Seed Germination Responses Research Articles

Seed germination response to diurnally alternating temperatures: Comparative studies on alpine and subalpine meadow populations

Seed germination response to diurnally alternating temperatures: Comparative studies on alpine and subalpine meadow populations

Seed Germination Ecology of the Medicinal Plant Peganum harmala (Zygophyllaceae).

Seed germination is a crucial stage in the life cycle of annuals in arid, saline regions and is particularly vulnerable to abiotic stresses. Peganum harmala, a valuable medicinal plant, has limited research on its seed germination response to different environmental stresses in the arid, saline regions of Central Asia. To investigate this, we studied the effects of various temperature regimes (ranging from 20/5 to 35/20 °C), light exposure (12 hours light/12 hours dark and continuous dark), seven levels of polyethylene glycol (PEG-6000) concentration (ranging from 0-30%), and four types of salinity (ranging from 0-600 mmol L-1). Our findings show that photoperiod and temperature significantly influence germination. Optimal temperature range for seed germination was observed at 30/15 °C, with simulated critical and limit values of drought tolerance being highest (17.30% and 24.98%). However, higher temperatures (35/20 °C) and lower temperatures (20/5 °C) reduced the critical and limit values of drought tolerance. Additionally, the type and concentration of salinity had a significant effect on the seed germination, shoot, and root lengths of P. harmala. Regression analysis indicated that the critical values of NaCl, Na2SO4, NaHCO3, and Na2CO3 tolerance during germination were 178 mmol L-1, 101 mmol L-1, 106 mmol L-1, and 54 mmol L-1, respectively. Salinity inhibition on seed germination followed the order: NaCl < NaHCO3 < Na2SO4 < Na2CO3. Moreover, NaCl, Na2SO4, NaHCO3, and Na2CO3 significantly inhibited the growth of P. harmala seedlings in both shoots and roots. Our study demonstrates the sensitivity of P. harmala to environmental factors such as light, temperature, drought, and salinity. The study provides valuable information on the germination ecology of P. harmala under diverse ecological scenarios, which can be useful in developing efficient propagation and utilization of this medicinal plant.

Onion (Allium cepa L.) seed germination affected by temperature and water potential: Hydrothermal time model

A useful implement for seed ecological studies is quantifying the germination behavior against variable environmental conditions. The influences of temperature and water potential on the germination response of onion seeds can be described by using the thermal time (TT), hydrotime (HT), and hydrothermal time (HTT) models. The germination behaviour of onion seeds (Allium cepa L.) was studied over a range of constant temperatures and water availability. The efficiency of hydrothermal time models was evaluated by the germination parameters for two onion cultivars (‘Sepidan’ and ‘Zargan’). The onion seeds were germinated in the laboratory over a water potential range from 0 to − 1 MPa at 5, 10, 15, 20, 25, 30, 35, and 40 °C. Final germination dropped with decreasing water potential, particularly at water potential less than − 0.2 MPa. The model analysis indicated that the dynamics of seed germination was generally well described by the TT model within water potential less than − 1 MPa (R2 = 0.69–0.97), HT (R2 = 0.94–0.99), and HTT models (R2 = 0.95–0.96). The Dent-like was found to be the best model to predict germination rate (RMSE = 0.00006, and 0.000133, R2 = 0.98, and 0.97 for ‘Sepidan’ and ‘Zargan’, respectively). The base, sub-optimum, supra-optimum and the ceiling temperatures for onion seed germination were estimated − 2.5, 19.3, 29.8, and 39.3 °C for ‘Sepidan’ and 0, 25.19, 27.37, and 42.39 °C for ‘Zargan’ at 0 MPa. Thermal time constants were 2650 and 3329.67 °C.h at − 0.8 MPa and 1602.83 and 1521.44 °C.h for ‘Sepidan’ and ‘Zargan’ seeds at 0 MPa. Hydrotime constants for ‘Sepidan’ and ‘Zargan’ seeds were 115.54 and 128.037 MPa.h at 5 °C and 20.8 and 26.93 MPa.h at 30 °C. Hydrothermal time constants for ‘Sepidan’ and ‘Zargan’ seeds were 1249.792 and 1122.78 MPa.°C.h.

