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1.
Plant-derived smoke, its water extract—the smoke water (SW), and karrikin (KAR 1) present in the smoke stimulate seed germination in plants from fire-prone and fire-free areas, including weeds and cultivated plants. There are also plants, the seeds of which can respond only to smoke, but not to KAR 1, and vice versa. Smoke and/or KAR 1 can be applied in horticulture, agriculture, and revegetation. This review describes effects of smoke and KAR 1 on weed seed germination and focuses mainly on the recent knowledge about the physiological role of these factors in dormancy release and germination of Avena fatua caryopses. The involvement of gibberellins, ethylene, and abscisic acid (ABA) in the response to smoke or KAR 1 is discussed. Effects of smoke or KAR 1 on the contents of reactive oxygen species (ROS), non-enzymatic antioxidants, and activity of the enzymes participating in ROS removal are presented. Cell cycle activity in the response to SW and KAR 1 is also considered. Effects of KAR 1 on thermodormancy release in A. fatua caryopses are highlighted, as well. 相似文献
2.
Background and AimsTersonia cyathiflora (Gyrostemonaceae) is a fire ephemeral with an obligate requirement for smoke to germinate. Whether it is stimulated to germinate by 3-methyl-2 H-furo[2,3- c]pyran-2-one (karrikinolide, KAR 1), the butenolide isolated from smoke that stimulates the germination of many other smoke-responsive species, is tested. MethodsSeeds of T. cyathiflora were buried in autumn following collection and were exhumed 1 year later, as this alleviates dormancy and enables seeds to germinate in response to smoke-water. Exhumed seeds were tested with smoke-water and KAR 1. Fresh preparations of these solutions were again tested on seeds exhumed 2 months later under a broader range of conditions. They were also tested on Grevillea eriostachya (Proteaceae) and Stylidium affine (Stylidiaceae) to confirm the activity of KAR 1. Key ResultsT. cyathiflora seeds germinated in response to smoke-water but not to KAR 1. In contrast, G. eriostachya and S. affine germinated in response to both smoke-water and KAR 1. ConclusionsAlthough many smoke-responsive seeds germinate in the presence of KAR 1, this does not apply universally. This suggests that other chemical(s) in smoke-water may play an important role in stimulating the germination of certain species. 相似文献
3.
Plant‐derived smoke and smoke‐isolated compounds stimulate germination in seeds from over 80 genera. It has also been reported that smoke affects overall plant vigour and has a stimulatory effect on pollen growth. The effect of smoke on orchid seeds, however, has not been assessed. In South Africa, orchid seeds from several genera may be exposed to smoke when they are released from their seedpods. It is therefore possible that smoke may affect their germination and growth. Therefore, the effects of smoke [applied as smoke‐water (SW)] and two smoke‐derived compounds, karrikinolide (KAR 1) and trimethylbutenolide (TMB), were investigated on the germination and growth of orchid seeds in vitro. The effect of SW, KAR 1 and TMB were investigated on the endangered epiphytic orchid, Ansellia africana, which is indigenous to tropical areas of Africa. Smoke‐water, KAR 1 and TMB were infused in half‐strength MS medium. The number of germinated seeds and number of seeds and protocorm bodies to reach predetermined developmental stages were recorded on a weekly basis using a dissecting microscope for a 13‐week period. Infusing SW 1:250 (v:v) into half‐strength MS medium significantly increased the germination rate index (GRI) and the development rate index (DRI) of the A. africana seeds. All the SW treatments significantly increased the number of large protocorm bodies at the final stage of development. Infusing KAR 1 into the growing medium had no significant effect on germination or development of the seeds. The TMB treatment, however, significantly reduced the GRI and DRI of A. africana seeds. 相似文献
4.
