Scarified Seeds Research Articles

Pelleting of Physical Dormancy Small-Seeded Species in Astragalus sikokianus Nakai

Astragalus sikokianus is a rare Japanese perennial of the seashore that was reported to be extinct in the wild. The small seed size and deep dormancy of A. sikokianus make it difficult for direct seeding restoration in aspects of seed handling, transport, planting, and seedling establishment. For the large-scale economic restoration of dormant small-seeded species, seed pelleting combined with the breaking of dormancy was studied. Physiological (prechilling and plant hormones) and physical (hot water, hydrochloric acid, and sulfuric acid) seed dormancy break treatments were evaluated. The dormant broken seeds were used for pelleting. The effects of the substrate, pellet sizes, and their interactions on germination were measured. The scarification of five rubs of seeds placed between sandpapers completely broke the physical dormancy of A. sikokianus. Seed coat impermeability inhibited germination. Pelleted seeds ranging from 2.0 to 4.0 mm in diameter showed more than 90% germination on filter paper. The germination of the pelleted seeds was measured in commercial, field, and sand soil conditions. The highest germination was shown in sand (70–74% GP), regardless of the pellet size, whereas unpelleted scarified seeds germinated only 48%. These results suggest that small-seeded species with physical dormancy can be used for seed-based restoration after seed pelleting.

Photoluminescent Sensor of Scarification Efficiency of Fodder Plants' Seeds.

Optoelectronic sensors open up new possibilities for predicting the yield for their possible correction, including increasing the seed germination of forage plants. The luminescent properties of unscarified and scarified seeds of various germination galega, clover and alfalfa are compared. The dependence of germination on the photoluminescence flux is approximated by linear equations with a determination coefficient R2 = 0.932-0.999. A technological process for analyzing the scarification quality of forage seed plants is proposed, including sample preparation, photoluminescence excitation and registration, amplification of the received electrical signal and determination of germination based on calibration equations. This is followed by a decision on sowing, or re-scarification. The scheme of the scarification quality control device has been developed for which the LED, as well as the radiation receiver and other elements, has been selected according to the energy efficiency criterion. Mechanical scarification of the forage plants' seed surfaces has a significant effect on their photoluminescent properties. The flux increases by 1.5-1.7 times for galega, 2.0-3.0 times for clover and 2.3-3.9 times for alfalfa. Linear approximation of the flux dependence on germination with a high coefficient of determination allows us to obtain reliable linear calibration equations. Preliminary mock-up laboratory tests allow us to talk about the developed method's effectiveness and device.

Использование гуминовых препаратов для выращивания посадочного материала древесных растений в аридном регионе

Abstract. The purpose is to study the effect of the organic preparation “Ekobiosfera” of various spectrum of action on morphophysiological processes during the germination of seeds of Pinus nigra subsp. pallasiana (Lamb.), Quercus robur L., Robinia pseudoacacia L., Calligonum aphyllum (Pall.). Research methodology. The experiments were carried out in laboratory conditions in three variants of applying the drug – 10, 15 and 20 ml/l of water, stratified and scarified seeds were soaked in a working solution for 12 hours to a day, their growth and development were observed in the laboratory in the plant rooms, and immediately before planting in the substrate (zonal lightchestnut soil + peat) conditions. The repetition of the experiment is three-fold, with control, 20 plants in each variant of the experiment. Results. In the course of research, the authors have established the necessity and expediency of using the drug “Ekobiosfera” as a biostimulator for the growth of phytomass and roots. The most optimal dosage for the growth and development of samples of woody species is 10 and 15 ml/l. With an increase or decrease in the dose, plants experienced wilting and inhibition of growth, a lower percentage of preservation. Also, the positive effect of LED lighting on seedlings of oak and Crimean pine was found. For robinia pseudoactation, the selection of the optimal dose of the drug and lighting is required, for the leafless juzgun, the drug is ineffective due to the inconsistency of soil and climatic conditions of cultivation, which requires further study. Thus, the positive effect of the organic preparation “Ekobiosfera” on the growth and development of coniferous and deciduous species for nursery breeding in the arid zone was noted. Scientific novelty. In the conditions of the arid region, the effect of the organic preparation “Ekobiosfera” on tree species was studied for the first time. Taking into account the reaction of the seeds of the studied plants, effective doses of introducing a growth stimulant have been developed, optimal lighting options for plants in the process of growing have been proposed.

