Effects of salinity and source of inocula on germination of Anabaena akinetes from a tidally influenced lake

1. Sedimentary akinetes (resting stages) may represent significant potential inocula for nuisance blooms of cyanobacteria. We studied the effects of salinity and sediment source on the germination and subsequent growth of Anabaena flos‐aquae akinetes from a shallow, tidally influenced lake. 2. Surface sediments collected from littoral and open‐water sites were used as inocula to culture A. flos‐aquae akinetes in four salinities (0.1, 2.2, 4.4 and 6.5) over 22 days. Akinete germination and development was followed by counting developmental stages every second day. 3. Filament growth, but not akinete germination, was inhibited by salinity and there were significantly fewer filaments at 6.5 than at 0.1 and 2.2. Cultures inoculated with littoral sediment had more akinetes, germlings and filaments than those inoculated with open‐water sediment. 4. Sediment is a potential source of inocula for Anabaena blooms in the lake, which potentially could develop solely from this source because germination and subsequent filament growth do not depend on the existence of an initial pelagic Anabaena population.     

Seed moisture content affects afterripening and smoke responsiveness in three sympatric Australian native species from fire‐prone environments

Germination of freshly collected seeds of three sympatric herbaceous species native to fire‐prone environments in south‐western Australia was significantly improved through the application of novel combinations of dry heat, gibberellic acid, smoke water and dry afterripening. For fresh seeds, combinations of dry heat, gibberellic acid and/or smoke water resulted in >80% germination in Austrostipa elegantissima (Poaceae) and Stylidium affine (Stylidaceae) seeds and >60% germination in Conostylis candicans (Haemodoraceae) seeds, compared with <10% germination of control seeds. For fresh seeds, two broad germination patterns were observed in response to smoke water: nil – low germination for both control and smoke water‐treated seeds (A. elegantissima and S. affine); and a significant smoke response (35%) compared with control seeds (1%) (C. candicans). During afterripening, high germination for A. elegantissima seeds was achieved following 3 months storage of seeds at equilibrium relative humidities of 23–75%, but seeds stored at 5–13% equilibrium relative humidities took 6–36 months to achieve similar levels of germination. Germination of C. candicans seeds also increased after 3 months storage, to >60% at each equilibrium relative humidity and further increases over time were slight. For S. affine seeds >60% germination was achieved only after 36 months storage at 50% equilibrium relative humidity. Seeds from all three species were smoke‐responsive at some point, but the interaction/effects of afterripening on the smoke response varied significantly between species. This study highlights an apparent effect of seed dormancy status on response to smoke and a surprisingly high level of ecological variation in pre‐germination requirements (cues) for these co‐occurring species that may relate to variation(s) in microsite selection forces operating on the soil seed bank of the different species.     

The signalling mucin Msb2 regulates surface sensing and host penetration via BMP1 MAP kinase signalling in Botrytis cinerea

Botrytis cinerea is a necrotrophic fungus that infects a wide range of fruit, vegetable and flower crops. Penetration of the host cuticle occurs via infection structures that are formed in response to appropriate plant surface signals. The differentiation of these structures requires a highly conserved mitogen‐activated protein (MAP) kinase cascade including the MAP kinase BMP1. In yeast and several plant‐pathogenic fungi, the signalling mucin Msb2 has been shown to be involved in surface recognition and MAP kinase activation. In this study, a B. cinerea msb2 mutant was generated and characterized. The mutant showed normal growth, sporulation, sclerotia formation and stress resistance. In the absence of nutrients, abnormal germination with multiple germ tubes was observed. In the presence of sugars, normal germination occurred, but msb2 germlings were almost unable to form appressoria or infection cushions on hard surfaces. Nevertheless, the msb2 mutant showed only a moderate delay in lesion formation on different host plants, and formed expanding lesions similar to the wild‐type. Although the wild‐type showed increasing BMP1 phosphorylation during the first hours of germination on hard surfaces, the phosphorylation levels in the msb2 mutant were strongly reduced. Several genes encoding secreted proteins were found to be co‐regulated by BMP1 and Msb2 during germination. Taken together, B. cinerea Msb2 is likely to represent a hard surface sensor of germlings and hyphae that triggers infection structure formation via the activation of the BMP1 MAP kinase pathway.     

