Showing papers on "Germination published in 2013"
TL;DR: The present findings do not authenticate the involvement of F. mangiferae in the disease, however hormonal imbalance, most probably ethylene, might be responsible for deformed functional morphology of panicle and a signal transduction mechanism of stress-stimulated ethylene imbalance causing physio-morphological changes in reproductive organs of mango flower and thereby failure of fertilization and fruit set needs to be investigated.
Abstract: Mango malformation is the most important and threatening disease of recent times, primarily because of persistent lacuna in complete understanding of its nature. Diverse Fusarium spp, including F. mangiferae, were found to be associated with the disease. Here, F. mangiferae from mango cv Dashehri was morphologically characterized. Typically, oval-shaped microconidia without septum and crescent-shaped macroconidia with 3-septate were more often observed, whereas not a single chlamydospore was detected. The length and width of micro- and macro-conidia were 7.5, 55, 3.2, and 3.5, respectively. The plant growth regulators such as NAA, GA3, BAP and ethrel were found to induce in vitro germination of conidia of F. mangiferae after 12 h. In contrast, antimalformin silver nitrate (AgNO3) inhibits conidial germination in vitro and none of conidia was germinated beyond 500 ppm, however antimalformin glutathione was highly effective in stimulating conidial germination of F. mangiferae in vitro at > 1000 ppm after 24 h. We observed that the response of F. mangiferae to germinate the conidia in vitro under influence of plant growth regulators and antimalformins is not coincided with earlier findings of reduced disease incidence by exogenous application of these compounds. The present findings do not authenticate the involvement of F. mangiferae in the disease, however hormonal imbalance, most probably ethylene, might be responsible for deformed functional morphology of panicle. Further, a signal transduction mechanism of stress-stimulated ethylene imbalance causing physio-morphological changes in reproductive organs of mango flower and thereby failure of fertilization and fruit set, which needs to be investigated.
2,202 citations
TL;DR: The results suggest that the adverse effects of water stress can be minimized by the application of melatonin, and specifically on strengthening cucumber roots.
Abstract: A comprehensive investigation was carried out to determine the changes that occurred in water-stressed cucumber (Cucumis sativus L.) in response to melatonin treatment. We examined the potential roles of melatonin during seed germination and root generation and measured its effect on reactive oxygen species (ROS) levels, antioxidant enzyme activities, and photosynthesis. Melatonin alleviated polyethylene glycol induced inhibition of seed germination, with 100 μm melatonin-treated seeds showing the greatest germination rate. Melatonin stimulated root generation and vitality and increased the root:shoot ratio; therefore, melatonin may have an effect on strengthening cucumber roots. Melatonin treatment significantly reduced chlorophyll degradation. Seedlings treated with 100 μm melatonin clearly showed a higher photosynthetic rate, thus reversing the effect of water stress. Furthermore, the ultrastructure of chloroplasts in water-stressed cucumber leaves was maintained after melatonin treatment. The antioxidant levels and activities of the ROS scavenging enzymes, i.e., superoxide dismutase, peroxidase, and catalase, were also increased by melatonin. These results suggest that the adverse effects of water stress can be minimized by the application of melatonin.
442 citations
TL;DR: It is reported that ABI4 positively regulates primary seed dormancy, while negatively regulating cotyledon greening, by mediating the biogenesis of ABA and GA.
Abstract: Seed dormancy is an important economic trait for agricultural production. Abscisic acid (ABA) and Gibberellins (GA) are the primary factors that regulate the transition from dormancy to germination, and they regulate this process antagonistically. The detailed regulatory mechanism involving crosstalk between ABA and GA, which underlies seed dormancy, requires further elucidation. Here, we report that ABI4 positively regulates primary seed dormancy, while negatively regulating cotyledon greening, by mediating the biogenesis of ABA and GA. Seeds of the Arabidopsis abi4 mutant that were subjected to short-term storage (one or two weeks) germinated significantly more quickly than Wild-Type (WT), and abi4 cotyledons greened markedly more quickly than WT, while the rates of germination and greening were comparable when the seeds were subjected to longer-term storage (six months). The ABA content of dry abi4 seeds was remarkably lower than that of WT, but the amounts were comparable after stratification. Consistently, the GA level of abi4 seeds was increased compared to WT. Further analysis showed that abi4 was resistant to treatment with paclobutrazol (PAC), a GA biosynthesis inhibitor, during germination, while OE-ABI4 was sensitive to PAC, and exogenous GA rescued the delayed germination phenotype of OE-ABI4. Analysis by qRT-PCR showed that the expression of genes involved in ABA and GA metabolism in dry and germinating seeds corresponded to hormonal measurements. Moreover, chromatin immunoprecipitation qPCR (ChIP-qPCR) and transient expression analysis showed that ABI4 repressed CYP707A1 and CYP707A2 expression by directly binding to those promoters, and the ABI4 binding elements are essential for this repression. Accordingly, further genetic analysis showed that abi4 recovered the delayed germination phenotype of cyp707a1 and cyp707a2 and further, rescued the non-germinating phenotype of ga1-t. Taken together, this study suggests that ABI4 is a key factor that regulates primary seed dormancy by mediating the balance between ABA and GA biogenesis.
