Combinational dormancy in seeds of the Western Australian endemic species Diplopeltis huegelii (Sapindaceae)

Seeds of the endemic Western Australian species Diplopeltis huegelii Endl. were successfully germinated after the presence of combinational dormancy was identified, following the observation of selected seed characteristics. D. huegelii seeds were found to have large, fully developed, peripheral coiled embryos (with no endosperm) that are 7–8 mm long when uncoiled. Seed-coat dormancy was overcome by dipping seeds in hot water for ≥15 s, but seeds also required a period of after-ripening before they would germinate readily. After-ripening occurred while intact seeds were stored dry at ambient laboratory conditions for 13 months or when scarified (hot-water treated) seeds were stored at 13, 23 or 50% RH at 23°C for 6 weeks. Scarified 13-month-old seeds germinated readily at 7/18, 13/26 and 18/33°C in a 12-h photoperiod and in constant darkness, whereas scarified 1-month-old seeds germinated to ≤43%. Thus, seed dormancy in this species is caused by a water-impermeable seed coat (physical dormancy, PY) and a (non-deep) physiologically dormant embryo (PD), i.e. combinational dormancy (PY + PD). This is only the second report of combinational dormancy in seeds of Sapindaceae and the first report in this family of the PD component of (PY + PD) being broken during dry storage.

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Physical dormancy in seeds of Dodonaea viscosa (Sapindales, Sapindaceae) from Hawaii

Seed Science Research ◽

10.1079/ssr2003157 ◽

2004 ◽

Vol 14 (1) ◽

pp. 81-90 ◽

Cited By ~ 64

Author(s):

Jerry M. Baskin ◽

Barbara H. Davis ◽

Carol C. Baskin ◽

Sean M. Gleason ◽

Susan Cordell

Keyword(s):

Seed Coat ◽

White Light ◽

Red Light ◽

Dodonaea Viscosa ◽

Physical Dormancy ◽

Critical Moisture Content ◽

Temperature Regimes ◽

Wide Range ◽

Critical Moisture ◽

Impermeable Seed Coat

Dormancy in seeds ofDodonaea viscosais due to a water-impermeable seed coat (physical dormancy, PY). Thus, mechanically scarified seeds imbibed water (c.95% increase in mass) and germinated to high percentages over a wide range of temperature regimes in both white light and darkness, whereas non-scarified seeds did not take up water. Dry heat at 80–160°C and dipping in boiling water for 1–60 s also broke dormancy in a high percentage of the seeds, and continuous far-red light was not inhibitory to germination. However, dry storage in the laboratory for >1 year did not overcome dormancy. Seeds made water-permeable by boiling imbibed water, and thus germinated, at a much slower rate than those made water-permeable by mechanical scarification. We suggest that boiling opened the ‘water gap’ in the seed coat (not yet described inSapindaceaebut present in other taxa with PY) and that water entered the seed only through this small opening, thereby accounting for the slow rate of imbibition and subsequent germination. Physical dormancy has now been shown to occur in seeds of this polymorphic, worldwide species from Australia, Brazil, Hawaii, Mexico and New Zealand. The low level of dormancy reported for seed lots ofD. viscosain China, India and Pakistan is probably due to collection of seeds before they dried to the critical moisture content for development of water-impermeability of the seed coat. Germination of non-dormant seeds over a wide range of temperatures and in white light, far-red (leaf-canopy shade) light and darkness are part of the germination strategy ofD. viscosaand of other taxa whose seeds have PY at maturity.

