Interpreting Botanical Progress
October-December 1999
 
 
The Inflorescence:  Introduction
    Shirley Tucker and James Grimes...................................................303

Inflorescence Morphology, Heterochrony, and Phylogeny in the
  Mimosoid Tribes Ingeae and Acacieae (Leguminosae: Mimosoideae)
    James Grimes......................................................................317

Capitula in the Asterdae:  A Widespread and Varied Phenomenon
   Elizabeth M. Harris................................................................348

Morphologicl Traffic between the Inflorescence and the Vegetative
  Shoot in Helobial Monocotyledons
   W. Alan Charlton and Usher Posluszny...............................................370

Inflorescence Architecture:  A Developmental Genetics Approach
  Susan Singer, John Sollinger, Sonja Maki, Jason Fishbach, 
    Brad Short, Catherine Reinke, Jennifer Fick, Laura Cox, 
    Andrew McCall and Heidi Mullen....................................................386

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Inflorescence Morphology, Heterochrony, and Phylogeny in the
  Mimosoid Tribes Ingeae and Acacieae (Leguminosae: Mimosoideae)

      James Grimes
      Royal Botanic Gardens, Melbourne
      Birdwood Ave, South Yarra 3141
      Victoria, Australia



I. Abstract
In earlier work (Grimes, 1992) on inflorescence morphology in the mimosoid tribes Ingeae and 
Acacieae I proposed that differences in inflorescence morphology result from three properties: 
the organization of components of the inflorescence and their relative positions; the 
hierarchical arrangement of the axes of the inflorescence and the position they assume in total 
tree architecture; and the heterochronic development of components of the inflorescence. 
Further work shows that the first two properties are better stated in terms of heterochrony; 
namely, that the organization of components of the inflorescence differs due to differences 
in timing of the development of organ systems and that the hierarchy of axes likewise differs 
due to heterochronic changes. Neither de novo origin of organs or organ systems nor suppression
or loss of organs or organ systems accounts for the diversity in form. Observed heterochronic
differences in the inflorescence structure may be divided into three types: spatial differences
in the relationship between the unit inflorescence and the subtending leaf (hysteranthy); 
differences in the time of formation and/or the duration of whole axes; and changes in 
development pathways, leading to shoot dimorphism. These heterochronies are used as characters 
in a cladistic analysis, and it is shown that although some are homoplasious, many provide 
synapomorphies of clades of exemplars representing genera in the Ingeae and Acacieae.
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Capitula in the Asterdae:  A Widespread and Varied Phenomenon

   Elizabeth M. Harris
   The Ohio State University Herbarium
   Museum of Biological Diversity
   1315 Kinnear Road
   Columbus, OH  43212


I. Abstract	
The presence of capitula, the head-type of inflorescences, is widespread in the Asterideae. 
Several families, predominantly terminal in the clade, display the tendency of maximizing 
reproductive output by condensing indeterminate inflorescences to the point of capitulum
formation. This is accomplished by the process of halting or suppressing development of the 
internodes, an example of paedomorphosis of the progenesis type. This tendency is either 
infrequent or absent in the basal members of the Asteridae. When inflorescence condensation
is present, closely related taxa often demonstrate the progression of the paedomorphosis. More 
examples of capitulum formation are found in the more advanced families, culminating with the 
Asteraceae, almost all of which display fully condensed capitula of some sort. Other phenomena 
are also apparent besides the basic inflorescence condensation. Edge effects are often seen, 
ranging from a mere crowding of the outermost flowers to the formation of additional flower 
types. In some taxa, inflorescence condensation continues beyond the basic capitulum form, 
yielding even more condensed inflorescences that then become determinate. More highly 
condensed inflorescences have independently evolved several times in the Asteraceae, and some 
tertiarily condensed inflorescences have evolved as well. Click Here to Go to Back to Top

Zusammenfassung
Die Anwesenheit der Capitula oder der Kopftypen ist bei den Asterideae weit verbreitet. 
Mehrere Familien, besonders die in den Cladus endenden, zeigen die Tendenz zur 
Höchstproduktion indem sie unbestimmbare Infloreszenz bis zu dem Zeitpunkt der 
Capitulumbildung produzieren.  Dies kommt durch einen besonderen Prozess zustande, in dem 
die Architektur der Blütenentwicklung verzögert oder unterdrückt wird-ein Beispiel von 
Paedomorphose des Progenese Typs. Diese Tendenz erscheint anfänglich bei den Grundgruppen 
der Asteridae nur selten oder garnicht.