297 citations
Journal Article•
TL;DR: Reactive Oxygen Species play a key role in various events of seed life by regulating cellular growth, ensuring a protection against pathogens or controlling the cell redox status and can therefore be also beneficial for seed germination and seedling growth.
Abstract: Reactive Oxygen Species (ROS) play a key role in various events of seed life. In orthodox seeds, ROS are produced from embryogenesis to germination, i.e. in metabolically active cells, but also in quiescent dry tissues during after ripening and storage, owing various mechanisms depending on the seed moisture content. Although ROS have been up to now widely considered as detrimental to seeds, recent advances in plant physiology signaling pathways has lead to reconsider their role. ROS accumulation can therefore be also beneficial for seed germination and seedling growth by regulating cellular growth, ensuring a protection against pathogens or controlling the cell redox status. ROS probably also act as a positive signal in seed dormancy release. They interact with abscisic acid and gibberellins transduction pathway and are likely to control numerous transcription factors and properties of specific protein through their carbonylation.
297 citations
TL;DR: The results indicate that the positive effect of MWCNTs on the germination and growth of seedlings is reproducible between crop species and can be observed for different methods of delivering carbon nanotubes.
Abstract: Multiwalled carbon nanotubes (MWCNTs) affected seed germination, growth, and the development of three important crops (barley, soybean, corn). Early seed germination and activation of growth in exposed seedlings was observed when MWCNTs were added to sterile agar medium. Similarly, seed germination was activated for all tested crop species when MWCNTs were deposited on seed surfaces. The ability of MWCNTs to penetrate the seed coats of corn, barley, and soybean was proven by detection of nanotube agglomerates inside MWCNT-exposed seeds using Raman spectroscopy and transmission electron microscopy (TEM). Reverse transcription polymerase chain reaction (RT-PCR) analysis revealed that the expression of genes encoding several types of water channel proteins was increased in soybean, corn, and barley seeds coated with MWCNTs compared with uncoated control seeds. Our results indicate that the positive effect of MWCNTs on the germination and growth of seedlings is reproducible between crop species and can be obs...
295 citations
TL;DR: A hypothetical model illustrating the cellular physiology of priming-induced stress-tolerance is proposed, likely achieved via two strategies: first, seed priming sets in motion germination-related activities that facilitate the transition of quiescent dry seeds into germinating state and lead to improved germination potential, and secondly, priming imposes abiotic stress on seeds that represses radicle protrusion but stimulates stress responses.
283 citations
TL;DR: Current knowledge of ABA crosstalk with ethylene and NO, both volatile compounds that have been shown to counteract ABA action in seeds and to improve dormancy release and germination are described.
Abstract: Dormancy is an adaptive trait that enables seed germination to coincide with favorable environmental conditions. It has been clearly demonstrated that dormancy is induced by abscisic acid (ABA) during seed development on the mother plant. After seed dispersal, germination is preceded by a decline in ABA in imbibed seeds, which results from ABA catabolism through 8'-hydroxylation. The hormonal balance between ABA and gibberellins (GAs) has been shown to act as an integrator of environmental cues to maintain dormancy or activate germination. The interplay of ABA with other endogenous signals is however less documented. In numerous species, ethylene counteracts ABA signaling pathways and induces germination. In Brassicaceae seeds, ethylene prevents the inhibitory effects of ABA on endosperm cap weakening, thereby facilitating endosperm rupture and radicle emergence. Moreover, enhanced seed dormancy in Arabidopsis ethylene-insensitive mutants results from greater ABA sensitivity. Conversely, ABA limits ethylene action by down-regulating its biosynthesis. Nitric oxide (NO) has been proposed as a common actor in the ABA and ethylene crosstalk in seed. Indeed, convergent evidence indicates that NO is produced rapidly after seed imbibition and promotes germination by inducing the expression of the ABA 8'-hydroxylase gene, CYP707A2, and stimulating ethylene production. The role of NO and other nitrogen-containing compounds, such as nitrate, in seed dormancy breakage and germination stimulation has been reported in several species. This review will describe our current knowledge of ABA crosstalk with ethylene and NO, both volatile compounds that have been shown to counteract ABA action in seeds and to improve dormancy release and germination.