Effects of temperature, provenance, drought stress and salinity on seed germination response and early seedling stage of Thymus atlanticus (Ball) Roussine

Thymus atlanticus (Ball) Roussine is a valuable aromatic and medicinal species endemic to Morocco. Climate change and anthropogenic threats are factors driving this species to vulnerability and extinction. Therefore, the current study aims to examine the effects of provenance, temperature, drought stress, and salinity on the germination parameters of T. atlanticus seeds and seedling vigor. Seeds are collected from two provenances (Saghro and Tizi n’Telghemt). Treatments included six alternating temperature regimes (10/0, 15/05, 20/10, 25/15, 30/20, and 40/25 °C), five osmotic potentials of aqueous solutions of polyethylene glycol (PEG-6000) (0, −0.1, −0.3, −0.6, and −0.9 MPa), and five concentrations of sodium chloride (NaCl) (0, 1, 2.5, 5, and 7 g/l). The two-way ANOVA test reveals that alternating temperatures, drought, salinity, and their interactions with provenance almost all have a significant impact on germination parameters. However, no significant effect is registered for the interaction between provenance and alternating temperatures on the final germination percentage (FGP). The highest FGP is recorded at several alternating temperatures (15/05, 20/10, 25/15, and 30/20 °C), and the maximum one is at 20/10 °C for both populations (Saghro and Tizi n’Telghemt, respectively 93% and 89%). This temperature regime is also the best in terms of germination time and speed. The most vigorous seedlings are obtained at 20/10 and 30/20 °C for Tizi n’Telghemt and Saghro populations, respectively. Concerning salinity and moisture stress, the results show that the increase in NaCl and PEG-6000 concentrations leads to a significant reduction in the germination capacity (FGP) and seedling vigor index as well as an increase in the mean germination time (MGT) of the two populations studied. The Saghro population tolerates the studied stresses better than the Tizi n’Telghemt population. These results may serve as guidelines for the domestication and rehabilitation of this medicinal plant.

Avian gut passage reduces the germination light response of pokeweed (Phytolaca americana)

It has been shown that passage through a bird's gut has the potential to alter seed germinability (overall percent germination) and the timing of germination. However, little is known about the potential of avian gut passage to alter the germination response of seeds to abiotic gradients, such as light availability. Specifically, it is unclear whether gut passage makes seeds more or less sensitive to variability in light. We addressed this issue using a growth chamber experiment where the germination rate of both gut-passed and control (de-pulped) seeds of the understory herb Phytolaca americana (pokeweed) was compared across three light levels. Both avian gut passage and light increased germination rate. Additionally, it was found that gut passage and light interacted to influence the germination rate, such that gut-passed seeds showed no response to light and control seeds had a strong, positive light response. Results from this experiment suggest that avian gut passage has the potential to reduce seed's sensitivity to light, which could play a role in the recruitment of avian-dispersed plant populations across variable light environments.

Pre-treatment of melatonin enhances the seed germination responses and physiological mechanisms of soybean (Glycine max L.) under abiotic stresses.

The germination of soybean (Glycine max L.) seeds is critically affected by abiotic stresses which resulting in decreasing crop growth and yield. However; little is known about the physiological mechanisms of germination and the potential role of melatonin on soybean seed germination under drought, salt, cold, and heat stresses. Therefore, the current study investigated the possible effects of melatonin to enhance germination indices and other physiological attributes by alleviating the harmful impacts of these stresses during germination. Seeds of soybean were pre-treated (seed priming) with melatonin at MT1 (20 μmol L-1), MT2 (50 μmol L-1), MT3 (100 μmol L-1), MT4 (200 μmol L-1), and MT5 (300 μmol L-1) and exposed to the four stresses (drought at PEG 15%, salt at 150mM, cold at 10 °C, and heat at 30 °C) . It was noted that MT1 (20 μmol L-1), MT2 (50 μmol L-1), and MT3 (100 μmol L-1) remarkably improved the germination potential, germination rate, radical length, and biomass under given stresses. Furthermore, MT1, MT2, and MT3 progressively increased the proline to minimize the impact of drought, salt, cold, and heat stresses. In addition, all stresses significantly induced oxidative damage however, salt (150 mM NaCl) and heat (30 °C) stresses highly increased the malondialdehyde content (MDA) and hydrogen peroxide (H2O2) as compared to drought (PEG 15%) and cold (10 °C) stresses. Moreover, MT2 and MT3 significantly enhanced the activities of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) to reduce the oxidative damage in soybean seeds during the germination. Overall, melatonin at 50 μmol L-1 and 100 μmol L-1 considerably mitigated the harmful impacts of drought, salt, cold, and heat stress by enhancing germination and other physiological mechanisms of soybean. This study could provide bases to enhance the melatonin-mediated tolerance of soybean and other related crops at early growth stages when exposed to abiotic stresses.

