Maturity critically impacts rational harvesting of Xanthoceras sorbifolia Bunge, influencing yield, oil quality, and postharvest handling. This study pioneered visible/near-infrared hyperspectral imaging (HSI) for non-destructive maturity assessment of Xanthoceras sorbifolia Bunge using a proposed maturity characterization factor (MCF) generated from nine key indicators. All 628 hyperspectral images across four maturity stages of Xanthoceras sorbifolia Bunge were collected, and 19 maturity-related physicochemical parameters were measured. Band variability was analyzed using principal component analysis (PCA), and maturity discrimination models were developed by partial least squares discriminant analysis (PLS-DA), genetic algorithm-support vector machine (GA-SVM), residual network (ResNet), and convolutional neural network-Transformer (CNN-Transformer), incorporating spectral preprocessing. For simplified models, feature wavelengths were extracted using principal component (PC) loading, successive projection algorithm (SPA), and stability competitive adaptive reweighted sampling (sCARS). Developed partial least squares regression (PLSR) showed that model based on second-order derivative spectra, SPA, and PLS-DA (FD2-SPA-PLS-DA) performed well (Accuracy = 98.73%, Kappa = 0.9830). Performance was then significantly improved by combining spectral, color, and texture features (Accuracy = 99.36%, Kappa = 0.9915). For MCF prediction, model based on first-order derivative spectra, SPA, and PLSR (FD1-SPA-PLSR) yielded the optimal results with R2 P = 0.7534, root mean square error of prediction (RMSEP) = 0.1853, and relative percent deviation (RPD) = 2.0138. Finally, an MCF distribution map generated using the preferred simplified model successfully visualized maturity heterogeneity in Xanthoceras sorbifolia Bunge. Our work demonstrates the first application of HSI for rapid, non-destructive Xanthoceras sorbifolia Bunge maturity assessment, establishing it as an effective tool for further field application.

Sassafras tzumu (Hemsl.) Hemsl., known as Chinese sassafras, is an exclusive species of tree found in China, belonging to the Sassafras genus in the Lauraceae family. Its primary mode of propagation is through seeds, which possesses a profound dormancy and irregular germination. In its natural environment, it takes approximately 2-3 years for the seeds to emerge from the ground and begin germinating. Consequently, a rapid and effective method for breaking dormancy would greatly benefitsbn edjhn the production of S. tzumu seedlings. The objective of this investigation was to identify the optimal treatment for breaking dormancy. The S. tzumu seeds were subjected to gibberellic acid (GA3) treatment and cold stratification. The findings indicated that the dormancy type of Sassafras tzumu seeds was combined (physiological + mechanical) dormancy. After 6 months of cold stratification, the germination percentage of seeds treated with various concentrations of GA3 (200 mg/L, 500 mg/L, and 1000 mg/L) all exceeded 50 %. Among these treatments, the most effective method was the application of 200 mg/L GA3 in combination with 5 months of cold stratification, resulting in a germination percentage of 55 %. During the process of cold stratification, soluble proteins, soluble sugars, starch, and fat were broken down into smaller molecules to support embryo growth. Interestingly, the content of soluble sugar exhibited an upward-downward trend, while the content of soluble protein displayed a downward-upward trend. The release of dormancy in S. tzumu seeds was jointly regulated by various endogenous hormones. The content of GA3 demonstrated an upward-downward trend, while the ABA content exhibited a continuous decline with a brief upward trend. In contrast, the IAA content displayed a continuous upward trend, and the ZR content showed no significant change. The ratios of GA3/ABA, IAA/ABA, and ZR/ABA all displayed an upward trend.