Effects of natural long storage duration on seeds germinative response of Argyrolobium uniflorum (Decne.) Jaub. & Spach

Little is known about the effect of seed natural long storage on the germination capacity of vascular plant species particularly those used in restoration programs. In the current paper, we aimed to study the effect of different seed storage durations (from 3 months to 22 years) on the germination of Argyrolobium uniflorum (Decne.) Jaub. & Spach, herbaceous legume of high pastoral value indigenous to the Mediterranean Basin. In this paper, we found that the seeds scarification, hasten germination capacity of scarified seeds (SS) to almost 80%. The seed germination is maintained for 14 years at the level of 78 to 60% and then decreases.
 Also, other measured parameters of water content, electric conductivity, seedling lengths and MGT were also modified along seeds age. The duration of storage affects the germination performance of Argyrolobium uniflorum seeds which decreases after approximately one decade and half which give us an idea about the longevity of soil seeds bank of this species.

English

The effect of seed presowing treatment on Guibortia coleosperma and Amblygonocarpus andongensis was investigated. Seeds of both species were subjected to four experiments, containing 10 levels of presowing treatments: mechanical scarification, soaking in concentrated sulphuric acid (for 15, 30, 45 and 60 min), immersion in boiling water (for 1, 3 and 5 min), and soaking in boiling water (and cooling down for 24 h) and the control. The germination data were subjected to ANOVA followed by Tukey’s HSD test to separate significantly different treatment means. The highest germination in G. coleosperma was recorded: mechanical scarified seeds, those soaked in sulphuric acid (15, 30, 45 and 60 min), hot water (and cooling down for 24 h) and the control seeds. For A. andongensis, seeds treated with mechanical scarification, exposure to sulphuric acid (15, 30, 45 and 60 min) and boiling water (1 min) had higher percent germination than the controls. Key words: Germination mean time, germination percentage, pre-treatment, scarification.

Impact of post scarification storage period on seed germination and quality in soapnut (Sapinduas emarginatus)

Soapnut (Sapinduas emarginatus) is one of the most primitive precious useful plants since ancient times. This plant was domesticated due to its multifarious usefulness. The study was conducted in College of Forestry, Sirsi during 2019-20 to know the influence of post scarification storage treatments on seed germination and quality in Sapinduas emarginatus. The seeds were collected from in and around Sirsi area. In soap nut, the basic problem is poor seed germination due to hard seed coat. The seeds were treated with concentrated H2So4 for 12min and stored under laboratory condition for six months. At monthly interval, seed samples were drawn and evaluated for post scarification germination. The germination behaviour remarkably influenced due to scarification and without scarification during experimentation. The untreated seeds recorded the maximum germination (68%) compared to scarified seeds (22.85%).Speed of germination was highest in seed without scarification treatment (2.7) compared to scarified seeds. Mean daily germination was highest in without scarified seeds (1.04) and lowest in the scarified seeds (0.32). Peak value was maximum in without scarified seeds (0.50) compared to scarified seeds (0.22). Seedling vigour index was significantly highest in without scarified seeds (1290) compared to scarified seeds (455). In general, scarified seeds with conc. H2SO4 for 12 min affected seed germination due high conc. H2SO4 because of chemical residues remaining in seed that affects the embryo. As the advancement in storage period the seed coat may lose the integrity so, germination was improved in without scarified seeds.

