To clarify the role of seasonal change, competitive response and nutrient availability in the competitive asymmetry of grassland species a competition experiment was conducted on Holcus lanatus, Anthoxanthum odoratum and Festuca ovina, which represent a successional sequence of decreasing nutrient availability. Seven harvests were taken over two growing seasons. At each harvest the dry weight of plant parts, dead leaves, leaf area and plant height were measured. Three key traits that determine the successional status of the species were studied: specific leaf area, specific shoot height, and dead leaf fraction.

The response of these traits to competition appeared to be limited and insufficient to change the competitive relations in the experiment. However, all three traits showed marked seasonal changes which resulted in superior growth and survival in winter of the species adapted to nutrient-poor environments. The findings support the theory that competitive asymmetry increases at higher nutrient levels. It is postulated that the directionality of light makes it possible for the dominant species to monopolize this resource more easily than nutrients.

A key element of most recently proposed plant strategy schemes is an axis of resource capture, usage and availability. In the search for a simple, robust plant trait (or traits) that will allow plants to be located on this axis, specific leaf area is one of the leading contenders. Using a large new unpublished database, we examine the variability of specific leaf area and other leaf traits, the relationships between them, and their ability to predict position on the resource use axis. Specific leaf area is found to suffer from a number of drawbacks; it is both very variable between replicates and much influenced by leaf thickness. Leaf dry-matter content (sometimes referred to as tissue density) is much less variable, largely independent of leaf thickness and a better predictor of location on an axis of resource capture, usage and availability. However, it is not clear how useful dry matter content will be outside northwest Europe, and in particular in dry climates with many succulents.

Laboratory experiments have shown a large difference in specific leaf area (SLA, leaf area: leaf mass) between species from nutrient-poor and nutrient-rich habitats, but no systematic difference in the construction costs (the amount of glucose required to construct 1 g biomass). We examined how far these patterns are congruent with those from field-grown plants. An analysis was made of the vegetation in a range of grasslands and heathlands differing in productivity. The SLA of the dominant species in 15 different habitats was determined, as well as chemical composition and construction costs of bulk samples of leaves. SLA in the field was generally lower than in the laboratory, but showed consistency in that the ranking across species remained the same. Species from highly productive habitats had higher SLA than those from sites of low productivity, although individual species sometimes deviated substantially from the general trend. Construction costs were similar for plants from different habitats. This was mainly due to the positive correlation between an expensive class of compounds (proteins) and a cheap one (minerals).

The apoplastic pH of intact green leaves of Bromus erectus was measured non-invasively by inserting blunt microelectrodes through stomatal openings. After making electrical contact, the recorded signal was stable for hours, yielding a pH of 4.67±0.10. The leaves responded to ‘light-off’ with an initial transient acidification and subsequent sustained alkalinization of 0.2–0.3 pH; ‘light-on’ caused the opposite response. Flushing the leaves with 280 nmol NH3 mol−1 air within 18±6 s alkalinized the apoplast by 0.22±0.07 pH, followed by a slower pH increase to reach a steady-state alkalinization of 0.53±0.14 after 19±7 min. This pH shift was persistent as long as the NH3 was flushed, and readily returned to its initial value after replacing the NH3 with clean air. The resultant [NH4+] increase within the apoplast was measured with a NH4+-selective microelectrode. In the presence of 280 nmol NH3 mol−1 air, apoplastic NH4+ initially increased within 15±10 s to 1.53±0.41 mM, to reach a steady state of 1.62±0.16 mM after 27±7 min. An apoplastic buffer capacity of 6 mM pH−1 unit was calculated from the initial changes of pH and [NH4+ ], whereas the steady-state values yielded 2.7 mM pH−1. Infiltrated leaves responded to NH4+ with concentration-dependent depolarizations, the maxima of which yielded saturation kinetics indicating carrier-mediated NH4+ uptake into adjacent cells, as well as a linear component indicating non-specific transport. We infer that the initial alkalinization is due to rapid conversion of NH3 to NH4+, whereas the slower pH increase would be caused by regulatory processes involving both membrane transport, and (mainly) NH4+ assimilation. Possible consequences of the NH3-induced pH shift for the development of plants growing in polluted areas are discussed.

