Maize Development: Cell Wall Changes in Leaves and Sheaths

Abstract

Developmental changes occur in maize (Zea mays L.) as it transitions from juvenile stages to the mature plant. Changes also occur as newly formed cells mature into adult cells. Maize leaf blades including the midribs and sheaths undergo cell wall changes as cells transition to fully mature cell types. As is common in grasses during cell wall maturation, the lignin in the plant tissue is acylated with p-coumarates (pCA). This work characterizes cell walls in maize that make up leaf blade, leaf midrib, and sheath tissues corresponding to tissue development. Maize plants grown in the greenhouse were harvested; leaf, leaf midrib, and sheath tissues from nodes 9 through 14 tissues were analyzed for cell wall composition. Cell wall carbohydrates varied with the type of maize tissue, but there was little change within a tissue type among the different nodes. Lignin concentrations were lowest in the leaf blade (70-88 g•kg −1 CW) followed by the sheath (123-140 g•kg −1 CW) and highest in the midrib (140-168 g•kg −1 CW). Incorporation of pCA into cell walls paralleled the lignifica-tion. Ferulates (FA) remained relatively constant as a proportion of the cell wall (3.1-6.4 g•kg −1 CW) across nodes and across all tissue types. The range of FA was 3.8 vs 5.7 g•kg −1 CW averaged over all nodes with leaf blades being the lowest. Lignin composition did not change significantly with cell wall ma-turation within a given tissue type. The aerial portions of maize plants excluding the stem showed little difference in cell wall composition along the different nodes. Higher levels of ferulates were found in the sheath and leaf midrib compared to the leaf blade tissues. Leaf midribs from the upper nodes of the plant contained the highest levels of lignin. Perhaps a reflection of the function to keep leaves extended and in an upward angle to help maximize photosynthetic capacity.