Effects of Aeschynomene histrix Poir. seed treatment on germination

Description of the subject. Poor germination associated with physical dormancy was experienced in the legume Aeschynomene histrix Poir. seeds and can reduce the establishment and growth of this species. Objectives. To evaluate the effects of different pre-planting treatments, including digestion by Lagune cattle or other preplanting treatments on the germinability of A. histrix seeds. Method. The experiment was divided into three phases. Firstly, six Lagune cattle (three young bulls and three heifers) were fed individually with 1,000 seeds and these seeds were subsequently collected from faeces. Secondly, seed germination was compared among seeds defecated by cattle and seeds submitted to seven other pre-planting treatments: control (intact untreated seeds); seeds scarified using sandpaper; and seeds immersed in 80 °C-hot water for 2, 4, 6, 8, and 10 min. Thirdly, we also assessed the effect of crumbling cattle faeces on A. histrix germinability. Results. The results show that Lagune cattle can disperse seeds of A. histrix with maximum recovery on the second day after ingestion. Of the number of seeds fed 13.42% were recovered. The germination percentage was greatest for sandpaper scarified seeds (96%) and seeds pre-heated during 2 min (86%), but least for digested seeds (4.27%). Breaking-down the dung doubled seedling emergence from digested seeds. Conclusions. As it is desirable to break dormancy of A. histrix seeds, the use of mechanical scarification using sandpapering or hot water scarification 80 °C at 2 min may be more beneficial than cattle digestion.

Tratamentos térmicos para a superação de dormência em sementes de uma espécie arbórea brasileira

Enterolobium contortisiliquum (Vell.) Morong., known as tamboril, is a promising species in the recovery of degraded areas. However, it presents integument dormancy in its seeds and it is necessary to find methods to overcome it. Therefore, the present study aimed to evaluate the dry heat efficiency on the viability and vigor of E. contortisiliquum seeds, as an alternative and practical method for overcoming dormancy. The experiment was conducted in the house of vegetation of the Specialized Agricultural Sciences Academic Unit of the Federal University of Rio Grande do Norte. The fruits, obtained from different matrices located in the municipality of Macaíba-RN, were manually processed. The heat treatments obtained through a drying oven during five minutes used: 60 (T1), 80 (T2), and 105ºC (T3), the mechanical scarification (T0) of the seeds were used as a mediating treatment of the efficiency of the others. The emergency, first emergency count, and the emergency speed index were evaluated. Observing the results obtained, the best performance corresponded to the scarified seeds. The thermal treatments in dry heat were not efficient to overcome the dormancy of E. contortisiliquum seeds when compared with the traditional method of mechanical scarification. However, the methodology presents practicality in its execution which can be considered advantageous. Therefore, new studies with different combinations of time and temperature for the species are encouraged.

Dormancy breakage in Cercis chinensis seeds

The seeds of Cercis chinensis Bunge are important for reproduction and propagation, but strong dormancy controls their germination. To elucidate the causes of seed dormancy in C. chinensis, we investigated the permeability of the hard seed coat and the contribution of the endosperm to physical dormancy, and we examined the effect of extracts from the seed coat and endosperm. In addition, the effectiveness of scarification methods to break seed dormancy was compared. Cercis chinensis seeds exhibited physical and physiological dormancy. The hard seed coat played an important role in limiting water uptake, and the endosperm acted as a physical barrier that restricted embryo development in imbibed seeds. Germination percentage of Chinese cabbage [Brassica rapa subsp. chinensis (L.) Hanelt] seeds was reduced from 98% (control) to 28.3% and 56.7% with a seed-coat extract and an endosperm extract, respectively. This demonstrated that both the seed coat and endosperm contained endogenous inhibitors, but the seed-coat extract resulted in stronger inhibition. Mechanical scarification, thermal scarification, and chemical scarification had positive effects on C. chinensis seed germination. Soaking non-scarified seeds in gibberellic acid (GA3) solution did not promote germination; however, treatment with exogenous GA3 following scarification significantly improved germination. The optimal method for promoting C. chinensis seed germination was soaking scarified seeds in 500 mg·L−1 GA3 for 24 h followed by cold stratification at 5 °C for 2 mo.

