Complete Inhibition Of Germination Research Articles

Characterization of the Phytotoxic Potential of Seven Copaifera spp. Essential Oils: Analyzing Active Compounds through Gas Chromatography-Mass Spectrometry Molecular Networking.

In recent years, there has been a need for environmentally friendly compounds for weed management in agriculture. This study is aimed to assess the phytotoxic constituents of oils obtained from oleoresins of seven Copaifera species (known as copaiba oils). Copaiba oils were separated from the resins by hydro-distillation, and the distillates were analyzed using gas chromatography-mass spectrometry (GC-MS) to characterize their chemical compositions. Multivariate analyses and molecular networking of GC-MS data were conducted to discern patterns in the chemical composition and phytotoxic activity of the oils, with the aim of identifying key compounds associated with phytotoxic activity. Seed germination bioassay revealed strong or complete germination inhibition against the monocot, Agrostis stolonifera but not the dicot Lactuca sativa. GC-MS analysis showed variations in composition among Copaifera species with some common compounds identified across multiple species. Caryophyllene oxide and junenol were associated with the observed phytotoxic effects. Automated flash chromatography was used to isolate the major compounds of the oils. Isolated compounds exhibited differing levels of phytotoxicity compared to the oils, suggesting the importance of interactions or synergism among oil components. These findings highlight the potential of copaiba oils as natural herbicidal agents and underscore the importance of considering species-specific responses in weed management strategies.

Selective Influence of Chromolaena odorata Extracts on the Germination and Growth of Vegetable Crops: A Comparative Study of Aqueous and Methanolic Solutions

This study conducted a thorough assessment of how germination and growth of shoots and roots in eight vegetable crops are influenced by aqueous and methanolic extracts from Chromolaena odorata. Findings reveal a broad spectrum of germination responses to leaf extracts (13.3% to 86.7%), signaling the intricate dynamics at play between the plant's chemical compounds and the germination mechanism. Notably, Cucumis sativus (70% at AQE 5%) and Phaseolus vulgaris (56.70% at AQE 10%), displayed remarkable resilience and even stimulation of germination under specific extract concentrations, suggesting a potential selective stimulatory effect. For root extracts, the introduction of AQE and MTE decreased germination percentages across crops. A. esculentus had the highest germination rate at AQE 20%, significantly lower than the control (60%). Solanum. melongena tolerated AQE 5% best, while MTE 20% was most inhibitory. Conversely, Solanum lycopersicum experienced complete germination inhibition in both AQE and MTE of leaf and root extracts, indicating species-specific vulnerability to the allelopathic compounds within the extracts. Shoot growth mostly declined with higher extract concentrations, except in Solanum melongena, Capsicum annuum, and Zea mays, which saw increased shoot lengths under certain conditions. Root growth responses were mixed; Abelmoschus esculentus and Zea mays showed growth increases at some concentrations, in contrast to Cucumis sativus and Solanum melongena, which had limited growth. Methanolic extracts had a stronger inhibitory effect, likely due to their potent bioactive compounds. These findings highlight the importance of extract type, concentration, and crop species in weed management, providing insights for sustainable agricultural practices.

Chitosan and salicylic acid as alternatives for the control of postharvest fungal diseases in blueberries (Vaccinium corymbosum)

Blueberry (Vaccinium corymbosum) has characteristics that make it a highly coveted fruit by the population that seeks benefits for their health, thus giving it economic and social relevance. However, it is a very perishable fruit. In the present work, Botrytis sp., Penicillium sp., and Alternaria sp. were isolated from blueberry, and molecularly identified. The in vitro effect of chitosan (CHI) and salicylic acid (SA) on the growth of these phytopathogens was then evaluated, as well as the incidence of the disease after the application of these treatments on blueberry. CHI at 1.5% achieved an in vitro mycelial growth inhibition of Botrytis sp., Penicillium sp., and Alternaria sp. by 93, 84, and 40%, respectively. Furthermore, a complete germination inhibition of Penicillium sp. and Alternaria sp. was accomplished; Botrytis sp. spores were less sensitive to chitosan treatment. The germination percentage of the phytopathogens was reduced by 90% using SA at 5 mM. The in vivo application of CHI at 1.5% and SA at 5 mM decreased the percentage of incidence of phytopathogens in blueberries harvested after storage period at 25°C, as compared to the control. Based on these results, SA and CHI represent an alternative for the control of phytopathogens in blueberry to eliminate the use of synthetic fungicides.

