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Thermoinhibition, the suppression of seed germination by high temperatures, is an adaptive trait that ensures successful seedling establishment in natural environments. While beneficial for wild plants, thermoinhibition can adversely affect crop yields due to uneven and reduced germination rates, particularly in the face of climate change. To understand the genetic basis of thermoinhibition, we conducted a comprehensive genetic analysis of a diverse panel of Lactuca spp. accessions. Our findings revealed that L. serriola , a wild ancestor of cultivated lettuce, showed relaxed thermoinhibition response compared to cultivated lettuce, suggesting that this trait may have been positively selected during early domestication in the Mediterranean region with hot, dry summers. Additionally, we found that thermoinhibition intensified with seed age but was less pronounced in dark-colored seeds, which showed increased germination under high temperatures. Genome-wide association studies identified genomic regions associated with thermoinhibition, including genes involved in ethylene and ABA signaling. Interestingly, some of these regions were also linked to seed color, suggesting a potential genetic coupling between black seed color and reduced thermoinhibition. These results highlighted the complex interplay between thermoinhibition, seed color, and domestication in lettuce, indicating a complicated nature of thermoinhibition regulation. By elucidating the genetic architecture of thermoinhibition, our study provides a valuable foundation for breeding strategies to enhance lettuce resilience to climate change.

is a dominant native perennial shrub on sand dunes in arid deserts of northwestern China, and is therefore widely used in sand dune stabilization in these regions. However, it remains largely unknown how seedling emergence of has adapted to unpredictable sand movement and extreme drought. Here we examined effects of seed burial depth, light intensity, and seed age on seedling emergence, and considered seed germination and seedling emergence strategies for the shrub's adaption to the desert environment. In our pot experiment, the optimum seeding depth for emergence of was 2 cm, indicating that for germination and seedling emergence only moderate sand burial is required. Light intensity at the surface soil (0 cm) was important for seedling emergence, while there was no significant difference between 50 and 20% light flux density, at burial depths of 1 and 2 cm, indicating that seeds had adapted to sand burial, while not exposure from sand erosion. We also found seedlings emerged in spring and in late summer to early autumn. Meanwhile, seedling emergence percentage for 3-year-old seeds was similar to that of 1-year-old seeds, which meant that seeds were well preserved under normal sand dune conditions, thus were capable of developing a persistent, but shallow soil seed-bank. These results indicated that germination and seedling emergence take a bet-hedging strategies to adapt to variable desert environments. Our study confirmed that desert shrubs combine strategies in its adaption to arid and variable sand environments.

Effective Microorganism (EM) is widely employed as a growth promoter in agricultural practices. The aging of oat seeds not only directly impairs agricultural production but also exerts adverse effects on biodiversity. The mechanism through which EM influence the germination of aging seeds remains unclear. In this experiment, the EM bacterial solution underwent pretreatment, which included the original-solution treatment (OrT), supernatant treatment (SuT), and sterile treatment (StT). Aging of oat seeds was induced using the pretreated EM bacterial solution. In this study, the EM bacterial solution facilitated the enhancement of the germination rate, germination index, and vitality index of aged seeds, with SuT demonstrating the most pronounced effects. Specifically, SuT resulted in a significant increase in APX and POD activities, while significantly reducing the malondialdehyde content. In addition, metabolic profiling highlighted the significance of 5-phosphoribosylamine in the purine metabolic pathway. Particularly in the SuT, the upregulation of 5-phosphoribosylamine facilitated the synthesis of (R)-Allantoin, consequently augmenting antioxidant enzyme activity.

We describe a new approach to determining the age structure of seed banks of natural plant populations and apply it to a natural population of the Sonoran Desert winter annual, Pectocarya recurvata (Boraginaceae). Unlike other14C techniques, tandem accelerator mass spectrometry (TAMS) counts the number of carbon isotope atoms, permitting high precision with small samples. Aboveground nuclear bomb tests caused atmospheric14C levels to peak in 1963. Their subsequent gradual decline provides a signal for aging seed banks with TAMS. We constructed a calibration curve using seeds with known dates of production during 1980-1995, then used it to age 53 seeds sampled from a natural seed bank in 1993, at the Desert Laboratory in Tucson, Arizona. Seed number declined with age at an approximately exponential rate, with the oldest recovered seed having an estimated age of 5 yr (95% CI = ± 2.3 yr). The seed bank age structure was judged more than adequate to buffer this population from typical fluctuations, based on an examination of 15 yr of population dynamic data. The TAMS technique has strong potential for answering a broad range of ecological and evolutionary questions requiring post-1963 age determinations and for which a several-year confidence interval is acceptable.