Wenn Infloreszenzkondensation in Erscheinung tritt, so demonstrieren die nahe verwandten 
Taxa oft die Entwicklung von Paedomorphose. In den mehr fortgeschrittenen Familien finden 
sich noch weitere Beispiele von Capitulumformation, die dann in den Asterideae gipfeln. Fast 
alle von ihnen zeigen voll kondensierte Capitula verschiedener Art. Neben der grundlegenden 
Infloreszenzkondensation sind auch noch andere Phänomene zu beobachten. Es zeigt sich oft, dass 
Randeffekte verschiedenartige Resultate haben-vom lediglichen Anhaüfen der aussensituierten 
Blüten bis zur Bildung von weiteren Blütentypen. In einigen Taxa wird die infloreszente 
Kondensation über die Grundform des Capitulum hinaus witergeführt. Dadurch vermehren sich 
die kondensierten Infloreszenzen, die schliesslich definitiv werden. Sekundärerweise haben 
sich kondensierte Infloreszenzen mehrere Male unabhängig zu Asteraceae entwickelt, und 
ausserdem existieren auch einige tertiäre Infloreszenzen.Click Here to Go to Back to Top



Morphologicl Traffic between the Inflorescence and the Vegetative
  Shoot in Helobial Monocotyledons

   W. ALAN CHARLTON        and     USHER POSLUSZNY 
   Biological Sciences             Department of Botany
   3.614 Stopford Building         University of Guelph
   Manchester University           Guelph, Ontario N1G 2W1
   Manchester M13 9PT              CANADA
   UNITED KINGDOM                            




1. Abstract
Previous studies of reproductive structures in the helobial monocotyledons (Alismatidae) 
indicate that partitioning between flower and inflorescence is not always clear (e.g. Lilaea, 
Scheuchzeria) and this may be the result of ancestral, unisexual modules coming together 
to form flowers and/or inflorescences. Later evolutionary changes may have included the 
inflorescence becoming involved or mixed in with vegetative growth. Substitution of 
vegetative buds for flowers is the simplest version, and there can be additional modifications 
to the growth behaviour of the inflorescence such as horizontal growth and dorsiventrality. 
In the Alismataceae and Limnocharitaceae the derivation of stolon-like structures from 
inflorescences is obvious: vegetative features have been incorporated into structures which 
are recognisably inflorescences. In the Hydrocharitaceae the inter-relationships between the 
inflorescence and the vegetative body are much less well-defined. We have previously suggested 
for Hydrocharis, where a single axillary complex can contain both inflorescence and stolons, 
that the stolon is basically a sterilised inflorescence, and features of the inflorescence have 
become incorporated into the vegetative body. Here we will explore this theme further for the 
Hydrocharitaceae, using information from within and outside the family.  
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INFLORESCENCE ARCHITECTURE: A DEVELOPMENTAL GENETICS APPROACH

   Susan Singer1, John Sollinger1, Sonja Maki2, Jason Fishbach1, 
   Brad Short1, Catherine Reinke1, Jennifer Fick1, 
   Laura Cox1, Andrew McCall1 and Heidi Mullen1

1 Department of Biology
  Carleton College
  Northfield, MN 55057

2 Department of Horticulture
  Clemson University
  Clemson, SC 29634





I. Abstract

We are characterizing a suite of Pisum sativum mutants that alter inflorescence
architecture to develop a model for the genetic regulation of inflorescence
development in a plant with a compound raceme. Such a model when compared with
those created for Antirrhinum majus and Arabidopsis thaliana, both of which have
simple racemes, should provide insight into the evolution of development of 
inflorescence architecture.  The highly conserved nature of cloned genes that 
regulate reproductive development in plants and the morphological similarities 
among our mutants and those identified in A. majus and A. thaliana enhance the 
probability that a developmental genetics approach will be fruitful.  Here we 
describe six P. sativum mutants that affect morphologically and architecturally 
distinct aspects of the inflorescence and analyze interactions among these genes.  
Both vegetative and inflorescence growth of the primary axis is affected by 
UNIFOLIATA which is necessary for the function of DETERMINATE (DET).  DET 
maintains indeterminancy in the first-order axis.  In its absence, the meristem 
differentiates as a stub covered with epidermal hairs.  DET interacts with 
VEGETATIVE1(VEG1). VEG1 appears essential for second-order inflorescence (I2) 
development.  veg1 mutants fail to flower or differentiate the I2 meristem into 
a rudimentary stub.  det veg1 double mutants produce true terminal flowers with 
no stubs indicating that two genes must be eliminated for terminal flower 
formation in P. sativum, whereas elimination of a single gene accomplishes this
in A. thaliana and A. majus.  NEPTUNE also affects I2development by limiting 
the number of flowers produced prior to stub formation to two.  Its role is 
independent of DET as indicated by the additive nature of the double mutant det 
nep.  UNI, BROC, and PIM all play roles in assigning floral meristem identity to
the third-order branch.  pim mutants continue to produce inflorescence branches 
resulting in a highly complex architecture and aberrant flowers.  uni mutants 
initiate a whorl of sepals but floral organogenesis is aberrant beyond that 
developmental point and the double mutant uni pim lacks identifiable floral 
organs.  A wild-type phenotype is observed in broc plants, but broc enhances 
the pim phenotype in the double mutant producing inflorescences that resemble 
broccoli.  Collectively these genes ensure that only the third-order meristem, 
not higher or lower order meristems, generates floral organs, thus precisely 
regulating the overall architecture of the plant.
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