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A new seed coat water-impermeability mechanism in Chaetostoma armatum (Melastomataceae): evolutionary and biogeographical implications of physiophysical dormancy

Seed Science Research ◽

10.1017/s0960258515000070 ◽

2015 ◽

Vol 25 (2) ◽

pp. 194-202 ◽

Cited By ~ 8

Author(s):

Rafaella C. Ribeiro ◽

Denise M.T. Oliveira ◽

Fernando A.O. Silveira

Keyword(s):

Phenolic Compounds ◽

Seed Coat ◽

Seed Weight ◽

Significant Fraction ◽

Distilled Water ◽

Physical Dormancy ◽

First Report ◽

Germination Ecology ◽

Impermeable Seed Coat ◽

Structure Water

AbstractDetermining the phylogenetic and biogeographic distribution of physical dormancy remains a major challenge in germination ecology. Here, our goal was to describe a novel water-impermeable seed coat mechanism causing physical dormancy (PY) in the seeds of Chaetostoma armatum (Melastomataceae). Although seed coat permeability tests indicated a significant increase in seed weight after soaking in distilled water, anatomical and dye-tracking analyses showed that both water and dyes penetrated the seed coat but not the embryo, which remained in a dry state. The water and dye penetrated the lumen of the exotestal cells, which have a thin outer periclinal face and thickened secondary walls with U-shaped phenolic compounds. Because of this structure, water and dye do not penetrate the inner periclinal face of the exotestal cells, indicating PY. Puncturing the seeds increased germination more than tenfold compared to that of the control, but GA3 did not increase germination further. A significant fraction of the seeds did not germinate after puncturing, indicating that embryos are also physiologically dormant (PD). This paper constitutes the first report of the water-impermeable seed coat in the Myrtales and the first report of physiophysical (PD+PY) dormancy in a shrub from a tropical montane area.

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Physical dormancy in Senna multijuga (Fabaceae: Caesalpinioideae) seeds: the role of seed structures in water uptake

Seed Science Research ◽

10.1017/s0960258514000087 ◽

2014 ◽

Vol 24 (2) ◽

pp. 147-157 ◽

Cited By ~ 26

Author(s):

Ailton G. Rodrigues-Junior ◽

José M.R. Faria ◽

Tatiana A.A. Vaz ◽

Adriana T. Nakamura ◽

Anderson C. José

Keyword(s):

Water Uptake ◽

Seed Coat ◽

Parenchyma Cell ◽

Hot Water ◽

Dormancy Breaking ◽

Physical Dormancy ◽

Short Term Exposure ◽

Hilar Region ◽

Senna Multijuga

AbstractStructural studies in seeds with physical dormancy (PY) are important to better understand its causes and release when subjected to treatments for dormancy breaking. The aims of this study were to (1) characterize the PY break; (2) examine the role of different seed structures in water uptake; and (3) identify the water gap in Senna multijuga seeds. Imbibition patterns of dormant and non-dormant (subjected to dormancy breaking treatments) seeds and the morphological changes during dormancy breaking and germination were evaluated. To identify the water gap, the micropyle and lens were blocked separately, and the water absorption by seed parts was determined. Structural characteristics of the seed coat were also examined. Immersion in water at 80°C was efficient in breaking seed dormancy and imbibition occurred first at the hilar region, through the lens. Water was not absorbed through the micropyle or the extra-hilar region. S. multijuga seeds have a testa with a linearly aligned micropyle, hilum and lens. The seed coat consisted of a cuticle, macrosclereids, one (hilar region) or two (extra-hilar region) layer(s) of osteosclereids and parenchyma cell layers. The lens has typical parenchyma cells underneath it and two fragile regions comprised of shorter macrosclereids. Heat treatment stimulated the lens region, resulting in the opening of fragile regions at the lens, allowing water to enter the seeds. It is concluded that short-term exposure to a hot water treatment is sufficient for the formation of a water gap in S. multijuga seeds, and only the lens acts in the imbibition process.

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Markedly different patterns of imbibition in seeds of 48 Acacia species

Seed Science Research ◽

10.1017/s0960258519000242 ◽

2019 ◽

Vol 29 (4) ◽

pp. 270-282 ◽

Cited By ~ 1

Author(s):

Geoffrey E. Burrows ◽

Rowan Alden ◽

Wayne A. Robinson

Keyword(s):

