A group of flowering plant species is known to germinate in less than 24 h from imbibition, but this phenomenon is often overlooked in the current literature. Here, I review this topic by searching the literature published since 1967 and listing the 28 most detailed cases found. Of these, 20 are species of Amaranthaceae (all formerly treated as Chenopodiaceae); 15 of these are from the subfamily Salsoloideae, which is characterized by the possession of spiral embryos. The non-chenopods listed are small numbers of species from the families Acanthaceae, Cruciferae, Gramineae (one species) and Salicaceae (Populus and Salix). Seeds of the Salsoloideae contain fully differentiated embryos. On imbibition, the embryo cells elongate and the spiral embryo uncoils and ruptures the thin seed coat. This can occur in as little as 10 min. Nearly all of the families showing very fast germination have small to very small seeds and little or no endosperm. Most species have soft, thin seed coats that imbibe water readily. All are from high-stress habitats, either arid or saline or from active floodplains, where they can rapidly exploit temporarily favourable conditions for germination. They exhibit one of two contrasting germination behaviours, either having seeds which all germinate within a very short time of wetting or having seed persistence whereby small amounts of rain cause germination of small fractions of seed from a long-living soil seed bank. Serious confusion in the literature in the use of the term ‘opportunistic’ is pointed out and clarified.

The spread of many invasive plants is facilitated through seed dispersal by frugivorous animals. The effectiveness of various frugivores as dispersers of the seeds of Melia azedarach, a highly invasive alien tree species, was evaluated in South Africa in savanna and bushveld vegetation. During 264 h of observation, seven bird species and one bat species were recorded foraging on fruiting trees of M. azedarach. The most common visitors were the dark-capped bulbul (Pycnonotus barbatus) followed by Wahlberg's epauletted fruit bat (Epomophorus wahlbergi), but both species dropped nearly as many seeds as they dispersed. Knysna turaco (Tauraco corythaix) dispersed the highest number of fruits per minute, but occurred in low abundance in our study sites. Seed germination differed significantly between de-pulped fruits and untreated fruits after 2 mo, but was similar after 4 mo. Germination success did not differ between animal-handled and hand-depulped fruits. In contrast to the high germination success in the greenhouse, seedlings showed very low recruitment in the field. Thus, M. azedarach seems likely to benefit from frugivores (particularly dark-capped bulbul and Wahlberg's epauletted fruit bat) dispersing seeds to suitable microsites.

Né en 1869, Gaston Contremoulins commence sa carrière comme artiste peintre avant derejoindre à l’âge de 22 ans le laboratoire du professeur Étienne-Jules Marey, inventeur dela chronophotographie, puis les hôpitaux de Paris en 1895 au moment de la découvert desrayons X par Wilhelm Röntgen. Passionné de photographie, ingénieur autodidacte ingénieux,Contremoulins publie dès 1896 avec le chirurgien Charles Remy une série de travaux surl’usage des rayons X pour la recherche anatomique et la localisation des corps étrangersdans le crâne qui seront récompensés par le prix Montyon de l’Académie des sciences en1897. Nommé chef des laboratoires de radiologie des Hôpitaux de Paris en 1898,Contremoulins met au point sa méthode de métroradiographie pour localisation précisémentdes corps étrangers dans tous les organes qui rendra d’immenses services pendant lapremière guerre mondiale. Très tôt conscient des dangers des rayonnements pour lesmédecins, le personnel hospitalier mais aussi le voisinage des postes de radiologie,Contremoulins développe des moyens de protection des sources mais aussi préconise leplombage des murs et des planchers des installations malgré l’opposition d’une partie desradiologues. Retraité des Hôpitaux de Paris, Contremoulins exercera encore pendant 16années ses talents à l’hôpital de Saint-Germain-en-Laye. Atteint d’une cataracteinopérable, il met fin à ses jours en 1950.

The effects of forest habitat, canopy light condition, vertebrate herbivory and species mean seed size on growth of tree seedlings were evaluated for six widely different species of North Queensland tropical rain forests. Two forest localities differing in size and rainfall intensity were used for the trial. In each forest, seedlings were transplanted three weeks after germination into small to medium-sized canopy gaps and into the forest interiors, with half protected by cages and the other half unprotected. Growth measurements were made over a period of 16 months. All growth parameters examined differed significantly between the six species. At the end of the study period, for most species, forest site and protection from vertebrates did not affect seedling biomass. For all species, growth was higher in gaps than in forest interior, but most biomass allocation patterns did not differ between the two habitats. This was attributed to the small difference in photosynthetically active radiation (PAR) levels between the two habitats (interior, 0.48–2.53% PAR; gap, 3.58–7.09% PAR). Between species, seedling growth in the forest interior and sensitivity to increasing light were significantly correlated with initial mean seed size. The growth ability of the six species in and out of canopy gaps is discussed in terms of regeneration status of forest tree species.

