Leaf-Stem Allometry, Hollow Stems, and the Evolution of Caulinary Domatia in Myrmecophytes

• Published in: The New phytologist Vol. 151; no. 2; pp. 391 - 406
• Main Authors: Brouat, C., McKey, D.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science 01.08.2001; Blackwell Science Ltd
• Subjects: Allometry; Ants; biomechanics; caulinary domatia; Corner’s rules; Formicidae; hollow stems; Internodes; Leaf area; leaf‐stem relationship; Leaves; myrmecophytes; Ontogeny; plant architecture; Plants; Stems; Surface areas; Trees
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1046/j.0028-646x.2001.00197.x

• Leaf-stem size relationships over ontogeny were studied here in three different lineages of hollow-stemmed myrmecophytes in order to understand how a new stem function affects morphology. • In each of six taxa, the primary cross-sectional area of a terminal internode and the area of the leaf borne by it were measured on plants representing all stages of ontogeny. Cross-sectional areas of both the cavity and the ring of wood were determined. • The leaf-stem relationship over ontogeny was allometric, in contrast to the isometry previously found in solid-stemmed relatives. Stem cross-sectional area was initially larger relative to leaf area than for solid-stemmed species, increasing less than proportionally with increasing leaf size. • Because mechanical stability requires a minimum ratio of t (thickness of the solid ring) to R (external radius of the cylinder), cross-sectional area of the ring of wood must vary with that of the cavity; both contributed to leaf-stem allometry. Relative to leaves, both are initially large and increase more slowly over ontogeny, suggesting that domatia are particularly costly for plants early in development.