Process Control ◽

Seed Coat ◽

Germination Percentage ◽

Rain Gauge ◽

Hot Water ◽

Physical Dormancy ◽

Acacia Species ◽

Rain Events

AbstractThe seeds of most Australian acacias have pronounced physical dormancy (PY). While fire and hot water (HW) treatments cause the lens to ‘pop’ almost instantaneously, for many Acacia species the increase in germination percentage can be gradual. If PY is broken instantly by HW treatment, why is germination often an extended process? Control and HW treatments were performed on seeds of 48 species of Acacia. Seeds were placed on a moist substrate and imbibition was assessed by frequently weighing individual seeds. In the two soft-seeded species all control seeds were fully imbibed within 6–24 h, while in hard-seeded species very few control seeds imbibed over several weeks. In 10 species over 50% of the HW-treated seeds imbibed within 30 h, but mostly the percentage of imbibed seeds gradually increased over several weeks. Some seeds in a replicate would imbibe early, while others would remain unimbibed for many days or weeks then, remarkably, become fully imbibed in less than 24 h. While HW treatment broke PY almost instantaneously, it appeared that in many Acacia species some other part of the testa slowed water from reaching the embryo. This process of having staggered imbibition may be a way of ensuring not all seeds in a population germinate after small rain events. Thus it appears the lens acts as a ‘fire gauge’ while some other part of the seed coat acts as a ‘rain gauge’.

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Water permeability/impermeability in seeds of 15 species of Caragana (Fabaceae)

PeerJ ◽

10.7717/peerj.6870 ◽

2019 ◽

Vol 7 ◽

pp. e6870 ◽

Cited By ~ 1

Author(s):

Dali Chen ◽

Rui Zhang ◽

Carol C. Baskin ◽

Xiaowen Hu

Keyword(s):

Seed Coat ◽

Water Permeability ◽

Water Entry ◽

The Other ◽

Palisade Layer ◽

Physical Dormancy ◽

Dry Storage

Majority legumes in the temperate and arctic zones have water-impermeable seeds (physical dormancy, PY). However, various authors have reported that seeds of some Caragana species are water-permeable and thus non-dormant. We (1) tested seeds of 15 species of Caragana matured in the same site in 2014, 2016 and/or 2017 for presence of PY, (2) determined if dry storage decreased or increased the percentage of seeds with PY and (3) located the site on the seed coat of 11 species where water enters the seed. Sixty-three percent and 45% of the seeds of C. roborovskyi had PY in 2016 and 2017, respectively, but only 0–14% of the seeds of the other 14 species had PY. The palisade layer in the seed coat of water impermeable seeds had no cracks in it, whereas cracks were present in the palisade layer of water-permeable seeds. Year of collection and dry storage had significant effects on imbibition of two species (C. acanthophylla and C. roborovskyi). In two (C. acanthophylla and C. roborovskyi) of the 11 species tested, the hilum was the site of water entry into seeds (control seeds, not any dormant broken treatments), but for the other nine species tested water entered through all parts of the seed coat.

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Water absorption and dormancy-breaking requirements of physically dormant seeds of Sophora tomentosa L. and Erythrina speciosa Andr. (Fabaceae-Faboideae)

Revista de Biología Tropical ◽

10.15517/rbt.v63i1.13903 ◽

2014 ◽

Vol 63 (1) ◽

pp. 285 ◽

Cited By ~ 6

Author(s):

Carolina Maria Luzia Delgado ◽

Alexandre Souza de Paula ◽

Marisa Santos ◽

Maria Terezinha Silveira Paulilo

Keyword(s):