BACKGROUND AND AIMS:Seed covering structure hardness may play a role in defence/predation, physical dormancy and in situ longevity/persistence. However, research to date has been limited regarding quantification methods, plant diversity and geographical distribution. In this study, we determined global variation in seed covering structure hardness of woody species with desiccation-tolerant seeds and analysed its relationships with relevant climatic variables, seed traits and ecological processes. METHODS:We measured seed covering structure hardness of 476 species from 459 genera and 113 families using puncture force. We used phylogenetically informed regressions to test covering structure hardness against potential quantitative predictors [19 climate variables (n = 405), ten seed morphological traits (n = 413), elevation (n = 405), genus age (n = 375)] and response variables [ex situ seed longevity (n = 67), germination rate (n = 82), species distribution/range size (n = 403)]. Categorical predictors [geographical region (n = 444), plant lifeform (n = 428), seed dormancy type (n = 146), seed physical dormancy in the family Fabaceae (n = 76), dispersal unit or mechanism (n = 484), fruit type (n = 427)] were tested using pairwise comparisons. KEY RESULTS:Seed covering structure hardness ranged from 0.13 to 366.38 N and seed and fruit (seed/fruit) size, seed/fruit roundness, seed/fruit colour (lightness) and precipitation of the driest quarter were significantly associated with hardness. In addition, dormancy types (vs non-dormancy), dispersal as fruit (vs seed) or certain fruit types (fleshy vs dry, drupes vs other types), as well as animal dispersal (vs other mechanisms) showed higher levels of hardness. Furthermore, covering structure roundness was higher in animal-dispersed seeds/fruits (vs other dispersal strategies). Finally, covering structure hardness was shown to predict germination rate but not ex situ seed longevity or species range size. CONCLUSIONS:Our results suggest roles for morphology, dormancy, dispersal and precipitation in explaining part of the global variation in seed covering structure hardness of woody species with orthodox seeds. However, we showed that the presence of physical dormancy does not always imply having a harder covering structure than non-dormant seeds and therefore terms such as 'hardseeded' or 'hard coat' should no longer be used as synonyms for this trait.

In this study, a germination test was conducted using the seeds of Tilia miqueliana, a rare tree species in China. The seeds were treated with H2SO4, H2SO4-gibberellic acid (GA3), or H2SO4-magnetically treated water (MTW)GA3 and then incubated in wet sand at a constant temperature (i.e., 5 degrees C, 10 degrees C, 15 degrees C, 20 degrees C, or 25 degrees C) or at alternating temperatures (i.e., 15 degrees C/25 degrees C or 5 degrees C/25 degrees C/5 degrees C). Additionally, the effect of relative humidity (RH) on seed germination was assessed (i.e., at 40 % or 50 % RH). These analyses revealed that the optimal temperature and RH for H2SO4-MTW-GA3 treated T. miqueliana seed germination were 15 degrees C and 50 % RH, respectively. T. miqueliana produces deeply dormant woody seeds. During dormancy release following H2SO4MTW-GA3 treatment, consistent with the observed metabolic enzyme activities, the contents of protein and fat showed a downward-upward-downward trend, whereas the sugar and starch contents showed an upward-downward trend. Hence, the H2SO4-MTW-GA3 treatment enhanced the conversion of glycogen, starch, protein, and fat to nutrients and energy, while also increasing the activities of diverse metabolic enzymes. Furthermore, the abundance of different hormones promoting seed dormancy release peaked at different time points. Specifically, the GA content peaked before the trans-zeatin-riboside (ZR) content, which may be related to the different mechanisms by which various hormones induce dormancy release.

Sassafras tzumu (Hemsl.) Hemsl., known as Chinese sassafras, is an exclusive species of tree found in China, belonging to the Sassafras genus in the Lauraceae family. Its primary mode of propagation is through seeds, which possesses a profound dormancy and irregular germination. In its natural environment, it takes approximately 2-3 years for the seeds to emerge from the ground and begin germinating. Consequently, a rapid and effective method for breaking dormancy would greatly benefitsbn edjhn the production of S. tzumu seedlings. The objective of this investigation was to identify the optimal treatment for breaking dormancy. The S. tzumu seeds were subjected to gibberellic acid (GA3) treatment and cold stratification. The findings indicated that the dormancy type of Sassafras tzumu seeds was combined (physiological + mechanical) dormancy. After 6 months of cold stratification, the germination percentage of seeds treated with various concentrations of GA3 (200mg/L, 500mg/L, and 1000mg/L) all exceeded 50%. Among these treatments, the most effective method was the application of 200mg/L GA3 in combination with 5 months of cold stratification, resulting in a germination percentage of 55%. During the process of cold stratification, soluble proteins, soluble sugars, starch, and fat were broken down into smaller molecules to support embryo growth. Interestingly, the content of soluble sugar exhibited an upward-downward trend, while the content of soluble protein displayed a downward-upward trend. The release of dormancy in S. tzumu seeds was jointly regulated by various endogenous hormones. The content of GA3 demonstrated an upward-downward trend, while the ABA content exhibited a continuous decline with a brief upward trend. In contrast, the IAA content displayed a continuous upward trend, and the ZR content showed no significant change. The ratios of GA3/ABA, IAA/ABA, and ZR/ABA all displayed an upward trend.

