Showing papers on "Seedling published in 2013"

SUPPRESSOR OF MORE AXILLARY GROWTH2 1 Controls Seed Germination and Seedling Development in Arabidopsis

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.

Identification of QTLs associated with seedling root traits and their correlation with plant height in wheat

Abstract: Genetic relationships between plant height and root morphology were investigated in a diverse set of wheat germplasm [199 double-haploid progeny derived from a cross between Avalon and Cadenza (Triticum aestivum L.), Rht near-isogenic lines (NILs), and accessions from the Watkins Collection] to investigate whether Rht genes controlling shoot height also control seedling root growth. A germination paper screen was developed to measure seedling root length (distinguishing seminal axes from seminal lateral roots), surface area, volume, and dry weight, and these were compared with shoot dry weight and the root to shoot ratio. Field experiments were conducted to measure mature plant height (PH) and grain characteristics for the mapping population. Forty-three quantitative trait loci (QTLs) for PH, root and seed traits were identified. Some QTLs for roots and either height or seed characteristics were coincident: chromosome 2D had co-locating root and PH QTLs; chromosomes 4D had co-locating root, PH, and seed QTLs; chromosome 5A and 6A had co-locating root and seed QTLs; and other non-co-locating root and PH QTLs were found on chromosomes 3A and 3B. Rht NILs illustrated that some known dwarfing genes reduce both PH and root proliferation. However, analysis of 25 short and 23 tall lines from the Watkins wheat germplasm collection indicated that PH and root proliferation are not simply related.

Effects of litter on seedling establishment in natural and semi‐natural grasslands: a meta‐analysis

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.

Environmental effects of nanosilver: impact on castor seed germination, seedling growth, and plant physiology

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.

Seed Priming with Ascorbic Acid Improves Drought Resistance of Wheat

Abstract: The study, consisting of two independent experiments, was conducted to evaluate the role of seed priming with ascorbic acid (AsA) in drought resistance of wheat. In the first experiment, seeds of wheat cultivars Mairaj-2008 and Lasani-2008 were either soaked in aerated water (hydropriming) for 10 h or not soaked (control). In the second experiment, seeds of same wheat cultivars were soaked in aerated (2 mm) AsA solution (osmopriming) or water (hydropriming) for 10 h. In both experiments, seeds were sown in plastic pots (10 kg) maintained at 70 % and 35 % of water-holding capacity designated as well watered and drought stressed, respectively. Both experiments were laid out in a completely randomized design with six replications. Drought caused delayed and erratic emergence and disturbed the plant water relations, chlorophyll contents and membranes because of oxidative damage; however, root length in cultivar Lasani-2008 was increased under drought. Hydropriming significantly improved the seedling emergence and early growth under drought and well-watered conditions; however, improvement was substantially higher from osmopriming with AsA. Similarly, osmopriming with AsA significantly improved the leaf emergence and elongation, leaf area, specific leaf area, chlorophyll contents, root length and seedling dry weight. Owing to increase in proline accumulation, phenolics and AsA, by seed priming with AsA, plant water status was improved with simultaneous decrease in oxidative damages. These improved the leaf emergence and elongation, and shoot and root growth under drought. However, there was no difference between the cultivars in this regard. In conclusion, osmopriming with AsA improved the drought resistance of wheat owing to proline accumulation and antioxidant action of AsA and phenolics, leading to tissue water maintenance, membrane stability, and better and uniform seedling stand and growth.

Effect of Nanoscale Titanium Dioxide Particles on the Germination and Growth of Canola (Brassica napus)

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.

Effect of short-term heat stress on growth, physiology and antioxidative defence system in wheat seedlings

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.

Effect of different foliar zinc application at different growth stages on seed zinc concentration and its impact on seedling vigor in rice

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 ...

Ionomic responses and correlations between elements and metabolites under salt stress in wild and cultivated barley.

Abstract: A thorough understanding of ionic detoxification and homeostasis is imperative for improvement of salt tolerance in crops. However, the homeostasis of elements and their relationship to metabolites under salt stress have not been fully elucidated in plants. In this study, Tibetan wild barley accessions, XZ16 and XZ169, differing in salt tolerance, and a salt-tolerant cultivar CM72 were used to investigate ionomic profile changes in tissues in response to 150 and 300 mM NaCl at the germination and seedling stages. At the germination stage, the contents of Ca and Fe significantly decreased in roots, while K and S contents increased, and Ca and Mg contents decreased in shoots, after 10 d of treatment. At the seedling stage, the contents of K, Mg, P and Mn in roots and of K, Ca, Mg and S in shoots decreased significantly after 21 d of treatment. Moreover, Na had a significant negative correlation with metabolites involved in glycolysis, α-ketoglutaric acid, maleic acid and alanine in roots, and metabolites associated with the tricarboxylic acid (TCA) cycle, sucrose, polyols and aspartate in leaves. The salt-tolerant genotypes XZ16 and CM72 showed a lower Na content in tissues, and less reduction in Zn and Cu in roots, of Ca, Mg and S in leaves, and shoot DW than the sensitive genotype XZ169, when exposed to a higher salt level. The results indicated that restriction of Na accumulation and rearrangement of nutrient elements and metabolites in barley tissues are possibly attributable to development of salt tolerance.

