Biological scarification of Erythrina crista-galli: germination responses, performance costs, and implications for riparian forest restoration.

Lucerne (Medicago sativa), a major perennial pasture legume, belongs to a species complex that includes several subspecies with wild and cultivated populations. Stand establishment may be compromised by poor germination. Seed scarification, deterioration and temperature have an impact on germination. The objective of this study was to analyse the genetic diversity of lucerne germination in response to three factors: (1) temperature, with seven constant temperatures ranging from 5 to 40°C, was tested on 38 accessions, (2) seed scarification was tested on the same accessions at 5 and 22°C, (3) seed deterioration was tested on two accessions and two seed lots at the seven temperatures. The germination dynamics of seed lots over time was modelled and three parameters were analysed: germinability (germination capacity), maximum germination rate (maximum% of seeds germinating per time unit), and lag time before the first seed germinates. Seed scarification enhanced germinability at both temperatures and its effect was much higher on falcata and wild sativa accessions. Incomplete loss of the hardseededness trait during domestication and selection is hypothesised, indicating that the introduction of wild material in breeding programmes should be followed by the selection for germinability without scarification. Seed lots with altered germinability had low germination at extreme temperatures, both cold and hot, suggesting that mild temperatures are required to promote germination of damaged seed lots. A large genetic diversity was revealed for germination (both capacity and rate) in response to temperature. All accessions had an optimal germination at 15 or 22°C and a poor germination at 40°C. The sativa varieties and landraces had a high germination from 5 to 34°C while the germination of falcata and the wild sativa accessions were weakened at 5 or 34°C, respectively. These differences are interpreted in terms of adaptation to the climate of their geographical origin regions in order to escape frost or heat/drought risks. These new findings give insights on adaptation and domestication of lucerne in its wide geographic area. They suggest further improvement of germination is needed, especially when introducing wild material in breeding pools to remove scarification requirements and to limit differences in response to temperature.

Background and Aim: Osyris lanceolata (Hochst. & Steud) is an evergreen shrub or small tree of the Santalaceae family, valued for its fragrant heartwood and essential oils used in perfumery and traditional medicine. However, its propagation is limited due to poor seed germination and challenges in vegetative methods. This study aimed to evaluate the effects of different pre-sowing seed treatments, germination substrates, and fruit maturity stages on the germination and early growth performance of O. lanceolata from naturally growing populations in Tehri Garhwal, Uttarakhand. Study Design: The study was conducted through two separate experimental setups using a completely randomized design (CRD) to evaluate the effects of fruit maturity stages, germination substrates, and various pre-sowing treatments on the seed germination and early growth of Osyris lanceolata. In the first experiment, conducted at the Forest Tree Seed Laboratory, ICFRE-FRI, seeds collected at three different maturity stages (green, light orange, and bright red) were subjected to mechanical scarification followed by soaking in boiling water for 12 hours. The seeds were then sown on two different substrates: sand and vermiculite, incubated under controlled laboratory conditions at 25 ± 1 °C, >90% relative humidity, and a 24-hour photoperiod. Each treatment included four replicates of 20 seeds.The second experiment was carried out in the nursery of Jakh-Koti Botanical Garden, Tehri, Uttarakhand where seeds were subjected to eight different pre-sowing treatments: T1 – Control, T2 – Mechanical scarification + 500 ppm GA₃ (24 h), T3 – Mechanical scarification + 1000 ppm GA₃ (24 h), T4 – 30% Hydrogen peroxide (24 h), T5 – 0.2% Potassium nitrate (24 h), T6 – 2% Thiourea (24 h), T7 – 20% Sulfuric acid (1 min), and T8 – Hot water (1 min). Each treatment included four replicates of 80 seeds. Across both experiments, germination performance was evaluated using key parameters: Germination Percentage (GP), Mean Germination Time (MGT), Germination Value (GV), Peak Value (PV), Germination Index (GI), Seedling Vigor Index (SVI), Sturdiness Quotient (SQ), Vigor Index (VI) and Quality Index (QI). Results: In the laboratory experiment, substrate and fruit maturity stage had a significant impact on germination parameters. Seeds sown on vermiculite showed a significantly higher germination percentage (46.66 ± 7.63%) compared to those sown on sand (33.33 ± 7.63%). Pretreatment improved all germination parameters, while fruit maturity stage played a critical role. Seeds collected at the bright red maturity stage (moisture content: 52.62 ± 2.51%) recorded the highest germination percentage and germination value, along with a low mean germination time (MGT), indicating their physiological readiness for germination. In the nursery experiment, the highest germination percentage (66.66 ± 8.32%) was observed in T3 – Mechanical scarification followed by soaking in 1000 ppm GA₃ for 24 hours, which was significantly superior to all other treatments. This was followed by T2 (Mechanical scarification + 500 ppm GA₃; 49.33 ± 4.61%) and T7 (20% Sulphuric acid for 1 min; 41.33 ± 2.30%). The lowest germination percentages were recorded in T4 (30% Hydrogen peroxide; 18.66 ± 2.30%), T8 (Hot water; 18.66 ± 6.11%), and the untreated control T1 (13.33 ± 2.30%), with significant differences among them. Among all treatments, T3 proved to be the most effective for enhancing seed germination. Conclusion: The study highlights effective strategies for improving the germination and early growth of Osyris lanceolata. Vermiculite was identified as the optimal germination medium, while seeds collected at the bright red maturity stage (~52% moisture content) exhibited the highest germination performance, including superior germination percentage (GP), germination value (GV), and reduced mean germination time (MGT). Among pre-sowing treatments, mechanical scarification followed by soaking in 1000 ppm GA₃ for 24 hours (T3) resulted in the highest germination percentage and significantly enhanced seedling vigor. These findings provide valuable guidance for optimizing seed propagation and support the domestication and conservation of O. lanceolata.