269 citations
TL;DR: A seed ecology syndrome for Cistaceae is postulated, featuring small seed size, hardcoatedness (primary dormancy), short-distance dispersal, long-term persistence in soil seed banks, fire- or heat- induced seed “softening”, an opportunistic strategy of germination (germination at a wide range of temperature and light conditions), and a slow germination rate of “ softened” seeds.
Abstract: An examination of 203 seed lots from 42 Old World species (or 54 taxa), with representatives from all five genera (Cistus, Fumana, Halimium, Heliarthemum, and Tuberaria) and an additional seed lot of the New World Lechea maritima shows that the phenomenon of haidseededness is a prominent characteristic of the entire Cistaceae family. Promotion of seed germination in the laboratory can be obtained by mechanical scarification and thermal pretreatment, while light seems to be totally ineffective. A seed ecology syndrome for Cistaceae is postulated, featuring small seed size, hardcoatedness (primary dormancy), short-distance dispersal, long-term persistence in soil seed banks, fire- or heat- induced seed “softening”, an opportunistic strategy of germination (germination at a wide range of temperature and light conditions), and a slow germination rate of “softened” seeds. This syndrome is suggested to endow Cistaceae, a principally Mediterranean family, with a considerable ecological advantage in the ...
239 citations
TL;DR: It is concluded that SMAX1 is an important component of Karrikin- and strigolactone-insensitive mutant max2 signaling during seed germination and seedling growth but not necessary for all MAX2-dependent responses.
Abstract: Abiotic chemical signals discovered in smoke that are known as karrikins (KARs) and the endogenous hormone strigolactone (SL) control plant growth through a shared MORE AXILLARY GROWTH2 (MAX2)-dependent pathway. A SL biosynthetic pathway and candidate KAR/SL receptors have been characterized, but signaling downstream of MAX2 is poorly defined. A screen for genetic suppressors of the enhanced seed dormancy phenotype of max2 in Arabidopsis (Arabidopsis thaliana) led to identification of a suppressor of max2 1 (smax1) mutant. smax1 restores the seed germination and seedling photomorphogenesis phenotypes of max2 but does not affect the lateral root formation, axillary shoot growth, or senescence phenotypes of max2. Expression of three transcriptional markers of KAR/SL signaling, D14-LIKE2, KAR-UP F-BOX1, and INDOLE-3-ACETIC ACID INDUCIBLE1, is rescued in smax1 max2 seedlings. SMAX1 is a member of an eight-gene family in Arabidopsis that has weak similarity to HEAT SHOCK PROTEIN 101, which encodes a caseinolytic peptidase B chaperonin required for thermotolerance. SMAX1 and the SMAX1-like (SMXL) homologs are differentially expressed in Arabidopsis tissues. SMAX1 transcripts are most abundant in dry seed, consistent with its function in seed germination control. Several SMXL genes are up-regulated in seedlings treated with the synthetic SL GR24. SMAX1 and SMXL2 transcripts are reduced in max2 seedlings, which could indicate negative feedback regulation by KAR/SL signaling. smax1 seed and seedling growth mimics the wild type treated with KAR/SL, but smax1 seedlings are still responsive to 2H-furo[2,3-c]pyran-2-one (KAR2) or GR24. We conclude that SMAX1 is an important component of KAR/SL signaling during seed germination and seedling growth but is not necessary for all MAX2-dependent responses. We hypothesize that one or more SMXL proteins may also act downstream of MAX2 to control the diverse developmental responses to KARs and SLs.
223 citations
TL;DR: Some of the factors that determine the ability of seeds of halophytes to germinate when conditions are optimal for seedling growth and survival are examined.
195 citations
TL;DR: Gene expression profiling in two seed compartments uncovers two transcriptional phases during seed germination that are separated by testa rupture, and indicates a role for mechano-induced signaling at this stage and highlights the fates of the endosperm and radicle: senescence and growth, respectively.
Abstract: Seed germination is a critical stage in the plant life cycle and the first step toward successful plant establishment. Therefore, understanding germination is of important ecological and agronomical relevance. Previous research revealed that different seed compartments (testa, endosperm, and embryo) control germination, but little is known about the underlying spatial and temporal transcriptome changes that lead to seed germination. We analyzed genome-wide expression in germinating Arabidopsis (Arabidopsis thaliana) seeds with both temporal and spatial detail and provide Web-accessible visualizations of the data reported (vseed.nottingham.ac.uk). We show the potential of this high-resolution data set for the construction of meaningful coexpression networks, which provide insight into the genetic control of germination. The data set reveals two transcriptional phases during germination that are separated by testa rupture. The first phase is marked by large transcriptome changes as the seed switches from a dry, quiescent state to a hydrated and active state. At the end of this first transcriptional phase, the number of differentially expressed genes between consecutive time points drops. This increases again at testa rupture, the start of the second transcriptional phase. Transcriptome data indicate a role for mechano-induced signaling at this stage and subsequently highlight the fates of the endosperm and radicle: senescence and growth, respectively. Finally, using a phylotranscriptomic approach, we show that expression levels of evolutionarily young genes drop during the first transcriptional phase and increase during the second phase. Evolutionarily old genes show an opposite pattern, suggesting a more conserved transcriptome prior to the completion of germination.