Apera spica-venti is a weed that is threatening agricultural crops worldwide. Current reports do not fully agree on the biology of the weed, regarding the viability of diaspores, nor is there sufficient information on how different factors affect the germination of its seeds, such as the abundance of soil where the mother plant (plants from which diaspores (caryopsis) were collected) has grown or the effect of biostimulants on their germination. Therefore, the main aim of this study was to compare the germination of newly harvested seeds of A. spica-venti (3 months after harvest) with seeds that had been stored for 1, 2, 3, 4, or 5 years. Furthermore, the influence of seed age, weed location, and biostimulants (silicon and algal liquids) on the germination of A. spica-venti diaspores was checked. Three-year-old seeds showed the highest percentage of germination, and their germination process was positively correlated with soil abundance (from sites of mother plant material collection) and macronutrients (N, P, K). The strongest correlations were recorded for 3- and 4-year-old seeds. A. spica-venti seeds treated with biostimulant preparations were characterized by varying percentages of germination. No clear trend was noted regarding the germination capacity of the harvested seeds as the diaspores aged, and it depended on the type of stimulant and the place of origin of the seed. Moreover, seeds from the harvest year treated with the stimulant were characterized by a higher germination percentage. A. spica-venti is a highly fecund weed, a trait that makes it very common in crops, appearing en masse and providing formidable competition to crops, thus causing significant yield losses. Awareness of the vitality of diaspores will allow for the possible regulation and control of this weed in order to prevent yield loss in crops. The theme of diaspore viability warrants further investigation. Further research should include observations of factors affecting germination, including new stimulants emerging on the agricultural market.

Plant emergence, apical dominance, tuber set, and size are affected by the physiological age of seed tubers, which can substantially impact overall crop value. This study investigated the efficacy of seed spacing (15, 25, and 35 cm) and 1-naphthaleneacetic acid (NAA) seed treatments in altering these variables in cv. Ranger Russet to improve yield and tuber size distribution of seed expressing low (2.8 stems/seed piece) and high (4.8–5.4 stems/seed piece) apical dominance. Age primed, high-stem seed produced more tubers per plant and per ha than non-aged seed; however, tuber number per ha from both seed lots fell to the same extent with decreasing plant density. Importantly, tuber set per plant increased substantially more for the physiologically older, high-stem seed as plant spacing increased. Average tuber weight also increased with decreasing plant density but the response was greatest for the physiologically younger, low-stem seed. Regardless of seed age, marketable yields were comparable at 25- and 35-cm spacing. Tuber size distributions from the 2.8-stem seed shifted from oversize (>340-g) tubers to higher percentage 113–284-g tubers as spacing decreased from 35 to 15 cm. The 5.4-stem seed produced less undersize (<113 g) tubers and a greater proportion of >284-g tubers when planted at 35-cm spacing. Adjusting in-row spacing relative to seed age and expected stem numbers improved tuber size distribution and value. However, because plants from older seed set more tubers in response to decreasing plant density than younger seed, average tuber weight and size distribution never matched the younger seed at any spacing. Restoration of apical dominance by treatment of seed with NAA was more effective in this regard. Depending on seed age, NAA delayed plant emergence (22–74 %) and decreased stem (24–38 %) and tuber numbers per plant (8–13 %). Stem numbers from age-primed seed fell from 4.8 to 3.0 as NAA concentration increased. Marketable yields were not affected by seed age but decreased slightly (7.3 %, P  < 0.01) with increasing NAA concentration. NAA effectively shifted the tuber size distribution from age-primed seed toward larger (>284-g) tubers, resulting in a yield profile approaching that of the non-treated younger seed. Although seed spacing and NAA treatments are effective techniques for altering tuber size distribution to maximize crop value in relation to seed age and expected stem numbers, tuber age had a small but residual effect on productivity beyond that attributable to apical dominance.

Investigations on seed biology and ecology are of major importance for the conservation of threatened plants, both providing baseline information and suggesting practical approaches. In our study, we focused on the germination behavior of Silene hicesiae Brullo & Signor., a narrow endemic species to Panarea and Alicudi (Aeolian Archipelago, Italy), as well as one of the 50 most threatened Mediterranean island plants. Specifically, the effects of temperature, light, seed age, seed source, and collection year were evaluated; in addition, threshold temperatures and thermal–time parameters were estimated. The thermal range for fresh seed germination resulted between 5 and 15 °C, reaching up to 20 and 25 °C at increasing seed age, with 30 °C being clearly beyond the ceiling temperature. This behavior indicates that fresh seeds exhibit the Type 1 non-deep physiological dormancy, and that germination is regulated by conditional dormancy. This dormancy syndrome emerged as a highly efficient adaptation strategy for this species and, together with thermo-inhibition, would allow seeds to counteract or take advantage of Mediterranean environmental conditions. The comparison between the wild Panarea population and the corresponding ex situ cultivated progeny has enabled the identification of the latter as a suitable seed source for sustainable in situ reinforcement actions, at least in the short-term; indeed, plant cultivation for a single generation did not produce significant modifications in the germination behavior of the offspring.