Eight different species of the red algal genus Porphyra from different biogeographic regions in Europe, Africa, North America, Asia and Australia were collected over the course of the respective growth season and surveyed for the qualitative and quantitative occurrence of the low molecular weight carbohydrates, floridoside, D-isofloridoside and L-isofloridoside. Except for Porphyra saldanhae from South Africa, all species tested exhibited clear seasonal variations in their heteroside composition. Whereas Porphyra dioica and Porphyra umbilicalis from the North Sea showed highest carbohydrate concentrations in spring and summer, those of Porphyra leucosticta from Spain were highest in winter. The red algae studied exhibited highest concentrations of heteroside at different seasons, some in winter, others in spring or summer. The composition of the three compounds varied among the species studied. In P. columbina from Australia, L-isofloridoside was always quantitatively dominant, while floridoside was the major component in P. dioica. Usually D-isofloridoside was present in small concentrations, except in P. perforata from the Pacific coast of the USA where it occurred in equal concentrations with floridoside and L-isofloridoside. The results point to species-specific different enzymic activities of the underlying anabolic pathways. Correlations between the heteroside concentrations and various prevailing environmental parameters are detectable but do not reveal a general response of Porphyra. Data from the literature prove that numerous physical factors determine the growth patterns of various Porphyra species in different biogeographic regions. Of these, photoperiod, temperature and nutrients are the most important. Highest heteroside concentrations in the Porphyra species studied always coincided with enhanced growth, and this relationship determined that growth, though related to abiotic conditions, was also promoted by maximum carbohydrate content. The multiple physiological function of floridoside, D-isofloridoside and L-isofloridoside as osmolytes, compatible solutes and carbon reserves is discussed in relation to the environmental stresses that Porphyra species usually experience in their upper intertidal habitats.

Several physiological processes controlling tree phenology remain poorly understood and in particular bud dormancy. Many studies have emphasised the action of chilling temperatures in breaking dormancy. However, the effect of the preceding summer temperatures has rarely been investigated although there is some evidence that they may be involved in the settlement and intensity of dormancy as well as cold acclimation. In this paper, thermal time to budburst in relation to the duration of chilling outdoors, preceding summer temperatures and forcing temperatures was studied by outdoors experiments in seedlings of Platanus acerifolia, Vitis vinifera, Quercus pubescens and Castanea sativa. Results showed that temperatures of the preceding summer had no significant effect on the timing of budburst, P. acerifolia and Q. pubescens showed a very weak response to the duration of chilling, and the phenological characteristics of each species were found to be adapted to the climate conditions of its own geographical area. The phenological model used in this study explained 82–100% of the variance of the data without taking into account summer temperatures. Thus, although summer temperatures may be well involved in the intensity of dormancy and cold hardiness, they do not significantly affect budburst and therefore may not need to be considered in phenological models for predicting budburst.

Nutrient conservation plays an important role in plants adapted to infertile environments. Nutrients can be conserved mainly by extending the life span of plant parts and/or by minimizing the nutrient content of those parts that are abscissed. Together these two parameters (life span and resorption) define the mean residence time (MRT) of a nutrient. In this review we summarize available information on nitrogen resorption and life span, and evaluate their relationship to the MRT of nitrogen, both between and within species. Abundant information with respect to nitrogen resorption efficiency and life span is available at the leaf level. By definition, woody evergreen plants have a much longer leaf life span than species of other life-forms. Conversely, differences in resorption efficiency among life-forms or among plants in habitats differing in soil fertility appear to be small. Inter-specific variation in leaf life span is much larger than intra-specific variation (factor of >200 compared with 2, respectively), while resorption efficiency varies by about the same magnitude at both levels (factor of 3.8 compared with 2.7, respectively). The importance of resorption efficiency in determining leaf-level MRT increases exponentially towards and above the maximum resorption efficiency observed in nature. This effect is independent of leaf life span, which may explain the lack of life-form related differences in resorption efficiency. When scaling up from the leaf to the whole-plant level, fundamental differences in turnover rate among different plant organs must be considered. Woody species invest c. 50% of their net productivity into their low-turnover stems, while in herbaceous species the life span of stems is only slightly longer than that of leaves. As a result, nutrient turnover of woody (evergreen and deciduous) plants is generally lower than that of herbaceous species (herbs and graminoids) on a whole-plant basis. At the intra-specific level empirical data show that both biomass life span (i.e. the inverse of biomass loss rate) and resorption efficiency are important sources of variation in MRT. However, we argue that the relative importance of resorption efficiency in explaining variation in MRT is lower at the inter-specific level, whereas the reverse is true for life span. This is because variation in MRT and life span is much larger at the inter-specific level compared with variation in resorption efficiency. Plant traits related to nutrient conservation are discussed with respect to their implications for leaf structure, plant growth, competition, succession and ecosystem nutrient cycling.