Urbanization increases seed dispersal interaction diversity but decreases dispersal success in Toxicodendron radicans

Urbanization is increasing at a rapid pace with negative consequences for native biodiversity. While it is well-known that urbanization can lead to biotic homogenization (dominance of a few competitive species), effects of urbanization on ecological functions that rely on the frequency and efficiency of species interactions are less understood. Seed dispersal success depends on seed disperser feeding rate and diversity, which can affect the probability of fruit removal (i.e. seed dispersal) and germination rates. However, how these factors are affected by urbanization is unknown. In this study, we evaluate the effects of urbanization on factors that contribute to seed dispersal success (seed disperser diversity, frequency, probability of fruit removal and germination rate using Toxicodendron radicans and its seed disperser community as a model system. We found that urban sites had three times more disperser species and two times higher feeding rate compared to natural sites. However, the probability of individual fruit removal did not differ between natural and urban sites. Moreover, germination rate after dispersal was 20% lower in urban sites, leading to overall negative effects of urbanization on T. radicans seed dispersal. We propose differences in seed germination rate are driven by changes in seed disperser species composition and their differences in seed gut transit time. This in turn affects disperser species’ ability to successfully scarify seeds. Overall, our results highlight the need to evaluate urbanization’s effects on functional ecological processes, in addition to biotic homogenization effects, in order better understand and mitigate its negative impacts on biodiversity.

Purple prairie clover seed viability and germinability after passing through the digestive tracts of yearling steers

Endozoochory by cattle has been considered an important method for population self-regeneration; however, the effects of cattle digestive tracts on the viability and germinability of purple prairie clover (Dalea purpurea Vent.), a native North American species, remain understudied. The experiment was conducted at the Agriculture and Agri-Food Canada Swift Current Research and Development Centre in the semiarid prairie of western Canada. Purple prairie clover seeds extracted from cattle dung pats were tested for germination and compared with uningested and scarified seeds from the same paddock. The germination percentage (within 200 d) of the ingested seeds was 16.5% ± 0.8%, two times higher after passing through digestive tracts than uningested seeds (8.3% ± 1.2%), while 76.6% ± 1.5% of ingested seeds remained dormant. As many as 92.4% ± 0.9% of purple prairie clover seeds survived digestion due to their high hard seed rate (90.5% ± 1.0%), which was lower than the uningested seeds by 6.9%. Therefore, cattle dispersing purple prairie clover seeds with high viability and germinability is a low-cost method to increase and rejuvenate purple prairie clover for late-season grazing pastures.

Biometria, características físicas e absorção de água de sementes de <i>Enterolobium maximum</i> Ducke

Enterolobium maximum Ducke é uma Fabaceae (Mimosoideae), arbórea, de crescimento rápido, com comportamento excelente para reflorestamento e recomposição de áreas degradadas. Objetivou-se com este trabalho estudar a biometria, a absorção de água e a qualidade fisiológica de sementes de Enterolobium maximum. Foram analisados: comprimento, largura, espessura, massa de sementes, umidade inicial, massa de 1000 sementes e número de sementes por quilograma. O estudo da embebição foi realizado com sementes intactas e escarificadas, utilizando-se três métodos de embebição: água (sementes submersas em água destilada), sobre papel e rolo de papel. A determinação do volume das sementes durante a embebição foi feita utilizando-se rolo de papel e três tipos de água: comum (água de abastecimento), destilada e deionizada. As sementes apresentam homogeneidade nas características físicas e biométricas, com média de 19,0 mm de comprimento, 11,5 mm de largura, 6,43 mm espessura e 1,05 g de massa. Não há grande variação para o tamanho e peso das sementes. Sementes recém-colhidas apresentam dormência primária imposta pela impermeabilidade do tegumento. As sementes escarificadas e embebidas pelo método do rolo de papel apresentam germinação após 72 horas, caracterizada pela protrusão da raiz primária e identificação da fase III da germinação.

