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'Dust seeds' with an undifferentiated embryo and unipolar germination are produced by holoparasitic species in 10 families of angiosperms. However, aside from a few Orobanchaceae species important in agriculture (crop weeds) and in Chinese traditional medicine we know little about seed germination in these achlorophyllous plants. Our primary purpose was to review the literature on seed germination in nine families of the mostly economically-nonimportant taxa of holoparasites and (briefly) of Cynomoriaceae, an economically important medicinal family for which several publications on its germination are in Chinese. A second purpose was to pull together information on sizes of dust seeds and their undifferentiated embryos and endosperm in both economically- and noneconomically-important holoparasitic plants. We found that not much progress has been made in understanding dormancy- break/germination in these holoparasites since 1969, when the author of a book on parasitic flowering plants pointed out how little we know about their germination. Lack of progress on germination of dust seeds of these holoparasites is not necessarily due to lack of research but at least in part to their nonresponsiveness to well-known treatments used to break dormancy in seeds of autotrophic and hemiparasitic flowering plants. For most species, seed length is Keywords Endoparasitism * Haustorium formation * Heterotrophic angiosperms * Organless embryo * Post-germination meristem formation * Seed dormancy * Tuber formation * Unipolar germination, Introduction Holoparasitic species ('xenoparasites' sensu Teryokhin, 2006) that cannot photosynthesize, obtain all of their carbon and other nutrients from host plants and produce extremely small dust seeds (Eriksson & Kainulainen, [...]

Seed rain and the soil seed bank represent the dispersal of seeds in space and time, respectively, and can be important sources of recruitment of new individuals during plant community regeneration. However, the temporal dynamics of seed rain and the mechanisms by which the seed rain and soil seed bank may play a role in plant community regeneration with increased grazing disturbance remain unclear. Seed rain, soil seed bank, aboveground vegetation, and rodent density were sampled along a grazing gradient in an alpine marsh on the eastern Tibetan Plateau. We described the temporal dynamics of seed dispersal using Bayesian generalized mixed models, and nonmetric multidimensional scaling and the structural equation model were used to examine the effects of grazing disturbance on the relative role of seed rain and soil seed bank on aboveground plant community regeneration. The temporal dynamics of seed rain changed from a unimodal to a bimodal pattern with increased grazing disturbance. Both species diversity and seed density of the seed rain and seed bank increased significantly with increased grazing disturbance. Increased grazing disturbance indirectly increased the similarity of composition between seed rain, seed bank, and aboveground plant community by directly increasing species diversity and abundance of aboveground plant community. However, increased grazing disturbance also indirectly decreased the similarity of seed rain, soil seed bank, and aboveground plant community by directly increasing rodent density. The similarity between seed rain and aboveground plant community was greater than that of the soil seed bank and aboveground plant community with increased grazing disturbance. Grazing disturbance spreads the risk of seed germination and seedling establishment by changing the temporal dynamics of seed dispersal. Plants (positive) and rodents (negative) mediated the role of seed rain and soil seed bank in plant community regeneration. The role of seed rain in plant community regeneration is higher than the seed bank in disturbed alpine marshes. Our findings increase our understanding of the regeneration process of the plant community, and they provide valuable information for the conservation and restoration of alpine marsh ecosystems. [ABSTRACT FROM AUTHOR]

Astragalus is the largest genus of seed plants; however, information on its reproductive biology and life histoiy is widely scattered in the literature. About 96% of the species are perennials and 4% annuals; many are rare endemics. Astragalus species are obligate or facultative outcrossers, and inbreeding depression is higher in self-compatible (SC) than in self-incompatible (SI) species. The most frequent pollinators are Bombus, Osmia and Anthophora. On average, 48% of ovules produce seeds, and 40% of flowers produce fruits. Seed/ovule and fruit/flower ratios are lower in SC than in SI species. Predispersal insect seed predation ranges from 0 to 93%, and major predators are Acanthoscelides, Bruchophagus and Tychius. Seeds have physical dormancy and typically form a seed bank. [C.sub.3] is the only photosynthetic pathway in the genus. Population growth may be cyclic or noncyclic, and genetic diversity of a taxon may or may not be related to size of geographic range. Keywords Breeding system * Inbreeding depression * Life cycle * Reproductive success * Soil seed bank, Introduction Astragalus L. (Fabaceae, subfam. Papilionoideae, tribe Galageae) is the world's largest genus of seed plants, with an estimated 2500 to 3200 species (Frodin, 2004; Mabberley, 2008; Azani et al., [...]