TL;DR: An overall neutral effect of litter presence on seedlings emergence and survival and a positive effect on seedling biomass is found and whereas for field experiments the response remained neutral, it was positive for common garden studies.
Abstract: 1. Plant litter is a key component in terrestrial ecosystems. It plays a major role in nutrient cycles and community organization. Land use and climate change may change the accumulation of litter in herbaceous ecosystems and affect plant community dynamics. Additionally, the transfer of seeds containing plant material (i.e. litter) is a widespread technique in grassland restoration.2. Ecosystem responses to litter represent the outcome of interactions, whose sign and strength will depend on many variables (e. g. litter amount, seed size). A previous meta-analysis (from 1999) reported that litter had an overall negative effect on seed germination and seedling establishment in different ecosystems. However, recent studies indicated that this might not be the case in grassland ecosystems.3. We used 914 data from 46 independent studies to analyse the effects of litter on seedling (i) emergence, (ii) survival and (iii) biomass, employing meta-analytical techniques. Each data set was stratified according to methodology, grassland type, irrigation conditions, litter amount and seed size.4. We found an overall neutral effect of litter presence on seedling emergence and survival and a positive effect on seedling biomass. However, whereas for field experiments the response remained neutral, it was positive for common garden studies. In glasshouse experiments, litter effects were negative for emergence and positive for biomass.5. Litter may have a positive effect on seedling recruitment in dry grasslands or under water-limited conditions, or in the presence of low to medium litter amounts ( 500 g m(-2)) will inhibit seedling recruitment. Large seeds showed a more positive response to litter presence with respect to seedling emergence and survival, but not concerning biomass.6. Synthesis. Under dry conditions (e. g. dry grasslands or dry periods) or with low to medium litter amounts, litter presence has a positive effect on seedling establishment. However, climate and land use change may promote litter accumulation and reduce seedling establishment, affecting grasslands composition and ecosystem functions.
TL;DR: The silver nanoparticle and silver nitrate application to castor seeds caused an enhanced enzymatic activity of ROS enzymes and phenolic content in castor seedlings, and high-performance liquid chromatography analysis of individual phenols indicated enhanced content of parahydroxy benzoic acid.
Abstract: Increasing use of nanoparticles in daily products is of great concern today, especially when their positive and negative impact on environment is not known. Hence, in current research, we have studied the impact of silver nanoparticle (AgNPs) and silver nitrate (AgNO3) application on seed germination, root, and shoot length of castor bean, Ricinus communis L. plant. Silver nanoparticles had no significant effects on seedling growth even at higher concentration of 4,000 mg L(-1), while the silver in bulk form as AgNO3 applied on the castor bean seeds inhibited the seed germination. Silver uptake in seedlings of the castor seeds on treatment with both the forms of silver was confirmed through atomic absorption spectroscopy studies. The silver nanoparticle and silver nitrate application to castor seeds also caused an enhanced enzymatic activity of ROS enzymes and phenolic content in castor seedlings. High-performance liquid chromatography analysis of individual phenols indicated enhanced content of parahydroxy benzoic acid. These kinds of studies are of great interest in order to unveil the movement and accumulation of nanoparticles in plant tissues for assessing future applications in the field or laboratory.
TL;DR: In this article, the effects of phytotoxic compounds in biochar, hydrochar, and process-water from kiln carbonization (HTC) were evaluated with spring barley (Hordeum vulgare) seed growth.
Abstract: Within the framework of climate change mitigation by sequestrating recalcitrant carbon in soil, biochar is considered as a promising soil amendment. Testing any such soil additives is vitally important, as they should not cause abiotic stress for plants due to chemical constituents they may contain. Thus, germination tests with spring barley (Hordeum vulgare) were conducted to assess phytotoxic effects of biochar, hydrochar and process-water from hydrothermal carbonization (HTC) as soil amendments. Additionally, single-component tests with substances found in process-waters were carried out with cress (Lepidium sativum). While biochars generally had no effect on germination, hydrochars and process-waters significantly inhibited germination. The dissolved organic carbon content predicted the germination-inhibiting effects observed. Three compounds resulted in partial (guaiacol) or total (levulinic acid and glycolic acid) inhibition of cress seed germination, and three others (acetic acid, glycolaldehyde dimer and catechol) had a negative impact on growth. Phytotoxic substances in chars appeared to be mostly water soluble and volatile. Pre-treatments of hydrochars and process-waters (i.e. storage and washing) were able to reduce germination inhibition. While phytotoxic substances that are generated during HTC stay in the products, biochars from kiln carbonization of the same feedstocks had no negative effects on germination, likely because volatiles evaporate during the conversion. Our study highlights the importance of comprehensively testing carbonized products for their compatibility with agricultural and horticultural systems.
