Germination Of Achenes Research Articles

Effect of gap size in grass cover on the percentage and rate of dandelion achene germination

AbstractIn Central Europe, Taraxacum officinale Weber ex Wiggers (dandelion) is an economically important admixture in grasslands. Its spread is supported by its ability to germinate in gaps in grass stands. In a 5‐year experiment, we examined the effect of gap size on the germination rate and percentage of dandelion achenes. Each year, achenes were sown in late spring and mid‐summer in 90 square plots of six sizes, ranging from 2.5 × 2.5 cm to 80 × 80 cm. The plots were placed on a 2 × 6 m experimental area covered with low‐cut lawn. The course of germination varied among individual replicates depending on the weather. In each replicate, however, the rate of germination increased, and the percentage of germinated achenes decreased with increasing gap size. Differences in germination paralleled differences in the microclimate on the soil surface of plots where humidity decreased and temperature increased with plot size. The ultimate cause of this difference was the variance among gaps of different sizes in proportion to which the total area of the gap surface is insolated during the day. The colonization of lawns by dandelion is supported by the formation of small gaps in grass stands.

Ontogenesis of a rare Russian plant <i>Chephalaria litvinovii</i> Bobrov (Caprifoliaceae Juss.) in the Penza Region

This article examines the features of ontogenesis, the formation of biomorphs (in the ontogenetic aspect) and the phytocoenotic confinement in the Penza Region of a rare plant of Russia endemic Chephalaria litvinovii Bobrov. Field research methods are complemented by a laboratory experiment on the effect of low positive temperatures on the germination of achenes. The conducted studies showed that the individual development of individuals of this species includes 4 periods and 9 ontogenetic states, the morphometric indicators of which are presented in the work. It is shown how the monocentric biomorph of this caudex polycarpic in the old generative age state is replaced by an implicitly polycentric one due to the formation of hypogeogenic rhizomes. The stimulating effect of a temperature of +2°C for 2 weeks on the germination of achenes is shown. There is a phytocoenotic association of C. litvinovii with swampy, and, less often, true and steppe meadows in river floodplains, as well as in forest clearings and edges. The obtained materials can serve as a basis for the development of more effective measures for the protection of the species, including in cultural conditions during introduction in botanical gardens.

Effect of Polyethylene glycol, Sorbitol and Absolute Ethanol on Achene Dormancy to Enhance Achene Germination in Sunflower

Effect of Polyethylene glycol, Sorbitol and Absolute Ethanol on Achene Dormancy to Enhance Achene Germination in Sunflower

Dormancy attributes in sunflower achenes ( Helianthus annuus L.): II. Sowing date effects

AbstractSunflower (Helianthus annuus L.) seed industry needs nondormant seeds (i.e., seeds with the capacity to germinate in a wide range of environmental conditions) for processing and packaging. Thus, the presence of persistent seed dormancy is an undesirable trait. Dormancy level depends on the genotype and on the maternal environment. The aim of the present work was to study, in a wide range of sunflower genotypes, the effect of variations in sowing date on achene dormancy level and to investigate if these changes are related to variations in (a) embryo or coat‐imposed dormancy, (b) dormancy expression at high or low incubation temperatures, and (c) embryo sensitivity to abscisic acid (ABA). Two experiments were performed. In Experiment I, 20 sunflower genotypes were sown in two contrasting planting dates during three consecutive years, whereas in Experiment II, 1579 genotype was sown in five dates along a 5‐mo period. At harvest and during postharvest storage, fruit structures were incubated at different incubation temperatures in water and ABA. Descriptive multivariate analyses showed that late sowings provoked an enhancement of achene germination at harvest and a faster dormancy release during postharvest storage in all genotypes. However, the magnitude of the response, the temperature at which dormancy was expressed, and the tissue responsible for achene dormancy varied among genotypes. The mechanism that partially explains this dormancy alleviation appears to be the sensitivity of embryo germination to ABA inhibition. Result suggest that sowing date can be managed to obtain less‐dormant sunflower seed lots without significant yield loss.