Seed germination is a pivotal stage in the plant life cycle, with endosperm weakening and radicle elongation serving as crucial prerequisites for successful endospermic seed germination. Tilia henryana seeds exhibit deep dormancy, necessitating a period of 2-3 years to germinate in a natural environment, and the germination rate is extremely low. This study employed morphological and physiological approaches to dynamically analyzing the hydrological mechanism and the endosperm weakening process during the dormancy release of T. henryana seeds. It was found that there was no physiological post-ripening effect of embryos, but there were mechanical and physiological obstacles in endosperm. During the dormancy release process of T. henryana seeds, initial endosperm weakening occurred at the radicle-endosperm interface. In this process, the GA/ABA level is imbalanced along with a continuous decrease in IAA and SA levels. Substantial depletion of storage materials within cells resulted in degradation of endosperm cell contents, forming numerous cavities through which significant amounts of free water entered. As moisture content increased, endosperm hardness gradually decreased to approximately 5 N/0.09 cm2. Furthermore, the area and content of lignin and cellulose were reduced by 58.91% and 84.49%, respectively, while the hemicellulose and pectin contents were decreased by 72.11% and 83.50%, in that order. Following treatment, the activity of pectin lyase, propectinase, galacturonase, and cellulase was observed to be 5.81, 8.72, 5.96, and 9.43 times higher, respectively, in comparison to their respective activities before treatment. The physiological changes facilitated the rapid rupture of the endosperm cell wall, leading to a transition in cell morphology from palisade-like to irregular and interlocking, thereby further expediting the weakening and cleavage of the endosperm. Additionally, T. henryana seeds exhibited high carbohydrate composition content throughout their dormancy release process, this extensive utilization of storage substances provided energy for radicle elongation and expansion.

The assessment of seed quality and physiological potential is essential in seed production and crop breeding. In the process of rapid detection of seed viability using tetrazolium (TZ) staining, it is necessary to spend a lot of labour and material resources to explore the pretreatment and staining methods of hard and solid seeds with physical barriers. This study explores the TZ staining methods of six hard seeds (Tilia miqueliana, Tilia henryana, Sassafras tzumu, Prunus subhirtella, Prunus sibirica, and Juglans mandshurica) and summarizes the TZ staining conditions required for hard seeds by combining the difference in fat content between seeds and the kinship between species, thus providing a rapid viability test method for the protection of germplasm resources of endangered plants and the optimization of seed bank construction. The TZ staining of six species of hard seeds requires a staining temperature above 35 degrees C and a TZ solution concentration higher than 1%. Endospermic seeds require shorter staining times than exalbuminous seeds. The higher the fat content of the seeds, the lower the required incubation temperature and TZ concentration for staining, and the longer the staining time. And the closer the relationship between the two species, the more similar their staining conditions become. The TZ staining method of similar species can be predicted according to the genetic distance between the phylogenetic trees, and the viability of new species can be detected quickly.

