Water-impermeable fruits of the parasitic angiosperm Cassytha filiformis (Lauraceae): confirmation of physical dormancy in Magnoliidae and evolutionary considerations

2013 ◽  
Vol 61 (4) ◽  
pp. 322 ◽  
Author(s):  
Niranjan Mahadevan ◽  
K. M. G. Gehan Jayasuriya
Keyword(s):  
Moisture Content ◽  
Palisade Layer ◽  
Physical Dormancy ◽  
Basal Angiosperms ◽  
Parasitic Species ◽  
Parasitic Angiosperm ◽  
Physiological Dormancy ◽  
Evolutionary Aspects

Physical dormancy (PY) in seeds or fruits has been reported in 17 angiosperm families but not in basal angiosperms, magnoliids or gymnosperms. Here, we report PY in fruits (germination unit) of Cassytha filiformis, a parasitic species in the magnoliid clade. Moisture content of fruits ranged from 10% to 16%, and the seeds are orthodox (desiccation tolerant). Manually scarified fruits increased in mass >80% during imbibition, whereas untreated fruits increased <16%, via only a few fruits imbibing. Thus, the fruits are water impermeable. Dye did not penetrate the lignified palisade layer in the endocarp. Dye tracking of innately non-dormant fruits suggested that the carpellary micropyle is the water gap in C. filiformis fruits. Manual scarification broke dormancy of most, but not all, C. filiformis fruits. Thus, a high percentage of the germination units have PY and a low percentage PY + physiological dormancy. This is the first verified report of PY in the magnoliids; PY is now known to occur in four of the five major angiosperm clades. The evolutionary aspects of PY in Cassytha, an isolated genus in Lauraceae, are discussed.

Seed development in Malva parviflora: onset of germinability, dormancy and desiccation tolerance

2007 ◽  
Vol 47 (6) ◽  
pp. 683 ◽  
Author(s):  
Pippa J. Michael ◽  
Kathryn J. Steadman ◽  
Julie A. Plummer
Keyword(s):  
Moisture Content ◽  
Seed Development ◽  
Desiccation Tolerance ◽  
Dry Weight ◽  
Physical Dormancy ◽  
Seed Moisture Content ◽  
Physiological Maturity ◽  
Seed Moisture ◽  
Physiological Dormancy ◽  
Malva Parviflora

Seed development was examined in Malva parviflora. The first flower opened 51 days after germination; flowers were tagged on the day that they opened and monitored for 33 days. Seeds were collected at 12 stages during this period and used to determine moisture content, germination of fresh seeds and desiccation tolerance (seeds dried to 10% moisture content followed by germination testing). Seed moisture content decreased as seeds developed, whereas fresh (max. 296 mg) and dry weight (max. 212 mg) increased to peak at 12–15 and ~21 days after flowering (DAF), respectively. Therefore, physiological maturity occurred at 21 DAF, when seed moisture content was 16–21%. Seeds were capable of germinating early in development, reaching a maximum of 63% at 9 DAF, but germination declined as development continued, presumably due to the imposition of physiological dormancy. Physical dormancy developed at or after physiological maturity, once seed moisture content declined below 20%. Seeds were able to tolerate desiccation from 18 DAF; desiccation hastened development of physical dormancy and improved germination. These results provide important information regarding M. parviflora seed development, which will ultimately improve weed control techniques aimed at preventing seed set and further additions to the seed bank.

Sensitivity cycling and its ecological role in seeds with physical dormancy

2009 ◽  
Vol 19 (1) ◽  
pp. 3-13 ◽  
Author(s):  
K.M.G. Gehan Jayasuriya ◽  
Jerry M. Baskin ◽  
Carol C. Baskin
Keyword(s):  
Life Cycle ◽  
Environmental Conditions ◽  
Common Phenomenon ◽  
Ecological Role ◽  
Dormancy Breaking ◽  
Physical Dormancy ◽  
Physiological Dormancy ◽  
Seed Coats

AbstractCycling of physically dormant (PY) seeds between states insensitive and sensitive to dormancy-breaking factors in the environment has recently been demonstrated inFabaceaeandConvolvulaceae, and it may be a common phenomenon in seeds with water-impermeable seed coats. In contrast to seeds of many species with physiological dormancy (PD), those with PY cannot cycle between dormancy and non-dormancy (ND). In this paper, we evaluate the role of sensitivity cycling in controlling the timing of germination of seeds with PY in nature, and show that sensitivity cycling in seeds with PY serves the same ecological role as dormancy cycling in seeds with PD. Thus, sensitivity cycling in seeds with PY ensures that germination in nature occurs only at (a) time(s) of the year when environmental conditions for growth are, and are likely to remain, suitable long enough for the plant to complete its life cycle or to form a perennating structure. Further, we describe the experimental procedures necessary to determine whether sensitivity cycling is occurring, and discuss briefly the possible relevance of sensitivity cycling to dormancy classification.

