Seed Germination Assay Research Articles

Major latex protein-like protein 43 (MLP43) functions as a positive regulator during abscisic acid responses and confers drought tolerance in Arabidopsis thaliana.

Drought stress is one of the disadvantageous environmental conditions for plant growth and reproduction. Given the importance of abscisic acid (ABA) to plant growth and abiotic stress responses, identification of novel components involved in ABA signalling transduction is critical. In this study, we screened numerous Arabidopsis thaliana mutants by seed germination assay and identified a mutant mlp43 (major latex protein-like 43) with decreased ABA sensitivity in seed germination. The mlp43 mutant was sensitive to drought stress while the MLP43-overexpressed transgenic plants were drought tolerant. The tissue-specific expression pattern analysis showed that MLP43 was predominantly expressed in cotyledons, primary roots and apical meristems, and a subcellular localization study indicated that MLP43 was localized in the nucleus and cytoplasm. Physiological and biochemical analyses indicated that MLP43 functioned as a positive regulator in ABA- and drought-stress responses in Arabidopsis through regulating water loss efficiency, electrolyte leakage, ROS levels, and as well as ABA-responsive gene expression. Moreover, metabolite profiling analysis indicated that MLP43 could modulate the production of primary metabolites under drought stress conditions. Reconstitution of ABA signalling components in Arabidopsis protoplasts indicated that MLP43 was involved in ABA signalling transduction and acted upstream of SnRK2s by directly interacting with SnRK2.6 and ABF1 in a yeast two-hybrid assay. Moreover, ABA and drought stress down-regulated MLP43 expression as a negative feedback loop regulation to the performance of MLP43 in ABA and drought stress responses. Therefore, this study provided new insights for interpretation of physiological and molecular mechanisms of Arabidopsis MLP43 mediating ABA signalling transduction and drought stress responses.

Hairy root induction and phytoremediation of textile dye, Reactive green 19A-HE4BD, in a halophyte, Sesuvium portulacastrum (L.) L.

In this study, we report phytoremediation of textile dyes using hairy roots derived through Agrobacterium rhizogenes (NCIM 5140) infection of in vitro leaf and stem explants of a halophyte Sesuvium portulacastrum (L.) L. Leaf explants showed higher frequency of hairy root induction (70%) than stem explants (30%), and maximum number of roots (leaf 42.3±2.4 and stem 50.3±1.7). Transformed nature of hairy roots was ascertained by amplifying 970bp region of T-DNA of Ri plasmid. Hairy roots were screened for phytoremediation of various textile dyes and results showed that HRs were able to degrade Reactive green 19A HE4BD upto 98% within 5 days of incubation. Spectrophotometric analysis showed decrease in dye concentration while HPLC and FTIR analysis confirmed its degradation. Seed germination assay demonstrated non-toxic nature of the extracted metabolites. This is the first report on induction of hairy root culture in Sesuvium portulacastrum and phytoremediation of textile dyes.

Differential Effects of Plant Growth-Promoting Rhizobacteria on Maize Growth and Cadmium Uptake

Maize is a plant known for food, feed, and energy value, but being a greater biomass, it may also be utilized to extract pollutants from soil. Plant growth-promoting rhizobacteria (PGPR) may act as biofertilizer to improve plant health and indirectly may enhance metal extraction. This study focuses on five bacterial strains isolated from the vegetable (Bitter gourd) rhizosphere irrigated with industrial effluent and characterized for various plant growth-promoting activities. Based on 16S rRNA gene sequencing, bacterial strains belonging to the genera, Bacillus (CIK-517, CIK-519), Klebsiella (CIK-518), Leifsonia (CIK-521), and Enterobacter (CIK-521R), were tested for their ability to promote maize growth in axenic conditions. Results showed negative and positive regulation of maize growth by the exogenous application of Cd and PGPR, respectively. Seed germination assays revealed significant reduction in relative seedling growth of maize cultivars upon Cd exposure (0–80 mg Cd L−1). The tested strains showed tolerance to Cd (1.78–4.45 mmol L−1) and were positive for catalase, oxidase, phosphate solubilization, exopolysaccharide (EPS), and auxin production, whereas CIK-518, CIK-519, and CIK-521R were negative for EPS, phosphate solubilization, and oxidase activities, respectively. Bacterial strains significantly increased shoot/root growth and their dry biomass in normal and Cd-contaminated soil as compared to their respective controls. None of the strains showed significant effects on relative water content or membrane permeability; however, Cd uptake significantly increased in plant tissues upon bacterial inoculation. Bacterial strains CIK-518 and CIK-521R are effective colonizers and thus can be potential inoculants to promote maize growth and Cd extraction/stabilization in Cd-contaminated soil.