Using data from forest sites in Sarawak, East Malaysia, a demographic comparison is made of pioneer species in the genus Macaranga with understorey trees of the primary forest in the closely related genus Mallotus. In primary forest, saplings and trees of these genera arc uncommon and have low growth rates. For the six years following disturbance by logging, a Macaranga population was characterized by high rates of diameter growth and recruitment. Eleven years after disturbance, seedling and sapling abundance had declined sharply. In contrast, the Mallotus population was stable in size class distribution and increased slightly in total population size during the 11 years after logging. Growth rates of Mallotus trees increased after logging but were still much less than Macaranga trees.

A morphological comparison shows that most Macaranga species, in contrast with Mallotus species, have large hollow twigs that are occupied by ants and have larger, hairier, thicker, more toothed leaves with longer petioles, axillary inflorescences with more flowers, infructescences with more fruit, fruits that are smaller in size and smaller seeds.

Seasonal changes in the densities of dormant seeds in the soil around eight pioneer trees in the 50-ha Forest Dynamics Plot, on Barro Colorado Island, Panamá were studied, and how seed dispersal and seed dormancy influenced patterns of seed abundance and distribution were examined. Twenty-four, 3-cm-deep soil samples were collected on 30 m transects radiating out from each of the trees in each of four time-intervals through the year, and four 21-cm-deep samples were collected beneath the focal tree crowns. In the surface 0–3 cm of soil, germinable seed densities of all species combined declined from a peak of 1090 seeds m−2 in the mid-wet season in August, to 330 seeds m−2 by the end of the wet season in November. In contrast, at soil depths >3 cm, there was little variation in soil seed bank density through the year. Some variation in soil seed bank density for individual species could be accounted for by distance to reproductive conspecifics. Among species, abundance in the soil was negatively correlated with seed size. Seed persistence varied greatly among species at this site; after 1 y of burial in mesh bags, seed germinability of four species was near zero, while four other species showed no consistent decline in seed germinability after >2 y of burial. For at least one species, Trema micrantha, prolonged seed dormancy was also possible under natural conditions. Twenty-five percent of Trema seeds extracted from the soil at a site occupied by an isolated Trema tree that died between 1982 and 1985 were still germinable in 1994.

A close relationship has been reported between seed size and many different plant traits such as seedling size, relative growth rate, seedling survival, distance of dispersion, colonization and density of seeds in the soil (Coomes & Grubb 2003, Jurado & Westoby 1992, Lahoreau et al. 2006, Saverimuttu & Westoby 1996, Souza & Valio 2001). Although the association of seed size and shade tolerance is unclear (Westoby et al. 1996) some authors have suggested that a larger-seeded species is better able to tolerate low light availability (Foster 1986, Foster & Janson 1985, Leishman & Westoby 1994) by producing a vigorous seedling with a higher ability to withstand predation (Armstrong & Westoby 1993, Foster 1986) and delaying the beginning of carbon fixation so as to increase survival under a canopy and under leaf litter.

Traditional shade house experiments that expose plants to relatively uniform irradiance and light quality are inadequate to characterize the morphological, allocational and physiological plasticity that seedlings show to different gap environments. Here the design of a pot experiment is described that simulates the daily time course of irradiance and light quality in idealized gaps of six different sizes. Differences in response to gap size are illustrated using data from two pioneer species, Ochroma pyramidale, which recruits exclusively in large gaps and clearings, and Luehea seemannii, which colonizes small branchfall gaps as well as large gaps. Ochroma outperformed Luehea in relative growth rate in all except the smallest simulated gap size. Ochroma's superior performance in the larger gaps could be attributed to a larger proportional investment in leaf biomass (i.e. a higher leaf area ratio, LAR), and higher photosynthetic rates both on a leaf area and leaf mass basis. In the smallest simulated gaps LAR was not significantly different between the species, but Ochroma maintained a higher net assimilation rate. These results fail to support the suggestion that gap partitioning among pioneer species arises directly from morphological and biochemical specialization to particular gap light environments. Instead, it is suggested that partitioning may result from a trade-off between seedling growth and mortality determined by species allocational patterns and mediated by interactions with herbivores and pathogens.