Seed storage behaviour and seed germination in African and Malagasy baobabs (Adansonia species)

2006 ◽  
Vol 16 (1) ◽  
pp. 83-88 ◽  
Author(s):  
Juvet Razanameharizaka ◽  
Michel Grouzis ◽  
Didier Ravelomanana ◽  
Pascal Danthu
Keyword(s):  
Seed Germination ◽  
Moisture Content ◽  
Seed Storage ◽  
The Other ◽  
Arid Zones ◽  
Physical Dormancy ◽  
Interspecific Differences ◽  
Wet Forests

The Adansonia (baobab) genus comprises seven species in Africa, six of which are endemic to Madagascar. Depending on the species, baobabs develop in widely varying ecosystems, including arid zones and savannahs, as well as dry and wet forests. Seeds from all species exhibited orthodox behaviour, tolerating dehydration to a moisture content of around 5%. There was no physical dormancy in the two species belonging to the Brevitubae section, A. grandidieri and A. suarezensis. Their seeds germinated without any prior scarification. The five other species, belonging to Adansonia and Longitubae section, have seeds with water-impermeable coats. In the case of A. digitata and A. za, the proportion of water-impermeable seeds was around two-thirds, whereas with A. rubrostipa, A. madagascariensis and A. perrieri, the proportion was >90%. Treatments allowing for the removal of physical dormancy needed to be markedly more severe with A. madagascariensis than with the other species. None the less, it seems impossible to link these characteristics and the interspecific differences to a strategy for adaptation by these species to their environment.

Overcoming physiological dormancy in Prostanthera eurybioides (Lamiaceae), a nationally endangered Australian shrub species

2008 ◽  
Vol 56 (3) ◽  
pp. 214 ◽  
Author(s):  
P. J. Ainsley ◽  
M. K. Jones ◽  
T. E. Erickson
Keyword(s):  
South Australia ◽  
Physical Dormancy ◽  
Shrub Species ◽  
Dry Heat ◽  
Pulse Heat ◽  
Germination Process ◽  
Physiological Dormancy ◽  
Continuous Application ◽  
Persistent Calyx

Prostanthera eurybioides (Lamiaceae) is an endangered shrub endemic to South Australia. Fruits consist of four mericarps enclosed by a persistent calyx, with each seed characterised by the presence of what we are defining as a mericarp plug. Research focussed on understanding the role of the mericarp plug in the germination process, determining seed dormancy classification and germination cues. Treatments tested included combinations of pulse dry heat (60–120°C) for up to 60 min, continuous application of gibberellic acid (100 mg L–1), smoked water (10% (v/v)) and excision of the mericarp plug. Seed imbibition experiments dispelled the presence of physical dormancy. The mericarp plug was found to be acting as a mechanical barrier preventing germination. Pulse dry heat (80°C) significantly improved germination, as did removal of the mericarp plug. Smoked water inhibited germination. Based on germination response, seeds have been classified as having non-deep physiological dormancy, with maximum germination (86%) observed following a pulse heat treatment (80°C, 10 min) and removal of the mericarp plug. Natural mechanisms for overcoming dormancy are proposed.

Seed germination of coastal monsoon vine forest species in the Northern Territory, Australia, and contrasts with evergreen rainforest

2018 ◽  
Vol 66 (3) ◽  
pp. 218 ◽  
Author(s):  
Vidushi Thusithana ◽  
Sean M. Bellairs ◽  
Christine S. Bach
Keyword(s):  
Seed Germination ◽  
Seed Storage ◽  
Pioneer Species ◽  
Physical Dormancy ◽  
Climax Species ◽  
Seed Biology ◽  
Light Requirements ◽  
Physiological Dormancy ◽  
Germination Traits ◽  
Prevalent Form

Seed germination traits of seasonal rainforest species differ from permanently moist evergreen rainforest species due to the prolonged seasonal drought. We investigated whether seed germination traits used to categorise evergreen rainforest species into pioneer and climax guilds were applicable to seasonal rainforest species. Seed dormancy, light requirements for germination and seed storage types of five climax and thirteen pioneer species of a coastal vine thicket were studied. Results were compared with published studies of evergreen rainforest species. Evergreen rainforest pioneer species are typically dormant, require light to germinate and tolerate desiccation, whereas climax species are typically non-dormant, tolerate shade during germination and are sensitive to desiccation. In seasonal rainforest we found that a high proportion of pioneer species had seeds that were non-dormant (62%), and a high proportion of pioneer species germinated equally well in light and dark conditions. In seasonal rainforest, we found that the majority of climax species had desiccation tolerant seeds, whereas in evergreen rainforest the proportion of climax species producing desiccation sensitive seeds is equal to or greater than the proportion of species with desiccation tolerant seeds. In seasonal rainforest species physical, physiological and epicotyl dormancy types were found. Generally, for seasonal rainforest species, the prevalent form of dormancy in pioneer species was physical dormancy whereas physiological dormancy was most common in evergreen rainforest pioneer species with dormancy. Our results suggest that the contrasting seed biology traits that typically apply to pioneer and climax species of evergreen rainforest species don’t typically apply to seasonal rainforest species.