Two cultivars of sorghum (CSH-1 and Ochuti) were grown in the presence and absence of the root hemiparasite Striga hermonthica in uniform conditions in the field in Kenya, Africa. S. hermonthica had a marked influence on growth and photosynthesis of ‘CSH-1’; however, ‘Ochuti’ showed a less severe response to infection and tolerance of the parasite. The variation in genotype response might be partly explained by later attachment of the parasite and a lower level of infection. Laboratory studies were used to determine the importance of both variables in determining host response to infection. Early infection by S. hermonthica had a more negative effect on the host than late infection. The level of parasite biomass supported by the host also influenced host productivity but the relationship was nonlinear. Low degrees of parasite infection had a proportionately much greater effect on host grain weight than at greater parasite loading. Early infection of ‘Ochuti’ in laboratory conditions resulted in lower stem dry weight than in uninfected plants but not in smaller total plant biomass or lower rates of photosynthesis. In conclusion, the time of parasite attachment affected host performance and might explain much of the variation in host sensitivity both within and between studies. The level of parasite infection affected host performance to a lesser extent. In addition, late attachment and low levels of infection might have implications for control management strategies.

Endogenous polyamine content of the ectomycorrhizal fungus Paxillus involutus, as well as the activity of its biosynthetic enzymes in relation to mycelia ageing were investigated in this work. Polyamines in free, PCA-soluble and insoluble conjugated forms, are present in Paxillus involutus mycelia in relatively high amounts and the ratio of putrescine to spermidine is age-dependent. Both arginine- and ornithine-decarboxylases are present, but putrescine biosynthesis proceeds mostly via ornithine decarboxylase and decreases with the age of mycelia. There was a large release of free polyamines from mycelia which showed age-dependent features. Clear polyamine uptake was observed in 2-wk-old mycelia and no competition between putrescine and cadaverine was detected. Putrescine uptake seems to reduce ornithine decarboxylase activity, but does not affect arginine decarboxylase.

There is some evidence that traits of fresh leaves that provide structural or chemical protection (‘defence’) remain operational in the leaf litter and control interspecific variation in decomposition rate in or on the soil. We tested experimentally whether the negative relationship between foliar defence and litter decomposition rate is fundamental, i.e. whether it is seen consistently across higher plant species and life forms, and whether it is repeated in the floras of geographically and climatically distinct areas separated by an ocean. We employed the published results of two outdoor litter bag experiments, in which we simultaneously compared the relative mass losses (‘decomposibility’) of leaf litters of a wide range of plant species. One experiment was in Córdoba, Argentina, and included 48 Argentine species typical of the dry, subtropical landscapes along a steep altitudinal gradient. The other was in Sheffield, UK, and hosted 72 British species typical of the temperate–Atlantic landscape there. We linked the two experiments through a similar experiment in Sheffield that hosted litters of subsets of both the Argentine and British species. We also tested fresh leaves of all species from the same areas for tensile strength (‘toughness’) and relative palatability to generalist herbivorous snails in multi-species ‘cafeteria’ experiments. Both in Argentina and in Great Britain there were highly significant correlations between leaf palatability (r=0.61; 0.73) or leaf tensile strength (r=−0.60; −0.60) and litter mass loss across all species. These relationships could be explained by variation both between and within broad life-form groups. Specific leaf area (area[ratio ]dry mass) of fresh leaves was consistently correlated only with litter mass loss within British life form groups. We illustrated the possible ecosystem consequences of these relationships by comparing functional traits of British species differing in leaf habit. In comparison with deciduous species, evergreens generally had innately slow growth, which corresponded to their longer-lived leaves of lower specific leaf area, higher tensile strength and lower palatability to generalist invertebrate herbivores. Correspondingly, evergreens produced more resistant leaf litter. Thus, slow-growing evergreens might maintain their position in infertile ecosystems through leaf traits that help them to conserve their nutrients efficiently and to keep nutrient mineralization low, thereby not allowing potentially fast-growing deciduous species to outcompete them.