Water Absorption ◽

Atlantic Forest ◽

Seed Coat ◽

Temperature Fluctuation ◽

Hot Water ◽

Epifluorescence Microscopy ◽

Maximum Temperature ◽

Dormancy Breaking ◽

Physical Dormancy ◽

Seed Coats

The physical dormancy of seeds has been poorly studied in species from tropical forests, such as the Atlantic Forest. This study aimed to examine the effect of moderate alternating temperatures on breaking the physical dormancy of seeds, the morphoanatomy and histochemistry of seed coats, and to locate the structure/region responsible for water entrance into the seed, after breaking the physical dormancy of seeds of two woody Fabaceae (subfamily Faboideae) species that occur in the Brazilian Atlantic Forest: Sophora tomentosa and Erythrina speciosa. To assess temperature effect, seeds were incubated in several temperature values that occur in the Atlantic Forest. For morphological and histochemical studies, sections of fixed seeds were subjected to different reagents, and were observed using light or epifluorescence microscopy, to analyze the anatomy and histochemistry of the seed coat. Treated and non-treated seeds were also analyzed using a scanning electron microscope (SEM) to observe the morphology of the seed coat. To localize the specific site of water entrance, the seeds were blocked with glue in different regions and also immersed in ink. In the present work a maximum temperature fluctuation of 15ºC was applied during a period of 20 days and these conditions did not increase the germination of S. tomentosa or E. speciosa. These results may indicate that these seeds require larger fluctuation of temperature than the applied or/and longer period of exposition to the temperature fluctuation. Blocking experiments water inlet combined with SEM analysis of the structures of seed coat for both species showed that besides the lens, the hilum and micropyle are involved in water absorption in seeds scarified with hot water. In seeds of E. speciosa the immersion of scarified seeds into an aniline aqueous solution showed that the solution first entered the seed through the hilum. Both species showed seed morphological and anatomical features for seed coats of the subfamily Faboideae. Lignin and callose were found around all palisade layers and the water impermeability and ecological role of these substances are discussed in the work.

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Seed anatomical studies on dormancy and germination in Chamaecrista absus

Journal of Applied and Natural Science ◽

10.31018/jans.v8i2.888 ◽

2016 ◽

Vol 8 (2) ◽

pp. 868-873

Author(s):

H. M. Pallavi ◽

K. Vishwanath ◽

Bapurayagouda Patil ◽

N. Naveen ◽

Manjunath Thattimani

Keyword(s):

Seed Coat ◽

Hot Water ◽

Boiling Water ◽

Physical Dormancy ◽

Anatomical Studies ◽

Hard Seed ◽

Artificial Seed ◽

Germination Behaviour ◽

Hilar Region ◽

Hard Seed Coat

Present study was conducted to analyze the anatomical structure of seed to study the dormancy behaviour in Chamaecrista absus. Seed germination behaviour was also studied after breaking the seed dormancy by artificial seed treatments. The anotamical studies revealed that seed has apical hilar region and seed coat has four layers consisting of outer cuticle, sub cuticle, palisade layer and inner tegma leading to physical dormancy. Outer cuticle and sub cuticle layers are very hard to break naturally and hence seeds possess hard seed coat dormancy. This physically hard seed coat should be made soft to enhance germination. Studies to break dormancy were conducted involving treatments like hot water, hormones and in combinations of both. The results revealed that seeds dipped in boiling water made inner layers permeable for water absorption in hilar region and thus germination enhanced. In specific seeds treated with boiling water for 5 minutes recorded higher germination (82 %) over untreated control (26 %). . Other artificial treatments with hormones gibberellic acid (33 % ) and ethrel (34 % ) did not enhanced the germination significantly over control. C. absus has hard coat dormancy and can be overcame by treating seeds with boiling water treatment.

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Physical dormancy in seeds of Dodonaea viscosa (Sapindaceae) from India

Seed Science Research ◽

10.1079/ssr2004194 ◽

2005 ◽

Vol 15 (1) ◽

pp. 59-61 ◽

Cited By ~ 14

Author(s):

S.S. Phartyal ◽

J.M. Baskin ◽

C.C. Baskin ◽

R.C. Thapliyal

Keyword(s):

Seed Dormancy ◽

Seed Coat ◽

Geographical Range ◽

Western India ◽

Dodonaea Viscosa ◽

Physical Dormancy ◽

Impermeable Seed Coat ◽

North Western

In contrast to reports in the literature that seeds of Dodonaea viscosa from China and Pakistan are non-dormant, or nearly so, we found that a high percentage of seeds of this species collected in north-western India have a water-impermeable seed coat at maturity, i.e. physical dormancy. Thus, seeds that were mechanically scarified and boiled (to open a ‘water gap’ in the seed coat) germinated to much higher percentages (84% and 77%, respectively) than did those that were non-scarified (24%). Our results agree with studies of seed dormancy in this species in various other parts of its large geographical range.

