--Walton C. Galinat
Maize, like most grasses, is notoriously susceptible to stalk rots and carries young axillary buds which can not develop under a leaf sheath carrying a pool of water together with various debris such as drowned insects. The answer for the grasses was to evolve a collar or ligule that fits like a gasket against the stalk at the junction of the blade and leaf sheath. This excludes water from draining down the mid-rib of the leaf blade into the pocket of space between the leaf sheath and the internodal groove caused by divergence of the axillary bud. In doing this, the ligule also excludes conditions for possible stalk rot infection and allows the axillary bud to develop and respire.
In the related families of sedges and rushes that grow in a wetland
habitat, there are no ligules, the stalks are rot resistant and the leaf
sheaths collect water and drowned insects. Like a pitcher plant, the drowned
insects apparently provide the main source of nitrogen for these plants
that is necessary for survival in the nitrogen-poor wetland habitat.
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