Illinois bundleflower [ Desmanthus illinoensis (Michx.) MacMill. ex B.L. Rob. & Fernald] and showy ticktrefoil [ Desmodium canadense (L.) DC.] are legumes native to North America used during meadow restoration efforts. However, insufficient or slow germination or reduced emergence may result attributable to seedcoat-mediated reductions in permeability to water. The objective of this research was to determine the effectiveness of a single-speed electric scarifier lined with 40-grit sandpaper for increasing germination and seedling growth of two native legumes. Seeds of Illinois bundleflower and showy ticktrefoil were mechanically scarified for 3, 6, or 12 s before they were subjected to germination and vigor testing. After scarification, final germination percentage (FGP), germination rate, and uniformity at multiple temperatures (15, 20, and/or 20 to 30 °C) were improved for Illinois bundleflower. However, FGP decreased for showy ticktrefoil, whereas germination rate and uniformity increased. For both species, there was a decline in FGP with longer scarification durations. Illinois bundleflower seed subjected to scarification and accelerated aging (AA) had higher FGP than non-scarified seed subjected to AA (59% and 6%, respectively), whereas both scarified and non-scarified seed of showy ticktrefoil subjected to AA had low FGP (11% and 18%, respectively). Mechanical scarification increased electrical conductivity (EC) of leachates for both species, but scarified showy ticktrefoil seed subjected to AA resulted in the highest EC compared with all other treatments, indicating a reduction of vigor. Evaluation of a seedling grow-out test 3 weeks after sowing confirmed that emergence was enhanced after 3 s of mechanical scarification of Illinois bundleflower seed but that scarification of showy ticktrefoil seed decreased emergence and increased the number of abnormal seedlings. Mechanical scarification resulted in peripheral damage and seed tissue obliteration of both species as indicated by viewing with a stereomicroscope. We conclude that scarifier limitations caused excessive physical damage of showy ticktrefoil. For Illinois bundleflower, however, mechanical scarification using an electric scarifier increased emergence from 18% (non-scarified seed) to 77% after 3 s of scarification and FGP from 32% (non-scarified seed) to 87% after 3 s of scarification. Compared with responses from non-scarified Illinois bundleflower seeds, scarification treatment also resulted in 24% faster germination and 37% more uniformity.

