Seeds, Volume 1, Issue 2 (June 2022) – 7 articles

For a successful germination and plant growth, seeds must germinate at the right time. Seeds must become nondormant and must fulfill the seed germination requirements. These requirements include light/dark, moisture, temperature, and other environmental cues (e.g., ethylene, exudate from host roots, or chemicals from fire) in the habitat. Seeds come out from dormancy in response to environmental cues, but depending on the species, they may need to be exposed to a second set of environmental cue to germinate. That is, nondormant seeds require specific temperature and water conditions to germination, and sometimes unfavorable temperature and water conditions will cause seeds to enter secondary dormancy. There are still mysteries about how/what environmental cues help seeds detect the right time/conditions for germination after dormancy is broken. Our knowledge of species-specific conditions is incomplete and further studies are needed. Full article

Carignan is a black grape cultivar widely planted throughout the western Mediterranean Basin. The grape faces significant viticultural hazards such as soil salinization, which affects about 6% of the world’s total land area. The search for salt tolerance genotypes to be introduced in crossbreeding programs and obtaining new cultivars is a key factor. The seed germination and salt tolerance of Carignan were studied from different coastal vineyards across the Mediterranean Basin, and as well as whether the distance from the sea affected germination and salt tolerance. Carignan seeds, independently of the temperature and distance from the sea, germinated more than 50% under 125 mM NaCl concentrations. Seed recovery was elevated, including the capacity of gemination after high salt exposure (500 mM NaCl). The results on germination behavior related to the distance from the sea showed that all tested vineyards, except for the one farthest from the sea, had similar germination responses. The optimum germination condition to select salt-tolerant accessions is alternating temperatures 25/10 °C and 125 mM NaCl. Thanks to the ability of the Carignan to germinate in a saline substrate and their capacity for recovery, it could be useful to crossbreeding programs, for integrating as rootstock selection or for the improvement of cultivars through sexual reproduction. Full article

Seed production in Pinus pinaster Aiton is not usually considered a limiting factor for natural regeneration; instead, seed weight is a more limiting factor in successful pine recruitment. Divergent relationships between seed weight and germination rate were previously observed amongst maritime pine populations of central coastal Portugal. The present study followed cone-to-seed and seed-to-seedling approaches to decrease intra-specific variability and clarify the impact of cone size and seed mass on seedling recruitment. The main objectives of this study were (1) to determine and compare the mass of cones and seeds of three maritime pine populations located along a geographic gradient along the coastal center of Portugal and (2) to clarify the relations thereof between cone and seed traits with germination phenology and initial seedling growth. Results demonstrated that heavier cones tended to generate more mature seeds, but not necessarily heavier ones, although seed weight was suggested to be an indicator of robust seedlings. The outcomes of this study reinforce the great intra-population variability of maritime pine, showing the ecology of this species and its ability to adapt to various environments successfully. Full article

Earlier studies have considered the separate effects of temperature and gibberellic acid (GA₃) on plants and seeds. However, the combined effects of these factors on parent plants and their progeny have received little attention. We investigated the effects of two temperature regimes (24/20 °C and 28/24 °C, 16 h light/ 8 h dark) and two GA₃ treatments (for two weeks) on the reproductive yield of parent plants, the subsequent seed germinability, and the seedling traits of four local populations of evening primrose (Oenothera biennis). Mature seeds were harvested and germinated, and seedlings were grown under the two temperature regimes. Parent plants were phenotyped for flower area and diameter, capsule length and width, full and empty capsule masses, and seed number and mass per capsule. Additionally, seed total germination and germination rate were determined, alongside stem height and dry mass, leaf number, area and dry mass, root dry mass, and total dry mass in seedlings. GA₃ promoted the flowering of all populations in the first year. Maturation drying under higher temperatures resulted in more viable and faster germinating seeds. Higher GA₃ did not affect total germination, but increased the germination rate of seeds that produced seedlings with lower total dry mass under the higher temperature regime. In conclusion, all populations responded similarly to GA₃ treatment in terms of flowering, but responded differently to temperature during seed maturation, and subsequent seed germination and seedling growth. Full article