Moisture content (MC) is crucial for the storage, transportation, and processing of Camellia oleifera seeds. The purpose of this study was to investigate the feasibility for detecting MC in Camellia oleifera seeds using visible near-infrared hyperspectral imaging (VNIR-HSI) (374.98 ∼ 1038.79 nm) coupled with deep learning (DL) methods. Firstly, a method was proposed that utilized particle swarm optimization (PSO) to search for the optimal hyperparameters (batch size and learning rate) in the convolutional neural network regression (CNNR) model. The prediction performance of various models including partial least squares regression (PLSR), support vector machine regression (SVR), AlexNet, and CNNR was compared using both raw spectral data and preprocessed data. Then, four feature extraction algorithms (successive projection algorithm (SPA), competitive adaptive reweighted sampling (CARS), PSO, and the optimal DL framework) were used to extract spectral variables. The optimal hybrid prediction model PSO-CNN-SVR was determined, with coefficient of determination (R2P) of 0.918 in prediction set. In addition, the optimal simplified model was used to generate spatial distributions to visualize MC in Camellia oleifera seeds. The study results showed that the HSI technique combined with DL provides a reliable and efficient approach for achieving non-destructive detection and visualization of MC in Camellia oleifera seeds.

Germination inhibitors, which inhibit the germination of seeds, spores and other plant reproductive material, are abundant in the plant kingdom and include phenols, cyanides, alkaloids, essential oils, amino acids, etc. These inhibitors can be classified as germination destructors and germination retarders depending on whether they harm the morphology, structure and physiology of the seed. Germination retarders are closely related to seed dormancy, and exogenous retarders can be used to extend the "dormancy" period of non-dormant seeds or perishable seeds by applying the proper dosage. They have significant potential applications as preservatives for seed preservation following harvest or for the storage of long-term germplasm resources. Germination destructors, as a type of relatively high-efficiency, low-specificity "toxic chemicals", are of significant benefit in the application of effective and environmentally benign herbicides. At present, the main problems related to the research methods of germination inhibitors include difficulty in determining the specific endogenous substances and the minimum inhibitory concentration to induce dormancy, as well as whether the application of exogenous inhibitors will cause physiological damage to seeds. In the future, we should strengthen the tracking of germination inhibitors, explore the mechanisms of action of specific substances and deeper molecular mechanisms and finally explore new developments and new applications of different inhibitors.

In China, the wild population of Nanjing Linden (Tilia miqueliana M.) is experiencing a drastic decline, primarily due to high levels of empty seeds. This study aimed to measure the biochemical and physiological changes during fruit and seed development in T. miqueliana to determine the developmental mechanism. The weight method and photosynthetic respiration were used to determine the biological aspects of both fruits and embryos, while transmission electron microscopy and the anthrone colorimetric method were used to determine the endosperm content, including sugar, starch, protein, and fat. Enzyme-linked immunosorbent assays were conducted to determine the levels of endogenous plant hormones such as indole-3-acetic acid (IAA), gibberellic acid 3 (GA(3)), zeatin riboside (ZR), and abscisic acid (ABA). The nonlinear least-squares method was used to fit the model of nutrient and hormone levels, revealing that fruit size expanded from the 5th to the 65th day and that fruit moisture content exhibited a downward trend, along with a decrease in fruit respiration intensity. Embryos were found to be fully developed between 35 DAF and 65 DAF, while the nutrients in the endosperm, i.e., sugar, starch, protein, and fat, continuously accumulated after 50 DAF. Additionally, ABA, IAA, GA(3), and ZR contents were found to synergistically regulate seed development and maturation.

Persistence in the soil is a function of seed physiology, particularly non-germination and inherent lifespan. However, for seeds with mechanical dormancy, non-germination is also a function of the composition and activity of the soil microbiota. We attempted to screen out microorganisms in the soil that can specifically and rapidly decompose the hard fruit pericarps of Tilia miqueliana Maxim., a unique native tree species in China. Using the classical replica plating method, more than 100 different culturable microorganisms that could rapidly erode the pericarp were collected from the surface of pericarps under different culture conditions. At the same time, we successfully extended the concept of metagenomics and applied it to the identification of mixed artificial cultures. The decomposition process of the pericarps in soil was also simulated artificially. The physical and chemical data suggested a potential mechanism of microbial scarification and cracking in pericarp, whilst the embryos inside the eroded fruits retained good viability. Our discoveries could pave the way for the removal of physical and mechanical obstacles that prevent hard coat seeds from germinating. We anticipate that the use of this technology will improve the germination of other hard coat seeds. More research is needed to investigate the impacts on other seeds. The findings of this research can inform the design of experiments on the seed ecology of persistence.