Effect of the Soil Matric Potential on the Germination Capacity of Prosopis chilensis, Quillaja saponaria and Cryptocarya alba from Contrasting Geographical Origins.

As a consequence of the megadrought in Central Chile, it is expected that most of the distribution of woody species will be narrowed in the northern limits because of restrictions imposed by soil matric potential on seed germination. In this study, we analyzed the effect of the soil matric potential on seed germination and initial recruitment of the sclerophyllous species Prosopis chilensis, Quillaja saponaria and Cryptocarya alba from contrasting geographic origins (i.e., seed sources). We evaluated the germination capacity (%) under different matric potentials (i.e., 0, -6, -33, -750 and -1250 kPa) for 100 days. Soil matric potential of -1250 kPa negatively affected the germination capacity of the three species. P. chilensis seeds stopped germinating under soil matric potential close to -1200 kPa, whereas in Q. saponaria and C. alba the complete inhibition of germination was under -1000 kPa. Seed sources also differed in their germination capacity by soil matric potential: northern seed sources of P. chilensis germinated with the lowest soil matric potential. There was no clear trend in Q. saponaria and C. alba, but in general, southern seed sources performed better than the northern ones. The results showed that Ѱm in the soil played an important role in the germinative capacity against different seed source origins, but not in soils with a north-south gradient.

Moisture content and oxidative damage determine longevity of the seeds of potential cash crop halophyte Haloxylon stocksii

Haloxylon stocksii is a succulent halophyte with high potential to become edible-oil and medicinal crop for the arid-saline lands. Studies about germination ecology and mechanisms of salinity tolerance during vegetative stage of this plant exist. However, information about longevity and biochemical changes in H. stocksii seeds during storage is absent. This study thus examined longevity, and physio-chemical attributes of the H. stocksii seeds under different storage conditions. Fresh seeds were non-dormant with ∼96% germination in water. Storage of seeds for four months had little effect on their germination in most conditions. However, storage for 8 or 12 months caused a complete germination inhibition in laboratory and field respectively. Seed moisture increased with the storage time and was positively correlated with mortality. Antioxidant activity of the seeds increased with time in all conditions, which however was inadequate to prevent oxidative damage as hydrogen peroxide and lipid peroxidation levels increased, especially with >4 months of storage. Hence, these data indicate the short longevity of the H. stocksii seeds resulting from moisture-induced oxidative damages during storage.

Chemical and thermal profile of Plectranthus amboinicus essential oil for its application as a bioherbicide

The species Plectranthus amboinicus is an aromatic herb with great application in popular medicine due to the diversity of biological properties. Chemically, its essential oil (EO) is characterized by two chemotypes, thymol and carvacrol, which vary depending on factors such as seasonality. Despite being an extensively exploited species, studies of the bioherbicidal potential of this species are insufficient. In this context, the EO of P. amboinicus leaves, extracted in two different seasonal periods, were characterized regarding chemical profile (by gas chromatography mass spectrometry - GC-MS) and thermal profile (DTG) and was subjected to bioherbicide tests (germination test and seedling development) against Eragrostis plana, commonly known as capim annoni, an invader of pastures in the Pampas region. P. amboinicus EO was a potent inhibitor of E. plana germination, reducing accumulated germination by over 70% when exposed to 0.1% EO, and a complete inhibition of germination was observed when exposed to 0.5%. Following the effects observed in germination, the initial growth of E. plana was significantly affected by concentrations above 0.05%. The major constituent identified via GC-MS was carvacrol, representing 87.5% of the volatile composition of P. amboinicus leaves. In addition, P. amboinicus EO presented high thermal stability up to 100 °C, which is an interesting result regarding its use as a bioproduct.

