Fig 1.
Changes in the morphological parameters during internode development in the three genotypes.
Fig 1A: length of the principal ear internode, Fig 1B: cross-section surface and Fig 1C: cell size of the parenchyma cells. Data were averaged across the three blocks collected in 2011. Arrows = silking date. Smoothed curves were used only for graphical purposes.
Table 1.
ANOVA results of the fixed effects on the walls biochemical composition of cell walls in the principal ear internode for the three maize lines (F324, F66, and F7037) grown in 2009 and 2010 and sampled during 6 developmental stages.
Fig 2.
Changes in the lignin content, composition and structure during internode development in the three genotypes.
Fig 2A: Klason lignin content, Fig 2B: lignin units involved only in β-O-4 bonds (uncondensed lignin) and Fig 2C: S/G thioacidolysis ratio. Data were averaged across the blocks collected in 2009 and 2010. Arrows = silking date. Smoothed curves were used only for graphical purposes.
Fig 3.
Changes in tissue lignification during internode development in the three genotypes.
Fig 3A: whole internode Fasga-stained cross section. Pith, blue ring and rind were indicated on the F7037 cross section at silage stage, Fig 3B: rind region of the Fasga-stained cross section (bar = 100 μm) and Fig 3C: red/blue intensity ratio for each tissue (red = rind, blue = blue ring and pink = pith). Smoothed curves were used only for graphical purposes.
Fig 4.
Changes in p-coumaroylation and feruloylation content during internode development in the three genotypes.
Fig 4A: esterified p-coumaric acid content, Fig 4B: percentage of S lignin subunits acylated by p-coumaric acid, Fig 4C: esterified ferulic acid content and Fig 4D: etherified ferulic acid content. Data were averaged across the blocks collected in 2009 and 2010. Arrows = silking date. Smoothed curves were used only for graphical purposes.
Fig 5.
Schematic illustration of the spatiotemporal evolution of the internode cell walls in maize.
Blue part of the figure symbolize the period of fast deposition of the primary cell walls. Purple part of the figure symbolize the period of fast deposition of the secondary lignified cell walls. Pink part of the figure symbolize the period of slow deposition of the secondary cell walls in the rind region of the maize internode at late stages. Pith lignification (purple arrow) and Rind lignification (red arrow) both take place until silking. After silking lignification only occurred in rind. β-O-4 rich lignin: β-O-4 bonds between lignin subunits were established during all the cell wall internode lignification. From silking to silage few lignins were synthesized but these lignins are very rich in β-O-4 bonds. These lignins deposited in late stages were mainly present in the rind region. C-C rich lignin: lignin with less β-O-4 bonds. Xyl-Xyl-Xyl: xylose backbone of the main maize hemicelluloses. Ara: main maize hemicelluloses were arabinoxylanes. Ferulic (FA) was ester linked to Ara. These ferulic primers accumulated during all internode development even if new ferulic primers were not recruited for lignification after silking. PC: p-coumaric acid was mainly link to S lignin units. PC accumulated until the end of internode lignification. Thus, highly linear p-coumaroylated lignin accumulated in rind region at the end of lignification from silking to silage stage.