An analysis of the early floral development of Pittosporum tobira (THUNB.) AITON and some remarks on the systematic position of the family Pittosporaceae

In Pittosporum tobira all floral organs are initiated in a strictly acropetal succession. It is striking that sepals and petals show an extremely early hyponastical development. Important floral characters for placing the family Pittosporaceae near the Apiales (Araliaceae and Apiaceae) are the early sympetaly, only gradual differences in the gynoecium development and placentation, and the fact that a nectar secreting area is situated at the base of the dorsal carpel flanks (ovary superior in Pittosporaceae, inferior in Apiales).

Viscid latex, which plays an important role in the dispersal of the seeds by exozoochory, is produced by the multicellular epidermal hairs in the septal (placental) region.

Bei Pittosporum tobira werden alle Blutenorgane in einer streng akropetalen Folge am Blutenvegetationskegel ausgegliedert. Auffallig ist die extrem fruhe hyponastische Krummung der Sepalen und Petalen. Die u. a. von Seiten der molekularen Systematik postulierte Verwandtschaft der Pittosporaceae mit den Apiales (Araliaceae und Apiaceae) wird aus blutenontogenetischer und -morphologischer Sicht unterstutzt. Wichtige Argumente sind: die fruhe Sympetalie, die nur graduellen Unterschiede in der Gynoecealentwicklung und in der Plazentation sowie die Lage des Nektar sezernierenden Bereichs an der Basis der dorsalen Karpellflanken (Ovar oberstandig bei den Pittosporaceae, unterstandig bei den Apiales). Wir konnen annehmen, das die Araliaceae, Apiaceae und Pittosporaceae sowie letztlich die Campanulales-Asterales auf einen gemeinsamen Ursprung zuruckgehen. Legt man weniger Gewicht auf chemische Merkmale, dann kann man vielleicht sogar – im Moment noch etwas spekulativ – zusatzlich die Cornales auf diesen Grundstock zuruckfuhren.

Der klebrige Milchsaft, der eine wichtige Rolle bei der Ausbreitung der Samen durch Vogel spielt, wird bei Pittosporum von mehrzelligen Epidermishaaren im Bereich der Septen- (Plazentar-)Region produziert.

Sympetaly in Apiales (Apiaceae, Araliaceae, Pittosporaceae)

In all recent molecular sequence based analyses Apiales come out to be placed within a broadly defined group Asteridae. Within ‘euasterids II’ Apiales (Apiaceae, Araliaceae, Pittosporaceae, Aralidiaceae, as well as some former cornaceous taxa) form a monophyletic group in a position close to Asterales-Campanulales and Dipsacales. Also from a floral developmental point of view the mostly choripetalous Apiales are not out of place among these sympetalous orders: In members of Apiales (Apiaceae: Hydrocotyle; Araliaceae: Aralia, Hedera; Pittosporaceae: Sollya, Pittosporum) the corollas are initiated from a continuous ring primordium corresponding exactly to the development in Campanulales-Asterales and Dipsacales. Only in Pittosporaceae further growth of this primordium results in a weak sympetaly in adult flowers. Molecular data suggest that the subfamily Hydrocotyloideae is polyphyletic, with Hydrocotyle belonging to the lineage not placed within Apiaceae but more closely related to Araliaceae, a position fitting well with the mode of formation of the corolla.

Floral organ sequences in Apiales (Apiaceae, Araliaceae, Pittosporaceae)

It is remarkable that families like Apiaceae and Brassicaceae, characterised by uniform floral diagrams (i.e. stable positioning of floral organs relative to one another), show a great variability in initiation sequence of the floral organs. Within the subfamily Saniculoideae of the Apiaceae temporal overlaps in the initiation of the floral whorls (Astrantia), the formation of common stamen-sepal primordia (Astrantia), and segmentation in the formation of petals in pairs (Sanicula) occur. Reduction of the calyx and shortening of the plastochrons toward zero are trends found in the more advanced Apioideae (Foeniculum, Levisticum). Hydrocotyle, with its early sympetaly, resembles the Araliaceae more closely. Of interest is the fact that in Araliaceae the flower orientation is variable. Sometimes one sepal is opposite the subtending bract, a feature which becomes fixed in Cyphiaceae and Lobeliaceae of Campanulales, a sister group of Apiales.