신규 제초활성 물질 발굴을 위한 메타게놈 스크리닝 방법 연구

메타게놈(metagenome)은 연구실에서 배양이 불가능한 미생물을 포함한 자연계에 존재하는 미생물의 유전자를 직접 연구하는 학문분야이다. 지구상 거의 모든 자연, 인공 환경에서 살고 있는 미생물 DNA를 분리 정제하는 것이 가능하며, 재조합 DNA 기술 등을 이용하여 배양 가능한 숙주미생물에 메타지놈을 클로닝함으로서 메타지놈 라이브러리를 제작할 수 있다. 최근 메타게노믹스를 통하여 자연계에 존재하고 있는 대다수의 미생물들이 실험실에서 배양되지 않았던 이유를 구명할 수 있게 되었고, 그들이 가지고 있는 생태학적인 의미와 역할에 대한 이해와 더불어 점차 그 응용 분야와 범위도 확대되고 있다. 이와 같은 메타게놈의 응용 분야 확대의 한 방안으로 본 연구에서는 새로운 제초활성 물질 및 제초활성 물질 생산에 필요한 유전자를 확보하기 위해 메타게놈 라이브러리를 대상으로 오이 떡잎절편 검정, 미세조류 생장저해 검정, 종자발아 저해 검정의 HTS (high throughput screening) 시스템을 구축하였고, 구축된 시스템으로부터 선발된 최종 단일 클론인 9-G1과 9-G12의 바랭이에 대한 in vivo assay를 통해 본 연구에서 개발한 HTS 시스템의 유효성을 확인 하였다. 후속연구로서 활성단일클론이 만들어내는 제초활성물질의 동정 및 제초활성물질을 합성하는 유전자군에 대한 연구를 수행 중에 있다. Metagenomics is a powerful tool to isolate novel biocatalyst and biomolecules directly from the environmental DNA libraries. Since the metagenomics approach bypasses cultivation of microorganisms, un-cultured microorganisms that are majority of exists can be the richest reservoir for natural products discovery. To discover novel herbicidal substances from soil metagenome, we established three easy, simple and effective high throughput screening methods such as cucumber cotyledon leaf disc assay, microalgae assay and seed germination assay. Employing the methods, we isolated two active single clones (9-G1 and 9-G12) expressing herbicidal activity which whitened leaf discs, inhibited growth of microalgae and inhibited root growth of germinated Arabidopsis seeds. Spraying butanol fraction of the isolated active clones' culture broth led to growth retardation or desiccation of Digitalia sanguinalis (L) Scop. in vivo. These results represent that the screening methods established in this study are useful to screen herbicidal substances from metagenome libraries. Further identifying molecular structure of the herbicidal active substances and analyzing gene clusters encoding synthesis systems for the active substances are in progress.

Removal of atrazine from aqueous environment using immobilized Pichia kudriavzevii Atz-EN-01 by two different methods

In this study we examined the ability immobilized Pichia kudriavzevii Atz-EN-01 cells to remove atrazine from aqueous environment using two different immobilization methods viz. encapsulation in a sodium alginate-polyvinyl alcohol (SA-PVA) matrix and biofilm formation on clay brick particles. The experiments were carried out in batch and fed batch cultures, and atrazine degradation was monitored by High Performance Liquid Chromatography (HPLC). In addition, the efficiency of the atrazine degradation by the Atz-EN-01 biofilm was evaluated in packed bed column. The toxicity of the column eluent was evaluated using an Oryza sativa (rice plant) seed germination assay. The data obtained from the two immobilization methods suggest that the percentage of atrazine removal was more efficient for the Atz-EN-01 biofilm colonized on clay brick particles compared to the encapsulated SA-PVA beads. Data also showed the detoxification of atrazine in the packed bed reactor as a result of the biological treatment with Atz-EN-01. Together, our results show that there is a scope to develop a cost effective method for the efficient removal of atrazine from wastewater using yeast Atz-EN-01 biofilm immobilized on clay brick particles.