Argyreia is the most recently evolved genus in the Convolvulaceae, and available information suggests that most species in this family produce seeds with physical dormancy (PY). Our aim was to understand the evolution of seed dormancy in this family via an investigation of dormancy, storage behaviour, morphology and anatomy of seeds of five Argyreia species from Sri Lanka. Imbibition, germination and dye tracking of fresh intact and manually scarified seeds were studied. Scanning electron micrographs and hand sections of the hilar area and the seed coat away from the hilar area were compared. Scarified and intact seeds of A. kleiniana , A. hirsuta and A. zeylanica imbibed water and germinated to a high percentage, but only scarified seeds of A. nervosa and A. osyrensis did so. Thus, seeds of the three former species are non-dormant (ND), while those of the latter two have physical dormancy (PY); this result was confirmed by dye-tracking experiments. Since >90% of A. kleiniana, A. hirsuta and A. zeylanica seeds survived desiccation to 10% moisture content (MC) and >90% of A. nervosa and A. osyrensis seeds with a dispersal MC of ~12% were viable, seeds of the five species were desiccation-tolerant. A. nervosa and A. osyrensis have a wide geographical distribution and PY, while A. kleiniana , A. hirsuta and A. zeylanica have a restricted distribution and ND. Although seeds of A. kleiniana are ND, their seed coat anatomy is similar to that of A. osyrensis with PY. These observations suggest that the ND of A. kleiniana , A. hirsuta and A. zeylanica seeds is the result of an evolutionary reversal from PY and that ND may be an adaptation of these species to the environmental conditions of their wet aseasonal habitats. [ABSTRACT FROM AUTHOR]

Environmental factors, such as temperature and moisture, and plant factors, such as seed position on the mother plant, can affect seed viability and germination. However, little is known about the viability and germination of seeds in different positions on the mother plant after burial in soil under natural environmental conditions. Here, diaspores from three positions on a compound spike and seeds from two/three positions in a diaspore of the invasive diaspore‐heteromorphic annual grass Aegilops tauschii were buried at four depths for more than 2 years (1–26 months) under natural conditions and viability and germination monitored monthly. Viability of seeds in each diaspore/seed position decreased as burial depth and duration increased and was associated with changes in soil temperature and moisture. Germination was highest at 2 cm and lowest at 10 cm soil depths, with peaks and valleys in autumn/spring and winter/summer, respectively. Overall, seeds in distal diaspore and distal seed positions had higher germination percentages than those in basal diaspore and basal seed positions, but basal ones lived longer than distal ones. Chemical content of fresh diaspores/seeds was related to diaspore/seed position effects on seed germination and viability during burial. We conclude that seeds in distal diaspores/seed positions have a 'high risk' strategy and those in basal positions a 'low risk' strategy. The two risk strategies may act as a bet‐hedging strategy that spreads risks of germination failure in the soil seed bank over time, thereby facilitating the survival and invasiveness of A. tauschii. [ABSTRACT FROM AUTHOR]