Variations in Achene Traits, Germination and Seedling Growth of Pluchea dioscoridis (L.) DC. As affected by Maternal Climatic Aridity

The collection and germination of seeds for conspecific population distributed along climatic gradients can elucidate maternal environmental effects on achene traits, germination and seedling establishment and fitness. The current study explores this approach for the natural populations of Pluchea dioscoridis (L.) DC. (Asteraceae) which grows over a wide range of climatic regions in Egypt (Mediterranean, semiarid, and arid). The arid region showed the smallest achene size and pappus length, while the achenes size of Mediterranean region was > 36% and >27% larger than those of arid and semiarid regions, respectively. Generally, seed viability decreased with aridity and ranged from 41.96% at semiarid to 9.32% arid regions. Achenes from the three maternal climatic regions began germinating at approximately the same time, but germination rate proceeded differently. The achene germination percentage ranged from 10% to 33.54% for arid and semiarid regions, respectively. The study showed a significant effect of maternal climatic aridity on achene traits, germination rate and final germinating percentage of P. dioscoridis. However, survival rate of the three climatic regions was constant after 130 days of sowing. The results demonstrated how such widespread species acquire multiple maternal traits and mechanisms to optimize their adaptation, regeneration, and conservation of populations in stressful environments. However, further studies are required to demonstrate the phenotypic plasticity, reproductive efforts, and mechanism of dormancy loss of P. dioscoridis under different natural climatic conditions.

Seasonal Change in the Germination of Heteromorphic Achenes of Bidenspilosa

Seasonal Change in the Germination of Heteromorphic Achenes of Bidenspilosa

Dimethylhexadecylamine, a bacterial volatile compound, regulates achene germination, in vitro growth, and defense priming in Fragaria × ananassa

Dimethylhexadecylamine, a bacterial compound, promoted strawberry achene germination and a long-lasting effect on plant growth; furthermore, it induced necrotrophic pathogen resistance possibly through crosstalk with the jasmonic acid pathway. Dimethylhexadecylamine (DMHDA) is a volatile compound produced by different beneficial plant bacteria. DMHDA induces growth and activates the jasmonic acid (JA) signaling pathway in plants. In this study, we analyzed the effects of synthetic DMHDA on achene germination, as well as the long-term effect on plant growth and plant pathogen resistance in vitro in strawberry plants. Strawberry achenes treated with 32 µM DMHDA showed a three-fold increase in germination rates compared with untreated achenes, and plants from achenes germinated with 64 µM DMHDA grew four times larger than plants from untreated achenes. When plants were cultured in vitro with DMHDA as a continuous stimulus, they produced 40% less shoot growth but showed an up to four-fold increase in crown weight compared with control plants. DHMDA also induced resistance significantly against the necrotrophic pathogenic fungus Botrytis cinerea in strawberry. Our data showed that the bacterial volatile compound DMHDA regulated achene germination and produced a long-lasting effect on plant growth; furthermore, it induced a defense priming response against a necrotrophic pathogen. Crosstalk between DMHDA and the JA and salicylic acid pathways, as a potential mechanisms of action underlying these effects, is also discussed.

Effects of agroclimatic conditions on sunflower seed dormancy at harvest

At harvest sunflower seeds (Helianthus annuus L.) are dormant and poorly germinate at 10 and 25 °C. Seed sensitivity to low temperatures (10 °C) results from an embryo dormancy whereas the envelopes (pericarp and seed coats) inhibit the germination at 25 °C. Removal of pericarp greatly improved seed germination when the germination of whole achenes was higher than the critical value of 20 %. Using 107 seed batches corresponding to 26 genotypes cultivated in 2015, 2016 and 2017 in various production areas in France (Center and South) and Spain (South), we investigated the effects of agro-environmental factors on the depth of dormancy at harvest. A principal Component Analysis (PCA) performed with all the seed batches did not show any significant effect of the genotype (variety or female) and year of production on the intensity of dormancy, but it revealed the role of agro-climatic conditions. Experimental field trials performed with plants treated by a chemical desiccant after flowering demonstrated that accelerated desiccation during seed maturation on the mother plant was associated with lower dormancy. Our data also suggest that the longest the duration of the developmental cycle from sowing to harvest, the lowest the dormancy at harvest. We provide new insights into the modulation of dormancy intensity by genetic and environmental factors which might have practical applications in seed production.

Dormancy and germination of the trimorphic achenes of a cold desert annual: spreading the risk over time.

