Analysis of nonstructural carbohydrates in storage organs of 30 ornamental geophytes by high-performance anion-exchange chromatography with pulsed amperometric detection.

A comprehensive analysis of nonstructural carbohydrates in storage organs (bulbs and corms) of 30 ornamental geophytes was conducted by employing a variety of extraction techniques followed by high-performance anion-exchange chromatography with pulsed amperometric detection (HPAE-PAD). Among species, starch, fructan, glucomannan and soluble sugars accounted for 50-80% of storage organ dry weight (DW). Starch ranged from 24 to 760 mg g(-1) DW, fructan (commonly occurring with starch) from 25 to 500 mg g(-1) DW, and glucomannan from 15 to 145 mg g(-1) DW. An acid hydrolysis protocol for concurrent determination of fructan and glucomannan was developed. The average degree of polymerization (DP) of ethanol and water-soluble fructan and the man : glu ratio of glucomannan also varied between species. The 80% ethanol fraction contained soluble sugars and short-chain fructans (< 25 DP), whereas water extracts contained soluble sugars, fructans (both short- and long-chain, <or= 100 DP), and glucomannan. A substantial portion of the starch became 'soluble' in water during extraction, and depended on the species and extraction temperature. Our results indicate that extraction and analysis techniques of nonstructural carbohydrates for physiological and biochemical research on geophytic storage organs should be validated to accurately understand the identity of diverse carbohydrate pools, their physiological relevance and functions.