H.-Dietmar Behnke

Sieve-element plastids, exine sculpturing and the systematic affinities of theBuxaceae

The sieve-element plastids of members of several genera in theBuxaceae (Buxus, Pachysandra andSarcococca) were found to be of the specific subtype PVI, which contains a central globular protein crystal.Simmondsia (Simmondsiaceae) andDaphniphyllum (Daphniphyllaceae), on the other hand, were found to contain S-type sieve-element plastids. The occurrence of the highly restricted PVI plastids in theBuxaceae mitigates against a close relationship between theBuxaceae andSimmondsia, Daphniphyllum andEuphorbiaceae. Exine sculpturing of theBuxaceae andSimmondsiaceae also shows no close similarities. Both of these EM characters are discussed in connection with other available data and with respect to earlier systematic treatment of these families.

Ultrastructural, Micromorphological and Phytochemical Evidence for a “Central Position” of Macarthuria (Molluginaceae) within the Caryophyllales

Subtype PIII sieve-element plastids, anthocyanins, spinulose, perforate-tectate pollen grains and the specific seed-coat sculpturing found in twoMacarthuria species (M. australis, M. neocambrica) consolidate their placement withinMolluginaceae. The unique form of the sieve-element plastids, i.e. with cubic crystals and starch grains (PIIIc″fs), finds its closest counter-part inLimeum. The multiple intertwinement of different genera of theMolluginaceae with many other centrospermous families led to a consideration of their more central position withinCaryophyllales.

Sieve-element plastids ofCaryophyllales: Additional investigations with special reference to theCaryophyllaceae andMolluginaceae

The subtype PIII plastids found in 16 additional species ofCaryophyllales investigated here corroborate the homogeneity of this order with respect to the sieve-element plastids. While two new examples (Glinus, Allmania) which exhibit the rare presence of starch grains in the PIII-plastids are found, the restriction of the three forms of PIII-plastids to distinct taxa is maintained: PIIIf inChenopodiineae; PIII c′f inCaryophyllaceae (3 species added),Stegnospermataceae andAchatocarpaceae; PIII cf in all other families (among the 11 species investigated 5 fromMolluginaceae).

S-type sieve-element plastids and anthocyanins inVivianiaceae: Evidence against its inclusion intoCentrospermae

The presence of S-type sieve-element plastids and anthocyanins in theVivianiaceae indicates that it is not a member ofCentrospermae (Caryophyllales).

P-type sieve-element plastids and the systematics of theArales (sensuCronquist 1988)—with S-type plastids inPistia

The sieve-element plastids of 126 species of theArales were investigated by transmission electron microscopy. With the exception ofPistia (with S-type plastids) all contained the monocotyledon specific subtype-P2 plastids characterized by cuneate protein crystals. While the species studied from bothAcoraceae andLemnaceae have form-P2c plastids (i.e., with cuneate crystals only), those of theAraceae belong to either form P2c (14 species), P2cs (the great majority) or P2cfs (Monstera deliciosa, only, with form-P2cs plastids in the otherMonstera species studied). The form-P2cs plastids of theAraceae are grouped into different categories according to the quantity and quality of their protein and starch contents. The subfamilyLasioideae is redefined to comprise all aroid P2c-taxa and those P2cs-genera that contain only one or very few starch grains. Only little starch is also recorded in the sieve-element plastids ofGymnostachys (Gymnostachydoideae), with the other plastid data denying a close relationship toAcorus. While equal amounts of starch and protein are generally present in sieve-element plastids of the subfamiliesPothoideae, Monsteroideae, Colocasioideae, Philodendroideae, andAroideae, maximum starch content and only very few protein crystals are found in form-P2cs plastids ofCalla (Calloideae),Ariopsis (Aroideae), andRemusatia (Colocasioideae?). In the latter, both morphology and size of sieve-element plastids are close to those ofPistia.—In theAraceae the diameters of the sieve-element plastids exhibit a great size range, but are consistent within a species and within a defined part of the plant body. Comparative data are mainly available for stem and petiole sieve-element plastids.—The accumulated data are used to suggest an affiliation of the species to subfamilies and to discuss the phylogeny of theArales. Forms and sizes of their plastids support a separation of bothAcoraceae andLemnaceae from theAraceae. The presence of S-type plastids inPistia does not favour direct and close relationships to the form-P2c genusLemna.—The prevailing form-P2cs plastids might support proposals that place theArales (together with also form-P2cs plastid containingDioscoreales) in the neighbourhood of basal dicotyledons. BesidesAsarum andSaruma (Aristolochiaceae), with monocotyledonous form-P2c plastids,Pistia (with dicotyledonous S-type plastids) gives another example for a link between the two angiosperm classes.

