Marginal and laminar hydathode-like structures in the leaves of the desiccation-tolerant angiosperm Myrothamnus flabellifolius Welw.

The fan-shaped leaves of the resurrection plant Myrothamnus flabellifolius Welw. fold during episodes of drought and consequent desiccation of the tissue. The leaf teeth of M. flabellifolius have several features characteristic of hydathodes. Tracheary elements from the three vein endings that converge in each leaf tooth subtend and extend into a cluster of cells significantly smaller than those of the adjacent mesophyll. The stomata overlying this putative epithem are larger than the other stomata on the leaf surface. Crystal violet is absorbed via these stomata in non-transpiring leaves, suggesting that they are water pores. Two to four such water pores occur per hydathode and are readily distinguished in desiccated leaves. Laminar hydathodes apparently also occur in the leaves of M. flabellifolius. Branched vein endings that terminate in short, wide tracheary elements subtend the outer edges of the abaxial leaf ridge, which otherwise lack stomata, and coincide with regions of crystal violet uptake. Guttation could not be induced in M. flabellifolius. However, desiccated leaves readily absorb liquid water through the leaf surface. The use of Calcafluor White to trace the pathway of apoplastic water movement suggests a role for both types of hydathode in foliar water uptake during rehydration while the accumulation of Sulphorhodamine G (indicating solute retrieval from the apoplast) in the epithem of transpiring plants suggests the hydathodes may be a pathway of water loss in the desiccating leaf.     

Hydathode anatomy in Potentilla palustris (Rosaceae)

Guttating leaf teeth of Potentilla palustris plants from Wisconsin, USA, were cleared or processed for plastic sectioning or scanning electron microscopy. Anatomical features include: 1) long slender hydathode area occupying most of the tooth, 2) adaxial pad of small, flat epidermal cells with 50 or more sunken water pores about the size of ordinary abaxial stomates, 3) three converged bundles that extend distally, where their tracheary files are separated by intervening files of xylem parenchyma cells with sinuous walls, 4) adaxial mass of small, loosely arranged epithem cells above the xylem, 5) one slender phloem strand that extends only about a third of the way into the hydathode, and 6) bundle sheath extending distally only abaxially and along the flanks of the hydathode. Potentilla hydathodes differ significantly from non-guttating ones described earlier in Physocarpus (Rosaceae).     

Trichomes and stomata,and their taxonomic significance in theUrticales

Structure and ontogeny of stomata and trichomes have been studied in 23 species and 3 varieties of theUrticales. Stomata are anomocytic, more rarely paracytic; anisocytic and sometimes helicocytic and transitorial types are found inUrticaceae andDorstenia, rarely inArtocarpus. The ontogeny of anomocytic and actinocytic stomata is perigenous, of paracytic either mesogenous or perigenous, of anisocytic either mesogenous or mesoperigenous, and of helicocytic and transitional types mesogenous. Among trichomes eglandular unicellular (wide spread), bicellular or uniseriate filiform (Cannabis); glandular capitate with uni- or bicellular (Moraceae, Ulmaceae, Cannabaceae), uniseriate filiform (Ulmaceae) or multiseriate stalk (Cannabis); sunken glands (Artocarpus); uniseriate glandular with uniseriate stalk (Celtis), and stinging emergences (Urticaceae) have been observed. It is concluded that theUrticales represent a natural order with four families:Ulmaceae, Moraceae, Urticaceae andCannabaceae which are distinct but interrelated with each other.     

ERECTA is required for protection against heat-stress in the AS1/ AS2 pathway to regulate adaxial-abaxial leaf polarity in Arabidopsis

In seed plants, formation of the adaxial–abaxial polarity is of primary importance in leaf patterning. Since Arabidopsis thaliana (L.) Heynh. genes ASYMMETRIC LEAVES1 (AS1) and ASYMMETRIC LEAVES2 (AS2) are key regulators in specifying adaxial leaf identity, and ERECTA is involved in the AS1/AS2 pathway for regulating adaxial–abaxial polarity [L. Xu et al. (2003) Development 130:4097–4107], we studied the physiological functions of the ERECTA protein in plant development. We analyzed the effects of different environmental conditions on a special leaf structure in the as1 and as2 mutants. This structure, called the lotus-leaf, reflects a severe loss of adaxial–abaxial polarity in leaves. Higher concentrations of salt or other osmotic substance and lower temperature severely affected plant growth both in the wild type and the mutants, but did not affect lotus-leaf frequency in the as1 and as2 mutants. as1 and as2 mutants exhibited a very low lotus-leaf frequency at 22°C, a temperature that favors Arabidopsis growth. The lotus-leaf frequency rose significantly with an increase in growth temperature, and only in plants that are in the erecta mutation background. These results suggest that ERECTA function is required for reducing plant sensitivity to heat stress during adaxial–abaxial polarity formation in leaves.Abbreviations AS1, AS2 ASYMMETRIC LEAVES1, 2 - ER ERECTA     

Surface features of the leaves ofBalanophoraceae — A family without stomata?