Seeds with combinational dormancy have both physical (PY) and physiological (PD) dormancy. Chemical scarification and cold-moist stratification alleviate PY and PD, respectively. Therefore, we tested the effectiveness of mechanical scarification and cold-moist stratification for the release of combinational dormancy in Rhus javanica seeds to minimize the possibility of any internal damage and determine the optimal germination conditions. Mechanical scarification by a brushing machine and cold-moist stratification for 12 weeks weakened the pericarp and improved water absorption and percent germination. Prolonging mechanical scarification for up to 20 min further improved water absorption and percent germination; however, there was no significant difference in germination after 20 min (64.9%) and 40 min (63.1%) of mechanical scarification. The removal of blister-like structures in nontreated seeds by mechanical scarification enhanced water absorption. Further, cracks between the two inner pericarp cell-layers improved water absorption. Combined mechanical scarification (20 min) and cold-moist stratification (12 weeks) effectively broke combinational dormancy of R. javanica seeds and, therefore, comprise a suitable treatment for seed germination.

Germination and growth responses ofScirpus robustus Pursh were determined for a variety of environmental conditions. A period of after-repening was required for seed germination; the most effective pretreatment was chilling at 2 C. Alternate freezing and thawing, freezing, and warm dry storage resulted in lower germination. Scarification was effective in increasing seed germination. Low concentrations of salt depressed germination and growth. A definite light requirement was found, but photoperiod length had no effect on germination responses. Alternating temperatures promoted germination; the best overall response occurred with 35 C day/25 C night. Presence ofS. robustus within the marsh community is discussed in relation to germination and seedling establishment characteristics of the species.

Canola is seeded when ambient temperatures are below the optimum. Therefore, we wished to determine whether certified seedlots displayed variation in low temperature germination potential and, thereafter, to study the effects of low temperature during germination and early seedling development. Canola (Brassiea napus L. cv. Westar) seed was tested for germination potential at 22, 10, 6, and 2 °C. Two seedlots, designated L and H, which represented the extremes in germination potential at 10 °C, were chosen for further study. Under the optimal conditions of 22 °C the two seedlots exhibited similar germination rates and early seedling growth. At 10 °C, L reached 95% germination within 8 d and displayed rapid seedling growth. This was associated with high isocitrate lyase activities and rapid mobilization of total lipid and protein reserves. Seedlot H, at 10 °C, did not reach a high percentage of germination until Day 12, and seedling growth was slow relative to that of L. Seedlot H had more gradual increases in isocitrate lyase activity, mobidization of storage lipid, and protein mobilization at 10 °C. Both seedlots germinated poorly at 6 and 2 °C. At 6 °C, L displayed higher isocitrate lyase activity and higher rates of lipid and protein mobilization than H. From these studies we have determined that low temperature has a deleterious effect on the germination of canola and this may be reflected in a loss or a delay of coordination in the mobilization of reserves. In addition, differences within the Westar cultivar exist with respect to germination under low temperature.

Seed dormancy is a trait that has evolved to maximize germination when environmental conditions are optimal for successful recruitment of new individuals into a population. Physical dormancy is one such trait common in legumes and release from this condition is often associated with disturbance events, such as fire. Changes to the specific conditions (e.g., climate, fire regimes) that release seeds from dormancy can have negative effects on populations, especially of rare species. Therefore, understanding the species-specific requirements needed to release seeds from dormancy and induce germination provides insight into ecological processes, effects of changing environmental conditions, and potential conservation actions. Amorpha georgiana (Fabaceae) is a rare subshrub with indehiscent fruits (pods) found in fire-maintained longleaf pine habitats in the southeastern United States. The germination ecology of this species is largely unknown. The goals of this study were to determine the presence of physically dormant seed in A. georgiana and then, through a series of laboratory-based experiments, resolve the fire related factors that effectively overcome dormancy and promote germination. The seeds of A. georgiana exhibit physical dormancy and show significantly higher germination after brief exposure to hot water (94 °C) compared to all other temperatures and treatments assessed. Regardless of treatment, seeds have low germination when retained in their pods, but the pod is not the cause of physical dormancy. We found enclosure within an indehiscent pod and exposure to pyrogenic temperatures (> 80 °C) both affect dormancy release and germination of A. georgiana. The 3.5-fold increase in germination at pyrogenic temperatures suggests the response is highly fire-adapted and fits the definition of obligate pyrogenic dormancy release. While season of fire exposure was not significant in our study, we did find consistent negative effects on the germination response. Our results suggest pulses of heat from periodic growing season fires are likely necessary to promote recruitment and maintain populations of this rare species.