Remediation of saline soils by a two-step process: Washing and amendment with sludge

Soil salinization is a serious land-degradation problem that affects soil, plants and groundwater within ecosystems. In this work, the effect of washing saline–sodic soils with CaCl2 at 2% (w/v) and amendment with composted and dry sewage sludge was evaluated in a remediation assay. The effectiveness of amendments to improve the soil fertility was investigated with seed germination assays of Raphanus sativus L. Two different organic wastes were used: sewage sludge composted with pruning wastes (CP) and thermally dried sewage sludge (T) at rates of 1 and 2% (w/v) on organic matter basis. In general, there was an increase of germination percentage in the amended washed soils. The best indices were obtained at the 1% amendment dose with CP. The low exchangeable sodium percentage (ESP) in washed–amended soil (3 to 6 times lower than that of saline–sodic soil) could partially explain the increase in seed germination percentage of R. sativus L. The incorporation of organic amendments to washed soil also seemed to be beneficial as a step in the restoration process according to the chemical characteristics, especially by increasing the level of nutrients such as carbon, nitrogen, and phosphorus. A significant multiple linear regression of radish germination index in terms of pH values, sodium adsorption ratio of soil (SAR), and different forms of nitrogen (NH4+ and NO2−) was found.Overall, saline–sodic soil washing with CaCl2 followed by addition of organic amendments seems to be a promising strategy for restoration of such soils with simultaneous improvements of cation balance and nutrient/organic matter contents.

Potential of biofertilizers from selected Rhodopseudomonas palustris strains to assist rice (Oryza sativa L. subsp. indica) growth under salt stress and to reduce greenhouse gas emissions

The absence of phytotoxicity is one of the most important criterions for the use of biofertilizers, and their carriers must be able to maintain their activity efficiently until used. Hence, a carrier that consisted of a mixture of rice straw and rice husk ash in a 4:1 ratio with potential biofertilizers (Rhodopseudomonas palustris TK103, PP803, and P1) were investigated with a salt sensitive rice for seed germination assay and the efficacy of the biofertilizers to ameliorate rice growth under salt stress (0.25 % NaCl) by producing 5-aminolevulinic acid (ALA) and reducing gas emissions (CH4 and CO2). No phytotoxicity was found under optimal concentrations for any of the biofertilizers tested as the germination index (GI) in the range of 105–117 %; however, the carrier had a 94 % GI when compared with distilled water. Among the biofertilizers tested, strain PP803 was the best to ameliorate rice seedling growth in soil under salt stress, particularly on plant height and root length when compared with carrier and water controls. In a paddy field model study under microaerobic light conditions for 10 days, optimal concentrations of biofertilizers provided viable cells in the range of 6.7–6.8 log CFU mL−1 , and strain PP803 was the most effective fertilizer to produce maximum ALA (2.61 μM) and reduce 100 % CH4 and 47 % CO2 emissions. It can be concluded that the biofertilizers tested, particularly the strain PP803, could be powerful agents for use in saline paddy fields to ameliorate rice seedlings growth under salt stress and reduce greenhouse gas emissions.

A Comparison of Phytotoxic Potential among the Crude Extracts from <i>Parthenium hysterophorus</i> L. Extracted with Solvents of Increasing Polarity

There is a worldwide search for the safe, effective and eco-friendly compounds of plant origin to combat the weed species and other pests which are responsible for the great impact on the growth and productivity of agricultural crops. In this present study, a comparison was made to evaluate the phytotoxicity potential of sequentially extracted solvent (hexane, ethyl-acetate, methanol) extracts of Parthenium hysterophorus L. (aerial parts) in vitro through bench-top seed germination assay (Vigna radiata L.). One-way analysis of variance (ANOVA) followed by Duncan’s multiple range test (DMRT) were done for statistical analysis of the data. The study reveals that germination, growth and vigour was significantly (P<0.05) reduced by ethyl-acetate and methanol extracts. The present study concluded that phytotoxicity of ethylacetate and methanolic crude extracts of Parthenium hysterophorus could be exploited as potential bioherbicide for future weed management programme and the development of bioherbicide for commercial use.