While there is long‐standing interest in the role of inter‐ and transgenerational plasticity via the maternal line, it rarely has been studied via the paternal line. Thus, consequences of the paternal environment for parental fitness and for performance of offspring in the environments experienced by either fathers or mothers are not known. We studied the intergenerational plasticity (IGP) of the plant species Paeonia ostii (Paeoniaceae) and tested the hypothesis that exposure of fathers to environmental stress (i) reduces parental fitness and performance of offspring grown under non‐stressful conditions, but (ii) mitigates the negative effects of environmental stress on fitness of parents and performance of offspring.Crosses were made in a greenhouse within six families of P. ostii between parents grown under drought and in a mesic environment, and the offspring of each cross were grown under both dry and mesic conditions. Production and germination of seeds and morphological and physiological traits of offspring were measured as indicators of parental fitness and offspring performance, respectively.Paternal drought decreased seed number per fruit, except when maternal plants also were grown in drought conditions. Offspring drought decreased seedling performance. However, when fathers experienced drought this negative effect on the offspring was partly mitigated, in particular when mothers also had experienced drought. In contrast, offspring grown in mesic conditions had improved seedling performance, especially when either parent (or both) also were grown in mesic conditions. Such statistical differences remained when seed mass was included as a covariate.Overall, paternal pollen of P. ostii mediated IGP to drought almost as well as it did for maternal ovules. IGP was adaptive if environments remained constantly dry across generations but maladaptive if environments changed. Hence, under future climate changes, paternal IGP might be both a blessing and a curse, with the blessing occurring when the focal habitat becomes drier and pollen comes from already‐dry places, while the curse may dominate in predictably moist habitats surrounded by drier habitats. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Various treatments can be used to break physical dormancy (PY, i.e. water-impermeable seed coat) of legume species, but the effects of these treatments on seedling growth are of great importance in the success of afforestation projects. Our aims were to determine the effects of 20 PY-breaking treatments on (1) germination of Gleditsia caspica (Caspian locust) seeds and (2) seedling growth. Five germination and nine seedling growth and morphological traits were studied. Immersion in concentrated sulfuric acid (98%) for 60 minutes was optimal for all germination traits and for all seedling traits except root length. After seed coat removal or treatment with sulfuric acid (for 45 to 120 minutes), 99–100% of the seeds germinated, but seedling growth traits after 5 months were significantly lower in the former than in the latter treatment. Other treatments (e.g., different periods of exposure to cold water, boiling water, and KNO3) did not significantly increase germination or improve seedling growth. Thus, despite incurring adverse environmental impacts, sulfuric acid treatments have the best potential to break seed dormancy and produce high-quality seedlings (in terms of shoot length, root and shoot mass, root area, leaf number and area and collar diameter) of Caspian locust.

We determined the requirements for dormancy break/germination and kind of dormancy in seeds of the Hawaiian lobelioids Cyanea kunthiana, Delissea rhytidoperma, Lobelia grayana, L. hypoleuca, Trematolobelia grandifolia, and T. singularis. Fresh seeds were incubated in light/dark at 15/6, 20/10, and 25/15 [degrees]C, and germination monitored at two-week intervals for 14 weeks. For each species, the mean embryo length (E): seed (S) length ratio was determined for freshly matured seeds and for seeds at the time the seed coat split but before radicle emergence (germination). The embryo in seeds of all six species incubated at 25/15 [degrees]C grew inside the seed prior to germination (42%-148% increase in E:S ratio, depending on species). Seeds of L. grayana and L. hypoleuca have morphological dormancy (MD); they germinated to 82%-98% at the three temperature regimes in 4 weeks. Seeds of the other species have nondeep simple morphophysiological dormancy (MPD) and require >4 weeks for maximum germination to occur. Our results add to the growing body of knowledge about the kind (class) of seed dormancy in Campanulaceae, which suggests that seeds of members of this family have either MD or MPD and embryos grow at warm ([greater than or equal to]15 [degrees]C) temperatures. Key words: embryo growth, endemic species, morphological dormancy, morphophysiological dormancy, seed dormancy. Les auteurs ont déterminé les conditions de rupture de la dormance/germination et le type dormance de graines des lobélioïdes d'Hawai'i Cyanea kunthiana, Delissea rhytidoperma, Lobelia grayana, L. hypoleuca, Termatolobelia grandifolia et T. singularis. Des graines fraîches ont été incubées à la lumière/obscurité à 15[degrees]/6[degrees], 20[degrees]/10[degrees] et 25[degrees]/15 [degrees]C et la germination a été suivie toutes les deux semaines pendant 14 semaines. Pour chaque espèce, le rapport de la longueur moyenne de l'embryon (E) : longueur moyenne de la graine (S) a été déterminé pour les graines fraîchement mûres et pour les graines au moment de l'ouverture du tégument, mais avant l'émergence de la radicelle (germination). L'embryon des graines des six espèces incubées à 25[degrees]/15 [degrees]C se développait à l'intérieur de la graine avant la germination (augmentation du rapport E : S de 42 à 148% selon l'espèce). Les graines de L. grayana et de L. hypoleuca ont une dormance morphologique; elles germaient à 82-98% aux trois régimes de températures en 4semaines. Les graines des autres espèces ont une dormance morphophysiologique simple non profonde et nécessitent plus de 4 semaines pour que la germination soit maximale. Ces résultats ajoutent au corpus croissant des connaissances sur le type (classe) de dormance des graines chez les Campanulaceae, ce qui suggère que les graines des membres de cette famille ont soit une dormance morphologiqueouune dormance morphophysiologique, et que les embryons se développement à des températures chaudes ([greater than or equal to] 15 [degrees]C). [Traduit par la Rédaction] Mots-clés : croissance des embryons, espèces endémiques, dormance morphologique, dormance morphophysiologique, dormance des graines., Introduction The eudicot family Campanulaceae (APG IV 2016) consists of herbaceous annuals, biennials, and perennials and includes pachycaul rosette plants, subshrubs, shrubs, treelets, trees to 15 m tall (Lammers 2007), [...]