Introduction Tilia miqueliana is an endemic species whose population is declining. The permeability barrier and mechanical constraint of the pericarp (seed coat) are important causes of its seed dormancy. Although there has been considerable research on this subject, questions remain regarding how the permeability barrier and mechanical constraint of the seed coat are eliminated during dormancy release and how water enters the seed. Therefore, protecting the species by improving its germination/dormancy breaking in the laboratory is urgent Methods In this study, the changes in the cellular structure, mechanical properties, and components of the Tilia miqueliana seed coat after an H 2 SO 4 -gibberellic acid (GA 3 ) treatment were analyzed during dormancy release. Various analyses (e.g., magnetic resonance imaging, scanning electron microscopy, and paraffin section detection) revealed the water gap and water channel. Results The H 2 SO 4 treatment eliminated the blockage at the micropyle and hilum of the seeds. Water entered the seeds through the water gap (micropyle) rather than through the hilum or seed coat, after which it dispersed along the radicle, hypocotyl, and cotyledon to the endosperm. During the cold stratification period, the cellular structure was damaged and an increasing number of holes appeared on the inner and outer surfaces of the seed coat. Vickers hardness tests showed that GA 3 decreased the seed coat hardness. Additionally, the seed coat lignin and total phenol contents continuously decreased during the cold stratification period. Notably, the Liquid chromatography–mass spectrometry (LC–MS) analysis of the seed coat detected polyethylene glycol (osmoregulator), which may have destabilized the water potential balance inside and outside the seed and increased the water content to levels required for germination, ultimately accelerating seed dormancy release. Discussion This sophisticated and multi-level study reveals how H 2 SO 4 and GA 3 eliminate the permeability barrier and mechanical constraints of the seed coat during dormancy release of Tilia miqueliana seeds. This will be beneficial to artificially assist the natural regeneration and population expansion of Tilia miqueliana .

The deciduous tree species Sassafras tzumu (Hemsl.) Hemsl., unique to China, holds significant economic and ecological value. However, its seeds exhibit poor storage tolerance and rapid decline in seed vigor. This study primarily investigates the desiccation tolerance of S. tzumu seeds. The results show that S. tzumu seeds have recalcitrant seed characteristics, with a semi-inactivation water content (at which point half of the seeds lose viability) of 20.7%. As desiccation progresses, seed viability decreases significantly; at a reduced water content of 11.93%, only 18.3% of the seeds remain viable, while most lose their viability completely. Relative electrolytic leakage (REC) and H2O2 content gradually increase during this process, while MDA content initially decreases before increasing again, exhibiting distinct trends compared to antioxidant enzyme activities such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). SOD and POD activities exhibit an initial increase followed by a rapid decrease, whereas CAT activity shows a decline followed by a rapid increase. Dehydration to 15% water content in seeds is a key turning point in the process of seed desiccation in S. tzumu, and CAT is an enzyme key to maintaining seed viability. Both the accumulation of toxins and the decline in the activity of the antioxidant system contribute to the susceptibility of S. tzumu seeds to drought stress, a characteristic common to all recalcitrant seeds. To maintain high seed viability above 70% during storage, it is crucial to ensure water content above 23.58%.

Introduction Cryo treatment of dry seeds is known to attenuate the structure of fruit and seed coats, but little is known about the microstructural impacts of such treatment. The seeds of Tilia miqueliana are dispersed within a hard pericarp, the manual removal (hulling) of which is time-consuming and inefficient. Rapid hulling technology is urgently needed for sustainable production and convenience of edible nuts. Methods We explored the mechanistic basis of liquid nitrogen (N)-treatment weakening of the pericarp of T. miqueliana fruits using a range of microscopical, biophysical and chemical approaches. Results Liquid N treatment (40 s) resulted in lower pericarp contents of cellulose and hemicellulose, and increased amounts of lignin. Profound changes in cell structure and mechanical properties included the emergence of large holes and gaps between the mesocarp and endocarp cells. Also, the toughness of the pericarp decreased, whilst the hardness and brittleness increased, thereby changing the fracture type from ductile to brittle. Liquid N treatment of dry fruits followed by tapping with a hammer, reduced the number of damaged seeds three-fold and pericarp peeling time four-fold compared with manual hulling, whilst seed viability was not negatively affected. Discussion Comparable findings for the efficient and economical removal of hard covering structures from dispersal units of five more species from three other families following liquid N treatment indicates the potential application of our findings to large-scale production of seeds and seedlings for breeding, forestry and conservation/restoration purposes. Furthermore, it introduces a novel concept for postharvest treatment and pre-treatment of deep processing in nuts.