Background and AimsA major germination-promoting chemical in smoke-water is 3-methyl-2 H-furo[2,3- c]pyran-2-one (karrikinolide, KAR 1). However, not all species that germinate in response to smoke-water are responsive to KAR 1, such as Tersonia cyathiflora (Gyrostemonaceae). In this study, a test was made of whether two Gyrostemon species (Gyrostemonaceae) that have previously been shown to respond to smoke-water, respond to KAR 1. If not, then the smoke-derived chemical that stimulates germination of these species is currently unknown. Recently, glyceronitrile was isolated from smoke-water and promoted the germination of certain Anigozanthos species (Haemodoraceae). Whether this chemical promotes Gyrostemon racemiger germination is also examined. Furthermore, an investigation was carried out into whether these species germinate in response to smoke-water derived from burning cellulose alone. Methods Gyrostemon racemigerand G. ramulosus seeds were buried after collection and retrieved in autumn the following year when dormancy was alleviated and seeds had become responsive to smoke-water. Anigozanthos flavidus seeds were after-ripened at 35 °C to alleviate dormancy. Gyrostemon and Anigozanthos seeds were then tested with ‘Seed Starter’ smoke-water, KAR 1, glyceronitrile and cellulose-derived smoke-water. Key ResultsAlthough Gyrostemon racemiger, G. ramulosus and A. flavidus were all stimulated to germinate by ‘Seed Starter’ smoke-water, none of these species responded to KAR 1. Gyrostemon racemiger germination was not promoted by glyceronitrile. This is in contrast to A. flavidus, where glyceronitrile, at concentrations of 1–500 µ m, promoted germination, although seedling growth was inhibited at ≥400 µ m. Maximum A. flavidus germination occurred at glyceronitrile concentrations of 25–300 µ m. Some Gyrostemon germination was promoted by cellulose-derived smoke-water. ConclusionsKAR 1 and glyceronitrile, chemicals in smoke-water that are known to stimulate germination in other species, did not promote the germination of G. racemiger. This suggests that other chemical(s) which promote germination are present in smoke, and may be derived from burning cellulose alone. 相似文献
5.
Background and AimsThe smoke-derived chemical karrikinolide (KAR 1) shows potential as a tool to synchronize the germination of seeds for weed management and restoration. To assess its feasibility we need to understand why seeds from different populations of a species exhibit distinct responses to KAR 1. Environmental conditions during seed development, known as the parental environment, influence seed dormancy so we predicted that parental environment would also drive the KAR 1-responses of seeds. Specifically, we hypothesized that ( a) a common environment will unify the KAR 1-responses of different populations, ( b) a single population grown under different environmental conditions will exhibit different KAR 1-responses, and ( c) drought stress, as a particular feature of the parental environment, will make seeds less dormant and more responsive to KAR 1. MethodsSeeds of the weed Brassica tournefortii were collected from four locations in Western Australia and were sown in common gardens at two field sites, to test whether their KAR 1-responses could be unified by a common environment. To test the effects of drought on KAR 1-response, plants were grown in a glasshouse and subjected to water stress. For each trial, the germination responses of the next generation of seeds were assessed. Key ResultsThe KAR 1-responses of seeds differed among populations, but this variation was reduced when seeds developed in a common environment. The KAR 1-responses of each population changed when seeds developed in different environments. Different parental environments affected germination responses of the populations differently, showing that parental environment interacts with genetics to determine KAR 1-responses. Seeds from droughted plants were 5 % more responsive to KAR 1 and 5 % less dormant than seeds from well-watered plants, but KAR 1-responses and dormancy state were not intrinsically linked in all experiments. ConclusionsThe parental environment in which seeds develop is one of the key drivers of the KAR 1-responses of seeds. 相似文献
6.