Context: Seed banking is the most efficient and cost-effective method of preserving plant germplasm, but not all species can be conserved by conventional practices. Further, restoration of plant populations from seeds often is hindered by a lack of a priori knowledge of seed dormancy and germination requirements. Aims: Our objective was to determine seed desiccation, initial freezing tolerance and the dormancy-breaking and germination requirements of Coprosma kauensis , a dioecious shrub endemic to Kauaʻi Island in Hawaiʻi. Methods: The effects of temperature and gibberellic acid (GA3) on germination of fresh seeds were tested in light/dark at 15/5, 25/15 and 20/10°C with and without treatment with GA3. To test effects of desiccation and initial freezing on germination, seeds were dried to 15% relative humidity at 15°C and then stored at −20°C. Key results: Regardless of incubation temperature and treatment (or not) with GA3, final germination ranged from 78 to 88%; however, time to 50% germination decreased at 20/10°C for seeds treated with 500 ppm GA3. There was no significant difference in final germination percentage between freshly harvested seeds and those desiccated, nor of those desiccated and then subsequently frozen at −20°C. Conclusions: Fresh seeds of C. kauensis exhibit a low degree of nondeep physiological dormancy. They can germinate over a range of temperatures, but germination speed is increased by GA3. Fresh seeds are desiccation and freeze tolerant (after 6 months storage). Implications: This vulnerable Kauaʻi endemic species easily can be propagated from seeds. Future studies should investigate long-term longevity at various storage temperatures. Seeds of Coprosma kauensis , an IUCN Red List Vulnerable endemic Hawaiian species, germinate over a range of temperatures, but germination rate (speed) is increased by gibberellic acid (GA3). Fresh seeds are desiccation tolerant and can survive short-term storage at −18°C. However, future studies are needed to determine the optimal temperature for long-term storage. [ABSTRACT FROM AUTHOR]

Summary: Information on seed persistence and seedling emergence from the soil seed bank is critical for understanding species coexistence and predicting community dynamics. However, quantifying seed persistence in the soil is challenging; thus, its association with other life‐history traits is poorly known on a broad scale.Using germination phenology for 349 species in a 42‐yr experiment, we quantified the persistence–emergence correlations and their associations with intrinsic regeneration traits using Bayesian phylogenetic multilevel models.We showed no trade‐off between seed persistence and seedling emergence. Physically dormant seeds were more persistent but exhibited lower emergence than nondormant seeds. Monocarpic species had both higher persistence and emergence than polycarpic species. Seed mass posed a marginal proxy for persistence, while emergence almost doubled from the smallest to the largest seeds.This study challenges the traditional assumption and is the first demonstration of noncorrelation between persistence and emergence, probably owing to the complexity of regenerative strategies. Species with short persistence and low emergence would be the most vulnerable for in situ conservation. Our analyses of this unique, long‐term dataset provide a strong incentive for further experimental studies and a rich data resource for future syntheses. See also the Commentary on this article by Meitzel, 241: 521–522. [ABSTRACT FROM AUTHOR]

