CARBOHYDRATE METABOLISM AND DRY WEIGHT PARTITIONING IN THE EASTER LILY (LILIUM LONGIFLORUM THUNB.).

摘要

The underground bulb of the lily acts as a source of carbohydrate to the developing aerial shoot, and little is known about the physiology, biochemistry, or environmental factors influencing this process. Carbohydrate content and changes in dry weight between plant parts were followed during growth in normal or reduced light environments, and during cold storage. HPLC methodology was used to quantitate changes in soluble sugars, starch was measured enzymatically.; Outer (mother) scales decreased steadily in dry weight during bulb forcing, regardless of the light environment. Inner (daughter) scales exhibited little dry weight export when grown under full sun conditions. Under shade conditions, daughter dry weight export was detected after four weeks. Thereafter, more export occured with increasing levels of light reduction. Leaf carbohydrate level and leaf dry weight decreased with shading.; There was little change in starch concentration until 40 days after planting, when starch in outer (mother bulb) scales began to decline. Starch concentration of inner (daughter bulb) scales did not change when plants were grown in ambient greenhouse light, but declined as a result of shading. Starch degradation proceeded from the scale perifery inwards toward the vascular bundles.; The condition of sucrose export in lily scales was characterized by high concentrations of sucrose, glucose, fructose and mannose. Mannose apparently arises from hydrolysis of glucomannan, a secondary storage polymer. It appeared that free mannose was readily metabolized, probably into sucrose.; Pre-plant storage of -1.1 C resulted in massive starch hydrolysis and sucrose accumulation (up to 250 mg/g dry weight). Storage at 4.4 C resulted in about one-third as much sucrose, but most rapid flowering when subsequently forced in a greenhouse. The soluble sugar concentration was not related to the vernalization status of the bulb.