in HortScience
View More View Less
  • 1 Department of Plant Sciences, University of Arizona, Tucson, AZ 85721

Sucrose is the major form of translocated carbohydrate in most plants. While enzymes of sucrose degradation have been well studied in many agronomic crop sinks, little is known about the physiology of sucrose breakdown in most floral tissues. Invertase and sucrose synthase are accepted as the key enzymes responsible for sucrose breakdown. As the first step in studying sucrose breakdown in Lilium longiflorum, we characterized floral bud invertase enzymes. Three soluble invertases were present in developing buds, and were resolved by DEAE-Sephacel chromatography (Invertases I, II, and III, in order of elution). After further purification, each enzyme was characterized. Each was an acid invertase (pH optima of 4.0 to 5.0). each had Km values for sucrose of 5.0 to 7.0 mM. To determine if the enzymes had tissue-specific localization, anthers were dissected from tepal, pistil, and filament tissues. Invertase I was localized primarily in anthers, with invertases II and III being present in much smaller amounts. Invertases II and III were the major forms in the other floral tissues with essentially no invertase I detectable.