Background and AimsKarrikinolide (KAR 1) is a smoke-derived chemical that can trigger seeds to germinate. A potential application for KAR 1 is for synchronizing the germination of weed seeds, thereby enhancing the efficiency of weed control efforts. Yet not all species germinate readily with KAR 1, and it is not known whether seemingly non-responsive species can be induced to respond. Here a major agronomic weed family, the Brassicaceae, is used to test the hypothesis that a stimulatory response to KAR 1 may be present in physiologically dormant seeds but may not be expressed under all circumstances. MethodsSeeds of eight Brassicaceae weed species ( Brassica tournefortii, Raphanus raphanistrum, Sisymbrium orientale, S. erysimoides, Rapistrum rugosum, Lepidium africanum, Heliophila pusilla and Carrichtera annua) were tested for their response to 1 µ m KAR 1 when freshly collected and following simulated and natural dormancy alleviation, which included wet–dry cycling, dry after-ripening, cold and warm stratification and a 2 year seed burial trial. Key ResultsSeven of the eight Brassicaceae species tested were stimulated to germinate with KAR 1 when the seeds were fresh, and the remaining species became responsive to KAR 1 following wet–dry cycling and dry after-ripening. Light influenced the germination response of seeds to KAR 1, with the majority of species germinating better in darkness. Germination with and without KAR 1 fluctuated seasonally throughout the seed burial trial. ConclusionsKAR 1 responses are more complex than simply stating whether a species is responsive or non-responsive; light and temperature conditions, dormancy state and seed lot all influence the sensitivity of seeds to KAR 1, and a response to KAR 1 can be induced. Three response types for generalizing KAR 1 responses are proposed, namely inherent, inducible and undetected. Given that responses to KAR 1 were either inherent or inducible in all 15 seed lots included in this study, the Brassicaceae may be an ideal target for future application of KAR 1 in weed management. 相似文献
7.
Background and AimsThe smoke-derived compound karrikinolide (KAR 1) shows significant potential as a trigger for the synchronous germination of seeds in a variety of plant-management contexts, from weed seeds in paddocks, to native seeds when restoring degraded lands. Understanding how KAR 1 interacts with seed physiology is a necessary precursor to the development of the compound as an efficient and effective management tool. This study tested the ability of KAR 1 to stimulate germination of seeds of the global agronomic weed Brassica tournefortii, at different hydration states, to gain insight into how the timing of KAR 1 applications in the field should be managed relative to rain events. MethodsSeeds of B. tournefortii were brought to five different hydration states [equilibrated at 15 % relative humidity (RH), 47 % RH, 96 % RH, fully imbibed, or re-dried to 15 % RH following maximum imbibition] then exposed to 1 n m or 1 µ m KAR 1 for one of five durations (3 min, 1 h, 24 h, 14 d or no exposure). Key ResultsDry seeds with no history of imbibition were the most sensitive to KAR 1; sensitivity was lower in seeds that were fully imbibed or fully imbibed then re-dried. In addition, reduced sensitivity to KAR 1 was associated with an increased sensitivity to exogenously applied abscisic acid (ABA). ConclusionsSeed water content and history of imbibition were found to significantly influence whether seeds germinate in response to KAR 1. To optimize the germination response of seeds, KAR 1 should be applied to dry seeds, when sensitivity to ABA is minimized. 相似文献
8.
The discovery of karrikins as the chemical constituents responsible for the germination stimulatory effects of smoke has met with widespread interest from the botanical/scientific community. Although such beneficial properties of smoke in agriculture and environmental management have been known for several centuries, it is only in the last decade that this significant discovery has been made. The karrikins comprising KAR 1–KAR 6 have been shown to be potent promoters of germination in numerous model studies. KAR 1, the most abundant of the karrikins, has been revealed as the key germination cue present in smoke with activities as low as 100 ppt. Given the vast economic potential of these molecules as well as their low natural abundance, several strategies have been devised towards the synthesis of karrikins with the goal of elucidating structure–activity relationships. However, the targets of these structures as well as their mode of action are yet to be determined. To this end, we herein detail the first single crystal X-ray structure of KAR 3 with the aim that it may provide further insights to the molecular mechanism behind this group of compounds. 相似文献
9.
