the reserve carbohydrates in mother scales are degraded and soluble sugars are transported to developing sprouts and daughter scales. The effects of additional lighting during lily forcing on carbohydrates and dry matter changes in mother and daughter scales were investigated. The experiment was conducted on oriental lily 'Stargazer', grown in a greenhouse during the winter at two light levels: natural light and natural light with supplemental lighting. At three growth stages (I – visible flower buds, II – buds 3-4 cm and III - flowering) plants were harvested and the level of starch, sucrose, glucose and fructose together with fresh and dry matter changes were determined. Supplemental lighting significantly influenced degradation of reserves in mother scales and accumulation of carbohydrates in daughter bulbs. The natural low light level during forcing showed an increased hydrolysis of reserves in mother scales due to faster starch breakdown and higher concentration of glucose and fructose compared to plants grown under supplemental lighting. The sucrose concentration did not vary greatly among treatments; however, it was higher in plants grown at ambient light level. Proportionally to reserve carbohydrate depletion a decrease in fresh and dry weights (FW and DW) of mother scales was observed. During plant growth the concentration of glucose and fructose in daughter bulbs decreased, irrespectively of the light level. However, the starch and sucrose concentration increased significantly at this time. At flowering, due to the higher fresh and dry matter of daughter bulbs of plants grown with additional lighting, the accumulation of glucose, fructose, sucrose and starch were 237%, 164%, 870% and 270% higher, respectively compared with control plants.

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