TL;DR: There was a considerable response by fennel seed to nanosized TiO2 presenting the possibility of a new approach to overcome problems with seed germination in some plant species, particularly medicinal plants.
01 Jan 2013
TL;DR: In this paper, the toxicity of ZnO NPs and Zn 2+ in alfalfa (Medicago sativa), cucumber (Cucumis sativus), and tomato (Solanum lycopersicum) seedlings was investigated.
Abstract: Past reports indicate that some nanoparticles (NPs) affect seed germination; how- ever, the biotransformation of metal NPs is still not well understood. This study investigated the toxicity on seed germination/root elongation and the uptake of ZnO NPs and Zn 2+ in alfalfa (Medicago sativa), cucumber (Cucumis sativus), and tomato (Solanum lycopersicum) seedlings. Seeds were treated with ZnO NPs at 0-1600 mg L -1 as well as 0-250 mg L -1 Zn 2+ for comparison purposes. Results showed that at 1600 mg L -1 ZnO NPs, germination in cucumber increased by 10 %, and alfalfa and tomato germination were reduced by 40 and 20 %, respectively. At 250 mg Zn 2+ L -1 , only tomato germination was reduced with respect to controls. The highest Zn content was of 4700 and 3500 mg kg -1 dry weight (DW), for alfalfa seedlings germinated in 1600 mg L -1 ZnO NPs and 250 mg L -1 Zn 2+ , respectively. Bulk X-ray absorption spectroscopy (XAS) results indicated that ZnO NPs were probably biotransformed by plants. The edge energy positions of NP-treated samples were at the same position as Zn(NO 3 ) 2 , which indicated that Zn in all plant species was as Zn(II).
Journal Article•
TL;DR: In this paper, the effects of nanoscale titanium dioxide particles on plant growth and development were investigated in the case of canola seeds, which were separately treated with different concentrations of nano-scale titanium dioxide (10, 100, 1000, 1200, 1500, 1700 and 2000 mg l -1 ).
Abstract: An investigation was initiated to examine the effects of nanoscale titanium dioxide particles on plant growth and development. In view of the widespread cultivation of canola in Iran and in other parts of the globe and in view of the potential influence of titanium on its growth, this plant was chosen as the model system. Canola seeds were separately treated with different concentrations of nanoscale titanium dioxide (10, 100, 1000, 1200, 1500, 1700 and 2000 mg l -1 and the effect this treatment was studied on seed germination and seedling vigor. Treatment of nanoscale TiO2(20 nm mean particle size) at 2000 mg l -1 concentration promoted both seed germination and seedling vigor . The lowest and the highest germination rate were obtained in 1500 and 2000 mg l -1 treatments, respectively. Higher concentrations of nanoscale TiO2 (1200 and 1500 mg l -1 ) showed large radicle and plumule growth of seedling compared to other concentrations and control. The inhibitory effect with lower nanoparticle concentration reveals the need for judicious usage of these particles in such applications. This is the first report on the effect of nanoscale particles on canola growth.
TL;DR: The results show that such rhizobacterial strains may be used as an effective tool for enhancing plant growth under salinity stress and for maximizing the utilization of salt-affected soils.
Abstract: Salinity is one of the major environmental threats for successful crop production, hampering plant growth due to the osmotic effect and nutritional and hormonal imbalances. The application of naturally occurring plant growth-promoting rhizobacteria (PGPR) is an emerging technology aimed at ameliorating the negative impact of salinity. However, the results obtained in the laboratory can sometimes not be reproduced in the field. The aim of the study reported here was to evaluate the effect of PGPR inoculation on seed germination in a saline environment under axenic conditions and on enhancement of the growth and yield of wheat under natural salt-affected field conditions. Wheat seeds were inoculated with pre-isolated strains of Pseudomonas putida, Enterobacter cloacae, Serratia ficaria, and Pseudomonas fluorescens and sown at different salinity levels (1, 2, 3, 6, 9, 12, 15 dS m-1). Inoculation with these strains was found to enhance the germination percentage, germination rate, and index of wheat seeds up to 43, 51, and 123 %, respectively, over the uninoculated control at the highest salinity level. The potential of these PGPR for improving the growth and yield of wheat was also evaluated at two natural salt-affected sites. Inoculation with PGPR resulted a significant increase in the growth and yield parameters of wheat at both sites. The inoculated plants also improved the nutrient status of the wheat plants. The inoculated plants had low sodium and high nitrogen, phosphorus, and potassium contents. Our results show that such rhizobacterial strains may be used as an effective tool for enhancing plant growth under salinity stress and for maximizing the utilization of salt-affected soils.