Leaf anatomical parameters such as leaf mass per area (LMA) and biochemical composition can be used as indicators of leaf photosynthetic capacity. The aims of this study are to evaluate the potential of reflectance spectroscopy of fresh leaves for assessing and predicting various parameters, anatomical (LMA and tissue thickness) and biochemical (nitrogen concentration). This paper describes results obtained with fresh leaves of holm oak (Quercus ilex), an evergreen oak that is widely distributed from mesic to xeric habitats in the Mediterranean. Fresh leaves (560) were collected over 3 yr at six different sites, from the top to the bottom of the canopy. The reflectance of each leaf was obtained within 1 h of sampling with an NIRSystems 6500 spectrophotometer over the range 400–2500 nm. LMA was determined for all samples; biochemical and anatomical measurements were conducted over representative subsample populations of 92 and 87 leaves, respectively. Stepwise regression calibrations and partial least squares (PLS) calibrations were developed and compared with different spectral regions and mathematical treatments. Calibration equations had high coefficients of determination (r2 ranging from 0.94 for nitrogen to 0.98 for LMA and tissue thickness). The PLS regressions gave better results than stepwise regressions for all parameters studied. Compared with regressions calculated on raw spectral data, calculations on second derivatives of spectra improved results in all cases. The use of scatter corrections also improved results. These results show that visible and near-infra red reflectance can be used for accurately predicting anatomical parameters and the nitrogen concentration of fresh holm oak leaves. The results support the suggestion that high spectral resolution imaging spectrometry can be a useful tool for assessing functional processes in forest ecosystems.

Models have been formulated for monospecific stands in which canopy photosynthesis is determined by the vertical distribution of leaf area, nitrogen and light. In such stands, resident plants can maximize canopy photosynthesis by distributing their nitrogen parallel to the light gradient, with high contents per unit leaf area at the top of the vegetation and low contents at the bottom. Using principles from game theory, we expanded these models by introducing a second species into the vegetation, with the same vertical distribution of biomass and nitrogen as the resident plants but with the ability to adjust its specific leaf area (SLA, leaf area[ratio ]leaf mass). The rule of the game is that invaders replace the resident plants if they have a higher plant carbon gain than those of the resident plants. We showed that such invaders induce major changes in the vegetation. By increasing their SLA, invading plants could increase their light interception as well as their photosynthetic nitrogen-use efficiency (PNUE, the rate of photosynthesis per unit organic nitrogen). By comparison with stands in which canopy photosynthesis is maximized, those invaded by species of high SLA have the following characteristics: (1) the leaf area index is higher; (2) the vertical distribution of nitrogen is skewed less; (3) as a result of the supra-optimal leaf area index and the more uniform distribution of nitrogen, total canopy photosynthesis is lower. Thus, in dense canopies we face a classical tragedy of the commons: plants that have a strategy to maximize canopy carbon gain cannot compete with those that maximize their own carbon gain. However, because of this strategy, individual as well as total canopy carbon gain are eventually lower. We showed that it is an evolutionarily stable strategy to increase SLA up to the point where the PNUE of each leaf is maximized.

Short-term phosphate uptake rates were measured on intact ectomycorrhizal and non-mycorrhizal Pinus sylvestris seedlings using a new, non-destructive method. Uptake was quantified in semihydroponics from the depletion of Pi in a nutrient solution percolating through plant containers. Plants were grown for 1 or 2 months after inoculation at a low relative nutrient addition rate of 3% d−1 and under P limitation. Four ectomycorrhizal fungi were studied: Paxillus involutus, Suillus luteus, Suillus bovinus and Thelephora terrestris. The Pi-uptake capacity of mycorrhizal plants increased sharply in the month after inoculation. The increase was dependent on the development of the mycobionts. A positive correlation was found between the Pi-uptake rates of the seedlings and the active fungal biomass in the substrate as measured by the ergosterol assay. The highest Pi-uptake rates were found in seedlings associated with fungi producing abundant external mycelia. At an external Pi concentration of 10 μM, mycorrhizal seedlings reached uptake rates that were 2.5 (T. terrestris) to 8.7 (P. involutus) times higher than those of non-mycorrhizal plants. The increased uptake rates did not result in an increased transfer of nutrients to the plant tissues. Nutrient depletion was ultimately similar between mycorrhizal and non-mycorrhizal plants in the semihydroponic system. Net Pi absorption followed Michaelis–Menten kinetics: uptake rates declined with decreasing Pi concentrations in the nutrient solution. This reduction was most pronounced in non- mycorrhizal seedlings and plants colonized by T. terrestris. The results confirm that there is considerable heterogeneity in affinity for Pi uptake among the different mycobionts. It is concluded that the external mycelia of ectomycorrhizal fungi strongly influence the Pi-uptake capacity of the pine seedlings, and that some mycobionts are well equipped to compete with other soil microorganisms for Pi present at low concentrations in soil solution.