Influence of current and future climate on the seed germination of Cenostigma microphyllum (Mart. ex G. Don) E. Gagnon & G. P. Lewis

Seasonally tropical dry forests are among the most threatened environments by climate change. However, these forests, which are at risk of desertification, are still poorly studied and conserved. Seeds of several species endemic to the Caatinga, a Brazilian dry forest, are also understudied, mainly regarding their ability to cope with a hotter and drier climate predicted for the future. For the first time in seeds of Cenostigma microphyllum (Leguminosae), we aimed to study the presence of physical dormancy, temperature and salt tolerance to ascertain the effects of current and future climate on seed germination. Intact and scarified seeds were investigated by incubating at constant temperatures (15 to 40°C) or in NaCl solutions (−0.2 to −1.0 MPa) at 25 and 30°C. Thermal and osmotic thresholds, as well as thermal time and hydrotime constants, were calculated using linear regressions between the germination conditions and germination rate. To predict germination in the future, a heat sum model based on thermal time and hydrotime was applied to current and future climate scenarios. Seeds of C. microphyllum were permeable to water and did not have physical dormancy. The results indicated that increases in temperature are unlikely to affect germination, despite greater sensitivity to salinity presented at higher temperatures. In a future climate, the reduction in the number of weeks with at least 15 mm rainfall will affect the germination timing for the seeds. Thus, we can conclude that under the most pessimistic climate scenario predicted for the future, the seed germination of C. microphyllum may be restricted, likely leading to low seedling recruitment and establishment.

Conservation of Hibiscus acetosella germplasm by seed cryopreservation

Hibiscus acetosella (Malvaceae) is a shrub of great importance for landscaping, food and medicinal purposes. The objective of this study was to preserve H. acetosella germplasm by seed cryopreservation. Half of the seed batch was scarified and the other half was kept intact. Cryopreservation occurred by immersion in liquid nitrogen for 1 hour. Moisture content (MC%), germination percentage (G%), germination speed index (GSI), normal seedling formation (NS%), shoot length (SL), dry matter (DM), biometry and plant survival were evaluated after treatment. MC% ranged between 7.7% and 6.65% in intact and scarified seeds, respectively. Scarification raised G% and GSI compared to intact seeds. Intact and scarified seeds had 100% and 70% NS%, respectively, when not cryopreserved. Cryopreservation reduced NS% to 62% and 12.75%, respectively. The highest SL was observed in intact and non-cryopreserved seeds, with an average of 10.21 cm in height. However, the cryopreservation of intact seeds reduced SL by about 50%, and scarification led to a further reduction, either with (3.32 cm) or without (2.47 cm) cryopreservation. Seedlings from intact and non-cryopreserved seeds showed higher DM in relation to seedlings from cryopreserved seeds. The association of cryopreservation and scarification further reduced DM. The cryopreservation of intact seeds yielded 100% survival at the end of the acclimatization process. However, cryopreservation of scarified seeds reduced the survival percentage to 15%. Changes in color were observed for seeds scarified and subjected to cryopreservation. Thus, cryopreservation is considered an efficient technique for the conservation of intact H. acetosella seeds in the long term.

Ecological role of physical dormancy in seeds of Oxytropis racemosa in a semiarid sandland with unpredictable rainfall

Seed dormancy and the soil seed bank are crucial to plant regeneration strategy, especially in semiarid ecosystems with unpredictable precipitation. The aim of this study was to investigate how seed dormancy is controlled by environmental factors and how it is correlated with the soil seed bank and regeneration of the perennial legume Oxytropis racemosa, a dominant perennial herb in Mu Us Sandland of semiarid China. Germination and imbibition experiments on fresh intact and scarified seeds of O. racemosa were used to identify physical dormancy (PY) in seeds of this species. Soil seed bank dynamics, timing of seedling emergence and the fate of buried seeds in the natural habitat were investigated. PY was broken by mechanical scarification or wet heat/ice water cycles but not solely by dry heat or wet heat treatment. The soil seed bank exhibited seasonal changes in the number of seeds, which was highest in September and lowest in July. Seeds buried at different sand depths gradually lost dormancy; 20–42% of the seeds remained dormant after 20 months of burial. Dormancy break occurs gradually throughout the year. Our results indicate that O. racemosa exhibits hardcoatedness heterogeneity that spreads germination of a seed cohort between seasons and years in the semiarid environment, where the amount of precipitation during the growing season is highly variable.