Anticancer Activity ofMaytenus emarginataLeaves and Stems: A Comparative Study

Medicinal plants are the most exclusive source of life saving drugs for the majority of the world's population. The pharmacological evaluation of substances from plants is a method for the discovery of new compounds which can leads to the development of novel and safe medicinal agents. Based on traditional literature, Maytenus emarginata (Celastraceae) is an evergreen tree, commonly known as “thorny staff tree” in English. In present study the leaves and stems of Maytenus emarginata were extracted with methanol to produce respective extracts. The extracts were screened for anti cancer activity by using Antimitotic activity by Allium cepa method, Seed germination assay by green gram seeds and Brine shrimp lethality test using Artemia salina eggs. Methotrexate was used as standard anticancer drug. Current study demonstrates that the obtained results of leaves extracts were more potent than the stems extracts.

A Comparison of Phytotoxic Potential among the Crude Extracts from <i>Parthenium hysterophorus</i> L. Extracted with Solvents of Increasing Polarity

There is a worldwide search for the safe, effective and eco-friendly compounds of plant origin to combat the weed species and other pests which are responsible for the great impact on the growth and productivity of agricultural crops. In this present study, a comparison was made to evaluate the phytotoxicity potential of sequentially extracted solvent (hexane, ethyl-acetate, methanol) extracts of Parthenium hysterophorus L. (aerial parts) in vitro through bench-top seed germination assay (Vigna radiata L.). One-way analysis of variance (ANOVA) followed by Duncan’s multiple range test (DMRT) were done for statistical analysis of the data. The study reveals that germination, growth and vigour was significantly (P<0.05) reduced by ethyl-acetate and methanol extracts. The present study concluded that phytotoxicity of ethylacetate and methanolic crude extracts of Parthenium hysterophorus could be exploited as potential bioherbicide for future weed management programme and the development of bioherbicide for commercial use.

Optimization of parameters for decolorization of a textile azo dye, Remazol Black B (RBB) by a newly isolated bacterium, Bacillus thuringiensis BYJ1

Bacillus thuringiensis BYJ1, a newly isolated bacterium from textile effluent contaminated soil was exploited to decolorize a textile azo dye, Remazol Black B (RBB). Various process parameters like initial RBB concentration, temperature, pH and cultural conditions on the process of dye decolorization were studied in order to determine optimum condition. Decolorization process was largely affected under aerobic process. Despite the toxic and inhibitory effects of dye, B. thuringiensis BYJ1 was able to tolerate as high as 1200 mg L-1 of RBB. Optimum decolorization of RBB was achieved at 37°C and pH 7 under static culture condition. Decolorization process was also studied using immobilized cells of B. thuringiensis BYJ1. The decolorized dye products were analyzed by thin layer chromatography (TLC), UV-visible scanning and fourier transform infrared spectroscopy (FTIR) analysis. Seed germination assay was performed to analyze the effect of decolorized dye products. The plasmid isolation and its curing from B. thuringiensis BYJ1 was performed to study effect of plasmid on the process of biodegradation of RBB. Key words: Azo dye, decolorization, immobilization, plasmid curing, Bacillus thuringiensis.

Plant Growth Promoting Effect of Seaweeds Collected from East Coast of Tamil Nadu, India

The continuous use of chemical fertilizers in agriculture field is highly toxic to the nature and also disturbs the soil living beneficial microorganisms. Seaweeds are well known commercially available marine plants and it has many eco-friendly applications. Thus the present study was carried out develop a plant growth promoting seaweed liquid fertilizer (SLF) for agricultural crop plants. In this study commercially available eight different seaweeds such as Ulva fasciata, Enteromorpha intestinalis, Dictyota dichotoma, Sargassum wightii, Padina boergesenii, Amphiroa anceps, Avanthopleura spicifera and Spyridia hypnoides, were collected from the rocky shore areas of Mandapam Coast, Rameshwaram District, Tamil Nadu, India. The eight different seaweed liquid fertilizer (SLF) was prepared to determine their plant growth promoting ability in agriculturally important crop plants such as, Green gram, Black gram, Mustard and Paddy by seed germination and soil drenching methods in both sterilized and unsterilized soil at laboratory scale experimental setups. In seed germination assay, 100% germination was observed in seeds soaked with Sargassum wightii, Padina boergesenii and Ulva fasciata. In soil treatment and plant culture study after 15 days of sowing the root length, shoot length and fresh weight of all the seedlings were recorded in all the setups. In that, Sargassum wightii, Padina boergesenii and Ulva fasciata seaweed liquid fertilizer (SLF) have shown the maximum plant growth promoting activity in unsterilized soil than the sterilized soil. The results were well demonstrated the effect of seaweed liquid fertilizer (SLF) in plant growth promotion and suggested to use this fertilizer to enhance the profitability in agricultural field.