Fire and smoke have been used in traditional agricultural systems for centuries. In recent years, biologically active compounds have been isolated from smoke with potential uses in agriculture and horticulture. This article highlights the possibilities of using smoke-water or smoke-derived butenolide (3-methyl- 2H-furo[2,3- c]pyran-2-one, termed karrikinolide, KAR 1) for the cultivation of agricultural and horticultural crops. Treatments with smoke-water show promising results for improving seed germination, seedling growth and crop productivity. In certain cases, even under adverse conditions, such as low or high temperatures and low osmotic potentials, smoke-water or a KAR 1 solution can promote seed germination and seedling growth. This phenomenon is of great significance when seeds are sown under drought conditions. Smoke-technology, therefore, has potential for use in arid and semi-arid regions. Possibilities may also exist for controlling some plant diseases and managing weeds with the use of smoke or KAR 1 solutions. In addition, smoke-technology can possibly economize the use of commercial chemical fertilizers, pesticides and herbicides, making it a feasible technology for organic farming and for resource-poor farmers in developing nations. The positive role of smoke-water in flowering and fruiting of crops cannot be overlooked as the karrikins found in smoke are now recognized as potential new plant growth regulators. Very low concentrations of smoke-water or a KAR 1 solution are effective in promoting germination and post-germination growth. Thus, early harvesting and increasing the productivity of crops using smoke-technology may be possible. Here we review some of the effects of smoke and KAR 1 on various crop species and discuss the potential uses of smoke technology in agriculture and horticulture. 相似文献
10.
Wildfires are having both devastating and regenerative impacts on the ecosystems in the Pacific Northwest of North America. Balsamorhiza sagittata and B. deltoidea (balsamroot) are ecologically important species in this region, and B. sagittata populations are increasing, while B. deltoidea is critically imperiled. The aim of this research was to establish in vitro protocols for germination and regeneration of Balsamorhiza spp. to enable conservation efforts. It was hypothesized that karrikins, which are plant growth regulators released from burning plants during wildfires, would induce seed germination in Balsamorhiza spp. Three karrikins (KAR1, KAR2, and KAR11) were tested for the ability to enhance germination in these species at two levels (5 or 10 μM). KAR2 had the strongest positive effect on germination and induced 47% and 60% germination, respectively, in B. sagittata seeds compared to 14% germination obtained in the control (water agar media). In B. deltoidea, KAR2 treatment resulted in a germination rate of 73.1% and 100%, compared to 69% in the control. A germplasm collection of seedlings of both species was established for conservation and regeneration experiments. Thidiazuron treatment (10 μM) induced formation of embryo-like structures in seedlings of both B. sagittata and B. deltoidea, with regenerants originating from the crown of seedlings. The present study provides in vitro methods for conservation and mass propagation of Balsamorhiza species. 相似文献
11.
Discovery of the primary seed germination stimulant in smoke, 3-methyl-2 H-furo[2,3- c]pyran-2-one (KAR 1), has resulted in identification of a family of structurally related plant growth regulators, karrikins. KAR 1 acts as a key germination trigger for many species from fire-prone, Mediterranean climates, but a molecular mechanism for this response remains unknown. We demonstrate that Arabidopsis ( Arabidopsis thaliana), an ephemeral of the temperate northern hemisphere that has never, to our knowledge, been reported to be responsive to fire or smoke, rapidly and sensitively perceives karrikins. Thus, these signaling molecules may have greater significance among angiosperms than previously realized. Karrikins can trigger germination of primary dormant Arabidopsis seeds far more effectively than known phytohormones or the structurally related strigolactone GR-24. Natural variation and depth of seed dormancy affect the degree of KAR 1 stimulation. Analysis of phytohormone mutant germination reveals suppression of KAR 1 responses by abscisic acid and a requirement for gibberellin (GA) synthesis. The reduced germination of sleepy1 mutants is partially recovered by KAR 1, which suggests that germination enhancement by karrikin is only partly DELLA dependent. While KAR 1 has little effect on sensitivity to exogenous GA, it enhances expression of the GA biosynthetic genes GA3ox1 and GA3ox2 during seed imbibition. Neither abscisic acid nor GA levels in seed are appreciably affected by KAR 1 treatment prior to radicle emergence, despite marked differences in germination outcome. KAR 1 stimulation