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Nodulation and performance of exotic and native legumes in Australian soils

Australian Journal of Botany ◽

10.1071/bt03053 ◽

2003 ◽

Vol 51 (5) ◽

pp. 543 ◽

Cited By ~ 17

Author(s):

María A. Pérez-Fernández ◽

Byron B. Lamont

Keyword(s):

Native Species ◽

Treated Soil ◽

Retama Sphaerocarpa ◽

Australian Species ◽

And Performance ◽

Natural Stands ◽

High Degree ◽

Western Australian ◽

Cytisus Balansae ◽

New Habitats

Six Spanish legumes, Cytisus balansae, C. multiflorus, C. scoparius, C. striatus, Genista hystrix and Retama sphaerocarpa, were able to form effective nodules when grown in six south-western Australian soils. Soils and nodules were collected from beneath natural stands of six native Australian legumes, Jacksonia floribunda, Gompholobium tomentosum, Bossiaea aquifolium, Daviesia horrida, Gastrolobium spinosum and Templetonia retusa. Four combinations of soils and bacterial treatments were used as the soil treatments: sterile soil (S), sterile inoculated soils (SI), non-treated soil (N) and non-treated inoculated soils (NI). Seedlings of the Australian species were inoculated with rhizobia cultured from nodules of the same species, while seedlings of the Spanish species were inoculated with cultures from each of the Australian species. All Australian rhizobia infected all the Spanish species, suggesting a high degree of 'promiscuity' among the bacteria and plant species. The results from comparing six Spanish and six Australian species according to their biomass and total nitrogen in the presence (NI) or absence (S) of rhizobia showed that all species benefitted from nodulation (1.02–12.94 times), with R.�sphaerocarpa and C. striatus benefiting more than the native species. Inoculation (SI and NI) was just as effective as, or more effective than the non-treated soil (i.e. non-sterile) in inducing nodules. Nodules formed on the Spanish legumes were just as efficient at fixing N2 as were those formed on the Australian legumes. Inoculation was less effective than non-treated soil at increasing biomass but just as effective as the soil at increasing nitrogen content. Promiscuity in the legume–bacteria symbiosis should increase the ability of legumes to spread into new habitats throughout the world.

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Mechanical scarification technique breaks seed coat-mediated dormancy in wild oat (Avena fatua)

Weed Technology ◽

10.1017/wet.2021.94 ◽

2021 ◽

pp. 1-25

Author(s):

Roberto Lujan Rocha ◽

Yaseen Khalil ◽

Aniruddha Maity ◽

Hugh J. Beckie ◽

Michael B. Ashworth

Keyword(s):

Growth Rate ◽

Seed Coat ◽

Research Effort ◽

Economic Losses ◽

Wild Oat ◽

Weed Species ◽

Physical Dormancy ◽

No Donor ◽

Seedling Growth Rate ◽

Oat Seeds

Abstract Wild oat is a herbicide resistance-prone global weed species that causes significant economic losses in dryland and horticultural agriculture. As a result, there has been a significant research effort in controlling this species. A major impediment to this research is the seed coat-mediated dormancy of wild oat, requiring a labor-intensive incision or puncturing of the seed coat to initiate seed germination. This study defines the most efficient settings of a mechanical thresher to overcome wild oat seed dormancy and then validates these settings using multiple populations collected from the Western Australian grain belt. We also compare the effects of rapid mechanical scarification and known germination stimulus tactics such as scarification with sulfuric acid (H2SO4), partial endosperm removal, sandpaper scarification of the seed coat, and immersion in sodium nitroprusside (NO donor SNP) solution on wild oat seedling growth rate. Threshing treatment of 1,500 rpm for 5 s provides equivalent germination compared with manually puncturing individual wild oat seeds, with no difference in seedling relative growth rate. The mechanical scarification of seeds using the thresher resulted in greater germination (66%) than H2SO4 scarification (0%), partial endosperm removal (10%), sandpaper seed coat scarification (25%), and exposure to NO donor SNP (34%). This study demonstrates that the physical dormancy of wild oat can be rapidly overcome using a commercially available mechanical thresher.

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