Phillip G. Ladd

Context: Images on currency have varied over the time fiat money has been used. Initially money had intrinsic value based on metal content, but its value became increasingly reliant on that assigned to it by the issuing authority. Both coins and notes typically have images. Some, such as heads of state, indicate guarantees of value but others represent socially significant features, including plants. Aims: We aimed to examine the biogeographic patterns of plant categories that have been depicted on coins and banknotes to identify any trends in the symbolism of the designs on banknotes and coins for different parts of the world. Methods: We collected currency items and used web searches to compile information about plant images used on money from currently recognised modern and ancient countries. Key results: Governments give serious consideration to currency design because the images can be considered to provide a sense of community or national ‘belonging’. Plants most commonly depicted on currency are food plants, many of which are also emblems or motifs of the state. The images need to be recognisable to the users of the currency as there is normally no explanation of the importance of the organism or even its name. Currencies from different regions of the world have different patterns of plant types. Conclusions: It is unclear how observant people are of the images on currency. However, almost all countries or states have plant emblems that are very recognizable. Implications: With the current trend towards digital money there is a threat that cherished state emblems may disappear from public consciousness.

Context: Parasitic plants are widespread throughout the global flora and have diverse lifestyle strategies. In most cases these plants are detrimental to the host but may have some beneficial effects on the co-occurring plants in the sourrounding communities. Some have large macroscopic plant bodies and can photosynthesise, and are therefore able to produce some fixed carbon but do take water and nutrients from the host, especially if aerially attached. Very few species have vegetative parts completely enclosed in the host, having only reproductive structures externally displayed. Whether such internal parasites have as severe effects on the host as parasites with macroscopic plant bodies is unclear. Aims: The endoparasite Pilostyles hamiltoniorum infests pea species (predominantly Daviesia species) in the south-west of Western Australia. We investigated the effect of this parasite on the vegetative growth and reproduction of Daviesia angulata in heathland vegetation. Methods: Size, flowering and fruiting of parasitised and unparasitised host plants were recorded in three 6 × 30 m plots in a revegetated gravel pit in the Jurien Bay area of Western Australia. Key results: A proportion of 21% of host plants was parasitised and these were significantly taller than unparasitised plants. These plants had 52% fewer flowers on average than unparasitised plants and subsequently far fewer fruits. Conclusions: The reduction in reproductive output by this internal parasite was at least equal to or more severe than occurs in published examples of decreased productivity of other species parasitised by species with macroscopic plant morphology. Implications: The reduced reproductive output of the host plants would be inimical to seed stores in the soil that this species relies on for regeneration after fires that commonly affect the vegetation in this region.

Leaves of seed plants were evolutionarily derived through syngenesis (fusion) of the photosynthetic cylindrical axes of the earliest land plants and subsequent morphological diversification. However, in some later evolved taxa leaves became very reduced or entirely lost and photosynthesis was again restricted to stems. Reduction of photosynthetic area to stems is mostly found in plants from arid environments and is generally considered disadvantageous in competition for light with plants with leaves but may be useful if water is limiting. For taxa that cannot form normal leaves on adult plants, increasing photosynthetic area is only possible by modification of other plant parts. Some taxa produce leaf-like phylloclades that are developmentally different from leaves. We investigated Jacksonia floribunda and J. anthoclada (Fabaceae) leaves and phylloclades. In all Jacksonia species true leaves are only developed in the earliest ontogenetic stages, and subsequently are reduced to minor, nonphotosynthetic brownish scales. After several nodes on the seedling, photosynthetic phylloclades, each inserted in the axil of a scale, form the foliage. Immature phylloclades have vestigial nonphotosynthetic leaves borne on small projections from the edge of the blade. These soon abscise. The phylloclades are flattened branches and when mature have a distinctly reticulate venation and a sinuous margin with alternating mucronate tips where the vestigial leaves were attached. Jacksonia species demonstrate a transformational series where in most species foliage is reduced to branchlets. In a few others branchlets are winged forming cladodes or are condensed and laterally expanded to form phylloclades. Our findings on the more derived species in Jacksonia illustrate the complexity of plant morphological responses to evolutionary pressures of seasonal water limitation.

The majority of taxa with peltate leaves are perennial herbs native to swampy or aquatic habitats or to mesic shaded understorey habitats. These large peltate leaves are formed by a meristematic bridge at the lamina–petiole junction. However, there are also several strong-light exposed, small-leaved, xero- and scleromorphic Myrtaceae with leaf peltation which is formed without a meristem fusion/bridge. Here, abaxial laminar tissue at the insertion point of the petiole forms a basal extension, so that a weak peltation occurs. This shifts the petiole onto the adaxial laminar surface. The formation of micropeltation in Myrtaceae leads to erect leaves that are strongly appressed to the shoot axis and the entire foliate, vertical shoots appear as “green columns”, a result that is also the case in taxa with reflexed minute leaves. It seems that micropeltation achieves the same goal as leaf reflexion in small-leaved taxa—reduction of heat-load and transpiration during the hottest phases of the day by a lower light interception at midday compared to the morning and evening. Thus, physiologically micropeltation and reflexion of minute leaves seem to be the result of convergent evolution.