of Arabidopsis germination is light-dependent and reversible by far-red exposure, although limited induction of GA3ox1 still occurs in the dark. The observed requirements for light and GA biosynthesis provide the first insights into the karrikin mode of action.Germination is a critical event in the plant life cycle, as the timing of emergence from the protective seed coat is crucial for survival and reproductive success. A variety of abiotic stimuli, including light, temperature, and nitrates, provide information about the external environment that affects germination. Seed dormancy gates responses to these factors. Upon maturation, physiologically dormant seeds are in a primary dormant (PD) state, which is lost during afterripening. The transition between a PD and nondormant state is both gradual and reversible and results in relaxation of the set of environmental conditions under which a seed will germinate ( Baskin and Baskin, 2004; Finch-Savage and Leubner-Metzger, 2006).Despite decades of research, seed dormancy remains a complex physiological state that is not well understood. The plant hormones abscisic acid (ABA) and GA are mutually antagonistic central players in the germination decision ( Finch-Savage and Leubner-Metzger, 2006; Finkelstein et al., 2008). The role of dormancy establishment and maintenance has been attributed to ABA, while GA has been implicated in the initiation and completion of germination. The ratio of ABA to GA signaling, rather than absolute amounts of the hormones, appears to be critical to dormancy breaking ( Finch-Savage and Leubner-Metzger, 2006). Environmental stimuli and phytohormones influence the ABA/GA balance, although the mechanisms of signal integration and hormone cross talk are still largely unknown.In many biodiverse regions, fire events provide an irregular but important opportunity for seedling establishment by freeing up key resources such as light, space, and nutrients ( Van Staden et al., 2000; Dixon et al., 2009). A clear example of this is seen in the flush of new growth in the immediate postfire environment, indicating potent activation of the soil seed bank. Heat is not required for the germination response, as cold smoke application induced an up to 48-fold increase in the number of germinating seedlings and approximately 3-fold enrichment in species abundance in field trials ( Roche et al., 1997; Rokich et al., 2002). It has now been well established that smoke is a broadly effective stimulant that enhances germination of approximately 1,200 species in more than 80 genera worldwide ( Dixon et al., 2009). Attempts to study smoke effects on plant physiology have been confounded by the complex mixture of components within smoke, some of which confer toxicity at high concentrations. Bioassay-guided fractionation of smoke water culminated in the discovery and synthesis of the primary germination stimulant 3-methyl-2 H-furo[2,3- c]pyran-2-one (KAR 1; Flematti et al., 2004). With the recent identification of three analogous active compounds in smoke water fractions (; G. Flematti, unpublished data), this family of butenolide molecules have been designated karrikins, after “karrik,” the first recorded Aboriginal Nyungar word for smoke ( Dixon et al., 2009). Open in a separate windowPartial structural similarity between the karrikin family of plant growth regulators and strigolactones. A, Molecular structures of KAR 1 (3-methyl-2 H-furo[2,3- c]pyran-2-one), KAR 2 (2 H-furo[2,3- c]pyran-2-one), KAR 3 (3,5-dimethyl-2 H-furo[2,3- c]pyran-2-one), and KAR 4 (3,7-dimethyl-2 H-furo[2,3- c]pyran-2-one). B, Molecular structures of a natural (strigol) and a synthetic (GR-24) strigolactone.The parent molecule, KAR 1, is a potent stimulant that enhances germination in some species at subnanomolar concentrations ( Flematti et al., 2004; Stevens et al., 2007). In field trials, KAR 1 is effective at less than 5 g ha −1 compared with 10 ton ha −1 smoke water and thus may have practical value in agriculture, conservation, and restoration ( Stevens et al., 2007). Smoke water fractions containing KAR 1 have been reported to enhance seedling vigor of several weed and crop species, indicating potential use for KAR 1 as a seed priming agent to improve germination and seedling establishment ( Jain et al., 2006; Jain and Van Staden, 2006; Kulkarni et al., 2006; van Staden et al., 2006; Daws et al., 2007a). Since its discovery, a widespread capacity for KAR 1 germination response among angiosperms has been demonstrated ( Flematti et al., 2004; van Staden et al., 2004, 2006; Merritt et al., 2006; Daws et al., 2007a; Stevens et al., 2007). Thus, karrikins may be considered a novel class of plant growth regulators with broad impact. To gain a better understanding of the mechanism by which karrikins trigger seed germination and explore their interaction with ABA and GA, we examined KAR 1 responses in Arabidopsis ( Arabidopsis thaliana). 相似文献
12.