Germination response of palm seeds on a two-way thermogradient plate

Germination response of palm seeds on a two-way thermogradient plate

Hydrotime Analysis of Chenopodium quinoa Seed Germination Responses to Combined Effects of NaCl-Induced Osmotic Stress (Ψ), Chilling Temperature (T), and Ca2+-Priming Treatment

Hydrotime Analysis of Chenopodium quinoa Seed Germination Responses to Combined Effects of NaCl-Induced Osmotic Stress (Ψ), Chilling Temperature (T), and Ca2+-Priming Treatment

The halopriming of seeds improves the germination, growth, physiological and phytochemical attributes of tomato under saline conditions

The low seed germination response and seedling growth of crops to salinity is common problem in Pakistan. To overcome this problem,seed priming is used as an economic and effective approach. Present study was conducted to evaluate the effects of halopriming ofseeds on germination, growth and yield of tomato under saline conditions. The seeds of tomato variety ‘Raja’ were primed with 0, 50mM and 100mM of NH4NO3, KNO3, and (NH4)2SO4 solutions for 12 and 24 hours. The primed seeds were irrigated separately with tapwater, saline water, and Hoagland solution with saline water. The results indicated that halopriming of tomato seeds with KNO3, NH4NO3and (NH4)2SO4 significantly increased the germination percentage (GP) from 58% (unprimed) to 95% (primed) while decreased the meangermination time (MGT) from 7.44 days (unprimed) to 4.6 days (primed). A significant increase was observed in the height of plant, leafarea, number of leaves, shoot and root biomass, number of fruits per plant, etc. in primed plants irrigated with Hoagland solution undersaline conditions. Similarly, the halopriming with NH4NO3 and KNO3 also enhanced the chlorophyll pigments, lycopene contents, totalsoluble sugars, total proteins, total phenolic contents and total flavonoids in primed plants irrigated with Hoagland solutions under saltstress. Furthermore, proline contents were increased in primed plants irrigated with NaCl solution as compared to other treatments andcontrol. In conclusion, KNO3 and NH4NO3 are more effective priming agents than (NH4)2SO4 were positively affected the germination, plantheight, physiological and biochemical attributes in tomato plants under saline and non-saline conditions. The supplement of Hoaglandsolution under salt stress further improves the morphological, physiological and biochemical attributes of tomato.

Impact of extreme heatwaves and life-history traits on seed germination responses in Cumberland Plain Woodland native plant species

Context The Cumberland Plain Woodland (CPW) is a threatened ecological community that is expected to experience heatwaves of increasing intensity and frequency into the future. Given the central role that temperature plays in regulating seed germination, understanding the impacts of such heatwaves on key germination attributes is vital to identify potential impacts on plant community structure. Aims To determine the impacts of increased heatwave intensity and frequency treatments on seed germination within and across 15 native species of the CPW. We also examined the influence of interspecific variation in life-history traits on germination responses. Methods Seeds were exposed to seven heatwave treatments of increasing intensity and frequency. Life-history trait data were also collected for each species’ dormancy type, fire response traits, life form and seed mass. Key results There was evidence within the study species of a significant effect of heatwave treatment. Germination duration was prolonged for the two most extreme simulated heatwave events. Life-history traits could not explain germination responses after heatwave treatments, however, larger seeded species had quicker germination onset and shorter periods of germination over small-seeded species; and trees had lower proportions of germination than any other life form. Conclusions Increases in heatwave intensity and frequency have an impact on seed germination responses in native species of the CPW. Life-history traits could not explain germination responses across species along the heatwave gradient. Implications Projected increases in heatwave intensity and frequency are likely to impact seed germination, and thus community composition, in species from the CPW.