TL;DR: The results show that the germination potential, expressed through the final germination percentage and the Germination index, as well as the physiological parameters of maize seedlings (root and shoot lengths) decreased by increasing the irradiation dose.
Abstract: The effects of gamma radiation are investigated by studying plant germination, growth and development, and biochemical characteristics of maize. Maize dry seeds are exposed to a gamma source at doses ranging from 0.1 to 1 kGy. Our results show that the germination potential, expressed through the final germination percentage and the germination index, as well as the physiological parameters of maize seedlings (root and shoot lengths) decreased by increasing the irradiation dose. Moreover, plants derived from seeds exposed at higher doses (≤0.5 kGy) did not survive more than 10 days. Biochemical differences based on photosynthetic pigment (chlorophyll a, chlorophyll b, carotenoids) content revealed an inversely proportional relationship to doses of exposure. Furthermore, the concentration of chlorophyll a was higher than chlorophyll b in both irradiated and non-irradiated seedlings. Electron spin resonance spectroscopy used to evaluate the amount of free radicals induced by gamma ray treatment demonstrates that the relative concentration of radiation-induced free radicals depends linearly on the absorbed doses.
TL;DR: Rates of germination of individuals in spore populations are heterogeneous, and methods have been developed recently to simultaneously analyse the Germination of multiple individual spores, due to large variations in GR levels among individual spores.
Abstract: Summary
Spores of Bacillus species can remain dormant and resistant for years, but can rapidly ‘come back to life’ in germination triggered by agents, such as specific nutrients, and non-nutrients, such as CaDPA, dodecylamine and hydrostatic pressure. Major events in germination include release of spore core monovalent cations and CaDPA, hydrolysis of the spore cortex peptidoglycan (PG) and expansion of the spore core. This leads to a well-hydrated spore protoplast in which metabolism and macromolecular synthesis begin. Proteins essential for germination include the GerP proteins that facilitate germinant access to spores' inner layers, germinant receptors (GRs) that recognize and respond to nutrient germinants, GerD important in rapid GR-dependent germination, SpoVA proteins important in CaDPA release and cortex-lytic enzymes that degrade cortex PG. Rates of germination of individuals in spore populations are heterogeneous, and methods have been developed recently to simultaneously analyse the germination of multiple individual spores. Spore germination heterogeneity is due primarily to large variations in GR levels among individual spores, with spores that germinate extremely slowly and termed superdormant having very low GR levels. These and other aspects of spore germination will be discussed in this review, and major unanswered questions will also be discussed.
TL;DR: Evidence is provided that the tolerant genotypes were equipped with better management of physiological processes along with an efficient antioxidative defence system, sensitivity of which can be evaluated to a sufficient level of certainty at seedling stage.
Abstract: An experiment was conducted to find out the effect of short-term heat stress on morpho-physiological characters and antioxidants in 10 diverse wheat genotypes. Seed were aseptically grown in test tubes containing filter paper whose lower half was dipped in one-fourth MS media. Heat stress conditions were created by exposing the seedlings at 45 °C for 2 h after 7 days of their germination. Measurements were taken after 3 days of treatment. Heat stress significantly reduced the shoot dry mass, root dry mass, shoot length and root length in all the genotypes. The chlorophyll content and membrane stability index decreased, whereas proline content increased in heat-treated plants. There was significant increase in the activity of catalase, guaiacol peroxidase and superoxide dismutase under stress conditions. The genotypic variations were also significant. On the basis of a coordinated simulation of all these parameters, wheat genotypes Raj 4037 and PBW 373 were identified as tolerant to high temperature stress. The study provides evidence that the tolerant genotypes were equipped with better management of physiological processes along with an efficient antioxidative defence system, sensitivity of which can be evaluated to a sufficient level of certainty at seedling stage.
TL;DR: Reactive oxygen species (ROS) are continuously produced by the metabolically active cells of seeds, and apparently play important roles in biological processes such as germination and dormancy.
Abstract: Reactive oxygen species (ROS) are continuously produced by the metabolically active cells of seeds, and apparently play important roles in biological processes such as germination and dormancy. Germination and ROS accumulation appear to be linked, and seed germination success may be closely associated with internal ROS contents and the activities of ROS-scavenging systems. Although ROS were long considered hazardous molecules, their functions as cell signaling compounds are now well established and widely studied in plants. In seeds, ROS have important roles in endosperm weakening, the mobilization of seed reserves, protection against pathogens, and programmed cell death. ROS may also function as messengers or transmitters of environmental cues during seed germination. Little is currently known, however, about ROS biochemistry or their functions or the signaling pathways during these processes, which are to be considered in the present review.