Molecular diversity and functional variability of environmental isolates of Bacillus species.

In the present study, out of 264 phosphate (P) solubilizing Bacillus strains isolated from apple rhizosphere, only twelve isolates were found to be efficient (showed most of the plant growth promoting activity) which were further characterized at molecular level using 16S rDNA partial gene sequencing. Out of 12 isolates, MZPSB 207 was found to be most efficient P-solubilizing (864.71 μg/ml) isolate which also showed indole acetic acid production (51.83 μg/ml), siderophore production, ammonia production, antagonistic property (against Rhizoctonia solani and Fusarium oxysporum), hydrolytic enzymes productions (protease, chitinase and cellulase), 1-aminocyclopropane-1-carboxylate (ACC) deaminase production (7.7 μm αKB mg-1 h-1). The in-vitro seed germination assay showed that Bacillus (twelve isolates) inoculated seeds showed more seed germination and seedling vigor rate as compared to uninoculated control treatment.For the genetic diversity studies of efficient 12 strains, the polyphasic approach using 16S-rDNA, Repetitive element sequence (rep) based PCR (ERIC-PCR and BOX-PCR) were used. Based on 16S rDNA partial gene sequencing the isolated Bacillus genus was divide into four groups. First group (five isolates), second group (two isolates), third group (three isolates) and fourth group (two isolates) which showed close genetic relatedness to the B. subtilis, B. pumulis, B. megaterium and B. amyloliquefaciens, respectively. The rep PCR fingerprinting showed variability between and within the species. The large variability was showed by ERIC-PCR whereas some variability was showed by BOX-PCR. The results clearly showed that 16S rRNA gene sequencing is unable to discriminate the isolates at strain level. But rep-PCR fingerprinting is excellent tool to characterize and discriminate the strains at the genomic level.

Determinación del nivel de tolerancia a salinidad en condiciones <em>in vitro</em> de plantas de tomate de árbol (<em>Solanum betaceum</em>) provenientes de distintas localidades de la Sierra ecuatoriana

La salinidad de los suelos constituye una de las causas más importantes para la disminución de la productividad en cultivos agrícolas. Gran parte de los suelos de la Sierra ecuatoriana son considerados salinos, tanto por su naturaleza piroclástica como por la erosión y el mal uso del agua de riego. El tomate de árbol (Solanum betaceum) crece en la región interandina y en muchos casos se ve sometido al estrés salino. El objetivo del presente estudio fue determinar el grado de tolerancia del tomate de árbol a cloruro de sodio (NaCl) en cultivo in vitro. Se utilizó plantas de tomate de árbol provenientes de siete u ocho localidades dependiendo del ensayo realizado. Se evaluó la germinación de semillas, el desarrollo de plántulas a partir de nudo simple y el crecimiento de plántulas cultivadas in vitro en diferentes concentraciones de NaCl. En los ensayos de germinación de semillas se obtuvo un promedio de 62% de germinación para siete localidades analizadas en una concentración de 50mM de NaCl, y un promedio de 57% en una concentración de 75mM. En cuanto al cultivo de tomate de árbol a partir de nudo simple, se evaluó plantas de siete localidades de las cuales todas, con excepción de Quero, crecieron hasta en una concentración de 100mM de NaCl. Finalmente, en el ensayo para determinar el límite de tolerancia a NaCl en el crecimiento de plántulas, se observó diferentes respuestas al estrés salino en individuos de tomate de árbol de ocho localidades estudiadas, siendo las plántulas de Chaltura las que toleraron hasta 175 mM de NaCl. Estos resultados permiten afirmar que hubo variaciones en el grado de tolerancia a salinidad entre plantas de tomate de árbol de las diferentes localidades. La mayor tolerancia se encontró en las plantas provenientes de Chaltura, y la menor tolerancia en plantas provenientes de Quero. La información obtenida en este estudio es la base para posteriores análisis del transcriptoma donde se pueda identificar genes involucrados en la respuesta a la tolerancia a la salinidad en este interesante cultivo andino.