Assessment of Ecotoxicity of Incinerated Sewage Sludge Ash (ISSA)

Combustion in fluidised bed boilers is one of the most commonly used methods of treatment of municipal sewage sludge. Fly ash (FA) and air pollution control (APC) residues are the solid by-products generated by flue gas treatment. There are significant differences in the chemical composition of these wastes. FA is composed of mainly SiO2, P2O5, CaO and metals such as Zn, Ti, Cu, Cr, Pb and Ni. APC residues mainly contain SO3 and Na2O. The leachability tests that were carried out indicate that these wastes display very low leachability of heavy metals (for example leachability of Pb was equal 0.0004 mg·dm−3 in both wastes, leachability of Cd was equal 0.0012 mg·dm−3 in FA an 0.00004 mg·dm−3 in APC). On the other hand, very high sulphate concentrations (49,375 mg·dm−3) were found in water extract for the APC residues. In order to determine the toxicity of these wastes for plants, pot experiments with different additions of waste to the soil were carried out (on Lepidium sativum and Sinapis alba). Tests based on seeds germinations (on Lepidium sativum) in water extracts from waste (in different concentrations) were also performed. The results obtained indicate the very high toxicity of APC residues. Complete inhibition of germination and growth of the test plants was found for all concentrations of the tested waste in water extract and for all additions of waste to the soil in pot experiments. Seed germination tests on water extracts from FA did not show any toxicity of this waste. Pot tests with FA showed their toxicity only with a high (30%) addition in soil.

​Screening of Chickpea (Cicer arietinum L.) Genotypes for Germination and Early Seedling Growth under PEG 6000 Induced Drought Stress

Background: Drought stress at germination and early growth stages hinders the seedling establishment in chickpea which ultimately affects the economic yield. Such adverse affects of drought can be mitigated by screening and identifying the tolerant genotypes of chickpea which is commonly cultivated under rain-fed conditions during post-rainy season. Methods: Effect of drought stress on germination and early seedling growth of thirty three chickpea genotypes was studied under four different concentrations of PEG 6000 (-0.3, -0.6, -0.9 and -1.2 MPa) along with control and hydration under laboratory conditions during 2018-19. Result: Significant variation was observed among the genotypes for germination, root length, shoot length and seedling vigour index under different concentrations of PEG 6000. Complete inhibition of germination was observed in most of the genotypes at -1.2 MPa. Based on the results obtained, JG 11 and NBeG 3 were considered as tolerant since they showed comparatively higher germination, root length, shoot length and seedling vigour even at -1.2 MPa, while NBeG 723 and NBeG 833 were considered as susceptible genotypes because of their poor germination and seedling growth even at lower levels of drought stress.

​Influence of Temperature and Salinity Stress on Seed Germination and Seedling Growth of Soybean (Glycine max L.)

Background: The high salt level of a germinating environment can lead to reduced, delayed, and even complete inhibition of germination and seeding growth due to osmotic action and/or ion toxicity. Based on this viewpoint, the aim of this study was to investigate germination temperature and salinity effects on germination and early seedling growth of soybean, which can be sown as first and second crops. Methods: Soybean seeds were subjected to NaCl induced saline germinating media prepared in petri dishes under two different germination temperatures (20±2 and 25±2oC). Thirty sterilized seeds per petri dish were sown in ten salt treatments (0, 100, 150, 250, 750, 1000, 2250, 5000, 7500 and 10000 ppm NaCl L-1). The study was carried out according to the completely randomized design with four replications. Result: Lower temperature promoted seed germination, while the high temperature significantly inhibited the seed germination at all NaCl doses tested. As a result, 25oC temperatures, which can only be measured at the time of the second sowing, have been found to negatively affect germination and also increase the negative effects of salt. Due to the moderate tolerance of soybeans to salt stress, the germination rate was positively affected up to 750 ppm NaCl L-1 dose and resulted in severe reductions in subsequent doses. Also, the tolerance of soybean was negatively influenced by the interaction of temperature and NaCl concentration.

Phytotoxic Tryptoquialanines Produced In Vivo by Penicillium digitatum Are Exported in Extracellular Vesicles.

