The long-term storage of forest tree seeds holds critical significance for ecological restoration, forest resource conservation, and the sustainable development of forestry. In the context of plant biodiversity conservation, enhancing seed storability to achieve efficient utilization has garnered widespread attention. Seed storability, as a complex quantitative trait, is influenced by the combined effects of intrinsic seed characteristics and external environmental factors. The complexity of this issue presents significant challenges in maintaining seed longevity, particularly in the conservation of seeds from endangered species. This review discusses the essential factors affecting seed storability and the main causes of seed aging. It emphasizes the roles of molecular mechanisms, including raffinose family oligosaccharide (RFO), heat shock protein (HSP), late embryogenesis abundant (LEA) proteins, seed storage proteins (SSPs), and hormonal regulation, in modulating seed storability. Additionally, the evaluation criteria and methodologies for assessing seed storability are elaborated. The review highlights future research challenges, aiming to provide a comprehensive scientific foundation and practical guidance to improve seed storability. This will offer theoretical support for the sustainable management of forest resources.

Backgrounds: Sinojackia xylocarpa Hu is a deciduous tree in the Styracaceae family, and it is classified as a Class II endangered plant in China. Seed storage technology is an effective means of conserving germplasm resources, but the effects of different storage conditions on the quality and associated metabolism of S. xylocarpa seeds remain unclear. This study analyzed the physiological and metabolic characteristics of S. xylocarpa seeds under four storage conditions. Results: Our findings demonstrate that reducing seed moisture content and storage temperature effectively prolongs storage life. Seeds stored under that condition exhibited higher internal nutrient levels, lower endogenous abscisic acid (ABA) hormone levels, and elevated gibberellic acid (GA₃) levels. Additionally, 335 metabolites were identified under four different storage conditions. The analysis indicates that S. xylocarpa seeds extend seed longevity and maintain cellular structural stability mainly by regulating the changes in metabolites related to lipid, amino acid, carbohydrate, and carotenoid metabolic pathways under the storage conditions of a low temperature and low seed moisture. Conclusions: These findings provide new insights at the physiological and metabolic levels into how these storage conditions extend seed longevity while also offering effective storage strategies for preserving the germplasm resources of S. xylocarpa.

Polyamines (PAs) play critical roles in plant growth, somatic embryogenesis (SE), etc. Previous studies have demonstrated that exogenous PAs could promote SE in plants. However, the effects of PAs on Ginkgo biloba L. SE are still unknown, especially in the switch from the initial callus (IC) to the embryogenic callus (EC) stage or to the globular embryo (GE) stage. This work identified 34 genes involved in PAs metabolism in G. biloba using genome-wide analyses. These genes were clustered into six families and found to be unevenly distributed across 11 of the 12 chromosomes on the plant. These families contain 539 cis-acting elements that mainly respond to phytohormones, abiotic stress, meristem expression, etc. RNAseq analysis revealed that the expression of GbADC2, GbSAMDC2, GbSPMS1, GbCuAO1 and 3, and GbPAO3, 8, 6 and 13 genes in G. biloba were higher in the GE stage than in the IC stage. In addition, 1.0 mg·L⁻¹ spermine (Spm3) could promote the conversion of IC to EC, while 0.01 mg·L⁻¹ putrescine (Put1) could facilitate the transition from IC to EC and then to GE. During the conversion of IC to EC or to GE, higher levels of abscisic acid (ABA), superoxide dismutase (SOD), and peroxidase (POD) and lower levels of indole-3-acetic acid (IAA), gibberellin (GA3), and zeatin (ZT) were observed; concurrently, the H₂O₂ level was also observed to be high. Gene expressions of GbSPMS2, GbCuAO3, and GbPAO6 and 8 were upregulated, while GbADC2 expression was downregulated in the EC or GE stages under Spm3- or Put1- treatment. These results illustrate that exogenous PAs might alter the levels of the endogenous polyamine pool and lead to H₂O₂ production, which caused a certain oxidative stress. However, SOD and POD balanced H₂O₂ production and maintained homeostasis. The PAs–H₂O₂–ABA module might coordinate the regulation of early in of G. biloba. These relations were discussed in this work. These findings provide a foundation for comprehending the roles of PAs gene families in the key nodes of early SE in G. biloba.

Seed dormancy is an important adaptive mechanism in plants. However, some seeds, such as those of Xanthoceras sorbifolium (a valuable economic and medicinal species), exhibit strong dormancy, resulting in a very low natural germination rate. This work investigated the mechanism by which low temperatures (LT: −20 °C storage for 60 days) release seed dormancy and promote germination. This was achieved by examining seed germination conditions, applying scanning electron microscopy (SEM), and measuring physiological indicators of seeds and the hormone levels. Targeted metabolomic analysis of sugar and fatty acid metabolism was also performed. The results were as follows: (1) A high germination rate of 47.3% was observed under LT condition, compared to 32.7% at room temperature (RT: 25 °C). Of four germination methods, direct GMS (germination in moist sand) was the most effective. (2) The two stages of VI (after storage) and VII (on the 7th day of germination) were key stages to breaking the seed dormancy and triggering germination. At both stages, the high integrity of the seed shells and kernels—particularly, the kernels—was observed using SEM. The activities of SOD, CAT, and POD, as well as the levels of IAA and IPA, and the ratios of IAA/ABA and (IAA + GA3 + ZR + IPA)/ABA (tHor/ABA) were found to be higher, especially in stage VII, where tHor/ABA increased by 62.7%, while ABA decreased by 23.2% in the LT treatment compared to the RT treatment. An optimal germination condition (GMS) created a suitable microenvironment, and this could have maintained highly active antioxidant enzymes and kept H₂O₂ (one of reactive oxygen species, or ROS) within signal transduction levels, and cross-talk to hormones. These changes (enzymes, hormones, ROS, and microenvironment) ensured the seeds reaching an optimal state for dormancy release in the VI stage, and facilitated the seed germination in the VII stage. (3) LT treatment promoted the degradation of starch and fats in the seeds. Significant accumulations of eight soluble sugars, such as glucose, D-fructose, and trehalose, as well as three fatty acids, such as Cis-11,14,17-eicosatrienoic acid (C20-3n3) and γ-linolenic acid (C18-3n6), were observed, while two soluble sugars and one fatty acid decreased under LT conditions. In conclusion, low temperature, as an external signal, together with ROS and GA-ABA-IAA etc. the internal signals co-regulated the seed dormancy release and germination. The moist-sand microenvironment was also a key factor in awakening the embryos of X. sorbifolium seeds.