GEm-Related 5 (GER5), an ABA and stress-responsive GRAM domain protein regulating seed development and inflorescence architecture

We have identified an abscisic acid (ABA) and stress-responsive GRAM (Glucosyltransferases, Rab-like GTPase activators and Myotubularins) domain protein GER5 (GEm-Related 5) closely related to GEM (GLABRA2 Expression Modulator), a novel regulator of cell division and cell fate determination in epidermal cells. A loss-of-function T-DNA line (ger5-2) and transgenic lines silencing (GER5RNAi) or overexpressing (GER5OE) GER5 displayed several defects in reproductive development affecting seed and embryo development. RNA in situ studies revealed GER5 and related GRAM genes (GEM and GEm-Related 1 (GER1)) have both overlapping and unique expression domains in male and female reproductive organs. Hormone immunolocalization experiments further indicate GER5 transcripts preferentially localize to reproductive tissues which accumulate ABA. Expression analysis revealed members of the GRAM family (GER5, GER1, GEM) display tissue-specific expression patterns and are responsive to phytohormones and abiotic stress, in addition to genetic lesions (aba1, aba2, ctr1) affecting ABA biosynthesis or ethylene signalling. Mature seeds of ger5-2 mutants also exhibit reduced sensitivity to ABA during seed germination assays. Microarray analysis of aborting and developing seeds isolated from ger5-2 mutants revealed underlying transcriptional changes in carbohydrate metabolism, hormone signalling and catabolic processes (e.g. protein degradation, autophagy). Taken together, our results indicate ABA-responsive GRAM genes play a novel role in regulating the reproductive development of plants, and raise intriguing questions regarding the functional relationship between members of the GRAM gene family.

Environmentally benign synthesis and antimicrobial study of novel chalcogenophosphates

We report in this work an environmentally benign zinc mediated synthesis of aryl and benzyl phosphorochalcogenoates in ethanol within a short reaction time. In vitro antimicrobial study along with statistical analysis and seed germination assay were performed. These chalcogenophosphates possess strong antimicrobial activity against the reference strains. The antibacterial activity was determined against four standard strains (Bacilus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa). The antifungal activity was evaluated against one fungal strain Candida albicans.

A Simple Method for the Assessment of Fusarium Head Blight Resistance in Korean Wheat Seedlings Inoculated with Fusarium graminearum.

Fusarium head blight (FHB; scab) caused mainly by Fusarium graminearum is a devastating disease of wheat and barley around the world. FHB causes yield reductions and contamination of grain with trichothecene mycotoxins such as deoxynivalenol (DON) which are a major health concern for humans and animals. The objective of this research was to develop an easy seed or seedling inoculation assay, and to compare these assays with whole plant resistance of twenty-nine Korean winter wheat cultivars to FHB. The clip-dipping assay consists of cutting off the coleoptiles apex, dipping the coleoptiles apex in conidial suspension, covering in plastic bag for 3 days, and measuring the lengths of lesions 7 days after inoculation. There were significant cultivar differences after inoculation with F. graminearum in seedling relative to the controls. Correlation coefficients between the lesion lengths of clip-dipping inoculation and FHB Type II resistance from adult plants were significant (r=0.45; P<0.05). Results from two other seedling inoculation methods, spraying and pin-point inoculation, were not correlated with adult FHB resistance. Single linear correlation was not significant between seed germination assays (soaking and soak-dry) and FHB resistance (Type I and Type II), respectively. These results showed that clip-dipping inoculation method using F. graminearum may offer a real possibility of simple, rapid, and reliable for the early screening of FHB resistance in wheat.