Penicillium digitatum is the most aggressive pathogen of citrus fruits. Tryptoquialanines are major indole alkaloids produced by P. digitatum It is unknown if tryptoquialanines are involved in the damage of citrus fruits caused by P. digitatum. To investigate the pathogenic roles of tryptoquialanines, we initially asked if tryptoquialanines could affect the germination of Citrus sinensis seeds. Exposure of the citrus seeds to tryptoquialanine A resulted in a complete inhibition of germination and an altered metabolic response. Since this phytotoxic effect requires the extracellular export of tryptoquialanine A, we investigated the mechanisms of extracellular delivery of this alkaloid in P. digitatum We detected extracellular vesicles (EVs) released by P. digitatum both in culture and during infection of citrus fruits. Compositional analysis of EVs produced during infection revealed the presence of a complex cargo, which included tryptoquialanines and the mycotoxin fungisporin. The EVs also presented phytotoxicity activity in vitro and caused damage to the tissues of citrus seeds. Through molecular networking, it was observed that the metabolites present in the P. digitatum EVs are produced in all of its possible hosts. Our results reveal a novel phytopathogenic role of P. digitatum EVs and tryptoquialanine A, implying that this alkaloid is exported in EVs during plant infection.IMPORTANCE During the postharvest period, citrus fruits can be affected by phytopathogens such as Penicillium digitatum, which causes green mold disease and is responsible for up to 90% of total citrus losses. Chemical fungicides are widely used to prevent green mold disease, leading to concerns about environmental and health risks. To develop safer alternatives to control phytopathogens, it is necessary to understand the molecular basis of infection during the host-pathogen interaction. In the P. digitatum model, the virulence strategies are poorly known. Here, we describe the production of phytotoxic extracellular vesicles (EVs) by P. digitatum during the infection of citrus fruits. We also characterized the secondary metabolites in the cargo of EVs and found in this set of molecules an inhibitor of seed germination. Since EVs and secondary metabolites have been related to virulence mechanisms in other host-pathogen interactions, our data are important for the comprehension of how P. digitatum causes damage to its primary hosts.

Morphological and physiological characterization of seed heteromorphism in Medicago denticulata Willd.

Under natural conditions, Medicago denticulata produces heteromorphic seeds differing in seed coat colour—cream and brownish black. The present study was conducted in order to determine morphological and physiological differences among heteromorphic seeds of M. denticulata in relation to dormancy and germination behaviour. Brownish black seeds with high moisture content were non-dormant and germinated to a high percentage. However, cream seeds with low moisture content were dormant and exhibited lesser germination without dormancy breaking treatments. Scanning electron microscope studies revealed papillose surface pattern in both seeds. However, brownish black seeds differed from cream seeds by having small cracks scattered all over the surface. Various dormancy breaking treatments viz., sandpaper scarification, soaking in sulphuric acid and hot water significantly increased the germination of cream seeds indicating seed coat imposed dormancy in these seeds. Accelerated ageing of brownish black seeds for 20 or more days resulted in complete inhibition of germination. Whereas, some cream seeds (~ 13%) aged for 20 days were still able to germinate. With accelerated ageing, both seeds recorded decrease in starch and total soluble proteins with concomitant increase in membrane leakage, total soluble sugars and free amino acids. Persistence studies under field conditions revealed that cream seeds present on soil surface or at a burial depth of 2 and 10 cm were able to germinate up to 12 months; but no germination was observed in brownish black seeds buried for 12 or more months. Results of accelerated ageing studies and field persistence suggest longer persistence for cream seeds as compared to brownish black seeds.

Limonene, a Chemical Compound Related to the Resistance of Eucalyptus Species to Austropuccinia psidii.

The fungus Austropuccinia psidii is a major pathogen of Eucalyptus spp. that damages mainly early-stage leaves. Resistant clones are the most widely used control measure for the rust disease caused by A. psidii. Essential oils produced in the plant-host cells are associated with resistance. However, the chemical characteristics of Eucalyptus leaves at different stages of maturity, associated with resistance or susceptibility to A. psidii, need to be determined. The aims of this study were to characterize the chemical composition of essential oils in Eucalyptus leaves at three developmental stages of clones of three E. urophylla × E. grandis hybrids that exhibit different resistance levels to rust and to identify probable resistance-related compounds from them. The rust severity following inoculation and the quantity and quality of the essential oil extracted by hydrodistillation were determined at the first, third, and fifth leaf stages of the three clones. Identification of the compounds present in the essential oil was determined by gas chromatography coupled with mass spectrometry. No rust was observed on the three leaf stages of the resistant clone or on the fifth leaf stage of the susceptible clones. Limonene was found at high percentages in essential oils from the three leaf stages of the resistant clone and at low percentages in the susceptible clones. In vitro and in vivo tests indicated that low limonene percentages stimulated A. psidii urediniospore germination and were not fungitoxic, whereas high percentages caused complete inhibition of germination and degenerative changes in fungal reproductive structures. The limonene present in Eucalyptus leaves can be considered a chemical compound related to the rust resistance of Eucalyptus spp.