Induction of chilling tolerance in wheat during germination by pre-soaking seed with nitric oxide and gibberellin

Abstract: Chilling depresses seed germination and seedling establishment, and is one major constraint to grain yield formation in late sown winter wheat Seeds of winter wheat (Triticum aestivum L) were separately pre-soaked with sodium nitroprusside (SNP, as nitric oxide donor) and Gibberellic acid (GA3) before germination and then germinated under low temperature SNP and GA3 pre-treatment increased seed germination rate, germination index, weights and lengths of coleoptile and radicle, while they decreased mean germination time and weight of seeds germinating under low temperature Exogenous NO and GA3 increased seed respiration rate and promoted starch degradation along with increased amylase activities In addition, efficient antioxidant systems were activated by NO, and which effectively reduced concentrations of malondialdehyde and hydrogen peroxide (H2O2) Seedling growth was also enhanced by exogenous NO and GA3 as a result of improved seed germination and maintenance of better reactive oxygen species homeostasis in seedling growing under chilling temperatures It is indicated that exogenous NO was more effective than GA3 in alleviating chilling stress during seed germination and seedling establishment in wheat

Increased Growth and Germination Success in Plants following Hydrogen Sulfide Administration

Abstract: This study presents a novel way of enhancing plant growth through the use of a non-petroleum based product. We report here that exposing either roots or seeds of multicellular plants to extremely low concentrations of dissolved hydrogen sulfide at any stage of life causes statistically significant increases in biomass including higher fruit yield. Individual cells in treated plants were smaller (∼13%) than those of controls. Germination success and seedling size increased in, bean, corn, wheat, and pea seeds while time to germination decreases. These findings indicated an important role of H2S as a signaling molecule that can increase the growth rate of all species yet tested. The increased crop yields reported here has the potential to effect the world's agricultural output.

FAR-RED ELONGATED HYPOCOTYL3 and FAR-RED IMPAIRED RESPONSE1 transcription factors integrate light and abscisic acid signaling in Arabidopsis.

Abstract: Light and the phytohormone abscisic acid (ABA) regulate overlapping processes in plants, such as seed germination and seedling development. However, the molecular mechanism underlying the interaction between light and ABA signaling is largely unknown. Here, we show that FAR-RED ELONGATED HYPOCOTYL3 (FHY3) and FAR-RED IMPAIRED RESPONSE1 (FAR1), two key positive transcription factors in the phytochrome A pathway, directly bind to the promoter of ABA-Insensitive5 and activate its expression in Arabidopsis (Arabidopsis thaliana). Disruption of FHY3 and/or FAR1 reduces the sensitivity to ABA-mediated inhibition of seed germination, seedling development, and primary root growth. The seed germination of the fhy3 mutant is also less sensitive to salt and osmotic stress than that of the wild type. Constitutive expression of ABA-Insensitive5 restores the seed germination response of fhy3. Furthermore, the expression of several ABA-responsive genes is decreased in the fhy3 and/or far1 mutants during seed imbibition. Consistently, FHY3 and FAR1 transcripts are up-regulated by ABA and abiotic stresses. Moreover, the fhy3 and far1 mutants have wider stomata, lose water faster, and are more sensitive to drought than the wild type. These findings demonstrate that FHY3 and FAR1 are positive regulators of ABA signaling and provide insight into the integration of light and ABA signaling, a process that may allow plants to better adapt to environmental stresses.

Common arbuscular mycorrhizal networks amplify competition for phosphorus between seedlings and established plants.