Many studies have been done on the relationship between variation in morphology, dispersal ability and degree of dormancy of heterocarpic species with dimorphic diaspores. However, there are far fewer such studies on species that produce trimorphic diaspores. Our aim was to compare dormancy and germination of achenes from peripheral, intermediate and central positions in the capitulum of the diaspore-trimorphic cold desert annual Asteraceae species Heteracia szovitsii, an important component of plant communities in the cold deserts of NW China. Dormancy breaking/germination responses of the three achene morphs and of seeds isolated from the pericarp were tested in the laboratory using standard procedures, and seedling emergence phenology of the achene morphs was monitored under natural cold desert temperature conditions in an experimental garden with and without supplemental watering. Depth of dormancy of the three achene morphs was peripheral > intermediate > central. Seedlings from the three morphs emerged in spring and in autumn. Cumulative seedling emergence percentage from achenes during 47 months of burial was central > intermediate > peripheral. Central achene morphs emerged over a period of ~12 months after sowing, while intermediate and peripheral achene morphs did so for ~40 and 47 months, respectively. Thus, H. szovitsii exhibits a temporal dispersal strategy. No viable central or intermediate achene morphs were present after 16 and 40 months, respectively, but ~60 % of the non-emerged peripheral achenes morphs were viable after 47 months. Based on our results on diaspore dormancy and those of a previous study of diaspore spatial dispersal of H. szovitsii, we conclude that this species has a high–intermediate–low risk diaspore dispersal/dormancy strategy that likely increases the chances for population persistence over time and space.

Micropropagation of the Moroccan Endemic Plant <i>Thymus broussonetii</i> Boiss. with Aromatic-Medicinal Value and Conservation Concern

Micropropagation from shoot tips and nodal segments was carried out for the conservation and domestication of spontaneous Moroccan thyme, Thymus broussonetii Boiss. subsp. broussonetii (endemic threatened). The mineral composition of the culture medium, as well as the succession of different growth regulators, influenced the in vitro growth of this species. Sterilized achenes of T. broussonetii were able to germinate on an agar medium containing Gautheret macronutrients with a rate of 25% and a degree of contamination of less than 4%. Shoot apices of 15-day seedlings (two cotyledon leaves) were cultivated on SD + 0.46 μM Kin medium and the explants obtained were transplanted every month. Six macronutrients (MS, B5, SH, SD, MSm and N30K) were tested and N30K was chosen for the following experiments. Seven cytokinins (Kin, BAP, 2iP, DPU, adenine, Zeat and TDZ) at 0.46, 0.93 and 2.32 μM/l were evaluated and the addition of 0.93 μM adenine to N30K medium favored significantly the induction of buds and the elongation of explants. Three polyamines (putrescine, spermidine and spermine) at 2, 5, 10 and 20 μM/l were tested. A better multiplication of buds, shoots and roots was noted for N30K + 10 μM spermine. Cytokinin-auxin combinations led to better root multiplication and an increase in the number of buds and the length of explants, particularly for 0.46 μM Kin + 2.85 μM IAA. Acclimatization was successfully carried out using vitroplants developing a good root system. One month after the start of acclimatization, 97% of T. broussonetii plantlets were healthy. Three months later, they were transplanted into larger pots. 100% of the acclimatized plants developed flowers in the 2nd year between June and August. Re-initiation of the in vitro culture was carried out from sterilized twig segments collected from the acclimatized plants of T. broussonetii with 1 - 2 nodes on the medium N30K + 0.46 μM Kin, and 52.1% of the explants healthily proliferated. Finally, two micropropagation prototypes were developed: shoot tip culture from seedlings obtained after germination of achenes and node culture from acclimatized plants.

Evaluation of Plant Growth Promoting Ability of <i>Bacillus amyloliquefaciens</i> Bc2 and <i>Trichoderma harzianum</i> TR <i>In Vivo</i>

Bacillus amyloliquefaciens Bc2 and Trichderma harzianum TR were used to evaluate their growth-promoting activity on cultivated strawberries, under laboratory and field conditions, and we have noticed that the percentage of achene germination is important for ones treated with TR (=97%) followed by those treated with Bc2 strain (=90%) and the control (=84%). Inoculations on field showed that on untreated soil with insecticide, TR is effective and allows the development of plants and extends the duration of flowering and fruiting. On treated soil, Bc2 clearly promotes the growth and development of strawberry seedlings and its role as plant growth promoting microorganisms has been proved.

Endophytic bacteria Arthrobacter agilis UMCV2 and Bacillus methylotrophicus M4-96 stimulate achene germination, in vitro growth, and greenhouse yield of strawberry (Fragaria × ananassa)

Strawberries are one of the most popular fruits in the world. The strawberry production process includes generation of plants through in vitro germination of achenes, micropropagation, and production under greenhouse conditions. In this study, we tested the effect of the plant biostimulant bacteria, Arthrobacter agilis UMCV2 and Bacillus methylotrophicus M4-96, on those processes. Volatile compounds produced by A. agilis UMCV2 stimulated achene germination while B. methylotrophicus M4-96 induced germination through production of diffusible compounds. Growth of in vitro strawberry plants inoculated with A. agilis UMCV2 or exposed to their volatile compounds was also stimulated. Plants inoculated in vitro with A. agilis UMCV2 and B. methylotrophicus M4-96, and then cultured in a greenhouse for 10 months had a 42 % higher fruit yield than un-inoculated controls. Confocal microscopy, used to assess fluorescent in situ hybridization, showed that both bacteria were present in the leaf mesophyll of inoculated plants, but not in control plants. Our results showed that endophytic bacteria, such as A. agilis UMCV2 and B. methylotrophicus M4-96, can be inoculated into micropropagated strawberry plants and colonize the plant tissues, thereby increasing the yield and fruit quality under greenhouse conditions through different mechanisms of plant biostimulation.