Control of macroalgal blooms at early developmental stages: Pilayella littoralis versus Enteromorpha spp.

Although blooms of opportunistic fast-growing macroalgae now occur frequently in coastal ecosystems affected by eutrophication, their initiation and control is little understood. Most previous studies have focused on the ecophysiology of adult algae only. We show that spores and/or germlings may represent critical stages in the life cycles and mass-developments of co-occurring opportunistic macroalgae in the Baltic (Pilayella littoralis and Enteromorpha spp.). We investigated the overwintering of spores, timing of germination, subsequent growth, and grazing on spores and germlings, in order to explain the initiation of mass blooms and species dominance patterns. In the field, Enteromorpha spp. showed 10- to 50-fold higher abundances of overwintering microscopic forms (up to 330 individuals cm⁻²) than P. littoralis. Moreover, we found continuous production of spores (up to 1.2 million settling spores m⁻² h⁻¹) from April to October in Enteromorpha spp., while there was evidence of only a short reproductive period in Pilayella. However, in spring, germlings and adults of P. littoralis appeared earlier in the field and reached a 10-fold higher biomass than Enteromorpha spp. In factorial laboratory experiments including temperature and light, there were clear differences in timing of germination. P. littoralis germinated at 5°C whereas Enteromorpha spp. required temperatures of 10–15°C for germination. In contrast, we detected only minor differences in growth response among adults of P. littoralis and Enteromorpha spp. Germination, not growth of adults, appeared to be the ecophysiological bottleneck for initiating mass spring development. Following the spring Pilayella bloom, Enteromorpha germlings occurred massively in the field (April–September), but rarely developed into adults. In laboratory feeding experiments we tested whether crustacean mesograzers common in summer may control development of Enteromorpha germlings. Both germination of settled spores and growth of germlings were reduced by 93–99% in the presence of grazers (Idotea chelipes and Gammarus locusta). Thus in addition to ecophysiological constraints, grazers, if present, may play a decisive role in the early life stages of macroalgal mass developments. These results mirror patterns of overwintering of seeds, germination control, seed and seedling predation in terrestrial plant communities. Received: 7 March 1998 / Accepted: 18 November 1998     

Control of arabitol formation in Schizophyllum commune development

Summary Dikaryotic cells of S. commune synthesized polyols throughout the life cycle when grown on glucose, cellobiose, or cellulose. Basidiospores contained arabitol and mannitol which were depleted during germination. The mannitol content of the young germlings rose to normal levels within a day; arabitol accumulation remained depressed for 5 to 7 days and then returned to normal levels characteristic of vegetative cells. Individual homokaryons differed in their production of intracellular polyols, which, unlike germlings, remained constant with cultural age. Homokaryon (str. 699) produced low levels of arabitol but high levels of glycerol while another homokaryon (str. 845) was the reverse. Mixtures of these homokaryons as well as the dikaryon (699×845) produced arabitol and glycerol levels intermediate between the parent homokaryons. High concentrations of glucose did not change the nature of the polyols produced. Arabitol formation could be induced prematurely in germlings or elevated in the dikaryon by growth on acetate or ethanol. Both homokaryons responded to growth on acetate with elevated arabitol production; acetate induction of arabitol formation was repressed in all types of cells if glucose were added simultaneously with acetate. Maltose, cellobiose, and trehalose also stimulated arabitol formation in young germlings, suggesting that glucose repression was the cause of decreased arabitol formation in basidiospore germlings. There was no correlation between the formation of arabitol and the derepression of isocitrate lyase or change in specific activities of alkaline and acid phosphatase in germlings grown on various carbon sources.     