Tilia henryana is a rare tree of the Tilia family, found exclusively in China. Its seeds have severe dormancy features that limit its normal conditions of reproduction and renewal. Its seeds have severe dormant characteristics that limit its normal conditions of reproduction and renewal. The Dormancy in T. henryana seeds is a comprehensive dormancy (PY + PD) caused by mechanical and permeability barriers of seed coat and the presence of germination inhibitor in endosperm. L9 (34) orthogonal test was used to determine the best procedure for releasing the dormancy of T. henryana seeds, that is, first treating the seeds with H2SO4 for 15 min, followed by the application of 1 g L-1 GA3, stratification at 5 degrees C for 45 days, and finally germination at 20 degrees C, which can achieve a 98% seed germination rate. Large amounts of fat are consumed throughout the dormancy release process. As quantities of protein and starch marginally increase, soluble sugars are continuously decreased. Acid phosphatase and amylase activities increased rapidly, and the combined enzyme activities of G-6-PDH and 6PGDH related to the PPP were also significantly increased. The levels of GA and ZR continued to increase, while the levels of ABA and IAA gradually decreased, among which GA and ABA changed most rapidly. The total amino acids content continued to decrease. Asp, Cys, Leu, Phe, His, Lys and Arg decreased with dormancy release, while Ser, Glu, Ala, Ile, Pro and Gaba showed an upward trend. The physical dormancy of T. henryana seeds is broken with H2SO4 in order to make the seed coat more permeable, which is a prerequisite for germination. As a result, the seeds can absorb water and engage in physiological metabolic activities, particularly the hydrolysis and metabolism of fat, which supply a significant amount of energy for dormancy release. In addition, rapid variations in the levels of different endogenous hormones and free amino acids, induced by cold stratification and GA3 application, are another important factor promoting the quick physiological activation of seeds and breaking the endosperm barrier.

Sinojackia xylocarpa Hu, a member of the first new genus described and published by the Chinese botanist Hu, is an endangered plant endemic to China. We analysed mechanisms of seed dormancy in S. xylocarpa at the cytological level. Cell composition, structure, morphology, and hydration in fruit and seeds were observed using paraffin section detection, transmission electron microscopy, scanning electron microscopy, and magnetic resonance imaging. The results indicate that mechanical constraints in the endosperm and endocarp are important causes of dormancy. Germination tests indicated that embryos are non-dormant; rather, the endosperm imposes significant mechanical constraints on germination, particularly around the radicle.

Seed dormancy and germination are distinct physiological processes. The transition from dormancy to germination is a critical developmental step in the lifecycles of plants and is important for forestry production, particularly in deeply dormant woody seeds. The induction and release of dormancy are controlled by various regulators, some of which are plant hormones. Tilia seeds are deeply dormant for 2–3 years under natural conditions, although treatment with H2SO4-GA3 can rapidly break dormancy. In this study, changes in physiological (endosperm cell structure and morphology), biochemical (sugars, starch, protein, and fat), and endogenous hormones [gibberellin (GA), abscisic acid, trans-zeatin-riboside, and indole-3-acetic acid] during dormancy release were measured. The results showed that treatment with H2SO4-GA3 significantly improved the respiratory intensity. A considerable number of holes and cracks appeared in the outer and inner endosperm cells. Additionally, the metabolism of sugars, starch, protein, and fat was facilitated, and their content decreased significantly. The release from dormancy was also associated with increases in GA, ZR, and IAA, decreases in ABA, and higher ratios of GA/ABA, ZR/ABA, and IAA/ABA. The results of this study improve our understanding of the changes in endosperm metabolism and the roles of hormones during dormancy release in Tilia miqueliana seeds. They will enable the dormancy regulatory mechanism in Tilia to be determined and lead to practical applications in breeding.

