Abstract Species of Solanaceae grow in rainforests, grasslands and deserts and especially montane/subalpine habitats of South America. The highest number of genera and species occurs in South America, but centres of species richness also are found in Africa, Australia, China and Mesoamerica. Information on embryo morphology was found for all eight subfamilies of Solanaceae and 236 species in 87 genera. Cestroideae, Pentunioideae, Nicotianoideae and Solanoideae have spatulate and linear-full embryos, while Duckeodendroideae, Goetzeoideae, Schizanthoideae and Schwenckioideae have linear-full embryos. Information on seed dormancy/germination was found for 167 species in 32 genera: 10 tree and 1 vine species in the tropics; 53 and 31 shrubs species in tropical and temperate zones, respectively; and 47 and 25 herb species in tropical and temperate zones, respectively. Physiological dormancy (PD) occurs in 94.5% of the 167 species; the other nine species had nondormant seeds. Regardless of subfamily, embryo morphology and vegetation region, most species have seeds with PD that can be broken during dry storage or cold stratification. Of the six types of nondeep PD, Type 2 occurs in a few temperate species; other types have not been documented. Soil seed banks have been documented in four subfamilies, 12 genera and 39 species, many of which are agricultural weeds. We identified questions that need to be answered about cold and heat tolerance of Solanaceae species, world distribution, especially in northern latitudes with a cold winter, and development of Type 2 nondeep PD as an adaptation of Solanaceae species that enhances survival in cold climates.
Abstract Seed germination is a critical developmental transition regulated by coordinated physiological and biochemical processes during the triphasic imbibition process. Water uptake is followed by membrane repair, restoration of mitochondrial respiration, ATP production and activation of hydrolytic enzymes involved in reserve mobilization. In this context, silver nanoparticle (AgNP) seed priming has emerged as a promising strategy to enhance germination by modulating early biochemical events through controlled redox signalling, although its effects vary among species and experimental conditions. This review integrates physiological, biochemical and molecular evidence to propose a seed-centred mechanistic framework explaining how AgNPs regulate germination through redox-dependent signalling networks. During imbibition, low AgNP concentrations can induce transient reactive oxygen species production through the combined effects of nanoparticles and released Ag⁺ ions, together with moderate thiol-based redox shifts acting as developmental signals. These signals activate antioxidant systems, mitogen-activated protein kinase cascades and hormone-dependent pathways coordinating metabolic activation and membrane repair. Controlled redox modulation may also establish a primed physiological state that improves tolerance to abiotic stress during early seedling establishment. In contrast, excessive AgNP or Ag⁺ exposure disrupts glutathione-based redox buffering, causing oxidative damage, mitochondrial dysfunction and inhibition of germination. The magnitude and direction of these responses depend on intrinsic seed traits, including seed coat permeability, imbibition kinetics and antioxidant capacity, as well as nanoparticle properties such as size, surface chemistry and ion release dynamics. Distinguishing nanoparticle-specific effects from Ag⁺-mediated toxicity is therefore essential for interpreting nanopriming outcomes and developing safe, species-specific crop applications.
Abstract The testa (seed coat) plays an important role in the regulation of seed dormancy and germination as well as the exchange of water, gas and solutes from the environment. In this study, we investigated testa permeability and its relationship with germination kinetics in contrasting populations of three weedy Amaranthus spp.: A. palmeri, A. retroflexus and A. tamariscinus . The microstructure of the testa was observed for two of these species using scanning electron microscopy, and a bespoke image analysis solution was developed to quantify the thickness of the testa in different regions of the seed. The permeability of the testa in contrasting populations was assessed using a range of pesticidal compounds with varying physicochemical properties, and germination responses to gibberellic acid and norflurazon were evaluated. Our results revealed both within- and between-species differences in testa thickness and permeability; however, it was challenging to associate these differences with responses to germination stimulants. Burial experiments demonstrated that testa permeability is a dynamic trait which can change over time depending on the solute. This work provides insights for colleagues using germination stimulants or inhibitors to study seed physiology as well as a fundamental understanding for developing more effective weed management strategies. Future work could focus on the biochemical and molecular basis of differential testa permeability in seeds.
Dormancy and germination determine when and where plants recruit, and their occurrence reflects current environmental conditions as well as the evolutionary history of the species. As such, they are central to predicting how plants will respond to climate change. Here, we examined dormancy and germination responses in 21 species and subspecies representing four major and endemic Australian plant groups (Eucalyptus, Callistemon, Brachyscome and Deyeuxia). Seeds were collected along an elevational gradient (31-1,822 m a.s.l.), focusing on contrasting high- and low-elevation species. To assess physiological dormancy, seeds were subjected to two pretreatments: soaking in deionized water (control) or gibberellic acid (250 ppm) for 8 hours. Seeds were then incubated across six constant temperatures (5-30 degrees C) to quantify germination responses and thermal niches. High-elevation species exhibited stronger dormancy than lowland species, although responses to dormancy-breaking treatments were group-specific, reflecting phylogenetic differences. High-elevation species generally germinated more at warmer temperatures (20-30 degrees C) and less at cooler temperatures (10-15 degrees C), whereas lowland species showed broader thermal niches, with germination across most tested temperatures. These results indicate that elevation-related climatic conditions shape dormancy and germination traits, with implications for species persistence and distribution under climate change.
Vegetation structure is an important factor influencing the secondary dispersal distance of wind-dispersed seeds. How vegetation structure and seed characteristics interact to affect seed secondary dispersal strategies remains unclear. We collected data on seed morphological and aerodynamic traits, lift-off wind and dispersal velocities for 12 wind-dispersed species with six types of appendages using a large-scale wind tunnel simulating the seed secondary wind dispersal across six simulated vegetation structures of desert steppe, typical steppe and meadow steppe to analyze the effects of vegetation structures and seed traits on the seed secondary dispersal strategy. Seeds with pappi exhibiting large projected area, low mass, low wing loading and low terminal velocity were less affected by vegetation obstruction and tended to adopt telechory strategies across all vegetation structures. Conversely, seeds with one wing that demonstrated a small projected area, high mass, wing loading and terminal velocity were less affected by vegetation structures and tended to adopt an antitelechory strategy. Seeds with disc-shaped, four wings, balloons and thorns, characterized by higher mass, wing loading, density and terminal velocity, adopted a shift from telechory, atelechory or antitelechory strategies depending on vegetation structures. In sparse vegetation structures (bare ground or simulated desert steppe), they mostly adopt telechory or atelechory strategies, whereas in dense and high vegetation structures (simulated typical steppe and meadow steppe), they adopt antitelechory or atelechory strategies. In conclusion, secondary seed wind-dispersal strategies are jointly determined by the interaction between vegetation structure and seed morphology characteristics.