Soil water potential as a factor in the ecology ofFusarium roseum f. sp.cerealis ‘Culmorum’

Summary The soil water potential (inferred from vapor pressure measurements by thermocouple psychrometry) influenced both chlamydospore germination and continuing growth of germlings ofFusarium roseum f. sp.cerealis ‘Culmorum’ the same way in two different soils. Chlamydospore germination in both Ritzville silt loam (RSL) and Palouse silt loam (PSL) amended with about 2,500 ppm C (as glucose) and 250 ppm N (as ammonium sulfate) was 40–50 per cent in 24 hours at water potentials down to −50 to −60 bars. Some germination occurred by 72 hours at −80 to −85 bars in both soils but not at lower potentials. At a potential of −10 bars or higher, germ tubes lysed or converted into new chlamydospores within 48–72 hours after germination, whereas at lower potentials germlings branched and appeared to grow for at least 6 days. Bacterial numbers/g of RSL, 24 and 72 hours after adding nutrients, were 200 to 300 times greater in soil at water potentials of −5 bars or more than in comparably treated soil at about −14 to −17 bars or less. Markedly reduced bacterial activity appeared to coincide with a water potential of about −9 to −10 bars. When streptomycin and neomycin (300 ppm each) were mixed into the soil in addition to nutrients, the survival of germlings of Culmorum was greatly enhanced, even in soil at potentials of less than −1 bar. Indications were that soil water potentials of −10 bars or more favored bacterial activity, and that this in turn repressed growth of germlings of Culmorum. Culmorum infections of below-ground parts of wheat are serious primarily in drier soils, possibly because the fungus escapes bacterial antagonism but can still extract water for growth. Cooperative investigations, Crops Research and the Water and Soil Conservation Research Divisions, Agricultural Research Service, U.S. Department of Agriculture and the Agricultural Experiment Stations of Idaho, Montana, Oregon, Utah, and Washington. Scientific Paper No.3152, College of Agriculture, Washington State University, Pullman.     

Germination of desiccated aged akinetes of alkaliphilic cyanobacteria

Morphological and biochemical changes associated with synchronous germination of mature, aged and desiccated akinetes of two alkaliphilic cyanobacteria, Cyanospira rippkae and Cyanospira capsulata, are described. Akinetes of both strains proved to be highly resistant to desiccation, being able to germinate, in the presence of either N₂ or nitrate as nitrogen source, with a germination frequency of more than 90% after seven years of storage in a dried state. The first cell division occurred after 8–10 h of incubation, thereafter the germlings of the two strains followed a different pattern of cell differentiation. Heterocysts were first noted, in a terminal position, at 16–18 h in three-celled germlings of C. capsulata and at 21–24 h in C. rippkae, when germlings were at least seven cells in length. Akinetes of both species possessed, on a per cell basis, almost identical amounts of all photosynthetic pigments but, under nitrogen fixing conditions, photosynthetic activity (oxygen evolution) was detected only after new proteins had been synthesized, before a functional heterocyst was developed and while total nitrogen remained constant. With energy provided by aerobic respiration, a wide range of intracellular amino acids characteristic of proteins was utilised to sustain the new protein synthesis. The end of this biosynthetic activity coincided with the timing of the first cell division. From this stage on, no changes in protein concentration occurred until mature heterocysts were developed. In the presence of nitrate, no significant changes in the major germination events were observed.     

Seed germination and seedling growth of five desert plants and their relevance to vegetation restoration

Due to significant decreases in precipitation in northern China, knowledge of the response of seed germination and plant growth characteristics to key limiting factors is essential for vegetation restoration. We examined seed germination under different temperatures and water potentials, and we examined seedling growth under different amounts of water supply. Experiments were carried out in automatic temperature‐, humidity‐, and light‐controlled growth chambers. Under low water potentials, the final germination percentages of four herbaceous species were high, while seed germination of the shrub species Caragana microphylla was significantly inhibited. Under the different water supply amounts, seedlings of Agropyron cristatum allocated more biomass to the root and had a higher growth rate than those of Elymus dahuricus and C. microphylla. In light of these results and drier environmental conditions (annual mean precipitation is 366 mm, which falling mainly between June and August), potential selections for revegetation of different landscapes include the following: A. cristatum for shifting sand dunes, the establishment of the pioneer species Agriophyllum squarrosum, C. microphylla for semifixed sand dunes, E. dahuricus for fixed sand dunes, and Melilotus suaveolens and Medicago sativa for cultivation.     

Physiological characteristics underpinning successful cryopreservation of endemic and endangered species of Bromeliaceae from the Brazilian Atlantic Forest

The germination requirements and the basis of the optimal water content before and after cryopreservation were studied for ten endangered Brazilian species of Bromeliaceae. Constant and alternating temperature regimes were used to determine the best conditions for seed germination. The relationship between seed water content and relative humidity was evaluated using water sorption isotherms at 15 °C. Seeds were cryostored at four water contents (3, 5, 7 and 9%) and three storage periods (0, 180 and 365 days), and loss in viability and vigour were estimated. Fresh seeds of all species showed maximum germination in < 30 days at temperatures between 20 and 30 °C, indicating the absence of a physical/morphological dormancy. A sigmoidal relationship between seed water content and relative humidity was observed with no apparent differences in sorption characteristics among the species. The optimum water content for cryopreservation of most of these species was c. 7%. Ultra‐drying (3% seed water content) had a detrimental effect on seed viability and vigour. Our experiments suggested orthodox storage behaviour for all species of Bromeliaceae examined as they are able to survive desiccation and freezing. This study has shown the feasibility of ex situ conservation in seed cryobanks of endangered bromeliads from the Brazilian Atlantic Forest to support future reintroduction of these species in nature. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176 , 567–576.     

The nuclear protein Poly(ADP‐ribose) polymerase 3 (AtPARP3) is required for seed storability in Arabidopsis thaliana

The deterioration of seeds during prolonged storage results in a reduction of viability and germination rate. DNA damage is one of the major cellular defects associated with seed deterioration. It is provoked by the formation of reactive oxygen species (ROS) even in the quiescent state of the desiccated seed. In contrast to other stages of seed life, DNA repair during storage is hindered through the low seed water content; thereby DNA lesions can accumulate. To allow subsequent seedling development, DNA repair has thus to be initiated immediately upon imbibition. Poly(ADP‐ribose) polymerases (PARPs) are important components in the DNA damage response in humans. Arabidopsis thaliana contains three homologues to the human HsPARP1 protein. Of these three, only AtPARP3 was very highly expressed in seeds. Histochemical GUS staining of embryos and endosperm layers revealed strong promoter activity of AtPARP3 during all steps of germination. This coincided with high ROS activity and indicated a role of the nuclear‐localised AtPARP3 in DNA repair during germination. Accordingly, stored parp3‐1 mutant seeds lacking AtPARP3 expression displayed a delay in germination as compared to Col‐0 wild‐type seeds. A controlled deterioration test showed that the mutant seeds were hypersensitive to unfavourable storage conditions. The results demonstrate that AtPARP3 is an important component of seed storability and viability.     

Chitin synthetase activity in a developmental mutant of Phycomyces blakesleeanus

Chitin synthetase activity was analyzed in vitro and in vivo in two morphogenetic stages, namely, dormant spore cells and germlings of the wild type strain and the developmental mutant S356 of Phycomyces blakesleeanus. In vitro experiments showed a much higher specific activity in dormant spores of the mutant strain than in those of the wild-type. This difference was restricted to the dormant spore phase since germlings exhibited comparable levels of activity to those detected in the wild-type strain. Although no correlation was observed between chitin synthesis in vitro and in vivo in mutant spores, germination of these cells was accompanied by an earlier expression of chitin synthetase in vivo. Germination of mutant spores in liquid medium produced morphologically aberrant germlings. Contrary to the extended mycelial growth of the wild-type strain in solid medium, the mutant grew with a typical colonial morphology. Results are discussed in relation to the possible basis of the mutant phenotype.     

Effect of water activity and relative air humidity on the growth of Penicillium chrysogenum thom, Aspergillus repens (Corda) Sacc., and Trichoderma viride Pers. isolated from living spaces

Original data on the growth parameters of the fungi Penicillium chrysogenum Thom, Aspergillus repens (Corda) Sacc., and Trichoderma viride Pers. isolated from living spaces in Moscow are presented. Spore germination, fungal growth, and the radial growth rate of the colonies were investigated upon cultivation on agarized nutrient media with different water activity (a_w) values. Spore germination and fungal growth were studied in house dust under laboratory conditions at different relative air humidity (RH). It was shown that, at decreased a_w and RH, the spore germination time increased, as did the period from germination to mycelium and conidia formation, while the radial growth rate of colonies decreased. House dust was found to be a suitable growth substrate for A. repens and P. chrysogenum, supporting their complete life cycle. It was suggested that house dust is unsuitable as a substrate for the growth of T. viride. The a_w and RH ranges for development of these micromycetes were determined. On this basis, the A. repens, P. chrysogenum, and T. viride strains isolated from living spaces were identified as xerophilic, xerotolerant, and hygrophilic ones, respectively.     

Comparative longevity of Australian orchid (Orchidaceae) seeds under experimental and low temperature storage conditions

Seeds from ten terrestrial orchid species, nine from the south‐west Australian biodiversity hotspot (Caladenia arenicola, Caladenia flava, Caladenia huegelii, Diuris laxiflora, Microtis media ssp. media, Pterostylis recurva, Pterostylis sanguinea, Thelymitra crinita and Thelymitra macrophylla) and one from south‐east Australia (Diuris fragrantissima), were placed into experimental storage to assess their relative longevity and likely optimal conditions for long‐term conservation seed banking. Seeds from all species were desiccation tolerant, germinating after drying at 23% relative humidity (C. arenicola, C. huegelii, P. sanguinea and T. macrophylla) or 5% relative humidity (C. flava, D. laxiflora, M. media ssp. media, P. recurva and T. crinita) at 23 °C. From automatedly determined moisture adsorption and desorption isotherms at 23 °C, these equate to tolerance of drying to 0.03–0.06 g water g^?1 dry weight or 0.013–0.028 g water g^?1 dry weight, respectively. Results of storage experiments at a range of moisture contents and temperatures suggest conventional seed bank storage at ?18 °C after equilibration at c. 23% relative humidity (at 23 °C) may be suitable for most of the species, although there was higher germination of P. recurva seeds stored at ?80 °C and of M. media ssp. media seeds equilibrated at 75% relative humidity. However, there was considerable variation in germination of seeds sampled after different storage periods, making it difficult to identify optimal storage conditions definitively. Results of comparative longevity storage experiments at 60% relative humidity and 40 °C suggest seeds from these orchid species are short‐lived compared with non‐orchid species, and with Australian species in particular. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 164 , 26–41.     

The role of after‐ripening in promoting germination of arid zone seeds: a study on six Australian species

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 (GA₃) or karrikinolide (KAR₁; the butenolide, 3‐methyl‐2H‐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 GA₃ or KAR₁. 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.     

Kinetic and Thermodynamic Analysis During Dissimilatory γ-FeOOH Reduction: Formation of Green Rust 1 and Magnetite

The oldest sedimentary rocks on Earth, the 3.8‐Ga Isua Iron‐Formation in southwestern Greenland, are metamorphosed past the point where organic‐walled fossils would remain. Acid residues and thin sections of these rocks reveal ferric microstructures that have filamentous, hollow rod, and spherical shapes not characteristic of crystalline minerals. Instead, they resemble ferric‐coated remains of bacteria. Modern so‐called iron bacteria were therefore studied to enhance a search image for oxide minerals precipitated by early bacteria. Iron bacteria become coated with ferrihydrite, a metastable mineral that converts to hematite, which is stable under high temperatures. If these unusual morphotypes are mineral remains of microfossils, then life must have evolved somewhat earlier than 3.8 Ga, and may have involved the interaction of sediments and molecular oxygen in water, with iron as a catalyst. Timing is constrained by the early in fall of planetary materials that would have heated the planet's surface.

Because there are no earlier sedimentary rocks to study on Earth, it may be necessary to expand the search elsewhere in the solar system for clues to any biotic precursors or other types of early life. Evidence from Mars shows geophysical and geochemical differentiation at a very early stage, which makes it an important candidate for such a search if sedimentation is an important process in life's origins. Not only does Mars have iron oxide‐rich soils, but its oldest regions have river channels where surface water and sediment may have been carried, and seepage areas where groundwater may have discharged. Mars may have had an atmosphere and liquid water in the crucial time frame of 3.9–4.0 Ga. A study of morphologies of iron oxide minerals collected in the southern highlands during a Mars sample return mission may therefore help to fill in important gaps in the history of Earth's earliest biosphere.     