Tilia miqueliana is in the genus Tilia (Tiliaceae [part of the Malvaceae per APGIII]) of the Malvales family. The mechanisms responsible for dormancy in T. miqueliana were investigated by exploring changes in seed coat permeability, seed water and endosperm content, and endogenous hormones during dormancy release and germination. The structure and permeability of the seed coat and endosperm were assessed using magnetic resonance imaging, scanning electron microscopy, and paraffin section detection. The biological activities of key enzymes in the oxidation pathway were evaluated. Soluble sugar and starch content was determined using the anthrone colorimetric method. Protein contents were determined using Coomassie Brilliant Blue G-250 staining, and the Soxhlet extraction method was used to determine fat content. The endogenous hormones abscisic acid (ABA), gibberellic acid (GA), and zeatin riboside (ZR) contents were determined using enzyme-linked immunosorbent assays. The results indicate that poor permeability and mechanical constraints in the seed coat and endosperm are the key mechanisms regulating dormancy in T. miqueliana seeds. The dormancy types are physical and physiological dormancy. Concentrated sulfuric acid (H2SO4) + gibberellic acid 3 (GA(3)) + cold stratification treatments rapidly induced dormancy and accelerated germination. Activation of the tricarboxylic acid cycle and pentose phosphate pathway were critical for respiration. The metabolism of starch, protein, and fat in the endosperm was accelerated. The expression of endogenous GA(3), which promotes germination, increased, whereas that of ABA, which inhibits germination, decreased. The ratios of GA(3)/ABA and ZR/ABA increased. Our study provides a theoretical foundation for the development of breeding methods.

Pericarp structure and permeability in Tilia miqueliana were explored using anatomy, paraffin section detection, scanning electron microscopy, and magnetic resonance imaging. The pericarp of intact T. miqueliana seeds comprised an exocarp, mesocarp, and endocarp. The exocarp was densely covered with villi and consisted of irregular thin-walled cells. The mesocarp was highly lignified and impermeable, with slender, thick-walled, round and irregularly polygonal cells. The endocarp consisted of spherical parenchyma cells. The water gap provided an entry point for free water in intact seeds. The impermeable and highly lignified mesocarp creates a mechanical and permeability barrier, inhibiting germination in T. miqueliana. Liquid chromatography–mass spectrometry was used to identify the chemical composition of the pericarp. Identified compounds included phenols, esters, organic acid, lipids, aldehydes, as well as unsaturated fatty acids, which likely play a role in suppressing germination.

Tilia miqueliana produces woody seeds that exhibit deep dormancy. In this study, we used cell biology methods, including Paraffin section determination and Coomassie brilliant blue staining, as well as proteomics-based methods, including two-dimensional electrophoresis with matrix-assisted laser desorption/ionisation tandem time-of-flight mass spectrometry (2DE–MALDI–TOF/TOF), to examine the effects of H 2 SO 4 –GA 3 and cold stratification (3 °C) treatment on proteins during dormancy release and germination in T. miqueliana seeds. The results revealed that during cold stratification, the area and density of proteins in the endosperm cells of H 2 SO 4 –GA 3 -treated seeds were significantly altered. Total protein content was continuously consumed and utilised. Storage proteins (albumin, globulin, prolamin, and glutelin) were degraded to varying degrees. Sixteen differential proteins were identified using mass spectrometry. Kyoto encyclopedia of genes (KEGG) pathway analysis revealed that the glycolysis/gluconeogenesis, secondary metabolite biosynthesis, glyoxylate and dicarboxylate metabolism, amino acid biosynthesis, and metabolic pathways were critical during dormancy release and germination. Gene ontology analysis and KEGG pathway annotation of differential proteins in the co-expression network indicated that the differential proteins are implicated in photosynthesis, glucose metabolism, biosynthesis of plant hormones, and glycolysis/gluconeogenesis. Synergistic interactions among these proteins accelerated dormancy release and germination. Therefore, H 2 SO 4 –GA 3 cold stratification treatment is the best method for achieving rapid dormancy release and increasing the germination rate of T. miqueliana seeds.