Effect of pre-germinal treatment and temperature on the germination of achenes of Baccharis dracunculifolia DC

The species Baccharis dracunculifolia, known as alecrim-do-campo is very rough, of great economic importance, recommended for recovery of degraded areas, but is little explored by propagation through seeds. In order to understand aspects of reproductive biology of B. dracunculifolia of achenes, this study aims to verify the influence of pre-germination treatment and the influence of different germination temperatures in the performance of seed germination. The seeds were placed in translucent germination boxes, with four replicates of 30 seeds for each treatment. Germination was carried out with pre-germination treatment stratification (5°C) for 0, 1, 2, 3, 4 and 5 days, with a photoperiod of 14 h with light and 10 h in dark, in a germination chamber B.O.D. The 15°C treatment was carried out with 0, 1, 2, 3, 4 and 5 days with pre-germination treatment stratification (5°C) and successively for all treatments. After this period, the same photoperiod of 15, 20, 25, 30 and 35°C remained. The germination was evaluated for 30 days, considering the number of germinated seeds; those showing radicle protrusion of less than 2 mm, the speed index, the average time and average speed of germination. The temperature of 20°C without pre-germinative treatment provided 17.8% of germination. The highest speed of germination was obtained at 30°C with pre-germination treatment stratification (5°C) for 4 days. The temperature of 35°C inhibited germination and there was no significant effect on mean germination time. The pre-germinating treatment for three days, combined with the temperature of 20°C, provided a higher average speed of germination. Thus, it appears that the pre-germination treatment stimulated germination of achenes, suggesting that longer periods of chill accumulation increased seed germination subjected to high temperatures.

Sensitivity to hypoxia and microbial activity are instrumental in pericarp-imposed dormancy expression in sunflower (Helianthus annuus L.)

AbstractWe used two sunflower genotypes displaying pericarp-imposed dormancy at high incubation temperatures (i.e. 30°C) to investigate the role of the pericarp as a limitation to oxygen availability to the embryo (hypoxia), and its impact on embryo abscisic acid (ABA) content and sensitivity to ABA. Results showed that both genotypes displayed very different oxygen threshold values for inhibition of embryo germination when incubation was performed at 30°C. Expression of dormancy in one genotype was therefore related to exacerbated embryo sensitivity to hypoxia, whereas in the other genotype, the pericarp appeared to act as a more severe restraint to oxygen entry. Increased sensitivity to hypoxia was, in part, related to increased sensitivity to ABA, but not to alterations in ABA metabolism. The activity of pericarp-microbial communities (bacteria and fungi) at high temperatures was also assessed as a potential determinant of hypoxia to the embryo. Oxygen consumption in pericarps incubated at 30°C was attenuated with antibiotics, which concomitantly promoted achene germination. In agreement with the observed more severe oxygen deprivation to the embryo exerted by the pericarp, the bacterial load in the pericarp was significantly higher in the commercial hybrid than in the inbred line; however, the application of antibiotics strongly reduced the bacterial colony counts for each genotype. Different bacterial and fungal communities, assessed through their profiles of carbon-source utilization, were determined between genotypes and after treatment with antibiotics. This work highlights the relationship between enhancement of sensitivity to hypoxia with incubation temperature and seed dormancy expression, and suggests that microbial activity might be part of the mechanism through which hypoxia is imposed.

Reproductive compatibility studies between wild and cultivated strawberries (Fragaria × ananassa) to obtain “bridge species” for breeding programmes