TL;DR: This review discusses the most important compounds that are known to protect fungal spores and also addresses the biophysics of cell protection, which further covers the phenomena of dormancy, breaking of dormancies, and early germination.
Abstract: Spores are an integral part of the life cycle of the gross majority of fungi. Their morphology and the mode of formation are both highly variable among the fungi, as is their resistance to stressors. The main aim for spores is to be dispersed, both in space, by various mechanisms or in time, by an extended period of dormancy. Some fungal ascospores belong to the most stress-resistant eukaryotic cells described to date. Stabilization is a process in which biomolecules and complexes thereof are protected by different types of molecules against heat, drought, or other molecules. This review discusses the most important compounds that are known to protect fungal spores and also addresses the biophysics of cell protection. It further covers the phenomena of dormancy, breaking of dormancy, and early germination. Germination is the transition from a dormant cell toward a vegetative cell and includes a number of specific changes. Finally, the applied aspects of spore biology are discussed.
TL;DR: It is suggested that titanium itself is not phytotoxic, even though plants absorb titanium, and nano-TiO2 is not toxic to the three plant species, in vitro or in situ.
Abstract: Titanium dioxide nanoparticles (nano-TiO2) are manufactured and used worldwide in large quantities. However, phytotoxicity research on nano-TiO2 has yielded confusing results, ranging from strong toxicity to positive effects. Therefore, in this research, the effects of nano-TiO2 on the germination and root elongation of seed and seedlings were studied. Additionally, the uptake and physiological responses of mature plants were investigated. Physical chemistry data were analyzed to assess the availability of nano-TiO2. Finally, a hydroponic system designed to overcome nano-TiO2 precipitation was used to reproduce the environmental conditions of actual fields. Nano-TiO2 did not have any effect on seed germination or on most of the plant species tested. Nano-TiO2 had positive effects on root elongation in some species. No physiological differences in enzyme activities or chlorophyll content were detected, even though the plants absorbed nano-TiO2. Physical chemistry data showed that nano-TiO2 agglomerated rapidly and formed particles with much bigger hydrodynamic diameters, even in distilled water and especially in a hydroponic system. Furthermore, agglomerated nano-TiO2 formed precipitates; this would be more severe in an actual field. Consequently, nano-TiO2 would not be also readily available to plants and would not cause any significant effects on plants. Our results and other reports suggest that titanium itself is not phytotoxic, even though plants absorb titanium. In conclusion, nano-TiO2 is not toxic to the three plant species, in vitro or in situ.
TL;DR: It was concluded that heat stress leads to loss of pollen as well as stigma function and induces oxidative stress in the leaves that cause failure of fertilization and damage to the leaves, respectively.
Abstract: The mechanisms affecting the heat sensitivity of chickpea are largely unknown. Heat-tolerant (ICCV07110, ICCV92944) and heat-sensitive (ICC14183, ICC5912) chickpea genotypes were sown in February in the soil-filled pots. At the time of flowering, these were subjected to varying day/night temperatures of 30/20, 35/25, 40/30 and 45/35°C in the growth chambers (12 h light/12 h dark; light intensity, 250 μmol m−2 s−1, 80% relative humidity). The pollen viability, pollen germination, tube growth, pollen load and stigma receptivity decreased with increases in temperatures to 45/35°C. The heat-tolerant genotypes experienced significantly less damage to pollen and stigma function. Membrane integrity, chlorophyll content, photochemical efficiency and cellular oxidizing ability were inhibited by the increase in temperature, with greater impacts on the sensitive genotypes. Oxidative injury as lipid peroxidation and hydrogen peroxide content was significantly greater in sensitive genotypes at 40/30 and 45/35°C. Enzym...
TL;DR: NO-dependent protein post-translational modifications are proposed as a key mechanism underlying NO signaling during early seed germination, and their consequences on the investigations on both its signaling and its targets in seeds are discussed.
Abstract: Germination ability is regulated by a combination of environmental and endogenous signals with both synergistic and antagonistic effects. Nitric oxide (NO) is a potent dormancy-releasing agent in many species, including Arabidopsis, and has been suggested to behave as an endogenous regulator of this physiological blockage. Distinct reports have also highlighted a positive impact of NO on seed germination under sub-optimal conditions. However, its molecular mode of action in the context of seed biology remains poorly documented. This review aims to focus on the implications of this radical in the control of seed dormancy and germination. The consequences of NO chemistry on the investigations on both its signaling and its targets in seeds are discussed. NO-dependent protein post-translational modifications are proposed as a key mechanism underlying NO signaling during early seed germination.