Phytotoxicity of Methiozolin on Fine Fescue

Methiozolin is a new herbicide that controls annual bluegrass (Poa annua) in turfgrasses, but the differential tolerance levels of fine fescues (Festuca sp.) has received limited investigation. The objective of this study was to investigate the potential injury from methiozolin when applied to chewings fescue (Festuca rubra ssp. fallax), strong creeping red fescue (Festuca rubra ssp. rubra), and hard fescue (Festuca brevipila). Nine different fine fescue populations (14W2 Comp, Fairmont, and Survivor chewings fescue; FT345, Miser, and Fenway strong creeping red fescue; and 14H4 Comp, Stonehenge, and Oxford hard fescue) were sprayed with methiozolin at five different rates (0.42, 0.83, 1.25, 1.67, and 2.09 lb/acre) at four different application timings [4 weeks before seeding (WBS), 2 WBS, at seeding (AS), and 2 weeks after germination (WAG)]. Untreated controls were also included for each combination. Significant reduction in germination of fine fescue was observed when methiozolin was applied before emergence for all tested application rates. Methiozolin at 1.25, 1.67, and 2.09 lb/acre applied before or at the day of seeding led to complete inhibition of germination in all fine fescue species tested. It was less injurious compared with methiozolin applied at 2 WAG, although a reduction in the percentage of green cover and biomass was observed for application rates greater or equal to 0.83 lb/acre. The hierarchical ranking of species injury from high to low is as follows: hard fescue, chewings fescue, and strong creeping red fescue. A possible solution for annual bluegrass control in fine fescue species with methiozolin is multiple postemergence applications up to a maximum rate of 0.83 lb/acre. Turf managers need to make adjustments in methiozolin application rates and timings based on fine fescue species to maximize selectivity for annual bluegrass control.

Analysis of Genotypic Variability in Avena spp. Regarding Allelopathic Potentiality

ABSTRACT: The recognized allelopathic activity of oats as a soil-cover plant induces the study of the potential of their germplasm. The objective of this study is to verify if there is genotype variability in the Avena spp. with regard to allelopathic activity. Extracts of A. strigosa ‘Agro Quaraí’, ‘Agro Esteio’, ‘Embrapa139’, ‘AF 12104’, ‘AF 12109’, ‘AF 12202’, ‘AF 12209’, A. sativa ‘UPFPS Farroupilha’ and ‘AF 1345 Ucraniana,’ were prepared in three concentrations w/v (5 g, 10 g, and 20 g of dry mass 100 mL-1). The experiment was conducted in a germination chamber for 15 days, with lettuce (Lactuca sativa L.) as the recipient plant. There was complete inhibition of germination under 20% w/v extracts and partial inhibition at 10% w/v. Only 5% w/v observed a difference between the genotypes, in which the highest efficiency was obtained from the extracts of white oats and black oats ‘AF 12104’ and ‘Agro Quaraí’, which reduced germination between 92% and 97%. When the concentration increased above 5% w/v the harmful effect on germination was significantly greater. Only in extracts at 5% w/v there was a higher genotypic effect on germination, with variation in the germination rate index, root, and hypocotyl stretching. The genotype that had the least allelopathic effect was AF 12202, with an inhibitory mean in the evaluated attributes of 35%. The other genotypes inhibited the attributes of germination and seedling growth between 66% and 86%. With regard to the variability in the Avenaspp., the allelopathic activity could be applied to obtain cultivars with greater weed suppressive power.