AbstractThe Fragaria genus has become relevant due to worldwide economic importance of the octoploid hybrid F. × ananassa. Interspecific hybridizations are widely employed in breeding programmes to introduce useful characteristics from wild species to cultivated varieties, although many reproductive barriers prevent gene flow between species. Hybrid genotypes that can act as a bridge between related wild species and cultivated strawberry could be useful to overcome those barriers. The aim of this work was to obtain interspecific hybrids of Fragaria and to analyse possible reproductive barriers. In the Banco de Germoplasma de Frutilla‐UNT, crossings were carried out among wild species of Fragaria with different ploidy levels and cultivated strawberry. To confirm hybrid condition of genotypes obtained, histological techniques and microsatellite markers were used. When wild species were crossed with cultivated strawberry in both directions, there was low production of achenes, while in crosses between wild species of Fragaria genus, achene production was very high. The percentage of germination of achenes was high when crossed species had the same ploidy level, and very low or null when they presented different ploidy levels. Although pre‐zygotic incompatibility associated to the degree of domestication and postzygotic barriers related to different ploidy levels of the progenitors were detected, new hybrid genotypes of Fragaria were obtained. These new hybrids could be used as “bridge species” in breeding programmes, since preliminary results showed no incompatibility barriers when they were crossed with Duchesnea indica.

Germination Patterns of Dimorphic Achenes in Launaea nudicaulis (Asteraceae) Growing in Desert Environments

Launaea nudicaulis (Asteraceae) produces two morphologically distinct types of achenes (whitish brown and black) in a single capitulum. All L. nudicaulis achenes have a pappus and pappi were removed artificially in this study for experimental purposes. The germination of achenes of both colours, with and without pappi, under various temperature regimes and illumination conditions was tested. Different coloured achenes showed differences in their mass and germination behavior. Whitish brown achenes (with and without pappi) displayed greater germination than black ones. Whitish brown achenes without pappi generally displayed greater germination than achenes with pappi. Continuous darkness enhanced germination, regardless of the presence of pappi, indicating that L. nudicaulis seeds are negatively photoblastic.

Role of mucilage during achene germination and sprout growth of the endangered Tibetan medicinal herb Mirabilis himalaica (Nyctaginaceae) exposed to abiotic stresses

Role of mucilage during achene germination and sprout growth of the endangered Tibetan medicinal herb Mirabilis himalaica (Nyctaginaceae) exposed to abiotic stresses

Do the seeds of Solidago gigantea Aiton have physiological determinants of invasiveness?

Solidago gigantea Ait. (goldenrod) belongs to the most expansive environmental weeds, and it is the most dangerous plant-invader of American origin in Europe. The species easily propagates vegetatively, but it also produces large amounts of wind-disseminated achenes that contribute to the colonization of new areas. A sound knowledge of the germination biology of goldenrods is required to control the spread of this invasive species. The objective of this study was to investigate selected aspects of germination of giant goldenrod achenes and to determine: the influence of temperature and humidity on seed dormancy and germination, the content of soluble carbohydrates in seeds and the sensitivity of seeds to selected phytohormones. Unlike native weed species of the same family, S. gigantea seeds did not display symptoms of innate dormancy, and high seed vigor was maintained after storage in a wide range of temperatures, in both dry and moist conditions. The physiological mechanisms behind those traits have not yet been fully explored, but they could be associated with the relatively high sucrose-to-hexose ratio in seeds and significant sensitivity to abscisic acid. More extensive research is required to explain the internal causes for the atypical behavior of goldenrod seeds during dry and moist storage, especially in the context of its invasiveness, because the species has a preference for sites located close to river banks.

Atividade alelopática de óleos essenciais de plantas medicinais na germinação e vigor de aquênios de alface

In recent years, essential oils have gained commercial interest in the agricultural area, mainly for their allelopathic, insecticidal, antifungal, antimicrobial and antioxidant properties, and, also for their natural compounds, which have generally displayed low toxicity, relatively low cost and rapid degradation in the environment. Medicinal plants have emerged as potential suppliers of essential oils because of their ethnopharmacological utility. The aim of this study was to evaluate the allelopathic potential of essential oils extracted from fresh leaves of lemon grass ( Cymbopogon citratus ), wild basil ( Ocimum gratissimum L.) and sweet basil ( Ocimum basilicum L.) with regard to their major constituents (citral, eugenol and cineol, respectively) in different application forms (direct contact and the effect of volatile constituents) on the germination and vigor of lettuce seeds (cultivar Regina SF 3500). The effects of the oils and their major components were evaluated with regard to the variables: first germination count, total germination, GVI (germination velocity index), seedling dry weight and average lengths of shoots and lettuce roots. The essential oils from lemon grass and basil displayed allelopathic potentials on seed germination and vigor of lettuce achenes that can be assigned to their respective major constituents citral and eugenol. On the other hand, the allelopathic effect of the essential oil from basil was a consequence of the combined effect of all the components, regardless the application method.

Allelopathic activity of medicinal plant essential oils on seed germination and vigor of lettuce achenes

Allelopathic activity of medicinal plant essential oils on seed germination and vigor of lettuce achenes