Seed dormancy alleviation by warm stratification progressively widens the germination window in Mediterranean climate Rutaceae

Context In ecosystems where rainfall is episodic or highly seasonal, plant recruitment from a soil-stored seed bank occurs during periods of elevated soil moisture conducive to germination and seedling establishment. The release of seed dormancy in response to environmental conditions has significant consequences for the temperature window over which germination occurs, and as such the timing of germination can vary between years. Aims We aimed to understand in seeds of two species of Rutaceae, Diplolaena dampieri and Rhadinothamnus anceps, how dormancy loss and germination timing is influenced by warm stratification. Methods We tested the germination response to temperatures between 5 and 30°C following increasing durations (1–12 and 4–12 weeks) of warm stratification at 20, 25, or 30°C. Key results Warm stratification for 1–8 weeks at 30°C progressively alleviated seed dormancy in D. dampieri and R. anceps, increasing germination proportion from ~0.1 to ~0.5 in both species. Stratification duration was optimal at 30°C for between 4 and 8 weeks depending on species. Warm stratification was not affected by water stress down to −0.8 Mpa. Application of aerosol smoke did not significantly improve germination, and heat treatments had a negative effect on final germination proportion. Conclusions As dormancy was progressively alleviated, the range of temperatures that support germination increased for D. dampieri and decreased for R. anceps, allowing for confirmation of type 1 and type 2 non-deep physiological dormancy (PD), respectively. Implications Arising from this conclusion, we suggest that in Mediterranean climates, type 1 and 2 PD dictate risk-taking and risk-avoiding ecological strategies by shifting the thermal requirements for germination towards that characteristic of the early- or mid-germination season. Classification of non-deep PD may offer a structured approach to predict how temperature requirements shift during dormancy loss, which will provide insight into seed germination response to year-to-year variation in seasonal environmental conditions.

Genome-Wide Identification and Expression Profile of the HD-Zip Transcription Factor Family Associated with Seed Germination and Abiotic Stress Response in Miscanthus sinensis.

Miscanthus sinensis is an ornamental grass, non-food bioenergy crop, and forage with high feeding value. It can adapt to many kinds of soil conditions due to its high level of resistance to various abiotic stresses. However, a low level of seed germination restricts the utilization and application of M. sinensis. It is reported that the Homeodomain-leucine zipper (HD-Zip) gene family participates in plant growth and development and ability to cope with outside environment stresses, which may potentially regulate seed germination and stress resistance in M. sinensis. In this study, a complete overview of M. sinensis HD-Zip genes was conducted, including gene structure, conserved motifs, chromosomal distribution, and gene duplication patterns. A total of 169 members were identified, and the HD-Zip proteins were divided into four subgroups. Inter-chromosomal evolutionary analysis revealed that four pairs of tandem duplicate genes and 72 segmental duplications were detected, suggesting the possible role of gene replication events in the amplification of the M. sinensis HD-Zip gene family. There was an uneven distribution of HD-Zip genes on 19 chromosomes of M. sinensis. Also, evolutionary analysis showed that M. sinensis HD-Zip gene family members had more collinearity with monocotyledons and less with dicotyledons. The gene structure analysis showed that there were 93.5% of proteins with motif 1 and motif 4, while motif 10 was only found in group IV. Based on the cis-elements analysis, it appeared that most of the genes were related to plant growth and development, various hormones, and abiotic stress. Furthermore, qRT-PCR analysis showed that Misin06G303300.1 was significantly expressed in seed germination and Misin05G030000.1 and Misin06G303300.1 were highly expressed under chromium, salt, and drought stress. Results in this study will provide a basis for further exploring the potential role of HD-Zip genes in stress responses and genetic improvement of M. sinensis seed germination.

Seed germination responses to temperature and water availability in weedy rice.