Germination Ecology of Two Australian Populations of African turnipweed (Sisymbrium thellungii)

AbstractAfrican turnipweed (Sisymbrium thellungiiO. E.Schulz) is an emerging problematic broadleaf weed of the northern grain region of Australia. Laboratory experiments were conducted to evaluate the effects of temperature, light, salinity, pH, seed burial depth, and the amount of wheat crop residue on germination and emergence of two AustralianS. thellungiiweed populations (population C, cropped area; population F, fence line). Both populations behaved similarly across different environmental conditions, except in the residue study. Although the seeds of both populations ofS. thellungiicould germinate under complete darkness, germination was best (~95%) under light/dark conditions at the 20/10 C temperature regime. Both populations ofS. thellungiigerminated over a wide range of day/night temperatures (15/5, 20/10, 25/15, and 30/20 C). Osmotic stress had negative effects on germination, with 54% seeds (averaged over populations) able to germinate at −0.1MPa. Complete germination inhibition for both populations was observed at −0.8MPa osmotic potential. Both populations germinated at sodium chloride (NaCl) concentrations ranging from 50 to 100 mM, beyond which germination was completely inhibited. There were substantial reductions in seed germination, 32% (averaged over populations) under highly acidic conditions (pH 4.0) as compared with the control (water: pH 6.4). Seed germination of both populations on the soil surface was 77%, and no seedlings emerged from a burial depth of 1 cm. The addition of 6 Mg ha−1of wheat (Triticum aestivumL.) residue reduced the emergence of the C and F populations ofS. thellungiiby 75% and 64%, respectively, as compared with the control (no residue). Information gathered from this study provides a better understanding of the factors favorable for germination and emergence ofS. thellungii, which will aid in developing management strategies in winter crops, especially wheat, barley (Hordeum vulgareL.), and chick pea (Cicer arietinumL.).

Germination Ecology of Two Australian Biotypes of Ragweed Parthenium (Parthenium hysterophorus) Relates to Their Invasiveness

Ragweed parthenium is a highly invasive weed species in several countries, including Australia. Laboratory experiments were conducted to evaluate the effect of temperature, light, salinity, pH, and moisture on germination of two Australian biotypes of ragweed parthenium: Clermont (highly invasive) and Toogoolawah (noninvasive). Although seeds of both biotypes could germinate under complete darkness, germination was improved by 20% to 49% under a 12-h photoperiod. Both biotypes germinated over a wide range of constant (8 to 35 C), and alternating day/night (15/5 to 35/25 C) temperatures. However, the Clermont biotype exhibited significantly higher germination than Toogoolawah biotype over the range of temperatures studied. Highest germination of Clermont (100%) and Toogoolawah (97%) was observed at constant temperatures of 14 to 23 C and 23 C, respectively. The best alternating day/night temperature for germination of both biotypes was 25/15 C. Clermont also germinated better than Toogoolawah under osmotic- and salt-stress conditions. Osmotic stress had moderate negative effects on germination, with 52% and 36% of the Clermont and Toogoolawah seeds able to germinate at −0.60 MPa, respectively. Complete germination inhibition for both biotypes was observed at an osmotic potential of −1.2 MPa. Both biotypes also germinated at a very high sodium chloride (NaCl) concentration of 250 mM. A 50% reduction in germination of Toogoolawah and Clermont was caused by 99 and 154 mM NaCl, respectively. Germination of the Clermont biotype was not affected by a wide range of pH (4.0 to 10.0), whereas the strong acidic and alkaline pH levels (4.0 and 10.0) caused 18% and 25% reductions in germination of the Toogoolawah biotype compared with control. The Clermont biotype had a higher ability to germinate across all treatments compared with the Toogoolawah biotype, which might be a contributing factor toward the high invasive ability of the former compared with the latter.

Evaluation of the effects of polymeric chitosan/tripolyphosphate and solid lipid nanoparticles on germination of Zea mays, Brassica rapa and Pisum sativum

Although the potential toxicity of many metallic and carbon nanoparticles to plants has been reported, few studies have evaluated the phytotoxic effects of polymeric and solid lipid nanoparticles. The present work described the preparation and characterization of chitosan/tripolyphosphate (CS/TPP) nanoparticles and solid lipid nanoparticles (SLN) and evaluated the effects of different concentrations of these nanoparticles on germination of Zea mays, Brassica rapa, and Pisum sativum. CS/TPP nanoparticles presented an average size of 233.6±12.1nm, polydispersity index (PDI) of 0.30±0.02, and zeta potential of +21.4±1.7mV. SLN showed an average size of 323.25±41.4nm, PDI of 0.23±0.103, and zeta potential of −13.25±3.2mV. Nanotracking analysis enabled determination of concentrations of 1.33×1010 (CS/TPP) and 3.64×1012 (SLN) nanoparticles per mL. At high concentrations, CS/TPP nanoparticles caused complete inhibition of germination, and thus negatively affected the initial growth of all tested species. Differently, SLN presented no phytotoxic effects. The different size and composition and the opposite charges of SLN and CS/TPP nanoparticles could be associated with the differential phytotoxicity of these nanomaterials. The present study reports the phytotoxic potential of polymeric CS/TPP nanoparticles towards plants, indicating that further investigation is needed on the effects of such formulations intended for future use in agricultural systems, in order to avoid damage to the environment.