A series of experiments was performed to examine the germination responses of Baptisia australis (L.) R. Br. seeds. Germination tests were conducted at 23 °C and numbers of germinated seed were counted daily for 21 days. Seeds were separated into two size fractions using standard sieves. Seeds in the large-seeded fraction were heavier than those in the small-seeded fraction, but seed size/weight did not affect the germination percentage at 21 days (G21), the number of days to 50% of final germination (T50), or the number of days between 10% and 90% germination (T90 – T10). Seeds were classified into two groups based on testa color. Light-brown seeds (17% of total) were heavier and had lower G21 and higher T50 and T90 – T10 values than medium- to dark-brown seeds (83% of total). Seeds scarified mechanically germinated nearly 100% and had lower T50 and T90 – T10 values than untreated seeds. Untreated seeds had a higher T50 value than seeds soaked overnight in 20°C water, but the G21 and T90-T10 values were similar for the two treatments. Mechanical scarification followed by overnight soaking in 20 °C water yielded a G21 value of only 12%, and the low germination percentage was attributed to imbibition damage. When seeds were scarified in concentrated H2SO4 for 0, 1, 5, 20, 40, or 80 min, G21 values increased quadratically while T50 and T90 – T10 values decreased quadratically as the immersion time increased. To test the effects of moist heat on germination responses, seeds were immersed for 0, 0.5, 1, 2, 4, or 8 minutes in 85 °C water. G21 values increased linearly as the immersion period increased from 0 to 2 min but remained similar when the immersion time exceeded 2 min. The duration of immersion in hot water did not affect the T50 values whereas T90 – T10 values decreased linearly as the immersion period increased. We conclude that physical dormancy is responsible for temporal variation in germination of B. australis seeds. Scarifying seed in concentrated H2SO4 for 20 to 80 minutes may be the most practical means of treating bulk lots of B. australis seeds to obtain rapid and uniform (≥85%) germination.

The seeds of Elaeocarpus serratus, a tropical underutilized fruit tree are characterized by hard seed coat and consequent poor water uptake and low germination. To improve the regeneration through seeds, various parameters such as viability of seeds, water uptake, and effect of seed mass on germination and pretreatments were performed using a completely randomized design (CRD). Tetrazolium (TZ) test was conducted using fresh, mature seeds revealed 50 ± 2.56% mean viability. Seeds of different weight classes showed similar pattern of water uptake and the saturation level was achieved at 60 hrs of soaking. Seeds belong to weight class 2.6-3.5g were germinated (12.5 ± 1.26%) with 175 ± 1.75 days (d) of mean time taken for germination (MTG). Germination capacity of seeds varied significantly among different populations and Varkala population gave 12.5 ± 1.1% germination with 174.6 ± 2.5 d MTG. Among various seed treatments, mechanical scarification was superior in germination and significant reduction in MTG (p ≤ 0.05). The mechanical scarification by complete removal of seed coat resulted in 49.2 ± 1.52% germination within a short period of time (9.52 ± 0.89 d MTG). However, the complete removal of seed coat without damaging to embryo is a difficult task. An alternate treatment (Mechanical scarification II) by making cracks on nut faces vertically followed by soaking in distilled water for 24 hrs gave 48.4 ± 1.73% germination with significantly reduced MTG (12.14 ± 0.56 d) over unsoaked, untreated control (6.5 ± 1.84% germination and 197.18 ± 1.79 d MTG; p ≤ 0.05). This treatment (Mechanical scarification II) is therefore recommended for E. serratus seeds as it can adopt easily and can achieve 7 fold increases in germination over control. The recorded germination through mechanical scarification is in tune with realized viability percentage of the seeds.