An analysis of the early floral development of Pittosporum tobira (THUNB.) AITON and some remarks on the systematic position of the family Pittosporaceae

In Pittosporum tobira all floral organs are initiated in a strictly acropetal succession. It is striking that sepals and petals show an extremely early hyponastical development. Important floral characters for placing the family Pittosporaceae near the Apiales (Araliaceae and Apiaceae) are the early sympetaly, only gradual differences in the gynoecium development and placentation, and the fact that a nectar secreting area is situated at the base of the dorsal carpel flanks (ovary superior in Pittosporaceae, inferior in Apiales).

Viscid latex, which plays an important role in the dispersal of the seeds by exozoochory, is produced by the multicellular epidermal hairs in the septal (placental) region.

Bei Pittosporum tobira werden alle Blutenorgane in einer streng akropetalen Folge am Blutenvegetationskegel ausgegliedert. Auffallig ist die extrem fruhe hyponastische Krummung der Sepalen und Petalen. Die u. a. von Seiten der molekularen Systematik postulierte Verwandtschaft der Pittosporaceae mit den Apiales (Araliaceae und Apiaceae) wird aus blutenontogenetischer und -morphologischer Sicht unterstutzt. Wichtige Argumente sind: die fruhe Sympetalie, die nur graduellen Unterschiede in der Gynoecealentwicklung und in der Plazentation sowie die Lage des Nektar sezernierenden Bereichs an der Basis der dorsalen Karpellflanken (Ovar oberstandig bei den Pittosporaceae, unterstandig bei den Apiales). Wir konnen annehmen, das die Araliaceae, Apiaceae und Pittosporaceae sowie letztlich die Campanulales-Asterales auf einen gemeinsamen Ursprung zuruckgehen. Legt man weniger Gewicht auf chemische Merkmale, dann kann man vielleicht sogar – im Moment noch etwas spekulativ – zusatzlich die Cornales auf diesen Grundstock zuruckfuhren.

Der klebrige Milchsaft, der eine wichtige Rolle bei der Ausbreitung der Samen durch Vogel spielt, wird bei Pittosporum von mehrzelligen Epidermishaaren im Bereich der Septen- (Plazentar-)Region produziert.

Sympetaly in Apiales (Apiaceae, Araliaceae, Pittosporaceae)

In all recent molecular sequence based analyses Apiales come out to be placed within a broadly defined group Asteridae. Within ‘euasterids II’ Apiales (Apiaceae, Araliaceae, Pittosporaceae, Aralidiaceae, as well as some former cornaceous taxa) form a monophyletic group in a position close to Asterales-Campanulales and Dipsacales. Also from a floral developmental point of view the mostly choripetalous Apiales are not out of place among these sympetalous orders: In members of Apiales (Apiaceae: Hydrocotyle; Araliaceae: Aralia, Hedera; Pittosporaceae: Sollya, Pittosporum) the corollas are initiated from a continuous ring primordium corresponding exactly to the development in Campanulales-Asterales and Dipsacales. Only in Pittosporaceae further growth of this primordium results in a weak sympetaly in adult flowers. Molecular data suggest that the subfamily Hydrocotyloideae is polyphyletic, with Hydrocotyle belonging to the lineage not placed within Apiaceae but more closely related to Araliaceae, a position fitting well with the mode of formation of the corolla.

