Revealing the morphology and chemical distribution of nodes in wheat straw

Morphology and chemical distribution of wheat straw stem, including nodes and internodes, were profiled and thoroughly analysed through a combination of qualitative and quantitative analytical techniques. It was found that the morphology across node area has great variety when the longitudinal profile was investigated in the upwards direction to the grain head; the node core morphology revealed a very dense zone with elliptical shaped rings organised in order to provide the mechanical strength to the overall stem. ATR-FTIR results for the chemical functional groups of outer and inner surfaces of node and internode also showed differences in terms of concentration of functional groups present in each section. It was revealed that the outer surface of wheat straw stem has a higher concentration of aliphatic fraction of waxes compared to the inner surface, with the highest being in the node area. EDX-SEM results were averaged for node and internode and also for inner and outer surfaces for quantitative comparison. It was found that the outer surface of wheat straw had considerable higher Si contents than the inner surface. Also higher content of C in the node outer surface is an indication of high quantity of wax which is in agreement with ATR-FTIR results. The crystallinity of node and internode was investigated using XRD; it was found that node is more amorphous than internode with the crystallinity index of 34.73% compared to 45.00% of internode. The profile of wheat straw morphology in the nodes has never been reported; the results of the quantitative and qualitative structural analysis through in-depth microstructure interpretation, and detailed and accurate chemical composition improved the understanding of straw biomass.