Abstract: Common mycorrhizal networks (CMNs) influence competition between plants, but reports regarding their precise effect are conflicting. We studied CMN effects on phosphorus (P) uptake and growth of seedlings as influenced by various disruptions of network components. Tomato (Solanum lycopersicon) seedlings grew into established networks of Rhizophagus irregularis and cucumber (Cucumis sativus) in two experiments. One experiment studied seedling uptake of (32)P in the network in response to cutting of cucumber shoots; the other analysed seedling uptake of P and nitrogen (N) in the presence of intact or severed arbuscular mycorrhizal fungus networks and at two soil P concentrations. Pre-established and intact networks suppressed growth of tomato seedlings. Cutting of cucumber shoots mitigated P deficiency symptoms of seedlings, which obtained access to P in the extraradical mycelium and thereby showed improved growth. Solitary seedlings growing in a network patch that had been severed from the CMN also grew much better than seedlings of the corresponding CMN. Interspecific and size-asymmetric competition between plants may be amplified rather than relaxed by CMNs that transfer P to large plants providing most carbon and render small plants P deficient. It is likely that grazing or senescence of the large plants will alleviate the network-induced suppression of seedling growth.

N2-Fixation and Seedling Growth Promotion of Lodgepole Pine by Endophytic Paenibacillus polymyxa

Abstract: We inoculated lodgepole pine (Pinus contorta var latifolia (Dougl) Engelm) with Paenibacillus polymyxa P2b-2R, a diazotrophic bacterium previously isolated from internal stem tissue of a naturally regenerating pine seedling to evaluate biological nitrogen fixation and seedling growth promotion by this microorganism Seedlings generated from pine seed inoculated with strain P2b-2R were grown for up to 13 months in a N-limited soil mix containing 07 mM available N labeled as Ca(15NO3)2 to facilitate detection of N2-fixation Strain P2b-2R developed a persistent endophytic population comprising 102–106 cfu g−1 plant tissue inside pine roots, stems, and needles during the experiment At the end of the growth period, P2b-2R had reduced seedling mortality by 14 % and 15N foliar N abundance 79 % and doubled foliar N concentration and seedling biomass compared to controls Our results suggest that N2-fixation by P polymyxa enhanced growth of pine seedlings and support the hypothesis that plant-associated diazotrophs capable of endophytic colonization can satisfy a significant proportion of the N required by tree seedlings growing under N-limited conditions

Long‐term seed survival and dispersal dynamics in a rodent‐dispersed tree: testing the predator satiation hypothesis and the predator dispersal hypothesis

Abstract: Summary 1 Mast seeding in animal-dispersed plants has previously been accounted for by two main hypotheses: the predator satiation hypothesis (that it increases seed survival and establishment before dispersal) and the predator dispersal hypothesis (that it increases seed dispersal or dispersal distance) However, neither hypothesis has been rigorously tested with simultaneous data on seed production, seed predation and seed dispersal by vertebrate seed predators 2 We studied oil tea Camellia oleifera (Theaceae) seed production for eight years (2002–2009) in a subtropical forest in south-west China, and investigated how annual seed and rodent abundance determined per capita seed availability for rodent seed predators and seed dispersers and how seed and rodent abundance were related to seed dispersal and seed survival via scatter-hoarding We predicted the patterns of seed dispersal and survival to test the two hypotheses about mast seeding Edward’s long-tailed rat Leopoldamys edwardsi acted as the principal seed disperser of oil tea seeds because of scatter-hoarding, while other sympatric rodent species acted only as seed predators 3 We first provided a reasonable method to estimate per capita seed availability based on annual seed abundance and annual metabolic rodent abundance (corrected for metabolic-scaling body mass of each rodent species) We found that annual seed abundance, annual metabolic rodent abundance and per capita seed availability all had some significant effects on different estimators of seed fates (including dispersal distances) across each stage from seedfall to seedling establishment Both annual seed abundance and per capita seed availability were positively correlated with pre-dispersal seed survival, but negatively correlated with scatter-hoarding (and recaching), seed survival after dispersal and dispersal distances However, annual metabolic rodent abundance had a positive effect on scatter-hoarding, but had a negative effect on the time to cache recovery 4 Synthesis Since greater seed production was associated with improvement in pre-dispersal survival of oil tea seeds but a reduction in dispersal (including secondary dispersal and dispersal distance), our long-term study indicates that, compared with the predator dispersal hypothesis, the predator satiation hypothesis provides a better mechanism predicting seed dispersal and seed survival in animal-dispersed plants by integrating seed abundance and animal abundance

Effect of Anatase Nanoparticles (TiO2) on Parsley Seed Germination (Petroselinum crispum) In Vitro

Abstract: Nano priming is a new method for the increase of seedling vigor and improvement of germination percentage and seedling growth. The experiments to evaluate the effect of different concentrations of nano-anatase on germination parameters of parsley as a completely randomized design with five replications were performed in a tissue culture laboratory of the Department of Horticulture, Shahid Chamran University of Ahvaz. In addition, nano-anatase at four concentrations (10, 20, 30, and 40 mg/ml) was added to the Murashige and Skoog medium. At the end of the experiment, the percentage of germination, germination rate index, root and shoot length, fresh weight of seedlings, vigor index, and chlorophyll content were evaluated. The results showed that an increase in the concentration of nano-anatase caused a significant increase in the percentage of germination, germination rate index, root and shoot length, fresh weight, vigor index, and chlorophyll content of seedlings. The best concentration of nano-anatase was 30 mg/ml.