Lobularia maritima or sweet alyssum (Brassicaceae) is an annual littoral halophyte, naturally thriving on sandy beaches. In addition to its obvious interest as a naturally salt-tolerant plant, this species is mainly cultivated as an ornamental plant in many countries. Laboratory experiments were carried out to assess the effects of salinity on seed germination and on germination recovery from the effects of saline conditions after transfer to distilled water. Seed germination responses were determined at 0, 50, 100, 200 and 300 mM NaCl. Salt (NaCl) does not affect the germination of L. maritima if applied at a moderate dose of 50 mM. For higher concentrations of NaCl, there is a decrease in the germination rate at 100 and 200 mM NaCl or even a total inhibition of germination at 300 mM. Salt lowers or inhibits germination only through osmotic effects. To improve the germination of L. maritima under high salinity, seeds were pretreated with KNO₃, thiourea, proline and salicylic acid. The germination of seeds is improved by KNO₃ in the presence or absence of salt, while thiourea increases the final germination without affecting the germination rate. Salicylic acid amplifies the effect of salt, while proline delays germination without stopping it completely. These findings indicate that the application of KNO₃ and thiourea may be used to improve seed germination of L. maritima, which is of great interest for cultivating this plant for landscaping purposes in saline soils. Full article

Salinity is a dominant obstacle to the proper germination of seeds, growth of seedlings, and, consequently, the production of crops. The priming of seeds with different treating agents can efficiently impart salinity tolerance. Kidney bean is a nutritious and popular vegetable crop in the world. Literature shows that salt stress negatively disturbs the germination and growth of kidney beans. In the present research, we investigated the potentiality of salicylic acid (SA) and hydrogen peroxide (H₂O₂) as priming and exogenous agents to alleviate the salinity-inhibited germination and growth of kidney beans. The seeds were pretreated with SA (1 mM and 2 mM) and H₂O₂ (0.1 mM and 0.15 mM) and soaked in normal tap water (hydro-priming) for 60 min. In addition, for the control experiment, untreated seeds were used. Finally, primed seeds were subjected to salt stress (150 mM NaCl). Our results exhibited that salt stress considerably lowered the percentage of germination (GP), germination index (GI), seed vigor index (SVI), shoot length (SL), root length (RL), shoot–root fresh and dry biomass, and plant growth. The results also exhibited that salt stress significantly decreased the relative water content (RWC) and photosynthetic pigments such as chlorophyll, carotenoids, lycopene, and beta-carotene contents. The SA- and H₂O₂- and hydro-priming stimulated the GP, GI, SL, RL, SVI, and seedling growth. Data also revealed that the supplementation of SA and H₂O₂ enhanced RWC and photosynthetic pigments. When compared to other treatments, pretreatment with 1 mM SA was determined to be comparatively more effective at imparting the salt tolerance of kidney beans. Overall, these results, via a heatmap and principal component analysis, uncovered that priming and exogenous applications of SA and H₂O₂ can improve salt tolerance and enhance germination and seedling characteristics of kidney beans. Full article

Seed germination is the stage in which plants are most sensitive to abiotic stress, including salt stress (SS). SS affects plant growth and performance through ion toxicity, decreasing seed germination percentage and increasing the germination time. Several priming treatments were used to enhance germination under SS. The objectives of this study were (1) to identify priming treatments to shorten the emergence period, (2) to evaluate priming treatments against the SS, and (3) to induce synchronized seed germination. Salt-sensitive ‘Burpee Bibb’ lettuce seeds were treated with 0.05% potassium nitrate, 3 mM gibberellic acid, and distilled water. All the primed and non-primed seeds were subjected to 100 mM sodium chloride (NaCl) or 0 mM NaCl (control). The seven-day experiment, arranged in a complete randomized block design with four replications, was conducted in a growth chamber maintained with 16/8 h photoperiod (light/dark), 60% relative humidity, and a day/night temperature of 22/18 °C. The result indicated that hydro-primed (HP) seeds were better synchronized under SS. Similarly, fresh mass (FM) and dry mass (DM) of cotyledon, hypocotyl, and radicle were the highest in HP lettuce regardless of SS. Electrolyte leakage was the lowest in the HP lettuce, while other priming methods under SS increased membrane permeability, leading to osmotic stress and tissue damage. Overall, hydro-priming can be a good priming method for synchronizing germination and increasing FM and DM by creating the least osmotic stress and ion toxicity in lettuce under SS. Full article