Inflorescence - peduncle

[Felipe Zapata]

Dr. Mathieu,

Part of your confusion is perhaps due to the inaccurate definitions for 
inflorescence and stem that we adopted in POC.  Updates to 
APWeb-Glossary are in order for these terms (and few others), meanwhile 
let me give you these 3 definitions hoping to clarify the issue.

Stem: the axial system of plants which is usually above ground and more 
or less negatively geotropic, bears leaves and buds, is exogenous in 
origin, often indeterminate in growth and with secondary thickening.

Inflorescence: That part of the axial system of plants that bears 
flowers.

Peduncle: the stalk of an inforescene; that part of the inflorescence 
below the first flower or inflorescence branch and above the last 
foliage leaf.

Therefore, peduncle is part of inflorescence.

Felipe