Dormancy, germination requirements and storage behaviour of seeds ofConvolvulaceae(Solanales) and evolutionary considerations

2008 ◽  
Vol 18 (4) ◽  
pp. 223-237 ◽  
Author(s):  
K.M.G. Gehan Jayasuriya ◽  
Jerry M. Baskin ◽  
Carol C. Baskin
Keyword(s):  
Moisture Content ◽  
Initial Moisture Content ◽  
The Other ◽  
Physical Dormancy ◽  
Recalcitrant Seed ◽  
Evolutionary Pattern ◽  
Cuscuta Europaea ◽  
Orthodox Seeds ◽  
And Storage ◽  
Germination Requirements

AbstractConvolvulaceaeis the only family in the asterid clade with species that produce physically dormant seeds, and most studies on germination in this family have focused on scarified seeds. However, no study has been done on the taxonomic/evolutionary pattern of seed dormancy inConvolvulaceae. We determined the moisture content of non-treated seeds and water uptake and germination percentages for non-treated and manually scarified seeds of 46 species in 11 of the 12 tribes in this family. Germination was tested over a range of temperatures in light/dark and in the dark. The effect of drying and storage at low temperatures was tested on seeds ofErycibe henryiandMaripa panamensis, the only species with high initial moisture content. Non-treated fresh seeds ofBonamia menziesii,M. panamensisandE. henryiimbibed water, whereas those of the other 43 species did not. Manually scarified seeds of all these 43 species took up large amounts of water. Therefore, seeds of 43 of the 46 species are physically dormant, and three are non-dormant. Seeds of all 46 species germinated after imbibition, except those ofCuscuta europaea, which are reported to have combinational dormancy.M. panamensisandE. henryiseeds are recalcitrant and those of the other 44 species orthodox. InConvolvulaceae, basal tribes or tribes derived from basal tribes contain species with non-dormant recalcitrant, physically dormant orthodox and combinationally dormant orthodox seeds. Physical dormancy of seeds in this family possibly evolved from a non-dormant recalcitrant seed-producing ancestor closely related toErycibeae.

scholarly journals Efectividad de algunos tratamientos pre-germinativos para ocho especies leñosas de la Mixteca Alta oaxaqueña con características relevantes para la restauración

2017 ◽  
pp. 9
Author(s):  
Gilberto Martínez-Pérez ◽  
Alma Orozco-Segovia ◽  
Carlos Martorell
Keyword(s):  
Seed Coat ◽  
Native Species ◽  
Immature Embryo ◽  
New Method ◽  
Dodonaea Viscosa ◽  
Physical Dormancy ◽  
Mixteca Alta ◽  
Physiological Dormancy ◽  
Wearing Off ◽  
Do So

When restoring highly degraded areas such as the Mixteca Alta (Oaxaca State, Mexico), it is important to use native species that promote natural succession. To do so, we need to know whether their seeds have dormancy and how to break it. We compared different pre-germination treatments of eight species relevant for restoration. The results were analyzed with a new method that solves some of the statistical problems that arise when examining these experiments. In Acacia schaffneri, Ipomoea murucoides, Mimosa aculeaticarpa and Dodonaea viscosa wearing off the seed coat by means of abrasion or heating promotes rapid germination, proving the presence of physical dormancy. Despite belonging to families that show physiological dormancy only, the seeds of Arctostaphylos pungens and Juniperus flaccida germinate after immersion in acid. This procedure may have weakened the seed coat, allowing the immature embryo to break it. We found weak physiological dormancy in Quercus deserticola, and no apparent dormancy in Quercus castanea.

scholarly journals Seed anatomy and water uptake and their relation to seed dormancy of Ormosia paraensis Ducke

2018 ◽  
Vol 40 (3) ◽  
pp. 237-245
Author(s):  
Breno Marques da Silva e Silva ◽  
Camila de Oliveira e Silva ◽  
Fabiola Vitti Môro ◽  
Roberval Daiton Vieira
Keyword(s):  
Sulfuric Acid ◽  
Seed Dormancy ◽  
Water Uptake ◽  
Furniture Industry ◽  
Palisade Layer ◽  
Dormancy Breaking ◽  
Physical Dormancy ◽  
Seed Physiology ◽  
Breaking Dormancy ◽  
Hydrophobic Substances

