Shoot and compound leaf comparisons in eudicots: dynamic morphology as an alternative approach

Recent developmental studies suggest that the compound leaf is a more or less incompletely developed shoot. Instead of treating compound leaves and shoots as non-homologous, this interpretation draws a continuum between them. The present work considers the plant as a hierarchical series of units on which similar developmental processes are at work, and where each level (shoot, compound leaf, leaflet) is 'repeated' by the next higher level. Measurements related to the expression of developmental processes operating on leaves at the shoot level and on leaflets at the compound leaf level were used to determine if similar processes are at work at these different levels during early stages of organogenesis. Plants with compound leaves showing acropetal leaflet inception, representing a total of 16 species from ten eudicot families, were studied. Based on several types of quantitative analyses, there appears to be a continuum between so-called shoots, compound leaves and leaflets in the species studied. This perspective, qualified as dynamic morphology, both parallels and complements the classical interpretation.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society, 2003, 143, 219−230.     

Multivariate Analysis Confirms the Continuum View of Plant Form

Multivariate analysis, specifically principal components analysis,shows that in flowering plants structures occur that arc intermediatebetween the typical representatives of a root, a caulome (stemand stem homologues), a phyllome (leaf and leaf homologues),a shoot and a trichome. Since these intermediates span the wholerange between the typical forms, a morphological continuum isdocumented. Implications and consequences of these findingsare discussed (e.g. homology, homeosis). The telome theory andHagemann's theory of the evolution of plant form are interpretedas referring to changes in the patterning of the morphologicalcontinuum. Plant morphology, principal components analysis, morphological continoum, angiosperms, flower, shoot, stem, leaf, enation, trichome, root, telome, thallus, morphological categories, homology, partial homology, homeosis     

Interactions Between Physical and Biological Constraints in the Structure of the Inflorescences of the Araceae

A study of the inflorescences ofMonsteraandAnthuriumwas usedto establish a relationship between biological and physicalconstraints for the structure of plant organs. The physicalconstraint between flowers in the compact inflorescences ofAnthuriumandMonsteraisexpressed by Aboav-Weaire's law. The application of this lawto inflorescences indicates a linear relationship between thenumber of sides of a flower and the number of sides of neighbouringflowers. However, the slope of this straight line is significantlyhigher forAnthuriumandMonsterathan that expected in theory.This deviation from the law is attributable to a biologicalcause that can be estimated using Aboav-Weaire's law. Actingalone, the biological constraint tends to produce four-sidedflowers. The equilibrium between biological and physical constraintsreduces the number of sides per flower from six (theoreticalvalue) to 5.9 (inAnthurium) or 5.8 (inMonstera) with a varianceof the measures less than that expected in theory. Furthermore,when flower density in an inflorescence increases (towards themiddle of the inflorescence inMonsteraand towards the lowersection forAnthurium) the number of sides approaches six (i.e.the physical constraint dominates). When flower density decreases(towards the top of the inflorescence) the number of sides approaches5.5 (i.e. the biological constraint dominates). The geometryof the inflorescences ofAnthuriumandMonsterais the result ofthe joint action of biological and physical constraints.Copyright1998 Annals of Botany Company Monstera,Anthurium, Araceae, Aboav-Weaire, inflorescence, constraint, flower.