The Effects of Light, Temperature, After-ripening, Nitrate and Water on Chenopodium Album Seed Germination

Chenopodium album is a widespread and troublesome weed in Iowa and agricultural areas throughout the north temperate regions of the world. This study investigated the effects of various factors on the stimulation of germination of two populations of C. album seeds collected in 2007 and 2008 at a common location. These factors included light, temperature, after-ripening time, nitrate, and water level. Germination of both populations was generally stimulated by light, warm (15-25℃)and hot (25-35℃) temperatures, 0.01 M nitrate, 3 to 5 weeks of after-ripening (4℃, dark, moist), and with the 2008 population, 1.0 and 1.25 ml of water. The interaction of these factors, particularly light, warm temperatures and nitrate, stimulated higher germination than when applied individually. Germination was very low in cold (5-15℃) temperatures or darkness, regardless of other treatments applied. The goal of this experiment was to lay a foundation with two local Iowa populations to guide further studies developing a seed germination assay to determine variability of dormancy among individual seeds of and between populations. Insights about dormancy variability in C. album gained from the current research included positive responses by both populations to light, warm and hot temperatures, nitrate, and intermediate after-ripening times. However, the populations differed in their response to water quantity and, for most conditions, the 2008 population achieved greater overall germination. The overarching goal of this project is to build a condensed C. album seed germination assay to characterize individual populations to predict seedling emergence patterns in agricultural soils in an effort to decrease interference with crop productivity.

Potential plant growth promoting activity ofPseudomonas fluorescenssp. isolated from cotton (Gossypium hirsutum) crop

Plant-bacterial interactions in the rhizosphere are complex and determine the plant health, productivity and soil fertility. The Plant Growth Promoting bacterial strains were isolated from the rhizospheric soil of the cotton plant from various places of Haryana, India. One of the most promising isolate exhibiting maximum PGP traits was identified as Pseudomonas fluorescens based on the biochemical characterization, phenotypic microarray analysis and 16S rDNA sequencing. The isolate was initially screened on the basis of the seed germination assay and was then screened in vitro for their plant growth promoting traits like production of indoleacetic acid (IAA), ammonia production (NH3), hydrogen cyanide (HCN) production, siderophore production, phosphate solubilization, ACC deaminase activity and acetylene reduction activity (ARA). The isolate exhibited positive results for ammonia and siderophore production and phosphate solubilization. The isolate also showed acetylene reduction activity (ARA). The results indicated that P. fluorescens has significant potential when applied to soil-plant system to uncover its efficacy as effective PGPR.

Complex Regulation of &lt;i&gt;Chenopodium album&lt;/i&gt;&lt;i&gt; &lt;/i&gt;Seed Germination

<i>Chenopodium album</i> is a common, widespread and troublesome weed in agricultural areas throughout the north temperate regions of the world. A primary reason for this flexible adaptation relies on the complex regulation of seed germination and recruitment. The control of seed germination bythe interaction of light, temperature, after-ripening time, nitrate, and water level was investigated in a factorial experiment under controlled environmental conditions. Stimulation of germination was evaluated in two populations of <i>C. album</i>seeds collected in 2007 and 2008 at a common Iowa, USA location.Germination of both populations was generally stimulated by light, warm (15-25°C) and hot (25-35°C) temperatures, 0.01 M nitrate, 3 to 5 weeks of after-ripening (4°C, dark, moist), and with the 2008 population, 1.0 and 1.25 ml of water. The interaction of these factors, particularly light, warm temperatures and nitrate, stimulated higher germination than when applied individually. Germination was very lowin cold (5-15°C) temperatures or darkness, regardless of other treatments applied. The goal of this experiment was to lay a foundation with two local Iowa populations to guide further studies developing a seed germination assay to determine variability of dormancy among individual seeds of and between populations. Insights about dormancy variability in <i>C. album</i> gained from the current research included positive responses by both populations to light, warm and hot temperatures, nitrate, and intermediate after-ripening times. However, the populations differed in their response to water quantity and, for most conditions, the 2008 population achieved greater overall germination. The overarching goal of this project is to build a condensed <i>C. album </i>seed germination assay to characterize individual populations to predict seedling emergence patterns in agricultural soils in an effort to decrease interference with crop productivity.