Both adaxial and abaxial leaf surfaces were searched for stomata inBalanophora elongata, B. fungosa, Hachettea austro-caledonica, Langsdorffia hypogaea, Lophophytum mirabile subsp.mirabile, Scybalium jamaicense, andThonningia sanguinea (Balanophoraceae). Neither stomata nor guard cells were observed. The epidermal surfaces of these species are extremely diverse with respect to cell shape, cell size, and surface ornamentation, these features providing valuable systematic criteria.     

Phylogenetic relationships of theJuglandaceae

A cladistic analysis of molecular data from the chloroplast generbcL was used to examine the taxonomic relationships of the walnut family (Juglandaceae). In addition, chemical and morphological data from a previous study byHufford (1992) were incorporated, expanded, and analyzed independently and in combination with the molecular data. The results of these analyses suggest that theJuglandaceae are more closely related to theFagaceae, Betulaceae, Casuarinaceae, andUrticaceae and their relatives (sensuCronquist 1981) than they are to theAnacardiaceae (sensuThorne 1983). However, sequence data fromrbcL also suggest a relationship between the higherHamamelidae and certain families in theRosidae sensuCronquist 1981 (such asRosaceae andRhamnaceae), an outcome which would add credence to the widely accepted view of the polyphyletic nature of theHamamelidae.     

Evolutionary relationships in thePodalyrieae andLiparieae (Fabaceae) based on morphological, cytological, and chemical evidence

Taxonomic relationships amongst the genera of the southern African tribesPodalyrieae andLiparieae are discussed. Data gained from morphological, cytological and chemical investigations are analyzed cladistically to determine relationships. The genusCadia (tribeSophoreae) is included in the investigation to establish whether it should be transferred to thePodalyrieae. The results clearly indicate that thePodalyrieae andLiparieae are monophyletic and that they should be united, but thatHypocalyptus andCadia should be excluded. Within the monophyletic group, there are two distinct subclades each supported by three apomorphies. The results also show that there is a strong sister relationship betweenAmphithalea andCoelidium. In the taxonomic treatment theLiparieae are placed into synonymy under thePodalyrieae and two subtribes are recognized. A key to the genera in the tribe is given, followed by a synopsis of the genera.     

Eine blütenmorphologische Analyse derLagoecieae (Apiaceae)

An analysis of the morphology, anatomy and ontogeny of the flowers, particularly of the gynoecium ofLagoecieae is presented. 1. The gynoecial model of angiosperms can be applied to all three generaArctopus, Lagoecia andPetagnia. 2. In the case ofArctopus an additional Apikalseptum is developed. 3. In the synascidiate region of the gynoecium the adaxial carpel is reduced inArctopus andPetagnia, the abaxial inLagoecia. 4. The reduced carpel produces either one mature ovule inArctopus, a rudimentary ovule inPetagnia, or none inLagoecia. 5.Petagnia andLagoecia have a completely pseudomonomerous gynoecium. 6.Arctopus displays many flower characteristics which lack in theSaniculoideae but occur in theHydrocotyloideae. 7. ForPetagnia andLagoecia an independent phylogenetic development within theSaniculoideae is assumed.

Herrn Univ.-Prof. Dr.Walter Leinfellner zum 70. Geburtstag gewidmet.     

Beiträge zur Systematischen Anatomie derAnthemideae: Die Spaltöffnungsapparate

The subdivision of theAnthemideae into two subtribes purely on the grounds of the presence or absence of receptacular paleae can no longer be maintained. Anatomical data may serve as a basis for a more adequate division of the tribe. This survey of the stomatal apparatus types within theAnthemideae is based on the investigation of 29 species from 15 genera and the evaluation of literature data: Anomocytic stomatal apparatus occur in all species examined, anisocytic at least in all genera investigated by us. We even found representatives of some rare types, such as polo-, helico- or hemiparacytic apparatus, in nearly all species. Diacytic types were not found inOtanthus, Artemisia, Tripleurospermum, Tanacetum corymbosum, and they also appear to be lacking inSantolina andEriocephalus. Paracytic stomatal apparatus and a new type which links paracytic with actinocytic and cyclocytic was discovered inOtanthus maritimus andArtemisia stellerana.

     

Studies on the early floral development inCleomoideae (Capparaceae) with emphasis on the androecial development

Floral ontogeny ofCleome spinosa, Cleome violacea andPolanisia dodecandra subsp.trachysperma was studied in the context of the question whether the fascicled androecium ofReseda andCapparis (with fused fascicles) or the 2 + 4-pattern of theBrassicaceae is primitive in theCapparales. InPolanisia dodecandra, the 9–18 stamens show unidirectional initiation from the adaxial side toward the abaxial side of the flower. InCleome violacea, the six stamens also are formed in an unidirectional order, but development starts abaxially and a zigzag-like pattern is superimposed. InCleome spinosa, two stamen primordia in transversal (lateral) position are followed by four stamens which arise on a somewhat higher level in two pairs in front of the median sepals. It is assumed that the evolutionary steps in the androecial development proceed fromReseda viaCapparis andPolanisia/Cleome toBrassicaceae. This interpretation is supported byrbcL-studies (Chase & al. 1993,Rodman & al. 1993).Dedicated to emer. Univ.-Prof. DrFriedrich Ehrendorfer on the occasion of his 70th birthday     

The natural delimitation ofCentaurea (Asteraceae: Cardueae): ITS sequence analysis of theCentaurea jacea group

Taxonomic complexity has hindered partitioning the genusCentaurea into natural subdivisions, even though it has long been recognized as an unwieldy, artificial assemblage. Most of the remaining difficulties center in theCentaurea jacea group, whose taxa share a common advanced type of pollen. Because it comprises half the species of the genusCentaurea, as well as five other disputed genera previously segregated fromCentaurea (Chartolepis, Cheirolepis, Cnicus, Grossheimia andTomanthea), theCentaurea jacea group is a significant taxonomic challenge. Newer molecular approaches are useful for resolving complex relationships because they provide more precise inferences of evolutionary relationships than traditional morphological characters. Sequences of the Internal Transcribed Spacers (ITS) of nuclear ribosomal DNA were analyzed for a comprehensive sample of this group. Results indicated that theCentaurea jacea group is monophyletic and includes the segregated genera, but not two other genera (Oligochaeta andZoegea), whose inclusion in theCentaurea jacea group was doubtful. In addition to pollen morphology, the ITS phylogeny is also supported by karyological evidence and by good correlation with biogeographic distribution of the species. The monophyly of theCentaurea jacea group suggests that a natural delimitation ofCentaurea that minimizes nomenclatural changes is possible, but only if a new type of the genus is designated.     

喜树各器官解剖学及其喜树碱含量测定的研究

运用植物解剖学方法研究了喜树各器官的结构,对喜树不同器官中喜树碱含量进行了HPLC法测定。结果表明:(1)喜树根尖纵切面的结构由根冠、分生区、伸长区和根毛区4个部分组成。根和茎的初生结构都由表皮、皮层和维管柱3部分组成;在根和茎初生结构的皮层和髓部具有被锇酸染成黑色的嗜锇细胞;在次生生长中,根的木栓形成层起源于中柱鞘,茎的木栓形成层起源于皮层细胞;随着次生维管组织的增加,茎的中央形成髓腔。(2)叶片由表皮、叶肉和叶脉组成,叶肉细胞中分布有嗜锇细胞;光学显微镜和扫描电子显微镜观察显示,喜树叶的上表皮没有气孔器分布;下表皮气孔器的保卫细胞呈肾形,没有副卫细胞,被几个表皮细胞不规则的围绕,属于无规则型;在上下表皮均分布着单细胞非腺毛和2种类型的腺毛,其中下表皮的分布相对稠密;上表皮腺毛呈球形,下表皮腺毛大部分为长卵形,其中间杂着一些球形腺毛;观察发现,越幼嫩的叶中,分布的腺毛和非腺毛越多。(3)喜树不同器官中喜树碱含量以幼叶和种子中较高,木质部中较低,髓中含量最少;随着叶的发育成熟,叶中喜树碱的含量逐渐降低,且同一叶的不同部位,喜树碱含量也有差异;喜树幼苗发育过程中喜树碱含量也在不断变化。     

Ultrastructure of nuclear inclusions and the separation ofVerbenaceae andOleaceae (incl.Nyctanthes)

TEM observations were carried out on 40 taxa of the familyVerbenaceae and 35 taxa of the familyOleaceae, in order to ascertain distribution, ultrastructure and morphology of the intranuclear proteinic inclusions in the mesophyll parenchymatic cells. The investigated genera amount to some 25% and 60% respectively of the genera of the two families. Inside theVerbenaceae, lamellar inclusions (L-type) occur in 6 out of 23 investigated genera: they are mostly present inside the tribesCitharexyleae andVerbeneae (both belonging toVerbenoideae), while they are absent in other subfamilies. All of the investigatedOleaceae genera show intranuclear crystalline inclusions (C 1-type) of three different shapes. Among theAsteridae this is a character peculiar toOleaceae. They appear to be a well defined natural group, including the controversial genusNyctanthes.     

Flavonoids of some controversial members of theCaryophyllales (Centrospermae)

The absence or occurrence of C-glycolsylflavonoids in theAizoaceae andMolluginaceae, respectively, has been utilized to classify several controversial genera of centrospermous plants that have previously been placed in different families by systematists. The presence of these compounds in several further species of theMolluginaceae is reported. Their anomalous presence inGliscrothamnus (Aizoaceae) is discussed.     

STRUCTURE AND DEVELOPMENT OF THE PERIANTH IN DOWNINGIA BACIGALUPII

The structure and ontogeny of the calyx and corolla of Downingia bacigalupii Weiler (Campanulaceae; Lobelioideae) were investigated for the purpose of comparing perianth development with previous observations on the floral bract, as well as elucidating the mechanism of development of the zygomorphic, sympetalous corolla. Sepals are uni-traced with a palmate, reticulate venation. They have basal and apical hydathodes, as well as storage tracheids. Sepals show a reduction in size, venation and hydathode number when compared to the bract. The pentamerous, zygomorphic corolla is bilabiate, consisting of a three-lobed adaxial lip and a two-lobed abaxial lip connected by a short tubular region. The constituent petal lobes are also uni-traced and have a reticulate venation, resembling that of the sepal and bract, but lack storage tracheids and hydathodes. Sepals arise in an adaxial to abaxial succession and are initiated in the outer corpus layer of the floral apex. Expansion of the floral apex follows and is accompanied by the establishment of a second tunica layer. Sepals undergo apical, marginal, and intercalary growth accompanied by acropetal differentiation of procambium. The petals arise simultaneously and are initiated in the second tunica layer and the outer corpus cells. After initiation, the petals exhibit a period of apical and marginal growth followed by intercalary growth. Apical growth in petals is less protracted than in sepals, but plate meristem activity is more extensive. The free petal lobes become temporarily fused by an interlocking of marginal epidermal layers, but they separate at anthesis. Zonal growth beneath the originally free lobes forms the tube and lip regions of the sympetalous corolla. Zygomorphy is evident from the time of initiation of petals and is accentuated by later differential growth. Comparative observations of corolla ontogeny in autogamous species of Doumingia indicate that the reduced corollas in these taxa are derived by a simple process of neoteny.     

Taxonomy and phylogeny of the tribePlucheeae (Asteraceae)

The tribePlucheeae (Benth.)A. Anderb., has been analysed cladistically by means of a computerized parsimony program (Hennig 86), using theArctotideae as outgroup. The results of the analysis are presented in a consensus tree and one cladogram. Four major monophyletic subgroups can be recognized: TheColeocoma group (3 genera), thePterocaulon group (3 genera), theLaggera group (6 genera), and thePluchea group (12 genera). All recognized genera are described and most genera are supplied with taxonomical notes including comments on their taxonomic status. Genera such asBlumea, Pluchea, andEpaltes are demonstrated to be unnatural assemblages.Monarrhenus andTessaria are both closely related to thePluchea complex. The old generic nameLitogyne Harv. has been taken up for one species ofEpaltes, the genusRhodogeron is reduced to a synonym ofSachsia, and the following new combinations are made;Litogyne gariepina (DC.)A. Anderb., andSachsia coronopifolia (Griseb.)A. Anderb.     

Hydathode trichomes actively secreting water from leaves play a key role in the physiology and evolution of root-parasitic rhinanthoid Orobanchaceae

Background and Aims Root hemiparasites from the rhinanthoid clade of Orobanchaceae possess metabolically active glandular trichomes that have been suggested to function as hydathode trichomes actively secreting water, a process that may facilitate resource acquisition from the host plant’s root xylem. However, no direct evidence relating the trichomes to water secretion exists, and carbon budgets associated with this energy-demanding process have not been determined.Methods Macro- and microscopic observations of the leaves of hemiparasitic Rhinanthus alectorolophus were conducted and night-time gas exchange was measured. Correlations were examined among the intensity of guttation, respiration and transpiration, and analysis of these correlations allowed the carbon budget of the trichome activity to be quantified. We examined the intensity of guttation, respiration and transpiration, correlations among which indicate active water secretion.Key Results Guttation was observed on the leaves of 50 % of the young, non-flowering plants that were examined, and microscopic observations revealed water secretion from the glandular trichomes present on the abaxial leaf side. Night-time rates of respiration and transpiration and the presence of guttation drops were positively correlated, which is a clear indicator of hydathode trichome activity. Subsequent physiological measurements on older, flowering plants indicated neither intense guttation nor the presence of correlations, which suggests that the peak activity of hydathodes is in the juvenile stage.Conclusions This study provides the first unequivocal evidence for the physiological role of the hydathode trichomes in active water secretion in the rhinanthoid Orobanchaceae. Depending on the concentration of organic elements calculated to be in the host xylem sap, the direct effect of water secretion on carbon balance ranges from close to neutral to positive. However, it is likely to be positive in the xylem-only feeding holoparasites of the genus Lathraea, which is closely related to Rhinanthus. Thus, water secretion by the hydathodes might be viewed as a physiological pre-adaptation in the evolution of holoparasitism in the rhinanthoid lineage of Orobanchaceae.     

rbcL sequences support exclusion ofRetzia,Desfontainia, andNicodemia from theGentianales

The taxonomic positions ofRetzia, Desfontainia, andNicodemia have been much discussed, and all three genera have been included inLoganiaceae (Gentianales). We have made a cladistic analysis ofrbcL gene sequences to determine the relationships of these taxa toGentianales. Four newrbcL sequences are presented; i.e., ofRetzia, Desfontainia, Diervilla (Caprifoliaceae), andEuthystachys (Stilbaceae). Our results show thatRetzia, Desfontainia, andNicodemia are not closely related toLoganiaceae or theGentianales. Retzia is most closely related toEuthystachys and is better included inStilbaceae. The positions ofDesfontainia andNicodemia are not settled, butDesfontainia shows affinity for theDipsacales s.l. andNicodemia for theLamiales s.l.     

The phylogenetic relationships ofByblis andRoridula (Byblidaceae-Roridulaceae) inferred from partial 18S ribosomal RNA sequences

The phylogenetic relationships of the angiosperm generaByblis andRoridula have been the subject of ongoing taxonomic controversy. Twenty-eight taxa of varying degrees of alleged relationship, including 3 members of theWinteraceae (as an outgroup), were investigated using partial sequences of 18S rRNA (small subunit) and also compared against the morphological data set fromHufford's (1992) cladistic treatment of 80 members of theRosidae-Asteridae. The morphological analysis placed the two genera in a clade with theSarraceniaceae in theCorniflorae-Asterid group as a sister taxon to anEricales-Hydrangeales clade. The 18S rRNA analysis supports the recently publishedrbcL DNA analysis ofAlbert & al. (1992), withRoridula joined to taxa in the lowerRosidae, butByblis joining instead to members of theAsteridae near theSolanaceae. Comparisons for congruence between the three analyses placeByblis in the higher Asterid group near theSolanaceae, andRoridula possibly nearer theSarraceniaceae andEricales. These results imply that the traditional morphological characters used to relate the two genera are possibly the result of convergence towards similar ecological and life-history strategies rather than synapomorphies.     

A new pollen type,C-banded and fluorochrome counterstained chromosomes,and evolution inGuatteria and related genera (Annonaceae)

Guatteria, Guatteriopsis, Guatteriella andHeteropetalum share the same conspicuous pollen type which is new for theSpermatophyta. It is zonoaperturate with a folded aperture region and an extremely reduced exine. First chromosome counts and karyotype analyses forGuatteriopsis (4 species investigated) andGuatteriella (1 species) are identical with those ofGuatteria (19 species seen): 2n = 28. The genome is characterized by diploidization and partly telocentric chromosomes. Sequentially Giemsa C- and fluorochrome banded chromosomes and interphase nuclei are described. The cuticular folding pattern is distinct forHeteropetalum only. Growth forms and ecology are reported for many species. The evolutionary pattern of theGuatteria group is discussed and compared with other genera and families.