Context The Southwest Australian Floristic Region has exceptional plant evolutionary complexity for fire, nutrition and pollination traits. Aims Our aim was to allocate pollination strategies to all vascular plants in this biodiversity hotspot by analysing existing and new data. Methods Here we assigned a flower syndrome to ~8800 plants in this region, using floral traits and visitation records for insects, birds or mammals, which were well correlated. Key results Specific insect relationships were most common (3383), especially with native bees (2410), including buzz pollination (450). Others were pollinated by wind (1054 plants), water (35) or had relatively unspecialised flowers visited by diverse insects (3026). Specific associations with flies (588) or butterflies and moths (165) were less common. Approximately 14% were primarily pollinated by birds (601) or birds and insects (583) – with much larger flowers (corresponding with bird bill lengths), and less insect-attracting colours (e.g. red or green). Non-flying mammals, especially honey possums, visit certain flowers along with birds. Pollination complexity peaked in the Myrtaceae (11% bird, 25% bird and insect), Fabaceae (2% bird, 46% bee, 2% buzz pollination) and Proteaceae (40% birds, 31% specific insects). Bird pollination also has multiple origins in the Ericaceae (8%), Haemodoraceae (20%), Rutaceae (16%), Pittosporaceae (14%) and Eremophila (45%). Extreme specialisations included secondary pollen presentation (1231), post-pollination colour change (72), mobile columns (310), explosive pollen release (137) and visual (209) or sexual (171) deception in orchids. Pollination trait complexity included >275 evolutionary transitions, especially from insects to birds (130), more specific insects (100), or wind (15). These followed similar morphological pathways within families but differed between them. Conclusions This complexity appears to be globally unique, and peaks in highly speciose plant families with diversity centred in the region. Implications This has ecological and genetic consequences, especially for rare flora management, ecosystem restoration and assessing plant vulnerability to habitat degradation, fire and climate change.

Context: Most tissues of Myrtaceae plants have oil glands. The anthers of many species have an oil-containing apical gland that is larger than those in other tissues of the plant. Aims: Representative species in the family were examined for the diversity of gland form and their oil contents. Methods: Representative anthers were sectioned for light microscopy and scanning electron microscopy study and anthers from selected species were analysed for oil content. Key results: The most common gland form is globular and narrowly attached to the apex of the connective, but in members of certain tribes, the gland is completely enclosed in the connective. The greatest morphological diversity is in the Chamelaucieae. Anther glands vary from plesiomorphic globular forms to glands that are larger than the anther thecae and almost completely fill the connective. Conclusions: There are three possible functions for the glands, including the following: (1) protecting the anthers from herbivores, (2) mixing with the pollen to aid adhesion to stylar hairs on many Chamelaucineae, and (3) rewarding pollinators that use the oil–pollen mixture as food. Implications: It is generally considered that the oils in various tissues of the Myrtaceae deter herbivores. In Myrtaceae with abundant anthers, the glands could deter flower visitors from consuming the anthers. Gland oil of the Eucalyptus and Leptospermum species examined contained α pinene as did the leaves of all species examined. The gland oil composition in Chamelaucium uncinatum and Verticordia grandis that have pollen presenters was different from that in the leaves and also different from that in the anthers of the two Verticordia species where bees collect the pollen–oil mixture for food.

Key message: We examined leaves of a suite of microphyllous woody plants and describe a little-known form of leaf peltation for the first time and also investigate strongly reflexed leaves in two distantly related lineages. Plants cope with a range of environmental conditions, especially related to water relations, and have developed an array of physiological and structural solutions to maintain a functional water balance. There has been considerable recent work on physiological solutions to water deficit but little attention paid to leaf characteristics. In many species there is a change in leaf form from seedlings to adults. We examine such changes in several small-leaved species from the distantly related Asteraceae and Myrtaceae, some of which develop micropeltate or reflexed leaves as adults. All are native to dry or seasonally dry sites. Three major morphological groups were recognised as follows: (1) leaves erect, nonpeltate and scale-like (Ozothamnus hookeri), (2) leaves erect and peltate (Phaenocoma prolifera,Regelia inops), (3) Leaves reflexed (Olearia lepidophylla,Ozothamnus scutellifolius,Ozothamnus reflexifolius,Melaleuca diosmifolia). The microphyllous peltation inP. proliferaandR. inopsin the absence of a meristematic fusion/bridge differs from typically peltate leaves. These small-leaved taxa occur in open, high light environments which are very different from the mesic, shaded understorey habitats of typical peltate-leaved plants. Many small-leaved species have leaves closely appressed to the stem and often with recurved margins. The erect leaves are functionally similar to reflexed leaves. Environmental filtering leads to superficially similar plant forms that may have somewhat different ontological origins. Such morphological forms are examples of convergent evolution in distantly related species but within each family are likely phylogenetically related.

Key message: We examined the leaf structure of two basal Cupressus species with a distinct leaf dimorphism. Some foliar features are regarded as ancestral and it is suggested that drought adaptation was one of the important ecological drivers in the evolution of the Cupressus genus. Leaf morphology and anatomy of two Cupressus species, C. nootkatensis and C. vietnamensis, were investigated with classical paraffin technique and scanning electron microscopy (SEM). Like all Cupressus species these two are characterised by a dramatic change in the foliage. Juveniles have needle leaves first before they change abruptly to the mature scale leaf type. In C. vietnamensis, needle-leaved shoots occur next to scale-leaved ones even on mature trees, which is unique among today´s Cupressus species. Adults of C. nootkatensis develop only scale leaves throughout. In both taxa, the scale leaves show a distinct dimorphism between lateral and facial leaves, which are arranged in a flat spray; the foliate shoots are two-dimensionally flattened. These scale leaves show several xeromorphic features; e.g. strongly reduced leaf size, stomata with high, collar-like Florin rings, the presence of a distinct hypodermis as a continuous layer and well-developed transfusion tissue. The needle leaf type is found in Cunninghamia which is the basal member of the Cupressaceae and so is regarded as the ancestral condition and scale leaves as a derived one. Scale leaves are found in all the members of the cupressoid clade even within the basal taxa from mesic habitats. However scale leaves are a preadaptation to survival under xeric conditions and they are likely an evolutionary driver of the radiation of Cupressus into arid environments, as has also been the case in genera such a Callitris.