Male Cone Evolution in Conifers: Not All That Simple

2019

Fitzroya pollen cones show several features that are common for callitroid Cupressaceae including an uniaxial structure, the arrangement of microsporangiophores in trimerous whorls, and hyposporangiate microsporangiophores with several abaxial microsporangia, and a terminal scutellum. The strictly downward position of the pollen cones throughout their entire ontogeny distinguishes Fitzroya clearly from all other Cupressaceae s.str., but is similar to some basal Cupressaceae s.l. and other coniferous groups, including several Pinaceae and Taxaceae. The peltate scutellum which covers the microsporangia is unique among Cupressaceae and all other conifers. It seems to play an important role in protecting maturing microsporangia, and also within the anemophily syndrome. In Fitzroya the pollen is not removed from the cone directly from its place of origin, but from secondary deposits located in distal parts of the scutellum. A comparable pollen exposure is lacking in all other Cupressaceae but is common in other conifers, for example several Pinaceae and Podocarpaceae. Thus, pollen cones of Fitzroya comprise features which are the common family traits of Cupressaceae, but also features that are unique among this family, but common in other conifers. In addition, also features were found that are unique among all conifers.

Section: Discussionmentioning

confidence: 93%

About the morphology and anatomy of pollen cones and the pollen presentation within the genus Fitzroya (Cupressaceae)

2019

“…; Schulz et al. ; Dörken & Nimsch ). Within this scenario each of the lateral hyposporangiate microsporangiophores of the Torreya pollen cone can be regarded as homologous to a lateral perisporangiate microsporangiophore within Pseudotaxus and Taxus pollen cones, which can in turn be interpreted as derived from a former subunit within the inflorescence of Cephalotaxus .…”

Section: Discussionmentioning

confidence: 99%

“…; Dörken & Nimsch ), and some Podocarpaceae, including Podocarpus , Prumnopitys and Retrophyllum (Schulz et al. ; Dörken & Nimsch ). In all other conifers the pollen cones represent simple, uniaxial, flower‐like structures (Coulter & Chamberlain ; Pilger ; Krüssmann , ; Dallimore & Jackson ; Page ; Farjon , ; Eckenwalder ).…”

Section: Introductionmentioning

confidence: 99%

Are the male reproductive units of Juniperus drupacea Labill. (Cupressaceae s.str.) a compound, polyaxial inflorescence or a dense cluster of simple, uniaxial pollen cones?

2019

The Juniperus Section Caryocedrus (Cupressaceae) is one of the three putatively monophyletic sections of the genus. It is monotypic, presented only by J. drupacea. Male reproductive units of this species show several distinct features distinguishing it distinctly from all other Juniperus species, including an inflorescence‐like arrangement of pollen cones, an increased number of microsporangia per microsporangiophore, and microsporangia attached to the stalk in up to three subsequent rows. The male reproductive units in J. drupacea have been investigated with paraffin technique and SEM. They are hypothesized to represent a distal cluster of densely arranged, simple pollen cones, which are interpreted as being derived from an ancestral condition that is still presented in species of the Section Juniperus. This is assumed to have occurred by a profound reduction of internodes of the fertile shoot axis carrying the pollen cone and a distal shift. The increased number of microsporangia per microsporangiophore may be a response to the decreasing number of pollen cones per tree compensating for the loss of pollen, that occurred during the evolution of inflorescence‐like male reproductive units.

“…Podocarpus , Retrophyllum and Prumnopitys (Schulz et. al ; Dörken & Nimsch ). Within these compound pollen cones each subunit represents a single “flower”, which is typically inserted in the axil of a bract.…”

Section: Introductionmentioning

confidence: 99%

“…Cephalotaxus and Pseudotaxus (Wilde 1975;Mundry & Mundry 2001;D€ orken et al 2011;D€ orken & Nimsch 2016), and within Cupressaceae only Juniperus drupacea (Lemoine-S ebastian 1967) and some Podocarpaceae e.g. Podocarpus, Retrophyllum and Prumnopitys (Schulz et. al 2014;D€ orken & Nimsch 2015).…”

Section: Introductionmentioning

confidence: 99%

Pollen cone teratologies in Sequoia sempervirens (D. Don) Endl. and Widdringtonia nodiflora (L.) Powrie (Cupressaceae) in the light of conifer evolution

Stützel

2019

Self Cite

Different types of pollen cone teratologies in Sequoia sempervirens and Widdringtonia nodiflora were investigated. While wild type pollen cones are uniaxial and hyposporangiate, some teratological polyaxial pollen cones and also perisporangiate microsporangiophores were found. The teratological compound pollen cones in Sequoia seem to represent just random artifacts caused by a spitting of the pollen cone apex, maybe due to a pathogenic event in early developmental stages. In Widdringtonia it remains open, if the compound male reproductive units represent a dense distal cluster of pollen cones or a compound, polyaxial inflorescence comparable to other conifers, e.g. Cephalotaxus (Taxaceae). The perisporangiate microsporangiophores found in some of the teratological pollen cones in Widdringtonia are remarkable, because among extant conifers this type of microsporangiophores is developed only in Taxaceae. Previous studies showed that the perisporangiate type of microsporangiophores represents a radial synangium consisting of several fused hyposporangiate microsporangiophores. However, the perisporangiate microsporangiophores in Taxaceae and Widdringtonia show some distinct structural differences excluding the perisporangiate microsporangiophores in Widdringtonia as representing a radial synangium.