Interpreting Botanical Progress
April--June 2000
 


 

ASCERTAINMENT OF CARPEL NUMBERS IN
PAPAVERALES, CAPPARALES, and BERBERIDACEAE
  
CLAUDIA BRÜCKNER
Humboldt University
Institute of Biology
Division of Systematic Botany and Arboretum
Späthstrasse 80/81
D-12437 Berlin
Germany





Running head: Carpel Number


   I. Abstract...........................................................................157
  II. Introduction.......................................................................157
 III. Systematics of the Families........................................................160
	A. Ordinal Classification........................................................160
	B. Intrafamiliar Classification..................................................162
	     1. Papaveraceae.............................................................162
	     2. Fumariaceae..............................................................163
	     3. Capparaceae..............................................................163
	     4. Brassicaceae.............................................................164
	     5. Berberidaceae............................................................164
  IV. Fruit Forms........................................................................165
	A. Papaveraceae..................................................................165
	B. Fumariaceae...................................................................167
	C. Capparaceae...................................................................169
	D. Brassicaceae..................................................................171
	E. Berberidaceae.................................................................174
   V. What Is a Carpel?..................................................................176
  VI. Theories to Explain Bivalvate Gynoecia in Papaverales and Capparales
       (Also Considering the Monovalvate Pistils of Berberidaceae).......................180
	A. The nI Theory.................................................................180
	B. The nII Theory................................................................182
	C. The 2n Theory.................................................................183
	D. The 3n Theory.................................................................186
	E. Saunders's Theory of Carpel Polymorphism......................................186
	F. Other Theories................................................................187
 VII. Morphological Support of Carpel Number Theories....................................188
	A. Stigma Shape..................................................................189
	     1. Papaveraceae.............................................................189
	     2. Fumariaceae..............................................................189
	     3. Capparaceae..............................................................192
	     4. Brassicaceae.............................................................192
	     5. Berberidaceae............................................................194
	     6. Discussion...............................................................194
	B. Zones of Dehiscence...........................................................197
	     1. Papaveraceae.............................................................200
	     2. Fumariaceae..............................................................200
	     3. Capparaceae..............................................................200
	     4. Brassicaceae.............................................................201
	     5. Berberidaceae............................................................201
	     6. Discussion...............................................................201
	C. Structure of Placental Regions................................................205
	     1. Papaveraceae.............................................................205
	     2. Fumariaceae..............................................................207
	     3. Capparaceae..............................................................207
	     4. Brassicaceae.............................................................209
	     5. Berberidaceae............................................................211
	     6. Discussion...............................................................211
	D. Vascular Pattern..............................................................213
	     1. Papaveraceae.............................................................213
	     2. Fumariaceae..............................................................218
	     3. Capparaceae..............................................................219
	     4. Brassicaceae.............................................................220
	     5. Berberidaceae............................................................222
	     6. Discussion...............................................................223
	E. Ontogeny of the Gynoecium.....................................................233
	     1. Papaveraceae.............................................................233
	     2. Fumariaceae..............................................................237
	     3. Capparaceae..............................................................239
	     4. Brassicaceae.............................................................241
	     5. Berberidaceae............................................................242
	     6. Discussion...............................................................242
	F. Teratology....................................................................246
	     1. Homoeotic Phenomena......................................................247
	  	  a. Gynoecia in Virescent Flowers.......................................247
		  b. Petaloid Carpels....................................................250
		  c. Carpelloid Stamens..................................................250
			 i. Papaveraceae.................................................251
			ii. Brassicaceae.................................................253
		  d. Carpelloid Sepals...................................................257
		  e. Carpelloid Ovules...................................................257
	     2. Increase in Gynoecial Components.........................................258
		  a. Additional Carpel Whorls............................................258
		  b. Increase in Member Number within the Regular Carpel Whorl...........259
VIII. Summarizing Discussion.............................................................269
  IX. Acknowledgments....................................................................273
   X. Literature Cited...................................................................274
  XI. Appendix 1: Chronological List of Essential Literature Supporting the 
          nI Theory of Carpel Number.....................................................300
 XII. Appendix 2: Chronological List of Literature Dealing with Gynoecial Virescence.....302
XIII. Appendix 3: Chronological List of Literature Dealing with Carpelloid Stamens.......303
 XIV. Appendix 4: Chronological List of Literature and Unpublished Observations 
          Concerning Additional Encaptic Carpel Whorls...................................304
  XV. Appendix 5: Chronological List of Literature and Unpublished Observations
          Dealing with Increased Carpel Numbers in the Gynoecial Whorl...................305

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I. Abstract

For more than 170 years there has been a controversy about the organization of the 
siliqua, a fruit typical for the Brassicaceae and, in modified forms, also for members
of Capparaceae, Papaveraceae, and Fumariaceae. Because in the Berberidaceae fruit forms
resembling a "semi-siliqua" are produced, they are also controversial.   A siliqua is 
typically furnished with two placental regions joined by a septum and dehiscing through 
detachment of two sterile valves. Modified forms lack a septum and have only one or more 
than two valves, or are indehiscent. The controversial issue is the number of carpels 
composing a siliqua, typical or modified. Aside from the fact that the nature and 
phylogeny of the angiosperm organ "carpel" are still insufficiently known and therefore 
speculative, carpel numbers of two, four, and six have been proposed for a bivalvate 
siliqua; moreover, an "acarpellate" state as an axis-derived structure has been postulated. 
Within the framework of these theories there are additional theories concerning the 
position, shape, and fertility or sterility of what are believed to be carpels. Each of 
these concepts is reviewed here, and its morphological basis is checked. Gynoecial features 
used as evidence of the manifold hypotheses are shape of the stigma, zones of dehiscence, 
structure of the placental regions, vascular pattern, ontogeny, and teratological 
transformations.  They are discussed for each family and compared in the context of the 
conclusions derived from them. The result is that Robert Brown's (1817) classical theory, 
explaining the siliqua as a product of fusion of two transverse carpels with the valves 
being opercular structures and the septum formed of placental outgrowths, cannot be 
invalidated by any of the later theories. Stigmatic lobes should not a priori be equated 
with carpel tips, and their number is not a definite indication of carpel number.  The zones 
of dehiscence are not carpel borders but secondary separation tissues within the carpel blade. 
Massive placental regions with complex venation need not be solid carpels.  Number and 
course of vascular bundles may be interpreted in ontogenetic and functional terms, and the 
concept of vascular conservatism is unsound. Gynoecial growth centers must not uncritically 
be equated with carpel primordia. Terata, such as tetravalvate siliquae, are not atavisms. 
Thus, carpel numbers higher than those of placentae in the given gynoecium cannot be 
ascertained.  The gynoecium of Berberidaceae is truly monomerous. The identical organization 
of the gynoecia in the families concerned demands their explanation by a single theory. Many 
textbooks, floras, and monographs should be revised from this point of view.
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