Plant-derived smoke is a positive regulator of seed germination and growth with regard to many plant species. Of the several compounds present in plant-derived smoke, karrikinolide or KAR1 (3-methyl-2H-furo[2,3-c]pyran-2-one) is considered to be the major active growth-promoting compound. To test the efficacy of smoke-saturated water (SSW) and KAR1 on carrot (Daucus carota L.), two separate pot experiments were simultaneously conducted in the same environmental conditions. SSW and KAR1 treatments were applied to the plants in the form of aqueous solutions of variable concentrations. Prior to sowing, seeds were soaked in the solutions of SSW (25.8 µg L−1, 51.6 µg L−1,103.2 µg L−1 and 258.0 µg L−1) and KAR1 (0.015 µg L−1, 0.150 µg L−1, 1.501 µg L−1 and 15.013 µg L−1). Percent seed germination, vegetative growth, photosynthesis and nutritional values were the major parameters through which the plant response to the applied treatments was investigated. The results obtained indicated a significant improvement in all the plant attributes studied. In general, SSW (51.6 µg L−1) and KAR1 (1.501 µg L−1) proved optimum treatments for most the parameters. As compared to the control, 51.6 µg L−1 of SSW and 1.501 µg L−1 of KAR1 increased the percent seed germination by 58.0% and 54.4%, respectively. Over the control, the values of plant height and net photosynthetic rate were enhanced by 33.9% and 40.9%, respectively, due to 51.6 µg L−1 of SSW, while the values of these parameters were increased by 25.2% and 34.0%, respectively, due to 1.501 µg L−1 of KAR1. In comparison with the control, treatment 51.6 µg L−1 of SSW increased the contents of β-carotene and ascorbic acid by 32.7% and 37.9%, respectively, while the treatment 1.501 µg L−1 M of KAR1 enhanced these contents by 42.0% and 48.4%, respectively. This study provides an insight into an affordable and feasible method of crop improvement. 相似文献
13.
Smoke plays a positive role in promoting seed germination and enhancing post-germination processes. The compound in smoke is 3-methyl-2 H-furo[2,3- c]pyran-2-one (KAR 1). Recently a structurally related butenolide [3,4,5-trimethylfuran-2(5 H)-one, (trimethylbutenolide, TMB)], which inhibits germination and reduces the effect of KAR 1, was isolated. The mechanisms of action and interaction of these karrikins are unknown. In addition, the ecological significance of fires in altering soil-smoke-chemistry and the spatial dimensions of the influence on burnt sites and neighbouring areas are undetermined. This study quantified KAR 1 and TMB residues in soils following fire and assessed the germination activity of burnt soil extracts. Soil samples from 0 to 2, 2 to 4, 4 to 6 and 6 to 8 cm depths were extracted using dichloromethane and bioassayed using Lactuca sativa L. achenes (seeds). At all soil depths, L. sativa seeds exhibited significantly greater percentage germination when treated with burnt soil extracts compared to the no-burn soil (control). The L. sativa seeds also showed significantly greater percentage germination when treated with soil extracts from the adjacent plots. Compared to the no-burn soil, higher concentrations of KAR 1 and TMB were detected in the surface layers of the burnt soils. Considerable concentrations of KAR 1 and TMB were also detected in no-burn soil indicating that sources other than fire may also generate karrikins. Findings of this study imply that post-fire increases in KAR 1 residues in the soil may influence soil seed bank stimulation of certain smoke-responsive plant communities in both burnt and adjacent non-burnt areas. 相似文献
14.
- In degraded dryland systems, native plant community re‐establishment following disturbance is almost exclusively carried out using seeds, but these efforts commonly fail. Much of this failure can be attributed to the limited understanding of seed dormancy and germination traits.
- We undertook a systematic classification of seed dormancy of 26 species of annual and perennial forbs and shrubs that represent key, dominant genera used in restoration of the Great Basin ecosystem in the western United States. We examined germination across a wide thermal profile to depict species‐specific characteristics and assessed the potential of gibberellic acid (GA3) and karrikinolide (KAR1) to expand the thermal germination envelope of fresh seeds.