Floral organ sequences in Apiales (Apiaceae, Araliaceae, Pittosporaceae)

It is remarkable that families like Apiaceae and Brassicaceae, characterised by uniform floral diagrams (i.e. stable positioning of floral organs relative to one another), show a great variability in initiation sequence of the floral organs. Within the subfamily Saniculoideae of the Apiaceae temporal overlaps in the initiation of the floral whorls (Astrantia), the formation of common stamen-sepal primordia (Astrantia), and segmentation in the formation of petals in pairs (Sanicula) occur. Reduction of the calyx and shortening of the plastochrons toward zero are trends found in the more advanced Apioideae (Foeniculum, Levisticum). Hydrocotyle, with its early sympetaly, resembles the Araliaceae more closely. Of interest is the fact that in Araliaceae the flower orientation is variable. Sometimes one sepal is opposite the subtending bract, a feature which becomes fixed in Cyphiaceae and Lobeliaceae of Campanulales, a sister group of Apiales.

the chloroplast genome arrangement of lobelia thuliniana lobeliaceae expansion of the inverted repeat in an ancestor of the Campanulales

A clone-bank ofSac I restriction fragments was constructed from the chloroplast DNA (cpDNA) ofLobelia thulinianaE. B. Knox (Lobeliaceae). These cloned fragments and a set of 106 clones spanning the tobacco chloroplast genome were used as probes to determine the cpDNA restriction fragment arrangement forSac I and six other restriction enzymes (BamH I,EcoR V,Hind III,Nci I,Pst I, andXho I) and the chloroplast genome arrangement ofL. thuliniana relative to tobacco, which has been fully sequenced and is collinear with the hypothesized ancestral genome arrangement of angiosperms. The results confirm and refine our previous understanding of the chloroplast genome arrangement in the large single-copy region (LSC) and reveal (1) a roughly 11 kilobase (kb) expansion of the inverted repeat (IR) into the small single-copy region (SSC) and (2) apparent sequence divergence of the DNA segment inL. thuliniana that corresponds to ORF1901 in tobacco. The expansion of the IR into the SSC is present in all other examined members ofLobeliaceae, Cyphiaceae, andCampanulaceae, which indicates that the IR expansion was an early event in the cpDNA evolution of theCampanulales. The IR expansion into the SSC was not present inSphenoclea, which additionally supports exclusion of this genus from theCampanulaceae.

The chloroplast genome arrangement ofLobelia thuliniana (Lobeliaceae): Expansion of the inverted repeat in an ancestor of theCampanulales

A clone-bank of Sac I restriction fragments was constructed from the chloroplast DNA (cpDNA) of Lobelia thuliniana E. B. Knox ( Lobeliaceae ). These cloned fragments and a set of 106 clones spanning the tobacco chloroplast genome were used as probes to determine the cpDNA restriction fragment arrangement for Sac I and six other restriction enzymes ( Bam H I, Eco R V, Hind III, Nci I, Pst I, and Xho I) and the chloroplast genome arrangement of L. thuliniana relative to tobacco, which has been fully sequenced and is collinear with the hypothesized ancestral genome arrangement of angiosperms. The results confirm and refine our previous understanding of the chloroplast genome arrangement in the large single-copy region (LSC) and reveal (1) a roughly 11 kilobase (kb) expansion of the inverted repeat (IR) into the small single-copy region (SSC) and (2) apparent sequence divergence of the DNA segment in L. thuliniana that corresponds to ORF1901 in tobacco. The expansion of the IR into the SSC is present in all other examined members of Lobeliaceae, Cyphiaceae , and Campanulaceae , which indicates that the IR expansion was an early event in the cpDNA evolution of the Campanulales. The IR expansion into the SSC was not present in Sphenoclea , which additionally supports exclusion of this genus from the Campanulaceae.

Monophyly of the Asteridae and Identification of Their Major Lineages Inferred From DNA Sequences of rbcL

A parsimony analysis of 57 angiosperm rbcL sequences was conducted to test the monophyly of the Asteridae and to identify major lineages within the Asteridae. Three major clades, the Caryophyllidae, the Rosidae plus Dilleniidae, and the Asteridae sensu lato, emerge from an unresolved radiation in the «higher» dicots. The Asteridae sens. lat. include the Ericales, Cornales, and Apiales in addition to the Asteridae sens. str. Two major lineages within the Asteridae sens. lat. are identified: the Dipsacales, Apiales, Asterales, and Campanulales in one, and the Gentianales, Scrophulariales, Lamiales, Boraginales, and Solanales in the other (…)