Vulnerability of stem xylem to cavitation was measured in 10 species of conifers using high pressure air to induce xylem embolism. Mean values of air pressure required to induce a 50% loss in hydraulic conductivity (φ50) varied enormously between species, ranging from a maximum of 14.2±0.6 MPa (corresponding to a xylem water potential of −14.2 MPa) in the semi-arid species Actinostrobus acuminatus to a minimum of 2.3±0.2 MPa in the rainforest species Dacrycarpus dacrydioides. Mean φ50 was significantly correlated with the mean rainfall of the driest quarter within the distribution of each species. The value of φ50 was also compared with leaf drought tolerance data for these species in order to determine whether xylem dysfunction during drought dictated drought response at the leaf level. Previous data describing the maximum depletion of internal CO2 concentration (ci) in the leaves of these species during artificial drought was strongly correlated with φ50 suggesting a primary role of xylem in effecting leaf drought response. The possibility of a trade-off between xylem conductivity and xylem vulnerability was tested in a sub-sample of four species, but no evidence of an inverse relationship between φ50 and either stem-area specific (Ka) or leaf-area specific conductivity (K1) was found.

The coupling between leaf structure and function is illustrated with reference to two examples, the C4 photosynthetic pathway and leaf pubescence. A distinction is made between function and functional significance. The latter is defined as the role, significance or consequence of a structure, whereas the former is more simply the action that a structure is capable of performing. Using the two examples, four generalizations are made concerning the relationships between structure, function and functional significance: the functional significance of leaf structure is environment-dependent; the relationship between functional significance and structure is sometimes non-intuitive; functional equivalency means that there is often more than one ‘solution’ to the same ‘constraint’; and the consequences of leaf structure can exert profound effects at levels of organization beyond those of the individual organism and may play a critical role in determining community structure and function, through interactions with other species and trophic levels. The importance of understanding the consequences in variation in leaf structure at the global scale is illustrated with reference to the issue of global climate change.

Predictions of root architecture have been tested using only a narrow set of environmental conditions and species. There is little information on root architecture of plants growing on semi-arid grasslands where soil nutrient heterogeneity and defoliation might impose particular restrictions on root growth. We conducted a split-root study to evaluate the effect of nonuniform nutrient supply and clipping on root architecture and biomass allocation of three range grasses found in the Intermountain West of the USA: ‘Whitmar’, a cultivar of Pseudoroegneria spicata, Bromus tectorum (cheatgrass), and ‘Hycrest’, a hybrid between Agropyron desertorum and A. cristatum. Root systems of individual seedlings were equally divided between the two divisions of a partitioned 10-l pot, and each of the divisions was independently supplied with ‘high or ‘low’ nutrient solution. Plants were either clipped or not. Characteristics of root architecture (topology and link length), root size (root length and number of root tips), and biomass distribution (specific root length and root mass[ratio ]root volume ratio) were evaluated. Root topology (branching distribution) changed with nutrient treatments and defoliation in all three species. Length of links (a segment of root between two branches, or between a node and a root tip) responded to nutrient treatment only in defoliated plants of ‘Whitmar’, in which relative growth rate was associated with changes in architectural traits (external–external and internal–internal link length), while biomass accumulation and relative growth rate in cheatgrass and ‘Hycrest’ maintained allometric relationships with root length. Our results suggest that large plasticity in root architecture, together with inherently low relative growth rate are adaptations that allow ‘Whitmar’ to grow well in heterogeneous and poor soil-nutrient conditions. Cheatgrass and ‘Hycrest’ exhibited characteristics suggesting capability for rapid exploitation of nutrient patches.