- Of the tested species, 81% produce seeds that are dormant at maturity. The largest proportion (62%) exhibited physiological (PD), followed by physical (PY, 8%), combinational (PY + PD, 8%) and morphophysiological (MPD, 4%) dormancy classes. The effects of chemical stimulants were temperature‐ and species‐mediated. In general, mean germination across the thermal profile was improved by GA3 and KAR1 for 11 and five species, respectively. We detected a strong germination response to temperature in freshly collected seeds of 20 species. Temperatures below 10 °C limited the germination of all except Agoseris heterophylla, suggesting that in their dormant state, the majority of these species are thermally restricted.
- Our findings demonstrate the utility of dormancy classification as a foundation for understanding the critical regenerative traits in these ecologically important species and highlight its importance in restoration planning.
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15.
The effects of after‐ripening (storage under warm, dry conditions) on seed germination was examined in six plant species from the arid zone of Western Australia with the aim of improving germination and germination rate for rehabilitation objectives. Study species ( Acanthocarpus preissii, Anthocercis littorea, Dioscorea hastifolia, Eremophila oldfieldii, Thryptomene baeckeacea and Zygophyllum fruticulosum) were selected based on diverse plant habits, seed types and requirements for rehabilitation. After‐ripening was investigated by adjusting seed moisture content to 13 and 50 equilibrium relative humidity (eRH) at 23 °C and storing seeds at two temperatures (30 and 45 °C) from 1 to 18 months. Following storage, seeds were incubated in water, gibberellic acid (GA 3) or karrikinolide (KAR 1; the butenolide, 3‐methyl‐2 H‐furo[2,3‐ c]pyran‐2‐one). All after‐ripening conditions increased germination percentage and rate of A. littorea and D. hastifolia, with A. littorea only germinating when treated with GA 3 or KAR 1. The germination of Z. fruticulosum was dependent on after‐ripening temperature and seed moisture content. After‐ripening had a limited effect on the remaining three species. The restoration implications of the findings are discussed. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 161 , 411–421. 相似文献
16.
Questions Fire is a crucial component of many ecosystems. Plants whose seeds germinate in response to smoke may benefit from resource availability in the post‐fire environment. Smoke can influence germination timing and success, as well as seedling vigour, resulting in burgeoning research interest in smoke‐responsive germination. Research in this field has largely focused on four key ‘Mediterranean‐type’ fire‐prone ecosystems: the Mediterranean Basin, South African fynbos, Californian chaparral and Western Australia. There are far fewer studies from south‐eastern Australia, a fire‐prone but not “Mediterranean‐type” region. How does smoke‐responsive germination in this region vary according to ecological, phylogenetic, and methodological variables? Location South‐eastern Australia. Methods We investigated patterns of smoke‐promoted germination in south‐eastern Australian plants across habitat types, growth forms, fire response strategies, phylogeny, taxonomic levels and smoke application methods. We compiled and interrogated data comprising 303 entries on germination responses to smoke in 233 south‐eastern Australian plant species, from 33 different sources. Results Smoke‐responsive germination occurs at a lower rate (~41% of tested species) in south‐eastern Australian flora than it does in fynbos and Western Australian floras, and there is clear patterning within these data. Obligate‐seeding species were more likely to respond, Leguminosae and Rubiaceae were less likely to respond (although we question the generality of these results), while Poaceae were more likely to respond to smoke. Finally, studies using aerosol smoke and studies conducted in situ were most likely to find smoke‐promoted germination. Conclusions Obligate seeders and Poaceae may be selected for in habitats with higher fire frequencies, consistent with literature suggesting that short inter‐fire intervals favour grasslands over forests. These findings may be particular to south‐eastern Australia, or more widely applicable; more broad‐scale comparative research will reveal the answer. By synthesizing the south‐eastern Australian smoke germination literature we broaden our understanding beyond the better‐studied Mediterranean‐type floras. 相似文献
17.
- The response of seeds from 23 wild plant species to a range of seed enhancing treatments was studied. We tested the hypothesis that sensitivity of the 23 species to these compounds is related to their ecological niche. The three ecological niches considered were open land, open‐pioneer and woodland. Hence, the germination of a species is likely adapted to different light conditions and other environmental signals related to the niche.