Abstract: Ormosia paraensis Ducke has ornamental seeds widely used in the manufacture of bio-jewels and wood used in the furniture industry. For seedling production, the information on its seed physiology is scarce. Thus, the aim of this study was to assess methods for breaking dormancy and relate them to integument structure and water uptake by O. paraensis seeds. Seed dormancy-breaking was performed by mechanical scarification and soaking in sulfuric acid for 0, 15, 30, 60, 120, and 240 minutes. Dormancy‐broken seeds were compared with intact seeds. Seed integument is formed by a cuticle (hydrophobic substances), epidermis (macroesclereids of the palisade layer,), hypodermis (osteosclereids), and parenchyma cells. Intact seeds did not absorb water after 72 hours of soaking. The highest percentages and rates of seed germination were observed in treatments with mechanical scarification and soaking in sulfuric acid for 60 or 120 minutes. Seed soaking in sulfuric acid (H2SO4 p.a. 98.08%) for 60 or 120 minutes or mechanical scarification are adequate to overcome physical dormancy associated with O. paraensis seed integument impermeability to water or gases.

scholarly journals Water Uptake and Germination of Caper (Capparis spinosa L.) Seeds

Agronomy ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 838
Author(s):  
María Laura Foschi ◽  
Mariano Juan ◽  
Bernardo Pascual ◽  
Núria Pascual-Seva
Keyword(s):  
Moisture Content ◽  
Water Uptake ◽  
Sensu Stricto ◽  
Physical Dormancy ◽  
Seed Moisture Content ◽  
Mediterranean Countries ◽  
Capparis Spinosa ◽  
Viable Seeds ◽  
Two Phases ◽  
Almost All

Caper is a perennial deciduous sub-shrub that grows in almost all circum-Mediterranean countries. The specialized literature presents three possible dormancy types that can cause low germination of caper seeds: Physiological dormancy (PD), physical dormancy (PY), and combinational dormancy (PY + PD). We conducted three experiments to analyze the imbibition, viability, and germination of seeds of different ages, provenances, and the level of deterioration of the seed cover. None of the commercialized lots of standard seeds tested exceeded 6% germination, nor 35% viability, while the owned seeds reached 90% in both parameters, indicating that all viable seeds germinated. The seed moisture content along the soaking period followed the first two phases of the typical triphasic model of water uptake in seed germination: The imbibition and lag phases (phase I and II of germination, respectively). Seed hydration began through the hilar region. The fact that all viable owned seeds germinated, together with their moisture content being lower than that of standard seeds, indicated that caper seeds do not have a water-impermeable coat sensu stricto, i.e., they do not show PY; nevertheless, the need to use gibberellic acid to obtain high germination percentages, demonstrated the presence of PD.

Micropylar seed coat restraint and embryonic response to heat shock and smoke control seed dormancy in Grevillea juniperina

2016 ◽  
Vol 26 (2) ◽  
pp. 111-123 ◽  
Author(s):  
Candida L. Briggs ◽  
E. Charles Morris ◽  
Glenn Stone
Keyword(s):  
Heat Shock ◽  
Seed Coat ◽  
Cell Walls ◽  
Compressive Force ◽  
Growth Potential ◽  
Palisade Layer ◽  
Smoke Control ◽  
Control Seed ◽  
Physiological Dormancy ◽  
Minimum Force

AbstractSeeds of some eastern Australian Grevillea species show the characteristics of non-deep physiological dormancy, which is broken by exposure to heat shock and/or smoke. The current study tested whether the restrictive effect of the seed coat on germination was localized to specific regions, whether the fire cues affected the growth potential of the embryo, the mechanical strength of the seed coat itself, and the anatomy of fracturing of the seed coat. Removal of the micropylar seed coat allowed germination, while retaining it in place restricted germination. The growth potential of the embryo was increased by exposure to heat shock or to smoke, and increased the most if exposed to both cues. Estimation of the minimum force required by embryos to germinate from intact seeds suggested that this force was reduced for seeds treated with fire cues. The fire cues did not affect the resistance of the seed coat to compressive force when tested after 24 h of imbibition. Fracturing of the seed coat occurred between cell walls, except for the palisade layer, where fracturing occurred across palisade and sclerenchyma cells. While the micropylar end of the seed coat imposes dormancy, most likely by mechanical constraint, heat shock and smoke overcome dormancy by increasing the embryo's growth potential and possibly weakening the seed coat, either directly or via the embryo.

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