English

High salt level of a germination medium may induce a reduction, delay and even complete inhibition of germination due to osmotic effect and/or ion toxicity. The objective of this study was to investigate the effect of salinity due to NaCl on germination and early seedling growth of two crops, Pisum sativum var. abyssinicum and Lathyrus sativus. Seeds of these two crops were treated with NaCl induced saline germinating media prepared in Petri dishes. Fifty (50) surface sterilized seeds per Petri dish were sown in five salt treatments (0, 5, 7, 9 and 15 dSm-). Each treatment was replicated four times. Germination percentage, shoot length and root length of both crops decreased with an increase in salinity level. Although both crops are low salt tolerant legumes, P. sativum var. abyssinium was found to be less tolerant than L. sativus. This study could be strengthened by further work under field conditions and also at mature vegetative and reproductive stages of the crops. Key words: Germination time, water uptake percentage, salt tolerance, seedling biomass.

Boric acid inhibits germination and colonization of Saprolegnia spores in vitro and in vivo.

Saprolegnia infections cause severe economic losses among freshwater fish and their eggs. The banning of malachite green increased the demand for finding effective alternative treatments to control the disease. In the present study, we investigated the ability of boric acid to control saprolegniosis in salmon eggs and yolk sac fry. Under in vitro conditions, boric acid was able to decrease Saprolegnia spore activity and mycelial growth in all tested concentrations above 0.2 g/L, while complete inhibition of germination and growth was observed at a concentration of 0.8 g/L. In in vivo experiments using Atlantic salmon eyed eggs, saprolegniosis was controlled by boric acid at concentrations ranging from 0.2–1.4 g/L during continuous exposure, and at 1.0–4.0 g/L during intermittent exposure. The same effect was observed on salmon yolk sac fry exposed continuously to 0.5 g/L boric acid during the natural outbreak of saprolegniosis. During the experiments no negative impact with regard to hatchability and viability was observed in either eggs or fry, which indicate safety of use at all tested concentrations. The high hatchability and survival rates recorded following the in vivo testing suggest that boric acid is a candidate for prophylaxis and control of saprolegniosis.

Arabidopsis thaliana for testing the phytotoxicity of volatile organic compounds

Geosmin and C-8 hydrocarbons are among the major volatile organic compounds (VOC) responsible for the distinctive, musty odor of filamentous fungi. In this study, we developed a plant bioassay for testing the possible toxicity of these compounds, as well as four air freshener products sometimes used to mask their odor. Seeds and vegetative plants of Arabidopsis thaliana were exposed to 1 ppm of 14 different volatile treatments (both single compounds and mixtures) for 72 h and monitored for germination rate, seedling formation, vegetative plant vigor and chlorophyll concentration. All VOCs tested had some inhibitory effect on seed germination or seedling formation; 1-octen-3-one was the most active, giving almost complete inhibition of germination. Geosmin did not prevent germination (radicle protrusion) but seedling formation was arrested 90 %. Of solvents and fragrance products tested, only the scented oil product was as active as the C-8 biogenic compounds in inhibiting seed germination and seedling formation. Two-week-old plants exposed to 1 ppm of individual fungal VOCs for 72 h all exhibited some degree of stress symptoms including smaller leaf size and weight, discoloration, leaf curling, small necrotic lesions, and reduced chlorophyll concentration. Two-week-old vegetative plants exposed to solvents and air freshener products were generally smaller in size. The single most phytotoxic compound tested was 1-octen-3-one which almost completely inhibited seed germination and was lethal to vegetative phase plants. Formaldehyde at 1 ppm killed 2-week-old seedlings but had little effect on seed germination. In conclusion, the A. thaliana bioassay provides an inexpensive approach for testing the toxicity of gas phase molecules.