Lilium polyphyllum D.Don ex Royle is a critically endangered medicinal herb of Himalaya. Seeds have epicotyl morphophysiological dormancy, and in the field a minimum of 34 weeks is required for root emergence. To date, treatments to decrease the time for root protrusion and seed storage behaviour have not been determined. We evaluated the effects of plant growth regulators and nitrogenous compounds as well as seed scarification on root emergence, and determined the storage behaviour of seeds. Root emergence at 20 [degree]C was significantly increased by 100 ppm of indole butyric acid (IBA), KN[O.sub.3], and thiourea, and by the application of NaOCl solution for 30 min. The mean germination time was significantly decreased by 50 ppm of gibberellic acid (G[A.sub.3]; 28 days) compared with 100 ppm G[A.sub.3] (36 days). After 12 months of dry storage, the viability of seeds (TTC method) at room temperature (10-35 [degree]C), 0-4 [degree]C, and -20[+ or -]1[degree]Cwas 95%, 100%, and 100%, respectively; thus, the seeds have orthodox storage behaviour. Our recommendation for seedling production is to store the seeds at room temperature until they can be sown under warm wet conditions. Roots emerge after about 8 weeks, and then seeds should be given a 2-week cold moist treatment to break shoot dormancy. After 2 weeks of cold, transfer the seeds to warm (20 [degree]C) spring temperature conditions to promote growth.Keywords: conservation, critically endangered, seed dormancy, seed storage, seedling production.Lilium polyphyllum D.Don ex Royle est une herbe medicinale de l'Himalaya en voie de disparition. Les graines presentent un axe epicotyle soumis a une dormance morphophysiologique et, sur le terrain, un minimum de 34 semaines est necessaire a l'emergence des racines. Jusqu'a present, les traitements permettant de diminuer le temps requis a la protrusion des racines, de meme que la reponse des semences a l'entreposage n'ont pas ete determines. Les auteurs ont evalue les effets de regulateurs de la croissance des plantes, de composes azotes, et de la scarification des graines sur l'emergence des racines, et ils ont determine la reponse des semences a l'entreposage. L'emergence des racines a 20 [degree]C etait significativement accrue par 100 ppm d'acide indole butyrique, de KN[O.sub.3] et de thio-uree, et par l'application d'une solution de NaOCl pendant 30 minutes. Le temps moyen de germination etait significativement diminue par 50 ppm d'acide gibberellique (G[A.sub.3]) (28 jours) comparativement a 100 ppm de G[A.sub.3] (36 jours). Apres 12 mois d'entreposage au sec, la viabilite des graines (selon la methode au TTC) a la temperature de la piece (10-35 [degree]C), a 0-4 [degree]C et a -20 [degree]C[+ or -]1[degree]C etait de 95 %, 100 % et 100 %, respectivement; ainsi, les semences ont une reponse orthodoxe a l'entreposage. Leur recommandation pour la production de semis est d'entreposer les semences a la temperature de la piece jusqu'a ce qu'elles puissent etre ensemencees dans des conditions humides et chaudes. Les racines emergent apres environ huit semaines, apres quoi les semences doivent etre placees pendant deux semaines dans une humidite froide afin de faire sortir les semis de la dormance. Apres deux semaines au froid, il s'agit de transferer les semences a des temperatures printanieres chaudes (20 [degree]C) pour favoriser leur croissance. [Traduit par la Redaction]Mots-cles : conservation, en voie de disparition, dormance des semences, entreposage des graines, production de semis., IntroductionSeed germination and seedling establishment are critical stages in the life cycle of plants growing in their natural habitats (Fenner and Thompson 2005; Baskin and Baskin 2014) and have great [...]