Caesalpinia bonduc (L.) Roxb. is a medicinal plant belonging to the family Caesalpiniaceae was used for the present study. It is a prickly shrub widely distributed all over the world. Keeping the economic and social medicinal uses of C. bonduc seeds are being used widely in Folk, Ayurvedha, Siddha, Unani medicines to treat skin disease, eyesores, cancer, asthma, tuberculorosis, fever, toothaches etc. The aim of this study is to determine the requirements for breaking seed dormancy and germination of C. bonduc. The germination is prevented due to hard seed coat. C. bonduc seeds were experimented with various physical and chemical treatments to break the dormancy. The seeds were subjected to various treatments like mechanical scarification, dry heat method, light, hot water, acid scarification, inorganic compounds, plant growth regulators etc. The seeds treatment with mechanical scarification at 50, 40 and 30 seconds showed 100%, 80% and 10% of germination, whereas no changes was observed in dry heat. White light treatment showed 100% germination at 48 hrs, whereas darkness and red light showed least germination of about 10%. The hot-water treatment showed 100% germination. In chemical treatments, concentrated sulphuric acid scarification showed highest germination percentage, whereas lowest germination was found in nitric acid. Among the plant growth regulators, Gibberellic acid showed 100% germination whereas 2-isopentyl adenine showed least germination of 10% at 50 ppm. Results of this study prove that mechanical scarification was the most effective treatment to overcome dormancy of seeds in C. bonduc.

Fire ephemerals are short-lived plants that primarily germinate after fire. Fresh and laboratory-stored seeds are difficult to germinateex situ, even in response to fire-related cues such as heat and smoke. Seeds of eight Australian fire ephemeral species were buried in unburnt and recently burnt sites of natural bushland during autumn. Seeds were exhumed after 6 and 12 months and incubated in water and smoke water, either with or without a heat treatment at 70°C for 1 h. Generally, germination did not increase after 6 months of burial, but after 12 months of burial germination was enhanced in seven of the eight species.Actinotus leucocephalusproduced higher germination following 12 months of burial without any further treatment, and smoke water and heat further improved germination. The fourGyrostemonaceaespecies,Codonocarpus cotinifolius,Gyrostemon racemiger,Gyrostemon ramulosusandTersonia cyathiflora, only germinated in the presence of smoke water, and their germination was enhanced by burial. Burial improved germination in response to a heat treatment inGrevillea scapigeraandAlyogyne huegeliiseeds, but did not enhanceAlyogyne hakeifoliagermination. During concurrent dry laboratory storage of seeds at 15°C, onlyActinotus leucocephalusproduced increased germination in response to smoke water and heat over time. In summary, soil burial can alter the dormancy status of a number of Australian fire ephemeral seeds, rendering them more responsive to germination cues such as smoke water and heat. The requirement for a period of burial before seeds become responsive to smoke and/or heat would ensure that seeds persist in the soil until a subsequent fire, when there is an increase in nutrients available for growth and reduced competition from other plants.

Poor germination and the length of time required for the growth of seedlings appropriate for planting in the farm affect the cultivation of medicinal plants such as yarrow (Achillea millefolium L). This study investigated the abilities of different concentrations of gibberellic acid (GA3) and potassium nitrate (KNO3), mechanical scarification, and hydropriming to improve seed germination and dormancy release in yarrow. Seeds were germinated on filter paper in Petri dishes and supplemented with 0, 100, 200, 400, or 800 mg L−1 GA3; 0%, 0.2%, 0.5%, 1.0%, or 2.0% w/v KNO3; 0, 24, or 48 h of hydropriming; and mechanical scarification. Seed priming with GA3 (800 mg L−1) or 1% KNO3 at 48 h priming time improved the mean daily germination. Application of 1% KNO3 had the highest seed germination around 91%. Use of 0.5% KNO3 in 48 h priming time increased seedling length approximately 52% compared with unprimed seeds. Combinations of scarification and hydropriming increased germination. The use of priming with KNO3 at 48 h priming time was effective in improving seed germination.

Environmental factors affect the germination process, like the presence of seed coat and the quality of light; these informations are still scarce for many native species from Brazil, especially for Senna cana, which there are no adequate standards and methodologies to be used in germination tests. The aim of this research was to recommend adequate pre-germinative treatment(s) to overcome seed dormancy, and determine the degree of influence of different light regimes in seed germination of S. cana. Two experiments were carried out: T1-evaluation of different methods of dormancy overcoming (intact seeds (control), T2-imbibition of the intact seeds for 24 hours (in distilled water), T3-scarified seeds with sandpaper n° 100 in the hilum opposite region, T4-scarified seeds with sandpaper n° 100 in the region the hilo opposite region and imbibition in water (in distilled water) for 24 hours; T5-imbibition in water at 80°C); 2-Influence of light quality on seed germination and vigor (white light, red light, far red light and absence of light). The evaluated parameters were: first germination count, percentage of germination, IVG (Germination speed index), MGT (Mean germination time). Treatments were compared by Tukey at 5% probability. The best method for overcoming seed dormancy was mechanical scarification with sandpaper nº 100. The germination of the seeds of S. cana can be classified as indifferent to the luminosity, despite germinative response be greater under white and red light.

The Passifloraceae family is one of the most representative in tropical America, with food, pharmaceutical, and ornamental importance. This study evaluated seed morphometry and germination of eight accessions of four Passiflora edible species, P. edulis; P. ligularis; P. quadrangularis; and P. tripartita var. mollissima, by studying accessions conserved several years in the gene bank (−15 °C) and recently collected accessions. Four experimental phases were carried out as follows: (1) morphometric characterization of seeds with qualitative and quantitative variables; (2) evaluation of germination under two thermal regimes (20 °C/30 °C and 25 °C); (3) application of six pre-germination treatments to overcome dormancy; and (4) tetrazolium tests. In phase 1, P. quadrangularis stood out for its unique morphological characteristics according to multivariate analysis. In phase 2, the alternating thermal regime (20 °C/30 °C) promoted the highest germination. In phase 3, the germination response was specific to each species: mechanical scarification in P. edulis (85.7%), KNO3 (0.5%) in P. ligularis (35.7%), control in P. quadrangularis (71.1%), and gibberellic acid (GA3 400 ppm) in P. tripartita (71.4%). The tetrazolium phase 4 identified the viability status of the seeds. It is concluded that the differences in morphometry and germination reflect the intrinsic characteristics of each species, highlighting the importance of specific protocols for their germination. This study provides tools to optimize the conservation and regeneration of Passiflora spp. germplasm under ex situ conditions, as a genetic base to be utilized in the future.

Knowledge of the genetic variability of different species for conservation purposes and quality seedling production after longer storage time is important. The aim of the research paper was to examine the effect of longer seed storage periods (19–30 year) on seed viability, seed vigour and initial growth of seedlings from five provenances of Pterolobium stellatum (Forssk). Seeds collected from Dabena, Gambo, Agaro, Bishofitu, and Merti localities and stored for 19, 19, 21, 25, and 30 years, respectively used for the study. Different seed dormancy-breaking treatments such as; soaking in cold water for 48 h (CW-48); soaking in hot water for 10 min (HW-10); 20 min (HW-20) and mechanical scarification; i.e., nicking (NK) used for the germination of the seeds. A randomized complete block design was used for the experiment and the study undertaken in a greenhouse. For each treatment, four replications and for each replication, 50 seeds were used. One-way analysis of variance was used for germination index, early seedling growth and seed vigour index data. The results showed that for all the provenance seeds stored for different periods, NK treatment resulted relatively in a higher mean germination percentage and germination indices as compared to the other pre-treatments. The seed vigour index result showed significant differences among the different provenances (P < 0.001). Similarly, there were significant differences among the early growth of seedlings germinated from different provenance seeds (P < 0.001). The seeds collected from Merti provenance and stored for 30 years and Dabena provenance, stored for 19 years, have relatively resulted in higher mean germination index, seed vigour and seedling growth relative to the other studied provenance seeds. We observed that provenance had a more significant influence on germination, seed vigour and seedling growth than the seed storage period for the P. stellatum. Finally it is recommended that despite there is inter population variation, the seeds of P. stellatum can be stored for a longer time and application of nicking as a dormancy breaking treatment could enhance seed germination of the species.