Sensitivity cycling in physically dormant seeds of the Neotropical tree Senna multijuga (Fabaceae).

Cycling of sensitivity to physical dormancy (PY) break has been documented in herbaceous species. However, it has not been reported in tree seeds, nor has the effect of seed size on sensitivity to PY-breaking been evaluated in any species. Thus, the aims of this study were to investigate how PY is broken in seeds of the tropical legume tree Senna multijuga, if seeds exhibit sensitivity cycling and if seed size affects induction into sensitivity. Dormancy and germination were evaluated in intact and scarified seeds from two collections of S.multijuga. The effects of temperature, moisture and seed size on induction of sensitivity to dormancy-breaking were assessed, and seasonal changes in germination and persistence of buried seeds were determined. Reversal of sensitivity was also investigated. Fresh seeds were insensitive to dormancy break at wet-high temperatures, and an increase in sensitivity occurred in buried seeds after they experienced low temperatures during winter (dry season). Temperatures ≤20°C increased sensitivity, whereas temperatures ≥30°C decreased it regardless of moisture conditions. Dormancy was broken in sensitive seeds by incubating them at 35°C. Sensitivity could be reversed, and large seeds were more sensitive than small seeds to sensitivity induction. Seeds of S.multijuga exhibit sensitivity cycling to PY-breaking. Seeds become sensitive during winter and can germinate with the onset of the spring-summer rainy season in Brazil. Small seeds are slower to become sensitive than large ones, and this may be a mechanism by which germination is spread over time. Sensitive seeds that fail to germinate become insensitive during exposure to drought during summer. This is the first report of sensitivity cycling in a tree species.

EMBEBIÇÃO, OSMOCONDICIONAMENTO E VIABILIDADE DE SEMENTES DE <i>Apuleia leiocarpa</i> (VOGEL.) J. F. MACBR.

Objetivou-se, com este trabalho, caracterizar a embebição e avaliar a qualidade fisiológica de sementes de Apuleia leiocarpa após o osmocondicionamento. O estudo da embebição foi realizado em sementes intactas e escarificadas, em água destilada durante 96 horas. No estudo do osmocondicionamento, as sementes escarificadas foram separadas em três sublotes (L1; L2; L3), o primeiro foi condicionado em água destilada (controle), o segundo e o terceiro foram osmocondicionados em PEG 6000, nos potenciais de -0,4 e -0,8 MPa, respectivamente, por 10 horas. Posteriormente, as sementes foram acondicionadas em sacos plásticos e mantidas sob temperatura controlada de 3 ± 1°C. A semeadura foi realizada após 0, 30, 60, 90 e 120 dias do osmocondicionamento. A qualidade das sementes foi avaliada pelos testes: germinação, índice de velocidade de germinação, frequência relativa de germinação, comprimento da parte aérea e radicular e massa seca das plântulas. A embebição das sementes escarificadas de Apuleia leiocarpa segue o modelo trifásico de absorção de água, com início após três horas e culmina com a protrusão da raiz primária após 72 horas. As sementes osmocondicionadas em -0,8 MPa de PEG mantiveram a qualidade fisiológica, enquanto as sementes osmocondicionadas em água e em -0,4 MPa de PEG reduziram linearmente a porcentagem e a velocidade de germinação, o comprimento e a biomassa seca das plântulas.