Elektronenmikroskopische Untersuchungen zur Frage der verwandtschaftlichen Beziehungen zwischenTheligonum undRubiaceae: Feinbau der Siebelement-Plastiden und Anmerkungen zur Struktur der Pollenexine

Theligonum cynocrambe and 13 species ofRubiaceae contain S-type sieve-element plastids, wide-spread in Dicotyledons. Alignment ofTheligonum toCaryophyllales (Centrospermae), especiallyPhytolaccaceae, is unlikely, because this order is characterized by specific P-type plastids. SEM investigations show the pollen exine ofTheligonum to be microreticulate, with additional supratectate spinules.Asperula and other genera of the tribeRubieae have a tectum perforatum (punctitegillate sexine), also with supratectate verrucae or spinulae.—Thus ultrastructure suggests (but not definitely proves) relationships betweenTheligonum andRubiaceae, while affinities betweenTheligonum andCaryophyllales are excluded.

Hectorella caespitosa: Ultrastructural evidence against its inclusion intoCaryophyllaceae

The micromorphological structure of sieve-element plastids ofHectorella caespitosaHook. f., justifies its position withinCentrospermae, but excludes its alignment with the familyCaryophyllaceae. Both, its inclusion intoPhytolaccaceae, or treatment as a separate family,Hectorellaceae, appear possible.

Contributions to the knowledge of sieve-element plastids inGunneraceae and allied families

P-type sieve-element plastids were found in theGunneraceae, while S-type plastids are present in theHaloragaceae andHippuridaceae. The specific characters of the sieve-element plastids (e.g., their size and the morphology of their contents) are discussed in relation to other taxa of theRosidae containing P-type plastids and to the systematic position of theGunneraceae.

Sieve-element plastids ofCyrillaceae, Erythroxylaceae andRhizophoraceae: Description and significance of subtype PV plastids

A new subtype (PV) of protein-containing sieve-element plastids was found to contain a uniquely large number of polygonal protein crystals, sometimes with (PVcf) and sometimes without (PVc) protein filaments. These plastids do not accumulate starch. The PVcf-plastids occur inCyrillaceae only, while the PVc-plastids are limited toErythroxylaceae andRhizophoraceae. The significance of the new P-subtype with respect to the systematic position of the three families is discussed.

A tabulated survey of some characters of systematic importance in centrospermous families

Table 1 gives a brief survey on the results of pigment analysis, chromosome numbers and ultrastructural data (sieve-element plastids and pollen wall structure) in the centrospermous families and their allies. The sequence of the families listed is primarily arranged after E~GLE~S Syllabus (1964; families in italics). In addition, most of the smaller families split from the above and listed in ECKAI~DTS (1976) Table 10 are subordinated. Exclamation marks(i) denote results that do not correspond to those of either neighboring taxa or Centrospermae at all and suggest either a rearrangemen~ of a family within the order or its exclusion. Details on the characters incorporated came from the lectures of this symposium (BEHNKE 1976, El~EI~DORFE1% 1976, MABgY 1976, SKV~A~LA & lqO~CKV, 1976) and from the following sources: