Leaf architectural,vascular and photosynthetic acclimation to temperature in two biennials

Acclimation of leaf features to growth temperature was investigated in two biennials (whose life cycle spans summer and winter seasons) using different mechanisms of sugar loading into exporting conduits, Verbascum phoeniceum (employs sugar‐synthesizing enzymes driving symplastic loading through plasmodesmatal wall pores of phloem cells) and Malva neglecta (likely apoplastic loader transporting sugar via membrane transport proteins of phloem cells). In both species, acclimation to lower temperature involved greater maximal photosynthesis rates and vein density per leaf area in close correlation with modification of minor vein cellular features. While the symplastically loading biennial exhibited adjustments in the size of minor leaf vein cells (consistent with adjustment of the level of sugar‐synthesizing enzymes), the putative apoplastic biennial exhibited adjustments in the number of cells (consistent with adjustment of cell membrane area for transporter placement). This upregulation of morphological and anatomical features at lower growth temperature likely contributes to the success of both the species during the winter. Furthermore, while acclimation to low temperature involved greater leaf mass per area in both species, this resulted from greater leaf thickness in V. phoeniceum vs a greater number of mesophyll cells per leaf area in M. neglecta. Both types of adjustments presumably accommodate more chloroplasts per leaf area contributing to photosynthesis. Both biennials exhibited high foliar vein densities (particularly the solar‐tracking M. neglecta), which should aid both sugar export from and delivery of water to the leaves.     

Concentration and retention of chlorophyll around the extrafloral nectary of Mallotus japonicus

Plants need to allocate some of their limited resources for defense against herbivores as well as for growth and reproduction. However, the priority of resource allocation within plants has not been investigated. We hypothesized that plants with extrafloral nectaries (EFNs) invest more chlorophyll around their EFNs—to support a high rate of carbon fixation there—than in other leaf parts of young leaves. Additionally, this chlorophyll may remain around EFNs rather than in the other leaf parts. We used Mallotus japonicus plants to investigate the chlorophyll content at leaf centers and edges and around EFNs at four stages of leaf development: middle‐expanded young leaves, fully expanded mature leaves, senior leaves, and leaves prior to abscission. These four stages of development were located at the third, fifth, eighth, and eleventh leaf positions from the apex, respectively. The results revealed that the chlorophyll content around the EFN side of the third‐position leaves was higher than that at the leaf center or edge. Although the chlorophyll content in the fifth‐position leaves did not differ between those at the leaf edge and around EFNs, the chlorophyll content around EFNs in the eighth‐position leaves was higher than that at the leaf centre and edge. The volume of EF nectar was positively correlated with the chlorophyll content around EFN during the leaf stage, but it was not correlated with the chlorophyll content in the leaf center and edge, except in fifth‐position leaves. These findings suggest that M. japonicus plants facilitate and maintain secretion of EF nectar in their young and old leaves, respectively, through the concentration and retention of chlorophyll around EFNs.     

Anti-herbivory defense of two <Emphasis Type="Italic">Vicia</Emphasis> species with and without extrafloral nectaries

The effects of direct and indirect defenses differ among plant species, and the variation in the mode of plant defenses might reflect physiological and/or ecological constraints of each mode of defense related to the growth and reproduction of individual plant species. To evaluate the advantages and disadvantages of indirect ant-mediated defense via extrafloral nectaries (EFNs), we compared the herbivory pressure, leaf chemicals, vegetative growth, and reproduction between two species of vetches, Vicia sativa var. angustifolia (Reichard) Wahlenb (Leguminosae) with EFNs and V. hirsuta (L.) SF Gray without EFNs (or with very small EFNs). Indirect ant defense of V. sativa was not consistently reliable because of the low constancy of ant attraction. In addition, V. sativa was more vulnerable to attack by herbivores than V. hirsuta. The estimated total amount of sugars secreted by EFNs of V. sativa corresponded to 0.5% of total leaf biomass, and 0.07% of total plant biomass, indicating a low investment to the production of extrafloral nectar. Vicia sativa plants grew more rapidly than V. hirsuta plants during the reproductive stage. Therefore, we consider that V. sativa adopts the ant defense via EFNs in spite of its low reliability because the indirect ant defense supported by EFNs requires only low investment, allowing the plants to attain rapid growth in the early spring.     

Extrafloral Nectaries in Cipadessa (Meliaceae)

This is the first report of an extrafloral nectary (EFN) fromAsian Meliaceae and from subfamily Melioideae. The pinnatelycompound leaf of Cipadessa baccifera has 25–35 small,ellipsoidal EFNs abaxially on the rachis, with occasional EFNson leaflets. EFNs secrete nectar until leaf maturity, then graduallywither. Each convex, ellipsoidal EFN is parenchymatous, withouta palisade epidermis, a delimiting nectary sheath, or any vascularaffiliation. This EFN differs markedly from the typical ‘Flachnektarien’EFN described earlier from neotropical Swietenia species. Cipadessa baccifera (Roth.) Miq., extrafloral nectary, Meliaceae, nectary anatomy     

Extrafloral nectary-bearing plant Mallotus japonicus uses different types of extrafloral nectaries to establish effective defense by ants

Extrafloral nectary (EFN)-bearing plants attract ants to gain protection against herbivores. Some EFN-bearing plants possess different types of EFNs, which might have different effects on ants on the plants. Mallotus japonicus (Thunb.) Muell. Arg. (Euphorbiaceae) bears two types of EFNs, including a pair of large EFNs at the leaf base and many small EFNs along the leaf edge. This study aimed to determine the different roles of the two types of EFNs in biotic defense by ants. A field experiment was conducted to investigate the effect of leaf damage on EFN production and on the distribution pattern of ants. After leaf damage, the number of leaf edge EFNs increased in the leaves first-produced. The number of ants on the leaves also increased, and the foraging area of ants extended from the leaf base to the leaf tip. An EFN-covering field experiment revealed that leaf edge EFNs had a greater effect than leaf base EFNs on ant dispersal on leaves. The extended foraging area of ants resulted in an increase of encounter or attack rate against an experimentally placed herbivore, Spodoptera litura. These results suggest that M. japonicus plants control the foraging area of ants on their leaves using different types of EFNs in response to leaf damage, thus achieving a very effective biotic defense against herbivores by ants.

     

Bundle sheath lignification mediates the linkage of leaf hydraulics and venation

The lignification of the leaf vein bundle sheath (BS) has been observed in many species and would reduce conductance from xylem to mesophyll. We hypothesized that lignification of the BS in lower‐order veins would provide benefits for water delivery through the vein hierarchy but that the lignification of higher‐order veins would limit transport capacity from xylem to mesophyll and leaf hydraulic conductance (K_leaf). We further hypothesized that BS lignification would mediate the relationship of K_leaf to vein length per area. We analysed the dependence of K_leaf, and its light response, on the lignification of the BS across vein orders for 11 angiosperm tree species. Eight of 11 species had lignin deposits in the BS of the midrib, and two species additionally only in their secondary veins, and for six species up to their minor veins. Species with lignification of minor veins had a lower hydraulic conductance of xylem and outside‐xylem pathways and lower K_leaf. K_leaf could be strongly predicted by vein length per area and highest lignified vein order (R² = .69). The light‐response of K_leaf was statistically independent of BS lignification. The lignification of the BS is an important determinant of species variation in leaf and thus whole plant water transport.     

Testing the optimal defense hypothesis in Stryphnodendron adstringens (Fabaceae,Mimosoideae) leaves: the role of structure,number, position and nectar composition of extrafloral nectaries

Stryphnodendron adstringens is a common Cerrado tree that possesses extrafloral nectaries (EFNs) on its leaves, which are located at the base and apex of the rachis and along the secondary veins. The position of EFNs and their nectar production can be affected by defense strategies because plant organs possess different values and herbivory vulnerability. Here we aimed to elucidate anatomy, histochemistry, nectar composition and EFN number on leaves of S. adstringens in the light of the optimal defense hypothesis. We found a convergence on anatomy and histochemical characterization because the three studied types of EFNs have epidermis, secretory parenchyma and vascular tissue, showing phenolic compounds and polysaccharides in the secretory parenchyma cells. The nectar contained glucose, fructose and sucrose, which attract ants of the Camponotus and Cephalotes genus. We found differences in the number of EFNs along the secondary veins and in the nectar composition between EFNs located at the base and apex of the rachis of the leaf. The number of EFNs on the secondary veins increases from the base to the apex, suggesting a strategy to induce ant patrolling over the entire leaf region. EFNs at the base secreted more nectar, which should be related to the protection of the leaf base, which is the part most vulnerable to herbivore attack and the most valued organ. We concluded that EFNs of S. adstringens are anti‐herbivore defenses whose pattern matches the predictions of the optimal defense hypothesis.     

The anatomical and compositional basis of leaf mass per area

Leaf dry mass per unit leaf area (LMA) is a central trait in ecology, but its anatomical and compositional basis has been unclear. An explicit mathematical and physical framework for quantifying the cell and tissue determinants of LMA will enable tests of their influence on species, communities and ecosystems. We present an approach to explaining LMA from the numbers, dimensions and mass densities of leaf cells and tissues, which provided unprecedented explanatory power for 11 broadleaved woody angiosperm species diverse in LMA (33–262 g m^?2; R² = 0.94; P < 0.001). Across these diverse species, and in a larger comparison of evergreen vs. deciduous angiosperms, high LMA resulted principally from larger cell sizes, greater major vein allocation, greater numbers of mesophyll cell layers and higher cell mass densities. This explicit approach enables relating leaf anatomy and composition to a wide range of processes in physiological, evolutionary, community and macroecology.     

Leaf hydraulic conductance varies with vein anatomy across Arabidopsis thaliana wild‐type and leaf vein mutants

Leaf venation is diverse across plant species and has practical applications from paleobotany to modern agriculture. However, the impact of vein traits on plant performance has not yet been tested in a model system such as Arabidopsis thaliana. Previous studies analysed cotyledons of A. thaliana vein mutants and identified visible differences in their vein systems from the wild type (WT). We measured leaf hydraulic conductance (K_leaf), vein traits, and xylem and mesophyll anatomy for A. thaliana WT (Col‐0) and four vein mutants (dot3‐111 and dot3‐134, and cvp1‐3 and cvp2‐1). Mutant true leaves did not possess the qualitative venation anomalies previously shown in the cotyledons, but varied quantitatively in vein traits and leaf anatomy across genotypes. The WT had significantly higher mean K_leaf. Across all genotypes, there was a strong correlation of K_leaf with traits related to hydraulic conductance across the bundle sheath, as influenced by the number and radial diameter of bundle sheath cells and vein length per area. These findings support the hypothesis that vein traits influence K_leaf, indicating the usefulness of this mutant system for testing theory that was primarily established comparatively across species, and supports a strong role for the bundle sheath in influencing K_leaf.     

Ant foraging on extrafloral nectaries of Qualea grandiflora (Vochysiaceae) in cerrado vegetation: ants as potential antiherbivore agents

Summary Qualea grandiflora is a typical tree of Brazilian cerrados (savanna-like vegetation) that bears paired extrafloral nectaries (EFNs) along its stems. Results show that possession of EFNs increases ant density on Q. grandiflora shrubs over that of neighbouring non-nectariferous plants. Frequency of ant occupancy and mean number of ants per plant were much higher on Qualea than on plants lacking EFNs. These differences resulted in many more live termitebaits being attacked by foraging ants on Qualea than on neighbours without EFNs. Termites were attacked in equal numbers and with equal speeds on different-aged leaves of Qualea. The greatest potential for herbivore deterrence was presented by Camponotus ants (C. crassus, C. rufipes and C. aff. blandus), which together attacked significantly more termites than nine other ant species grouped. EFNs are regarded as important promoters of ant activity on cerado plants.     

Distribution and structural aspects of extrafloral nectaries in Cedrela fissilis (Meliaceae)

The occurrence of extrafloral nectaries (EFNs) in Meliaceae has been reported for some genera, but little anatomical data are available. Therefore, to determine the distribution and structural aspects of EFNs, Cedrela fissilis Vell. leaves in different stages of development were collected, fixed, and processed for light and scanning electron microscopy. On the petiole, rachis and petiolule, EFNs were found to be arranged predominantly towards the abaxial surface, while their occurrence in leaflet blades was restricted to the abaxial surface of the major veins, noticeably on the midrib. Basal leaflets displayed few EFNs; however, we observed an increase towards the leaf's apex. The leaf can contain more than 300 inconspicuous EFNs, which show secretory activity throughout the leaf's life. Two EFN morphotypes were visible: flattened or elevated, both circular or slightly elliptical and similar in origin and tissue composition. The secretory tissue is embedded in the rachis cortex or in the major veins of the leaf blade and EFNs are not vascularized. The EFN secretory pole shows a uniseriate epidermis with compactly arranged cells and a thin cuticle; stomata and trichomes are absent. The observation of ant visits at these structures reinforces the assumption that EFNs mediate ant–plant interactions and play a protective role against herbivores throughout the life of a leaf.     

Anatomical and physiological characteristics relating to ionic relations in some salt tolerant grasses from the Salt Range,Pakistan

Populations of three salt tolerant forage grasses (Cynodon dactylon, Imperata cylindrica, and Sporobolus arabicus) were collected from the salt-affected soils of the Salt Range and normal non-saline soils of the Faisalabad region to assess their mechanism of adaptation to saline stress by determining ion relations and some specific anatomical modifications. The population of S. arabicus from the Salt Range showed increased growth (root and shoot length, and root and shoot dry weights) under saline conditions. Salt tolerance in this species was related to structural modifications such as increased area of root, stem, leaf blade, and leaf sheath for toxic ion accumulation, increased vesicular hair density in leaves and aerenchyma formation in leaf sheath for ion exclusion. Uptake of toxic ions was high in the Salt Range population of C. dactylon and salt tolerance was related to ion exclusion through specific leaf structural modifications such as vesicular hairs. Salt tolerance in the Salt Range population of I. cylindrica was mainly associated with restricted uptake of toxic Na⁺ and Cl⁻ at root level, and accumulation of toxic ions via increased succulence in leaf blades and leaf sheaths in addition to some excretion of toxic ions through leaf sheath aerenchyma.     

DIFFERING ONTOGENETIC ORIGINS OF PCR (“KRANZ”) SHEATHS IN LEAF BLADES OF C4 GRASSES (POACEAE)

The origin and early development of procambium and associated ground meristem of major and minor veins have been examined in the leaf blades of seven C₄ grass species, representing different taxonomic groups and the three recognized biochemical C₄ types (NAD-ME, PCK, and NADP-ME). Comparisons were made with the C₃ species, Festuca arundinacea. In “double sheath” (XyMS+) species (Panicum effusum, Eleusine coracana, and Sporoboìus elongatus), the procambium of major veins gives rise to xylem, phloem, and a mestome sheath; associated ground meristem differentiates into PCA (“C₄ mesophyll”) tissue and the PCR (“Kranz”) sheath. Development in the C₃ species parallels this pattern, except that associated ground meristem differentiates into mesophyll and a parenchymatous bundle sheath. In contrast, major vein procambium of “single sheath” (XyMS–) species (Panicum bulbosum, Digitaria brownii, and Cymbopogon procerus) differentiates into xylem, phloem and a PCR sheath; associated ground meristem gives rise to PCA tissue. These observations of major vein development support W. V. Brown's hypothesis that the PCR sheaths of “double sheath” (XyMS+) C₄ grasses are homologous with the parenchymatous bundle sheaths of C₃ grasses, while in “single sheath” (XyMS–) C₄ species they are homologous with the mestome sheath. Although there are some similarities in the development of the major and minor vascular bundle procambium in the C₄ species examined, the ontogeny of the smaller minor veins is characterized by a precocious delineation of the PCR sheath layer that may even precede the appearance of the distinctive cytological features of ground meristem and procambium. This contracted development in minor veins appears to be related to their close spacing in mature leaves and to their comparatively late appearance during leaf ontogeny.     

Distribution, structural and ecological aspects of the unusual leaf nectaries of Calolisianthus species (Gentianaceae)

Nectaries in leaves of Gentianaceae have been poorly studied. The present study aims to describe the distribution, anatomy, and ecological aspects of extrafloral nectaries (EFNs) of three Calolisianthus species and in particular the ultrastructure of EFNs in Calolisianthus speciosus during leaf development, discussing its unusual structure. Leaves of Calolisianthus species were fixed and processed by the usual methods for studies using light, scanning microscopy and transmission electron microscopy (TEM). Ion chromatography was used to analyze the nectar exudates of C. speciosus. The distribution patterns of nectar secretion units were analysed by ANOVA and t-tests. Two EFNs that can be seen macroscopically were observed at the bases of C. speciosus and C. pendulus leaves. Such large nectaries are absent there in C. amplissimus. Another similarly large EFN is observed at the apex of each leaf in all species. The EFNs at the base of the young leaves in C. speciosus are visited by ants during the rainy season. EFNs are formed by several nectar secretory units (nectarioles) that are present throughout the leaves. Each nectariole is formed by rosette cells with a central channel from which the nectar is released. Channels of old C. speciosus and C. pendulus EFNs were obstructed by fungi. TEM of EFNs in young leaves showed cytoplasms with secretion, small vacuoles, mitochondria, cell wall ingrowth, and plasmodesmata. TEM of EFNs in old leaves demonstrated dictyosomes, plastids, mitochondria, segments of endoplasmatic reticulum, and lipid droplets. The nectar contains sucrose, glucose and fructose.     

Do extrafloral nectaries present a defensive role against herbivores in two species of the family Bignoniaceae in a Neotropical savannas?

Despite the general belief that the interaction between extrafloral nectaries (EFNs) and ants is mutualistic, the defensive function of EFNs has been poorly documented in South American savannas. In this article, we evaluate the potential impact of EFNs (benefits and costs) on two species of plants from the dry areas of Central Brazil, Anemopaegma album and Anemopaegma scabriusculum (Bignoniaceae). In particular, we characterize the composition of substances secreted by the EFNs, test whether EFNs attract ants, and whether ants actually present a defensive role, leading to reduced herbivory and increased plant fitness. Histochemical analyses indicated that EFNs from both species of Anemopaegma secrete an exudate that is composed of sugars, and potentially lipids and proteins. Furthermore, EFNs from both species were shown to present a significant role in ant attraction. However, contrary to common expectations, ants were not found to protect plants against herbivore attack. No effect was found between ant visitation and flower or fruit production in A. album, while the presence of ants led to a significant decrease in flower production in A. scabriusculum. These results suggest that EFNs might present a similar cost and benefit in A. album, and a higher cost than benefit in A. scabriusculum. Since the ancestor of Anemopaegma occupied humid forests and already presented EFNs that were maintained in subsequent lineages that occupied savannas, we suggest that phylogenetic inertia might explain the presence of EFNs in the species of Anemopaegma in which EFNs lack a defensive function.     

Suberized bundle sheaths in grasses (Poaceae) of different photosynthetic types I. Anatomy,ultrastructure and histochemistry

Summary We investigated the histochemistry and ultrastructure of the cell walls of mestome sheaths and parenchymatous bundle sheaths of ten species of grasses. The species surveyed included representatives from all the major photosynthetic types: C₃-Bromus tectorum, Phalaris arundinacea; C₄/NAD-ME-Eragrostis cilianensis, Panicum capillare; C₄/NAD-ME/PCK-Bouteloua curtipendula; C₄/PCK-Chloris gayana, Sporobolus elongatus; C₄/NADP-ME-Echinochloa crus-galli, Setaria glauca, Themeda triandra. All vein orders (designated here as major, minor and transverse) from mature leaves of each species were tested histochemically for lipids and phenols, and the majority of species were also examined with the electron microscope. A suberized lamella was detected ultrastructurally in at least some walls of major vein bundle sheath cells of all species examined. These lamellae were also present in some cells associated with the minor veins of the C₃ species and in the minor and transverse veins of the C₄/NADP-ME species. Histochemical tests for lipids and phenols consistently failed to differentiate this layer. Based on these tests, none of the vein orders in any species showed evidence of a Casparian band. In all suberized bundle sheaths, the compound middle lamella between cells with suberin lamellae is modified by the presence of phenols. These did not, however, confer resistance to acid digestion to the cell layer, in contrast to cell layers with Casparian bands. Therefore, although the mestome sheath has some features in common with the root endodermis (i.e. cells with a suberized lamella and thick, cellulosic walls which may be further modified), we could find no substantive anatomical or ultrastructural evidence for the presence of a Casparian band in any of the grass leaves investigated. The significance of these observations is discussed in the context of apoplastic permeability of these walls.     

真红树和半红树植物叶片性状的比较研究

红树植物是一类生长在热带、亚热带海岸潮间带的乔木、灌木或草本植物,根据其分布特征可分为真红树植物植物和半红树植物。为了探究两者对海岸潮间带高盐、高光和缺氧等环境的生态适应策略的异同,该文选取5种真红树植物植物[卤蕨(Acrostichum aureum)、木榄(Bruguiera gymnorrhiza)、老鼠簕(Acanthus ilicifolius)、桐花树(Aegiceras corniculatum)、秋茄(Kandelia candel)]和4种半红树植物[银叶树(Heritiera littoralis)、水黄皮(Pongamia pinnata)、黄槿(Hibiscus tiliaceus)、杨叶肖槿(Thespesia populnea)]为研究对象,对叶片解剖和功能性状进行了对比研究。结果表明:(1)9种红树植物叶片的共同特征表现为均具有角质层、叶肉具有栅栏组织和海绵组织分化、气孔下陷等。(2)不同之处在于真红树植物植物叶片有蜡质层和内皮层、无表皮毛、气孔仅分布在下表皮,而半红树植物的叶片则较少有蜡质层,部分有表皮毛,无内皮层,气孔在上下表皮分布不完全一致。(3)真红树植物植物的气孔密度和比叶面积显著小于半红树植物(P<0.05),而叶片厚度、含水量、比叶重和鲜干重比则显著大于半红树植物(P<0.05)。以上结果说明真红树植物植物的叶片性状使其在维持盐度平衡及贮水保水能力方面强于半红树植物,从而能更好地适应海岸潮间带高盐环境。     

Foliar architecture and anatomy of <Emphasis Type="Italic">Bernardia</Emphasis> and other genera of Acalyphoideae (Euphorbiaceae)

A comparative study of leaf architecture and anatomy of 42 species of Bernardia and other genera related of Acalyphoideae was undertaken to identify characters that support infrageneric and specific delimitation. Thirty variable foliar architectural and anatomical characters were studied. Some characters are consistent (e.g., venation pattern, secondary and tertiary vein arrangement, presence or absence of agrophic veins, type of areoles, bundle sheath cell type, presence or absence of fibers in the mesophyll, trichome type, stomata location, and type of crystals), and characterize genera. In addition, foliar character distribution within Bernardia supports the most recent infrageneric classification.     

Linking vein properties to leaf biomechanics across 58 woody species from a subtropical forest

• Leaf venations have elements with relatively lower elasticity than other leaf tissue components, which are thought to contribute to leaf biomechanics. A better mechanistic understanding of relationships between vein traits and leaf mechanical properties is essential for ecologically relevant interpretation of leaf structural variations.
• We investigated 13 major (first to third order) and minor (>third order) vein traits, six leaf mechanical properties and other structural traits across 58 woody species from a subtropical forest to elucidate how vein traits contribute to leaf biomechanics.
• Across species, vein dry mass density (ρ_v), total vein dry mass per leaf area (VMA) and minor vein diameter (VD_min), but not the lower‐order vein density (VLA_1?2), were positively correlated with leaf force to punch (F_p) and force to tear (F_t). Structural equation models showed that ρ_v and VD_min not only contribute to leaf mechanical properties directly (direct pathway), but also had impacts on leaf biomechanics by influencing leaf thickness and leaf dry mass per area (indirect pathway).
• Our study demonstrated that vein dry mass density and minor vein diameter are the key vein properties for leaf biomechanics. We also suggest that the mechanical characteristics of venations are potential factors influencing leaf mechanical resistance, structure and leaf economics spectrum.

     

Anatomy of extrafloral nectaries in Fabaceae from dry‐seasonal forest in Brazil

Extrafloral nectaries (EFNs) are found in many species of Fabaceae. The aim of this work is to describe the internal morphology of the EFNs from species of Fabaceae found in areas of dry‐seasonal forest in north‐eastern Brazil. All species of Fabaceae with EFNs found were collected and samples were submitted to conventional techniques for anatomical and scanning electronic microscopy analysis. EFNs were found in 35 species, of which 32 were examined anatomically. All types have epidermal cells, secretory tissues and vascular bundles in the EFNs. Sclerenchymatous cells were found between the secretory tissues and the vascular tissues, with a few exceptions. The function of these cells is not clear; however, a role in the transportation of the sap in the nectary or with the support of the secretory tissue is possible. The nectar is released through glandular trichomes, secretory pores or even by breaking the epidermal cells and cuticle. The internal patterns found in the EFNs from different species and genera can provide important information for taxonomic and evolutionary studies in the family. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 163 , 87–98.