Dianthus cruentus Griseb. (Caryophyllaceae) is an herbaceous perennial native to Greece with a strong ornamental potential when used as a pollinator-friendly component of xeric gardens and green roofs, where it is valued for its tolerance of poor, dry soils, and its showy colorful inflorescences. Aiming to develop an efficient mass propagation protocol appropriate for the introduction of the species as a novel floricultural crop, the in vitro seed and clonal propagation of a Greek native xeric ecotype were investigated in this paper for the first time. A total of 90–100% of the seeds, after being stored in the dark at room temperature for 12 months, germinated when incubated at 10 to 25 °C after their surface sterilization and transfer in vitro. Sixty-day-old seedlings grown in vitro were then used as a source of nodal explants for the initial establishment of micropropagation cultures, more efficiently on MS medium with 0.1 mg L−1 6-benzylaminopurine (BA). In the multiplication stage, either normal or hyperhydric micro-shoots were used as explant sources, assessing the possibility of incorporating usually discarded material in the propagation procedure. Different solid media were tested, with the highest multiplication indices (5.1) recorded in an MS medium containing 0.1 mg L−1 BA and 0.05 mg L−1 NAA, regardless of explants’ hyperhydricity, while an MS medium containing 0.1 mg L−1 BA and 12 g L−1 agar proved optimal for the effective reversal of hyperhydric explants (MI: 5.2). Despite higher hyperhydricity and reaction rates being observed when hyperhydric explants were used, modifications in the multiplication medium proved to be highly effective in controlling hyperhydricity, with the highest number of normal shoots (2.4–2.6) produced in BA-containing media. Micro-shoots rooted readily in ½ MS medium (60–100%), with rooting rates and quality positively affected by the presence of 0.5 mg L−1 IBA in the rooting medium and the absence of cytokinins in the multiplication one. Rooted micro-shoots were successfully acclimatized ex vitro at high rates (65–100%), their origin influencing their acclimatization and morphology. Thus, the concurrent use of normal and hyperhydric shoots in the proposed micropropagation protocol is proven to be both feasible and desirable, as it is able to significantly increase efficiency and facilitate the sustainable exploitation and dissemination of D. cruentus as a promising multivalent horticultural crop.

Seeds of Delphinium fissum subsp. sordidum are physiologically dormant at maturity, with underdeveloped embryos; thus they have morphophysiological dormancy (MPD). The aims of this study were to determine the requirements for embryo growth, dormancy break and germination, to characterise the type of seed dormancy and to evaluate the effects of light, seed age, pollination mechanism, and inter-annual and inter-population variability on germinative ability. After 3 months of incubation at 5°C (cold stratification) in darkness conditions, the mean embryo length increased from 5.6 to 2.07 mm, with 76% of seeds germinating. Conversely, embryos of seeds incubated during 3 months at 20/7 or 28/14°C hardly grew and no germination was recorded. Since cold stratification was the only requirement for the loss of MPD, and both dry storage in laboratory conditions and warm stratification prior to cold stratification shortened the cold stratification period required for germination, it could be concluded that D. fissum subsp. sordidum seeds have intermediate complex MPD. Cold stratification and incubation in darkness conditions promoted higher germination percentages than those in light. In addition, germinative ability increased with seed age up to 8 months (reaching 96% at 5°C in darkness), showed a pronounced inter-annual and inter-population variability, as well as a significant decrease in seeds coming from pollination by geitonogamy. High temperatures (25/10 or 28/14°C) induced seeds to secondary dormancy, so seedling emergence in the greenhouse was restricted to February-March. The requirements for dormancy break and germination reflect an adaptation to trigger germination in late winter. This study is the first one to document a gradual increase in germination percentage with seed age for plant species with intermediate complex MPD.

Common ragweed ( Ambrosia artemisiifolia L.) is an annual Asteraceae species native to North America which is highly invasive across Europe and has harmful impacts, especially on human health and agriculture. Besides its wide ecological range, particularly its high reproductive power by seeds is promoting its spread to various habitats and regions. To prevent further spread and to control the plant, the European Commission funded projects and COST-Actions involving scientists from all over Europe. A joint trial was set up comprising eight different laboratories from Europe to study seed viability variation in different seed samples. Three different testing methods (viability test with 2,3,5-triphenyltetrazolium chloride (TTC), a germination test combined with a subsequent TTC test and a crush test) were tested within the EU-COST-Action SMARTER network to four different seed origins. The viability test results from different laboratories were compared for variation amongst tests and laboratories. The main aim was to optimise the reliability of testing procedures, but results revealed not only significant effects of seed origin and seed age on seed viability, but also considerable differences between the output of the individual testing methods and furthermore between laboratories. Due to these significant differences in the results of the testing labs, additionally a second test was set up. Twelve Austrian ragweed populations were used for TTC testing to obtain a precise adjustment of the testing method as well as a tight guideline for interpreting the results, particularly for the TTC state “intermediate” since a proper classification of TTC-intermediate coloured seeds is still a challenge when determining viability rates.