Seed banking is the preferred strategy for the ex situ conservation of Seed Plants, due to its effectiveness in preserving whole organisms and genetic diversity at relatively low cost. However, not all seeds are suitable for long-term storage, particularly those classified as recalcitrant or desiccation-sensitive, which limits the applicability of seed banking for certain species. In Chile, the proportion and identification of recalcitrant species remain largely unknown. In this study, we investigated the storage behaviour of potentially recalcitrant species and evaluated two predictive models of seed recalcitrance based on morphological, ecological and taxonomic variables. One of these models was subsequently employed to estimate the incidence of recalcitrance among Chilean tree species. Most of the species assessed exhibited clear sensitivity to desiccation. The Seed Coat Ratio–Seed Mass model showed the highest precision and recall. Nevertheless, models incorporating ecological and taxonomic variables also performed well at the genus level. Using a Boosted Regression Tree model refined through experimental data and literature review, we estimate that 19% (n = 11) of Chilean tree species possess recalcitrant seeds. Among the tree and shrub species confirmed as recalcitrant in this study (n = 17), 71% are endemic to Chile (n = 12), and 53% are categorized as threatened (n = 9). These findings provide a stronger basis for prioritizing alternative ex situ conservation strategies beyond seed banking for species with recalcitrant seeds.

Healthy seeds are an important component of global food security, and their microbiome was recently identified as crucial for plant growth, resilience and health. Seed vigour is highly affected by storage conditions and aging. To study the impact of seed aging on the Brassica napus seed bacterial community, we conducted accelerated aging tests (45°C, humidity > 95%) with seed lots of four genotypes originating from two field sites in Germany. We found a strong effect of accelerated aging on germination, seedling phenotypes, as well as the seed bacterial community. Control seeds developed mainly into normal seedlings and were characterized by diverse bacterial communities comprising typical core seed microbes. Accelerated aging resulted in abnormal germination and reduced total germination. Furthermore, accelerated aging reduced diversity and evenness of the seed bacterial community and contributed to a shift from Gram-negative to Gram-positive bacteria. This effect, especially the enrichment of Firmicutes, was found irrespective of the genotype and field site; however, the way stress affected bacterial taxa varied, depended on both factors. Tumebacillus and Bacillus showed a significant negative correlation with germination phenotype, whereas alpha diversity correlated positively with a high total germination. At the functional level, the majority of isolated bacteria demonstrated plant-beneficial characteristics, showing a greater beneficial potential in the aged seeds. Our results show that accelerated aging tests affect the seed bacterial community structure and diversity, and correlate with the presence of certain taxa, which might have an effect on germination and seedling phenotype.

Developing cereal seeds contain photosynthetically active cells in the form of a thin green layer, the chlorenchyma, which surrounds the non-photosynthetic endosperm. The current understanding is that the chlorenchyma primarily supports endosperm respiration by supplying oxygen. However, despite the importance of such a function, photosynthetic electron transport is still poorly understood and would benefit from detailed study. This represents a technical challenge as bulky developing seeds are unsuitable for the classical spectroscopic methods routinely used for leaf material. In this study, we established a method that enables simultaneous measurement of photosystem I and photosystem II activities in dissected barley chlorenchymas with pulse amplitude modulation spectroscopy and also adapted it to measure electron transport with the electrochromic band shift. Comparative analyses of raw spectral signals and derived parameters measured on chlorenchymas and leaves demonstrate that this approach provides a reliable and detailed assessment of chlorenchyma photosynthesis. Establishing this method provides a new framework for investigating the physiological relevance of electron transport and carbon assimilation in non-foliar tissues such as chlorenchymas.

Variation in orchid seed size and shape can be linked to phylogenetic relationships, habitat preferences, germination behaviour or dispersal strategies. To investigate this, we compared 45 orchid species from 29 genera collected across different localities in Cameroon using optical microscopy. We categorized each species according to lifeform (38 epiphytic vs. 7 terrestrial), altitudinal range (11 mountain vs. 34 lowland) and geographic distribution (28 widespread vs. 17 range-restricted). We analysed seed morphology using phylogenetic signal tests, analysis of variance and principal component analysis. Our results confirm a clear distinction between epiphytic and terrestrial species, with intermediate morphologies observed in genera encompassing species with both lifeforms (Cynorkis, Graphorkis, Habenaria and Liparis). Certain traits, such as seed length and seed air space, show a strong phylogenetic signal, suggesting that these traits are more linked to ancient evolutionary history than to recent ecological adaptation. Among the 38 epiphytic species, no consistent relations were found between seed traits and either geographic range or altitudinal distribution. Our findings suggest that the variation observed in seed morphology among African orchids is influenced more by phylogenetic relationships than by present-day distribution.

Physical dormancy (PY), resulting from a water-impermeable seed coat, regulates germination timing in many angiosperms, including Dodonaea viscosa L. (Sapindaceae), a woody shrub widely distributed in tropical to warm temperate regions and coastal and inland habitats. Although PY has been previously documented in D. viscosa, the precise anatomical structure acting as the site for water entry, i.e., water gap, during dormancy release remains unclear. This study investigated the water gap’s morphology and function using microscopy, scanning electron microscopy (SEM) and imbibition assays. It also evaluate the effects of liquid nitrogen (LN₂) freeze–thaw cycles on seed coat integrity, dormancy break, and viability. Seeds possess a distinct hilar slit, which opens in response to hot-water treatment and serves as the exclusive water gap. Imbibition experiments showed that treated seeds (hot water , 10s) increased nearly 100% in mass over seven days, while control seeds absorbed no water. Further, covering the hilar slit with Vaseline restricted water uptake, confirming the absence of water-gap complex. Because the water gap opening was a small circular structure without any lid-like covering, it is classified as Type II. Seeds subjected to one or more liquid nitrogen (LN₂) freeze–thaw cycles experienced extensive seed coat cracking and severe damage to the embryo and cotyledons, leading to reduced viability and little to no germination. These findings demonstrate that while hot-water treatment effectively breaks dormancy, LN₂ exposure causes extensive mechanical injury and is ineffective for dormancy alleviation in D. viscosa. Thus, cryopreservation of some PY should be considered with caution.