The assumption that the mushroom stem has the ability to undergo autonomic straightening enables a mathematical model to be written that accurately mimics the gravitropic reaction of the stems of Coprinus cinereus. The straightening mechanism is called curvature compensation here, but is equivalent to the ‘autotropism’ that often accompanies the gravitropic reactions of axial organs in plants. In the consequently revised local curvature distribution model, local bending rate is determined by the difference between the ‘bending signal’ (generated by gravitropic signal perception systems) and the ‘straightening signal’ (proportional to the local curvature at the given point). The model describes gravitropic stem bending in the standard assay with great accuracy but has the virtue of operating well outside the experimental data set used in its derivation. It is shown, for example, that the mathematical model can be fitted to the gravitropic reactions of stems treated with metabolic inhibitors by a change of parameters that parallel the independently derived physiological interpretation of inhibitor action. The revised local curvature distribution model promises to be a predictive tool in the further analysis of gravitropism in mushrooms.

The revised local curvature distribution model, which provides accurate computer simulations of the gravitropic response of mushroom stems, was found to produce accurate simulations of the gravitropic reaction of wheat (Triticum aestivum) coleoptiles. The key feature of the mathematical model that enables it to approach universality of application is the assumption that the stem has an autonomic straightening reaction (curvature compensation or ‘autotropism’). In the model, the local bending rate for any segment of the organ is determined by the difference between the ‘bending signal’ (generated by the gravitropic signal perception system) and a ‘straightening signal’ (which is proportional to the local curvature of the segment). The model reveals three major differences between the gravitropic reactions of wheat coleoptiles and Coprinus mushroom stems. First, in Coprinus, the capacity for autonomic straightening is much more concentrated in the apical region of the stem. Second, local perception of the gravitropic signal, which is necessary for exact simulation in Coprinus, is not needed in wheat coleoptiles (the corresponding constant in the model can be set to zero). Third, the transmission rate of the gravitropic signal is about seven times faster in wheat coleoptiles than in the mushroom stem. Thus, we demonstrate that a single model, depending on the values given to its parameters, is able to simulate the spatial organization of the gravitropic reaction of wheat coleoptiles and Coprinus mushroom stems. The model promises to be a valuable predictive tool in guiding future research into the gravitropic reaction of axial organs of all types.

Colonization of mycorrhizal fungi was studied in a Pinus muricata forest on the coast in California, USA, burned by a stand-replacing wildfire in October 1995. Naturally established field seedlings of P. muricata were harvested 1 yr after the fire. The species composition of the mycorrhizal fungi on these field seedlings was dominated by Rhizopogon species, Wilcoxina mikolae and Tomentella sublilacina. Bioassays, set up with soil collected immediately after the fire, were used to determine which mycorrhizal species had colonized the burned area from resistant propagules. The P. muricata seedlings in these bioassays were dominated by suilloid and ascomycetous fungi, the same fungi which dominated the mycorrhizal flora of seedlings in pre-fire bioassays derived from the same forest site, suggesting that resistant propagules were the primary inoculum source for naturally establishing seedlings. Drying of post-fire soil for 1 month raised the number of bioassay seedlings associated with Rhizopogon olivaceotinctus, while the number of bioassay seedlings associated with Rhizopogon ochraceorubens was reduced. Fire appeared to have either stimulated or provided a competitive advantage to R. olivaceotinctus, which increased in abundance on the post-fire bioassay and field seedlings. Soil collected from the burned area was diluted with sterile soil in three different concentrations, and the number and frequency of mycorrhizal taxa on bioassay seedlings decreased with increased dilution. Although precise quantification was not possible, propagules of the Rhizopogon species were much more abundant than those of Tomentella or Wilcoxina species. Differences between the mycorrhizal associates of bioassay seedlings, naturally regenerated seedlings, and different inoculum sources are discussed.

Androdioecy (the coexistence of two genders, cosexuals and males, in a single population) is a rare breeding system. In terms of functional gamete production, androdioecy has been reported in a small number of wind-pollinated and insect-pollinated species. In this study we examine the floral biology, stability of gender, and fruit and seed production after self-pollination and outcrossing pollination in a potentially androdioecious tree, Fraxinus ornus, in southern France. Individual trees have either hermaphrodite flowers or male flowers, the latter lacking a well-developed gynoecium. The two genders produce morphologically similar pollen and were present in 1[ratio ]1 or slightly male-biased ratios. Only hermaphrodites set fruit during 2–4 yr of observation at four different sites in southern France. Experimental pollinations of eight trees in two different sites showed that hermaphrodites produce viable pollen in dehiscent anthers and viable seeds. Thus, in terms of functional gamete production, F. ornus is a new case of functional androdioecy. Seven hermaphrodites were self-compatible, and such self-compatibility of hermaphrodites might improve the colonizing ability of F. ornus in a region where this species is actively expanding its range.