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PurposeAll secondary dispersal by wind, important for predicting, modeling and regulating diaspore dispersal processes, and for biodiversity conservation and vegetation restoration, is influenced by underlying surface matrix. But little is known about how matrix determines diaspore secondary dispersal. Here we focus on how lift-off velocity, good proxy for secondary dispersal of seeds by wind, is linked to the underlying surface matrix.MethodsWe investigated the effect of the underlying surface matrix on diaspore lift-off velocity in a wind tunnel. Our study used 11 matrix types with different particle size, including four pure substrates (loam, aeolian sand, river sand, gravel) and seven mixtures thereof and diaspores of 28 species differing in length, width, height, mass, projected area, shape index, wing loading, and terminal velocity.ResultsDiaspores were more easily dispersed from loam, aeolian sand and river sand than from the gravel substrates. For mixed matrices, lift-off velocity was closer to that of the small-sized than of the large-sized component of the substrate. Underlying surface matrix contributed more to diaspore dispersal by wind than diaspore attributes. In addition to wing loading, terminal velocity, and projected area also were important diaspore attributes determining lift-off velocity of the diaspores.ConclusionLift-off velocity of diaspores is influenced by particle size of underlying surface matrix during secondary wind dispersal: lift-off velocity is the largest on large-sized particles for pure matrices, and determined by the small-sized component for mixed matrices.

Lift-off velocity may be the most useful surrogate to measure the secondary dispersal capacity of diaspores. However, the most important diaspore attribute determining diaspore lift-off velocity is unclear. Furthermore, it is not known whether terminal velocity used to characterize the primary dispersal capacity of diaspores can also be used to predict their secondary wind dispersal capacity. Here, we investigate how diaspore attributes are related to lift-off velocity. Thirty-six species with diaspores differing in mass, shape index, projected area, wing loading, and terminal velocity were used in a wind tunnel to determine the relationship between diaspore attributes and lift-off velocity. We found that diaspore attributes largely explained the variation in lift-off velocity, and wing loading, not terminal velocity, was the best parameter for predicting lift-off velocity of diaspores during secondary wind dispersal. The relative importance of diaspore attributes in determining lift-off velocity was modified by both upwind and downwind slope directions and type of diaspore appendage. These findings allow us to predict diaspore dispersal behaviors using readily available diaspore functional attributes, and they indicate that wing loading is the best proxy for estimating the capacity for secondary dispersal by wind.

In its nanoparticulate form, corundum (α-Al₂O₃) could lead to several applications. However, its production into nanoparticles (NPs) is greatly hampered by the high activation energy barrier for its formation from cubic close-packed oxides and the sporadic nature of its nucleation. We report a simple synthesis of nanometer-sized α-Al₂O₃ (particle diameter ~13 nm, surface areas ~140 m² g−1) by the mechanochemical dehydration of boehmite (γ-AlOOH) at room temperature. This transformation is accompanied by severe microstructural rearrangements and might involve the formation of rare mineral phases, diaspore and tohdite, as intermediates. Thermodynamic calculations indicate that this transformation is driven by the shift in stability from boehmite to α-Al₂O₃ caused by milling impacts on the surface energy. Structural water in boehmite plays a crucial role in generating and stabilizing α-Al₂O₃ NPs.

Interception by plant canopies during wind dispersal can affect the final destination of diaspores. However, how the interaction of wind speed, canopy type and diaspore attributes affects interception of diaspores by the plant canopy has rarely been studied. We investigated canopy interception for 29 species with different diaspore attributes, six canopy types and six wind speeds in controlled experiments in a wind tunnel. Shrub canopy interception of diaspores were controlled by wind speed and diaspore attributes, but the latter had a greater influence on canopy interception than the former. At low wind speed, diaspore wing loading had a large influence on canopy interception, whereas at high wind speed, diaspore projection area had a large influence. The chance of canopy interception at a particular wind speed was additionally affected by the type of canopy. This study increases our knowledge of the dispersal process, corrects the previous understanding of diaspore dispersal potential and improves the theoretical basis for predicting spatial pattern and dynamics of plant populations.

Plant dispersal mechanisms rely on anatomical and morphological adaptations for the use of physical or biological dispersal vectors. Recently, studies of interactions between the dispersal unit and physical environment have uncovered fluid dynamic mechanisms of seed flight, protective measures against fire, and release mechanisms of explosive dispersers. Although environmental conditions generally dictate dispersal distances, plants are not purely passive players in these processes. Evidence suggests that some plants may enact informed dispersal, where dispersal-related traits are modified according to the environment. This can occur via developmental regulation, but also on shorter timescales via structural remodelling in relation to water availability and temperature. Linking interactions between dispersal mechanisms and environmental conditions will be essential to fully understand population dynamics and distributions.