TL;DR: It is shown how mechanisms identified in the laboratory are coordinated in response to the soil environment to determine the dormancy cycles that result in winter and summer annual phenotypes.
Abstract: Seeds use environmental cues to sense the seasons and their surroundings to initiate the life cycle of the plant. The dormancy cycling underlying this process is extensively described, but the molecular mechanism is largely unknown. To address this we selected a range of representative genes from published array experiments in the laboratory, and investigated their expression patterns in seeds of Arabidopsis ecotypes with contrasting life cycles over an annual dormancy cycle in the field. We show how mechanisms identified in the laboratory are coordinated in response to the soil environment to determine the dormancy cycles that result in winter and summer annual phenotypes. Our results are consistent with a seed-specific response to seasonal temperature patterns (temporal sensing) involving the gene DELAY OF GERMINATION 1 (DOG1) that indicates the correct season, and concurrent temporally driven co-opted mechanisms that sense spatial signals, i.e. nitrate, via CBL-INTERACTING PROTEIN KINASE 23 (CIPK23) phosphorylation of the NITRATE TRANSPORTER 1 (NRT1.1), and light, via PHYTOCHROME A (PHYA). In both ecotypes studied, when all three genes have low expression there is enhanced GIBBERELLIN 3 BETA-HYDROXYLASE 1 (GA3ox1) expression, exhumed seeds have the potential to germinate in the laboratory, and the initiation of seedling emergence occurs following soil disturbance (exposure to light) in the field. Unlike DOG1, the expression of MOTHER of FLOWERING TIME (MFT) has an opposite thermal response in seeds of the two ecotypes, indicating a role in determining their different dormancy cycling phenotypes.
TL;DR: Zinc in rice grains can be effectively raised by foliar Zn application after flowering, with a potential benefit of this to rice eaters indicated by up to 55% increases of brown rice Zn, and agronomically in more rapid early growth and establishment.
Abstract: This study evaluated how zinc (Zn) concentration of rice (Oryza sativa L.) seed may be increased and subsequent seedling growth improved by foliar Zn application. Eight foliar Zn treatments of 0.5% zinc sulfate (ZnSO4 · 7H2O) were applied to the rice plant at different growth stages. The resulting seeds were germinated to evaluate effects of seed Zn on seedling growth. Foliar Zn increased paddy Zn concentration only when applied after flowering, with larger increases when applications were repeated. The largest increases of up to ten-fold were in the husk, and smaller increases in brown rice Zn. In the first few days of germination, seedlings from seeds with 42 to 67 mg Zn kg−1 had longer roots and coleoptiles than those from seeds with 18 mg Zn kg−1, but this effect disappeared later. The benefit of high seed Zn in seedling growth is also indicated by a positive correlation between Zn concentration in germinating seeds and the combined roots and shoot dry weight (r = 0.55, p < 0.05). Zinc in rice grains ...
TL;DR: The influence of a heat stress of 85°C for 10 min on germination, outgrowth, and subsequent vegetative growth was investigated in detail and the distribution and the mean outgrowth time and the generation time of vegetative cells, emerging from untreated and thermally injured spores, were similar.
Abstract: Spore-forming bacteria are a special problem for the food industry as some of them are able to survive preservation processes. Bacillus spp. spores can remain in a dormant, stress resistant state for a long period of time. Vegetative cells are formed by germination of spores followed by a more extended outgrowth phase. Spore germination and outgrowth progression are often very heterogeneous and therefore, predictions of microbial stability of food products are exceedingly difficult. Mechanistic details of the cause of this heterogeneity are necessary. In order to examine spore heterogeneity we made a novel closed air-containing chamber for live imaging. This chamber was used to analyze Bacillus subtilis spore germination, outgrowth, as well as subsequent vegetative growth. Typically, we examined around 90 starting spores/cells for ≥4 hours per experiment. Image analysis with the purposely built program “SporeTracker” allows for automated data processing from germination to outgrowth and vegetative doubling. In order to check the efficiency of the chamber, growth and division of B. subtilis vegetative cells were monitored. The observed generation times of vegetative cells were comparable to those obtained in well-aerated shake flask cultures. The influence of a heat stress of 85°C for 10 min on germination, outgrowth, and subsequent vegetative growth was investigated in detail. Compared to control samples fewer spores germinated (41.1% less) and fewer grew out (48.4% less) after the treatment. The heat treatment had a significant influence on the average time to the start of germination (increased) and the distribution and average of the duration of germination itself (increased). However, the distribution and the mean outgrowth time and the generation time of vegetative cells, emerging from untreated and thermally injured spores, were similar.