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Artifacts in the Analysis of Plant Tissues for Soluble Carbohydrates

Hendrix, Donald L., Peelen, Kimberly K.
Crop science 1987 v.27 no.4 pp. 710-715
Gossypium hirsutum, Citrullus lanatus, Beta vulgaris, Saccharum, tissue analysis, sucrose, glucose, fructose, phenolic compounds, beta-fructofuranosidase
A study of the soluble sugars in cotton (Gossypium hirsutum L.) leaf tissue was undertaken to explain preliminary results which indicated little or no fructose (ca. 0.03 g m⁻²) in this tissue. To further test the analytical methods employed, leaves of watermelon [Citrullus lanatus, (Thunb.) Matsum, & Nakai], sugar beet (Beta vulgaris L.), and sugarcane (Saccharum spp.) were also analyzed. Developing cotton seed coat tissue was also analyzed to test the suitability of these methods on extracts from tissues that are high in interfering substances (i.e., phenolics). Results using standard enzymatic methods to determine the carbohydrate content of aqueous ethanol extracts of these tissues were compared to those obtained by HPLC of the same extracts. Careful analysis showed that fructose was a minor soluble carbohydrate component in cotton leaf, contrary to numerous citations in the literature. An active soluble invertase in cotton leaf tissue degraded 28% of the sucrose within 15 minutes of thawing. Sucrose was degraded in the leaves of other species following freezing and thawing, but to a lesser extent than in cotton leaf. The enzymatic method worked well for the analysis of carbohydrates extracted from leaves but was susceptible to interference when used to analyze carbohydrates from cotton seed coats; however, the addition of powdered charcoal to seed coat extracts prior to analysis was found to alleviate such interference.