Prediction of planted seedling survival of five Mediterranean species based on initial seedling morphology

Abstract: Field performance can be predicted by evaluating nursery stock quality, but optimal morphological variables for use in these assessments may vary by species especially under dry Mediterranean conditions. Our objective was to identify initial seedling morphological characteristics that successfully predict field performance of five Mediterranean species (Pinus halepensis, Quercus ilex, Quercus coccifera, Ceratonia silqua and Pistacia lentiscus). Container seedling morphology was evaluated following the nursery phase, and then seedlings were outplanted in the field where field survival was monitored for two successive years. Results indicate that survival can successfully be predicted from seedling initial morphological characteristics for all these species, yet not all the initial characteristics were good predictors. Survival of P. halepensis and Pist. lentiscus seedlings was positively correlated to initial seedling root-collar diameter, total dry weight and Dickson’s quality index, and can be reliably predicted by these variables. In contrast, seedling field survival of the two Mediterranean evergreen oak species was correlated with few initial morphological attributes; initial diameter provided an accurate index to predict second-year outplanting survival for both species while height/diameter was a good survival predictor for Q. coccifera seedlings. For C. siliqua seedlings, seedlings with larger initial diameter and total biomass survive better in the field. Thus, diameter was the common variable that accurately predicted survival for all species, which should be >5 mm for P. halepensis seedlings and >7 mm for the remaining species.

Effects of two Glomus species on the growth and physiological performance of Sophora davidii seedlings under water stress

Abstract: Sophora davidii is an important leguminous scrub that is widely used for revegetation in the semiarid Loess Plateau and other arid valley areas of China, where it usually suffers drought stress This study investigated the effects of arbuscular mycorrhizal (AM) fungi (Glomus mosseae and Glomus constrictum) and water stress on the growth and physiological performance of S davidii seedlings under greenhouse pot conditions Two soil water availability treatments (well-watered (WW) −010 MPa; water-stressed (WS) −086 MPa) were applied for 61 days At the end of this experiment, G mosseae and G constrictum had colonized the roots of S davidii seedlings Water stress inhibited AM colonization, plant growth, chlorophyll concentration, gas exchange and chlorophyll fluorescence of S davidii seedlings Mycorrhizal seedlings had greater shoot dry weight, root dry weight, plant height, root length, instantaneous water use efficiency (iWUE), net photosynthetic rate (Pn), stomatal conductance (gs), maximal photochemical efficiency of PSII photochemistry (Fv/Fm), lower intercellular CO2 concentration and photochemical quenching values (qP), when compared with non-mycorrhizal seedlings under both WW and WS conditions Furthermore, G constrictum was found to be more efficient at improving the shoot and root mass, plant height, iWUE, Pn, gs, qP, and ΦPSII of S davidii seedlings, when compared with G mosseae under both WW and WS conditions Our results demonstrate that AM Glomus symbiosis enhanced S davidii seedling resistance by improving its growth and physiological performance under water stress conditions This suggests that Glomus inoculation is a potential tool for enhancing outplanting performance of S davidii in semiarid areas of China

Plant–soil feedback links negative distance dependence and light gradient partitioning during seedling establishment

Abstract: Tree species coexistence has often been explained through either negative distance-dependent/density-dependent (NDD) mortality or resource-based niche partitioning. However, these two influential mechanisms for structuring community dynamics have rarely been investigated simultaneously. Negative conspecific effects, like those caused by plant–soil feedbacks (PSF), could link these two mechanisms by being restricted to low-light environments and determined by seedling shade intolerance. We conducted a 10 week long greenhouse experiment where we assessed survivorship of eight temperate tree species that varied in local adult abundance and seedling shade tolerance, to non-sterile vs. sterile soils collected under the canopy of conspecific vs. heterospecific adult trees grown at low and high light. We found that half of our species experienced strong negative conspecific feedbacks. For three out of four species, the PSF were biotic mediated. However, their effects on survival were often restricted to low-ligh...

