Abstract
Histochemical staining reactions with acid phloroglucinol and ultraviolet (UV) absorption spectra of the individual cell walls in spring barley straw (Hordeum vulgare L.) were investigated in combination with spectrometric measurements of the dioxane-water soluble lignin. Changes in lignin structure of barley straw with ammonia treatment were also investigated. Parenchyma and metaxylem vessel walls in untreated straw stained red with acid phloroglucinol and had higher absorbances around 550 nm than did epidermis and sclerenchyma cell walls, being consistent with the λmax of coniferylaldehyde. Following a reductive treatment, the lignins isolated from untreated barley straw showed an increase in UV absorbance at 280 nm and a decrease in that around 320 nm. These regions in UV and IR absorption spectra are assigned to conjugated carbonyl groups as shown by the narrowing of the IR absorption band at 1660 cm−1, and this was consistent with the staining observation of the specific tissue walls. UV microspectrometry indicated that parenchyma cell walls were much less lignified tissues than metaxylem and protoxylem vessel walls and probably epidermal cell walls. The lignins isolated from untreated and ammonia-treated straw had similar values for empirical formulae of the C9 units, phenolic hydroxyl and methoxyl group contents, and molecular weight, although the lignin of ammonia-treated straw had a slightly higher contents of nitrogen and hydrogen. The IR bands of 1730–1680 cm−1 in ammonia-treated straw lignin also disappeared. Therefore, ammonia appeared to react with the carbon atoms of the propane side-chain. Key words: Ammonia treatment, barley straw, lignin distribution, lignin structure, staining with acid phloroglucinol, ultraviolet microspectrometry
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.