Weedy rice is one of the main agricultural weeds infesting transplanted and direct-seeded rice cultures across Japan. However, the environmental factors that facilitate its proliferation are largely unknown. This study investigated the effects of temperature and water availability on seed germination of Japanese weedy and cultivated rice strains differing in degree of seed dormancy and after-ripening. This information could help predict weedy rice infestation and design efficacious control measures. The germination responses of weedy rice to temperature and water availability varied among strains and after-ripening duration. The germination rate varied inversely with the degree of dormancy, increased with water availability, and fluctuated between low and high temperatures. The shallow-dormant tropical japonica-derived strawhull weedy rice (TRJ) germinated at 10°C unlike the temperate japonica-derived weedy rice strains, namely, the intermediate-dormant blackhull (BH) and the deep-dormant strawhull (SH). Seeds of all plant strains germinated below the permanent wilting point of clay loam soil, but the germination rates were higher for TRJ and BH than for cultivated rice. SH germination was more synchronous with rice than the other weedy rice strains. This study has confirmed the overall robustness of germination cold tolerance at 10°C in TRJ, high germinability at low-water availability and high temperature in TRJ and BH, and relatively more synchronous germination between SH and cultivated rice in seeds grown in different years. These observed characteristics are considered advantageous to the coexistence of weedy rice with cultivated rice. © 2022 Society of Chemical Industry.

Integrated metabolomic and transcriptomic strategies to reveal adaptive mechanisms in castor plant during germination stage under alkali stress

Castor (Ricinus communis L.) is an important oilseed crop worldwide, and is also considered as one of the most promising plants for alkali-affected soil amelioration in the northeast of China. Seed germination plays a vital role in seedling establishment, and is always sensitive to alkali stress. However, little is known about the dynamic changes and regulatory mechanisms of gene expression and metabolic processes of this species during germination stage under alkali stress. In the present study, physiological, metabolome and transcriptome responses in germinating seeds of castor were investigated when exposed to 0, 50, 100 and 150 mM alkalinity (NaHCO3). The results showed that alkali stress sharply decreased germination percentage. The Na+ content increased but K+ content decreased under alkalinity. In addition, the malondialdehyde and proline contents increased with the increasing alkalinities. Meanwhile, 50, 100 and 150 mM alkalinity induced 31, 48 and 113 differential metabolites, respectively. Furthermore, transcriptome profiling result showed that there were 138, 845 and 694 differentially expressed genes in the seeds under different concentrations alkali stresses, respectively. The integrating analysis of metabolite and gene expression changes indicating that germination response of castor seeds under alkali stress was closely related to amino acid metabolism, carbohydrate metabolism, lipid metabolism and nucleotide metabolism. The adaptive strategies of castor seeds under alkaline stress were promoting amino acid metabolism and tricarboxylic acid cycle to regulate osmotic balance and ROS level; as well as providing materials and energy for secondary metabolism, although alkali stress affected the membrane fluidity due to the reduction of unsaturated fatty acid content. Moreover, castor seeds increased metabolites on nucleotide biosynthesis to ensure their germination process under alkaline salt stress. The present research provides a deeper insight into overall understanding alkali-tolerant mechanisms of oil crops during germination in a holistic level.

Modeling seed germination response of maize with different shapes and sizes using halotime and halothermal time concept

Modeling seed germination response of maize with different shapes and sizes using halotime and halothermal time concept

Seed germination and salinity tolerance of habitat-indifferent halophytes as associated with geographical distribution

Germination response to environmental factors often depends on the seed source. Habitat-indifferent halophytes that can grow well under both saline (SH) and non-saline habitats (NSH) offer a good opportunity to understand salinity tolerance during the germination stage under varying environmental factors, such as temperature and light. This study compared seed germination responses among different populations of two common habitatindifferent halophytes (Salsola drummondii and Suaeda vermiculata) from subtropical hyperarid deserts of the United Arab Emirates (UAE) and semiarid warm sub-tropical areas in Pakistan. This study highlights many similarities and differences in the seed germination and recovery responses of habitat-indifferent halophytes occurring in two contrasting climatic regions. The germination window of UAE seeds was wider, i. e., they germinated at higher rates under all temperatures in both light and darkness. This indicates that seeds of UAE populations can germinate at any time of the year, if conditions are optimal, and faciltate a faster seedling establishment under fluctuating harsh environmental conditions compared to populations from semiarid warm sub-tropical areas in Pakistan. The eco-physiological significance of the responses is also discussed.

Influence of Lighting and Laser Irradiation on the Germination of Caper Seeds

Caper seeds present difficulties in their germination, which has been studied by several research teams. It is known that light can release dormancy in some seeds, but its effect on caper seed germination has not yet been deeply studied. The main aim of this study was to analyze the response of caper seeds germination to light exposure. The study analyzed the germination response of seeds to lighting with different wavelengths (white, red, blue, red + blue and darkness) and to the He-Ne laser light, using both dry seeds and seeds that had been previously soaked in water. Overall, it could be stated that caper seeds are insensitive to light during the germination process. Thus, germination could be carried out in lightness or darkness, so germination in nurseries could be carried out in the darkness, leading to substantial energy savings. Caper seed irradiation with a He-Ne laser during short exposure times improved the germination percentage for the seeds previously soaked in water, germinating all viable seeds. However, applying a solution of gibberellic acid was always required in all the cases studied.

Seed germination responses of broomrape species (Phelipanche ramosa and Phelipanche aegyptiaca) to various sanitation chemicals

AbstractBranched broomrape, an obligate root parasitic weed, has recently re-emerged in tomato fields in several California counties. California produces more tomato than any other state, and the outbreak of this noxious weed could potentially wreak havoc on the industry’s economy. Preventive measures must be taken to stop or reduce the spread of branched broomrape seeds to other areas. Branched broomrape can produce thousands of tiny seeds, which can easily spread with farm machinery over short and long distances. To prevent branched broomrape seed dispersal, sanitation and disinfection of farm equipment are necessary before entering a new farm. We tested the effectiveness of various ammonium compounds, including didecyl dimethyl ammonium chloride (DDAC), alkyl dimethyl benzyl ammonium chloride (ADBC), didecyl dimethyl ammonium bromide (DDAB), ammonium bromide (AB), and ammonium chloride (AC) on prevention of branched broomrape seed germination. Dose-response analysis showed that three chemical products, ADBC, DDAB, and DDAC, could completely inhibit branched broomrape seeds (potentially making them nonviable) at 1%, 1%, and 10% wt/vol concentrations, respectively. These three compounds were further tested in an exposure duration experiment that additionally included Egyptian broomrape. Only 10 min of exposure to these compounds was needed to prevent germination of both branched and Egyptian broomrape seeds at 1% (ADBC, DDAB) and 10% wt/vol (DDAC). Lower concentrations can provide similar inhibition effects when combined with longer exposure times. Egyptian broomrape seeds were more sensitive than branched broomrape seeds. Findings suggest that quaternary ammonium compounds could be used as potential sanitation agents to disinfect agriculture machinery from branched and Egyptian broomrape seeds.

Dormancy and germination response of Galbanum seeds (Ferula gummosa) under different hormonal pre-treatments and cold stratification

Dormancy and germination response of Galbanum seeds (Ferula gummosa) under different hormonal pre-treatments and cold stratification

Within-species variation of seed traits of dune engineering species across a European climatic gradient.

Within-species variation is a key component of biodiversity and linking it to climatic gradients may significantly improve our understanding of ecological processes. High variability can be expected in plant traits, but it is unclear to which extent it varies across populations under different climatic conditions. Here, we investigated seed trait variability and its environmental dependency across a latitudinal gradient of two widely distributed dune-engineering species (Thinopyrum junceum and Calamagrostis arenaria). Seed germination responses against temperature and seed mass were compared within and among six populations exposed to a gradient of temperature and precipitation regimes (Spiekeroog, DE; Bordeaux, FR; Valencia, ES; Cagliari, IT, Rome, IT; Venice, IT). Seed germination showed opposite trends in response to temperature experienced during emergence in both species: with some expectation, in populations exposed to severe winters, seed germination was warm-cued, whereas in populations from warm sites with dry summer, seed germination was cold-cued. In C. arenaria, variability in seed germination responses disappeared once the seed coat was incised. Seed mass from sites with low precipitation was smaller than that from sites with higher precipitation and was better explained by rainfall continentality than by aridity in summer. Within-population variability in seed germination accounted for 5 to 54%, while for seed mass it was lower than 40%. Seed trait variability can be considerable both within- and among-populations even at broad spatial scale. The variability may be hardly predictable since it only partially correlated with the analyzed climatic variables, and with expectation based on the climatic features of the seed site of origin. Considering seed traits variability in the analysis of ecological processes at both within- and among-population levels may help elucidate unclear patterns of species dynamics, thereby contributing to plan adequate measures to counteract biodiversity loss.