- As representatives of environmental signals, the effects of smoke‐related compounds (karrikinolide, KAR1), nitrate and plant growth regulator (gibberellic acid, GA3) on germination were studied. Seeds were exposed to these additives in the imbibition medium; all described as germination cues. We also investigated the effect of light regimes and additives on germination parameters, which included final germination, germination rate and uniformity of germination. Seeds were placed to germinate under three light conditions: constant red light, constant darkness and 12 h white light photoperiod.
- We observed inhibition by KAR under light in some species, which may have ecological implications. The results showed that no single treatment increased the germination of all the tested species, rather a wide variation of responsiveness of the different species to the three compounds was found. Additionally, no interaction was found between responsiveness to compounds and ecological niche. However, species in the same ecological niche and dormancy class showed a similar responsiveness to light.
- Species that share a similar environment have similar light requirements for germination, while differences exist among species in their responsiveness to other germination cues.
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18.
Caryopses of Avena fatua L. are dormant after harvest and germinate poorly at 20 °C. Dormancy was released by after-ripening the dry caryopses in the dark at 25 °C for 3 months. Karrikinolide (butenolide, 3-methyl-2 H-furo[2,3- c]pyran-2-one, KAR 1), in contrast to exogenous ethylene and the precursor of ethylene biosynthesis 1-aminocyclopropane-1-carboxylic acid (ACC), completely overcame dormancy. The effect of KAR 1 was not affected by aminoethoxyvinylglycine (AVG), α-aminoisobutyric acid (AIB) and CoCl 2, inhibitors of ACC synthase and oxidase, respectively. 2,5-Norbornadiene (NBD), a reversible inhibitor of ethylene binding to its receptor, counteracted the stimulatory effect of KAR 1. Ethylene, ethephon and ACC counteracted and AVG reinforced inhibition caused by norbornadiene. Inhibition due to norbornadiene, applied during the first 3 days of imbibition in the presence of KAR 1, disappeared after transfer to air or ethylene. The obtained results confirm that KAR 1 breaks dormancy and indicate that ethylene alone plays no role in releasing dormancy of Avena fatua caryopses. KAR 1 probably did not relieve dormancy via the stimulation of ethylene biosynthesis. Some level of endogenous ethylene is probably required for ethylene action, which might be required for releasing dormancy by KAR 1 or for subsequent germination of caryopses after removing dormancy. 相似文献
19.
Background The key enzymes of photosynthetic carbon assimilation in C 4 plants have evolved independently several times from C 3 isoforms that were present in the C 3 ancestral species. The C 4 isoform of phosphoenolpyruvate carboxylase (PEPC), the primary CO 2-fixing enzyme of the C 4 cycle, is specifically expressed at high levels in mesophyll cells of the leaves of C 4 species. We are interested in understanding the molecular changes that are responsible for the evolution of this C 4-characteristic PEPC expression pattern, and we are using the genus Flaveria (Asteraceae) as a model system. It is known that cis-regulatory sequences for mesophyll-specific expression of the ppcA1 gene of F. trinervia (C 4) are located within a distal promoter region (DR). 相似文献
20.
Plant-derived smoke water (SW), derived from combusted plant material, has been shown to stimulate seed germination and improve seedling vigor of a number of plant species from fire-dependent Mediterranean-type climate areas. The effects of SW on seed germination of 13 plant species from southern tropical and subtropical monsoon climate regions of South China are reported for the first time in this study using laboratory and pot trials. Among the 13 species tested, only Aristolochia debilis showed a significant positive response to commercial SW when diluted 1:10. Seed germination of A. debilis was also stimulated by 1–100 nM 3-methyl-2H-furo [2, 3-c] pyran-2-one (karrikin 1 or KAR 1) and by 10–1000 µM gibberellic acid (GA 3). GA 3 stimulated seed germination of Santalum album and significantly elongated the radicles of A. debilis while SW could not. The functions and/or metabolic pathways of Kar 1 and GA 3 are likely to be separate and/or distinct. 相似文献
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