Ecological role of physical dormancy in seeds of Oxytropis racemosa in a semiarid sandland with unpredictable rainfall

Seed dormancy and the soil seed bank are crucial to plant regeneration strategy, especially in semiarid ecosystems with unpredictable precipitation. The aim of this study was to investigate how seed dormancy is controlled by environmental factors and how it is correlated with the soil seed bank and regeneration of the perennial legume Oxytropis racemosa, a dominant perennial herb in Mu Us Sandland of semiarid China. Germination and imbibition experiments on fresh intact and scarified seeds of O. racemosa were used to identify physical dormancy (PY) in seeds of this species. Soil seed bank dynamics, timing of seedling emergence and the fate of buried seeds in the natural habitat were investigated. PY was broken by mechanical scarification or wet heat/ice water cycles but not solely by dry heat or wet heat treatment. The soil seed bank exhibited seasonal changes in the number of seeds, which was highest in September and lowest in July. Seeds buried at different sand depths gradually lost dormancy; 20–42% of the seeds remained dormant after 20 months of burial. Dormancy break occurs gradually throughout the year. Our results indicate that O. racemosa exhibits hardcoatedness heterogeneity that spreads germination of a seed cohort between seasons and years in the semiarid environment, where the amount of precipitation during the growing season is highly variable.

Seed longevity and physical dormancy break of two endemic species of Dimorphandra from Brazilian biodiversity hotspots

AbstractSeed longevity is dependent on seed traits and storage conditions. This study evaluated the seed longevity and physical dormancy (PY)-break of two species of Dimorphandra endemic to Brazilian biodiversity hotspots. Longevity was tested in situ, by burying seeds in their natural habitats (12 months), and ex situ, by storage in a cold chamber (5°C; 24 months). Seeds were taken at regular intervals to assess germinability at 30°C (12 h photoperiod) using intact and scarified seeds. Intact seeds (freshly collected, and after 12 months storage) were analysed using scanning electron microscopy. The germinability of freshly collected seeds of both species reached approximately 10% for intact seeds and >85% for scarified seeds. Cold storage maintained seed viability in both species, and broke dormancy for 35% of D. wilsonii seeds. After 12 months, only 55% (for D. exaltata) and 41% (for D. wilsonii) of the buried seeds were recovered; more than 90% of which remained viable in both species. Seeds gradually overcame PY during burial, with a higher germination increase for D. wilsonii (71%) than D. exaltata (32%). Dimorphandra exaltata seeds did not show clear structural changes after cold storage although D. wilsonii seeds evidently experience an increase in the depth of fracture lines. Burial promoted deep seed coat changes in both species, more intense in D. wilsonii, indicating that temperature and humidity variations throughout the year are among the main factors releasing Dimorphandra seeds from PY. The seeds of both studied species overcame PY during burial and are able to form small persistent soil seed banks.

Optimal and synchronized germination of Robinia pseudoacacia, Acacia dealbata and other woody Fabaceae using a handheld rotary tool: concomitant reduction of physical and physiological seed dormancy

The Fabaceae (legume family) is one of the largest families of plants with a worldwide distribution and a major role in agriculture and in agroforestry. A hard seed coat impermeable to water is a typical feature of several species. Physical dormancy delays and reduces germination so that mechanical, physical and chemical scarification methods have been classically used to break seed dormancy of many species. We evaluate the effectiveness of a methodology to scarify seeds of several woody Fabaceae of ecological and economical importance, including Robinia pseudoacacia and Acacia dealbata and the shrubs Cytisus scoparius, C. multiflorus and Ulex europaeus. We describe the optimized use of a handheld rotary tool (HRT), and compare its effectiveness with other scarification methods reported to break dormancy such as boiling or dry heating. Total germination and/or speed of germination were enhanced after the application of the HRT, with germination percentages significantly higher than those achieved by other methods of scarification. Based on a thorough literature review, a mode of action for the HRT is suggested which could operate by breaking the physical and physiological dormancy of treated seeds through the combined action of coat abrasion and moderate temperatures. Considering these results, we recommend the application of this rapid, effective, low-cost and highly reproducible HRT method to break seed dormancy and enhance germination of these species and others with similar dormancy constraints.