Main conclusionDifferences in dispersal and dormancy of heteromorphic diaspores of Aegilos tauschii may increase its flexibility to invade/occupy weedy unpredictable habitats by spreading risk in space and time.In plant species that produce dimorphic seeds, there often is a negative relationship between dispersal and dormancy, with high dispersal–low dormancy in one morph and low dispersal–high dormancy in the other, which may function as a bet-hedging strategy that spreads the risk of survival and ensures reproductive success. However, the relationship between dispersal and dormancy and its ecological consequences in invasive annual grasses that produce heteromorphic diaspores is not well studied. We compared dispersal and dormancy responses of diaspores from the basal (proximal) to the distal position on compound spikes of Aegilops tauschii, an invasive grass with heteromorphic diaspores. Dispersal ability increased and degree of dormancy decreased as diaspore position on a spike increased from basal to distal. There was a significant positive correlation between length of awns and dispersal ability, and awn removal significantly promoted seed germination. Germination was positively correlated with GA concentration and negatively correlated with ABA concentration, and the ABA: GA ratio was high in seeds with low germination/high dormancy. Thus, there was a continuous inverse–linear relationship between diaspore dispersal ability and degree of dormancy. This negative relationship between diaspore dispersal and degree of dormancy at different positions on a spike of Aegilops tauschii may facilitate seedling survival in space and time.

The spontaneous recovery of the plant cover of extracted peatlands is a long-lasting process, and re-vegetation depends largely on species emerging from the diaspore bank. Restoration also depends on the success of suppressing the expansion of alien species. To evaluate whether the covering of peat by Sphagnum shoots has an effect on the germination of bryophytes, a growth chamber experiment was conducted. Two acrocarpous moss species— Polytrichum strictum , a native moss, and Campylopus introflexus , the invasive moss in the Northern Hemisphere—were chosen for the study. Peat samples from the extracted peat field were taken and grown in a growth chamber for six months. Half of the samples were covered by Sphagnum shoots, and the other half were left bare for control. At the end of the experiment, the number of shoots and the cover of both species were estimated. In the second experiment Sphagnum cover effect was evaluated on shoot elongation where shoots of both species were grown at low and high water levels. Our aims were to compare native and alien species’ germination ability and to test the possibility of suppressing the expansion of alien species by raising the water level and covering the samples with Sphagnum . Our results showed that on extracted peatlands C. introflexus germinated better than P. strictum, but covering with Sphagnum shoots significantly suppressed its emergence. High water level promoted the growth of P. strictum , but not the growth of C. introflexus . Thus, we can conclude that restoration may help to control the expansion of non-native species in disturbed peatlands.

• Heteromorphic diaspores (fruits and seeds) are an adaptive bet-hedging strategy to cope with spatiotemporally variable environments, particularly fluctuations in favourable temperatures and unpredictable precipitation regimes in arid climates. • We conducted comparative analyses of the biophysical and ecophysiological properties of the two distinct diaspores (mucilaginous seed (M⁺) vs indehiscent (IND) fruit) in the dimorphic annual Aethionema arabicum (Brassicaceae), linking fruit biomechanics, dispersal aerodynamics, pericarp-imposed dormancy, diaspore abscisic acid (ABA) concentration, and phenotypic plasticity of dimorphic diaspore production to its natural habitat and climate. • Two very contrasting dispersal mechanisms of the A. arabicum dimorphic diaspores were revealed. Dehiscence of large fruits leads to the release of M⁺ seed diaspores, which adhere to substrata via seed coat mucilage, thereby preventing dispersal (antitelechory). IND fruit diaspores (containing nonmucilaginous seeds) disperse by wind or water currents, promoting dispersal (telechory) over a longer range. • The pericarp properties confer enhanced dispersal ability and degree of dormancy on the IND fruit morph to support telechory, while the M⁺ seed morph supports antitelechory. Combined with the phenotypic plasticity to produce more IND fruit diaspores in colder temperatures, this constitutes a bet-hedging survival strategy to magnify the prevalence in response to selection pressures acting over hilly terrain.

Aims How landscape configuration, dispersal agents and diaspore features interact to determine the input of seeds into the soil, which is the first part of the formation of a soil seed bank, is a major challenge. This study explored the role of diaspore traits and sand surface configuration in determining the number of seeds that become buried during wind dispersal. Methods We investigated seed burial probability of 36 species with different diaspore traits under eight wind speeds and three sand surface configurations during wind dispersal by using a wind tunnel. Results Wind speed rather than diaspore traits and sand surface configuration was the most important factor affecting the burial of seeds. Effects of slope direction and surface barrier on seed burial were regulated by wind speed. Effects of diaspore traits on seed burial were only significant at high wind speeds, and seed burial was more likely to be formed for small or flat elongated diaspores than for large or spherical ones. Conclusions The effect of diaspore traits on seed burial is modified by the shifts in wind speed and sand surface configuration.

‘Seed heteromorphism’ is a broadly- and loosely-defined term used to describe differences in size/mass, morphology, position on mother plants and ecological function (e.g. dispersal, dormancy/germination) of two or more seeds or other diaspores produced by an individual plant. The primary aim of this review paper was to characterize via an in-depth classification scheme the physical structural design (‘architecture’) of diaspore monomorphism and diaspore heteromorphism in angiosperms. The diaspore classification schemes of Mandák and Barker were expanded/modified, and in doing so some of the terminology that Zohary, Ellner and Shmida, and van der Pijl used for describing diaspore dispersal were incorporated into our system. Based on their (relative) size, morphology and position on the mother plant, diaspores of angiosperms were divided into two divisions and each of these into several successively lower hierarchical layers. Thus, our classification scheme, an earlier version of which was published in the second edition of ‘Seeds’ by Baskin and Baskin, includes not only heteromorphic but also monomorphic diaspores, the Division to which the diaspores of the vast majority of angiosperms belong. The scheme will be useful in describing the ecology, biogeography and evolution of seed heteromorphism in flowering plants.