Mars' surface is not universally biocidal

The Mars surface/near-surface is often considered to be biocidal. Here, diverse lines of evidence are presented indicating that some terrestrial microbes can survive the in-situ conditions albeit in an inactive state. For the purposes of planetary protection, it is important to consider what we mean by a planetary ‘surface’; this term has qualitatively distinct definitions fordifferent scientific disciplines, and can also have different meanings from a humanviewpoint versus that of a microbial cell. Most microbial cells spores or other cells deposited on Mars, even those that initially fall on the outward-facing part of the absolute surface, will fall within pores of the regolith or become covered by its dust. They are, therefore, protected from ultra-violet radiation. Desiccating conditions and low temperatures (−40 to −70°C) can act to preserve rather than kill all microbes, potentially maintaining cellular viability – especially for certain extremophiles – over geological timescales. Whereas salts are ubiquitous on Mars, many terrestrial microbes are highly tolerant to NaCl and other salts, and these substances (including potentially inhibitory chaotropes such as MgCl₂ and perchlorates) cannot access cells in the absence of a liquid milieu. Whereas the Mars regolith is nutrient-deplete and conditions may be acidic in places, oligotrophic conditions per se are not biocidal and many terrestrial microbes can thrive in acidic conditions (some acidophiles can proliferate at or below pH 0). The low temperatures of Mars' surface are not conducive to metabolic activity, but the biophysical sophistication and robust stress biology of many terrestrial microbes, and the protection afforded by Martian conditions, are likely to ensure the long-term viability of some extremophilic microbes if transported to Mars.     

Germination and Survival of Fusarium graminearum Macroconidia as Affected by Environmental Factors

The effects of temperature (4–20°C), relative humidity (RH, 0–100%), pH (3–7), availability of nutrients (0–5 g/l sucrose) and artificial light (0–494 μmol/m²/s) on macroconidial germination of Fusarium graminearum were studied. Germ tubes emerged between 2 and 6 h after inoculation at 100% RH and 20°C. Incubation in light (205 ± 14 μmol/m/s) retarded the germination for approximately 0.5 h in comparison with incubation in darkness. The times required for 50% of the macroconidia to germinate were 3.5 h at 20°C, 5.4 h at 14°C and 26.3 h at 4°C. No germination was observed after an incubation period of 18 h at 20°C in darkness at RH less than 80%. At RH greater than 80%, germination increased with humidity. Germination was observed when macroconidia were incubated in glucose (5 g/l) or sucrose (concentration range from 2.5 × 10^?4 to 5 g/l) whereas no germination was observed when macroconidia were incubated in sterile deionized water up to 22 h. Macroconidia germinated quantitatively within 18 h at pH 3–7. Repeated freezing (?15°C) and thawing (20°C) water agar plates with either germinated or non‐germinated macroconidia for up to five times did not prevent fungal growth after thawing. However, the fungal growth rate of mycelium was negatively related to the number of freezing events the non‐germinated macroconidia experienced. The fungal growth rate of mycelium was not significantly affected by the number of freezing events the germinated spores experienced. Incubation of macroconidia at low humidity (0–53% RH) suppressed germination and decreased the viability of the spores.     

Effects of powder and aqueous extracts of Euphorbia hirta on Phelipanche ramosa germination and haustorium initiation

Abstract

Phelipanche ramosa, a root parasitic weed, is a copious seed producer. A series of laboratory experiments was undertaken to investigate the effects of powder and aqueous extracts from Euphorbia hirta on germination, and haustorium initiation in P. ramosa. P. ramosa seeds conditioned in water and subsequently treated with diluted E. hirta extract (10–25% v/v) displayed considerable germination (47–62%). Increasing extract concentration to 50% or more reduced germination in response to the synthetic germination stimulants GR24 and Nijmegen^?i in a concentration dependent manner. P. ramosa germlings treated with diluted Euphorbia extract (10–75% v/v) displayed haustorium initiation comparable to the synthetic haustorium factor 2, 6-dimethoxybenzoquinone (DMBQ) at 20 µM. Euphorbia extract applied during conditioning reduced haustorium initiation in a concentration dependent manner. E. hirta extract or air-dried powder, applied to soil, induced considerable P. ramosa germination. The results indicate the plausibility of using E. hirta air-dried powder or extract as spot treatments to induce suicidal germination of Striga hermonthica.