Effect of nano zinc oxide on the germination parameters of soybean seeds under drought stress

Abstract: In order to study the effect of nano zinc oxide on germination parameters of soybeans seeds under drought stress conditions applied by poly ethylene glycol (PEG), a factorial experiment conducted based on completely randomized design with three replications. Treatments were drought stress (0, #0 .5, #1 MPa) and concentrations of nano zinc oxide (0, 0.5, 1 g lit #1 ). Results showed that the effect of different concentrations of PEG and nano zinc oxide on germination rate and germination percentage, root length, root fresh and dry weight, seed residual fresh and dry weight were significant. Nano zinc oxide increased germination percentage and rate over control. Length and fresh weight of radicle was greater in stressed seedlings. Application of nano zinc oxide and stress occurrence caused to decrease in seed residual fresh and dry weight which indicates that treatments were effective for using of seed reservoirs to seedling growth .

Effect of Different Plant Growth Promoting Rhizobacteria on Maize Seed Germination and Seedling Development

Abstract: Our study aimed at assessing the effects of 3 Plants Growth Promoting Rhizobacteria (PGPR) either singly or in combination on maize growth under laboratory and greenhouse conditions. Seeds were inoculated with single and combined solution of 108 CFU/ml of Rhizobacteria. Seeds were not inoculated for the control variant. The highest germination percentage was obtained with the combination of Pseudomonas fluorescens and Pseudomonas putida. This combination also recorded the best vigor index, plants circumferences number of leaves and the leaf area. The maximal heights of plants were observed with seeds treated with Azospirillum lipoferum with an increase of 37.32%. The highest rates of underground dry matter were recorded with A. lipoferum, with an increase of more than 56% comparative to control, while the combination P. fluorescens and P. putida increased the aerial dry matter of 59.11%. Finally, the highest value of the aerial biomass was obtained with the plants treated with the combination of P. fluorescens and P. putida and the highest underground biomass was obtained with plants treated only with A. lipoferum. These results suggest that specific combinations of PGPR can be considered as efficient alternative biofertilizers to promote maize seed germination, biomass and crop yield.

BLH1 and KNAT3 modulate ABA responses during germination and early seedling development in Arabidopsis

Abstract: Summary The signal transduction pathway governed by the phytohormone abscisic acid (ABA) regulates not only abiotic stress responses but also early developmental programs such as seed dormancy, germination and seedling growth in response to environmental signals. Optimal plant growth and development depend on the integration of environmental stimuli and intrinsic developmental programs. Here, we show that the homeodomain transcription factors BLH1 and KNAT3, previously implicated in embryo sac development, have additional functions in ABA-mediated seed dormancy and early seedling development. The ABA-dependent induction of BLH1 and KNAT3 expression required the presence of functional PYR/PYL/RCAR receptors. The blh1 and knat3 mutants were less sensitive than the wild-type to ABA or salinity exposure during seed germination and early seedling development. In contrast, BLH1 over-expressing lines were hypersensitive to ABA and salinity, and exhibited increased expression of ABA-responsive genes, such as ABI3 and ABI5. BLH1 interacted with KNAT3 and enhanced the retention of KNAT3 in the nucleus. BLH1 and KNAT3 synergistically increased the ABA responses by binding to and subsequently activating the ABI3 promoter. Taken together, we propose that BLH1 and KNAT3 together modulate seed germination and early seedling development by directly regulating ABI3 expression.

Use of cyanobacterial polysaccharides to promote shrub performances in desert soils: a potential approach for the restoration of desertified areas

Abstract: The importance of cyanobacterial polysaccharides of biological soil crusts in sand surface stabilization and soil nutrient retention has been long acknowledged. However, the role of cyanobacterial polysaccharides as a source of nutrition to vascular plants in crusted areas is ignored. In this study, the chemical composition of the polysaccharide synthesized by Phormidium tenue and the effects of its presence on seed germination and seedling metabolism of the shrub Caragana korshinskii were investigated. The crude polysaccharide synthesized by P. tenue was composed of 15 % protein and 58 % carbohydrate and showed the presence of 12 different types of monosaccharides. The addition of the polysaccharide significantly (P < 0.05) increased seed germination and metabolic activity of the seedling of the shrub C. korshinskii. The optimal concentration for vigor index, root length, root vigor, and total N and P contents was 10 mg/L polysaccharide; for the germination rate, nitrate reductase activity, carbohydrate content, chlorophyll, and Mg2+ content, the optimal was 60 mg/L polysaccharide, while for K+ and Ca2+ contents, photosynthetic efficiency and superoxide dismutase activity was 120 mg/L. The presence of the polysaccharide increased seed germination rate, ion uptake, and photosynthetic activity by affecting the electron transport chain and decreased oxidative damage by eliminating reactive oxygen species in C. korshinskii, thus promoting shrub performance in crusted desert areas.