Allocation of added selenium in lettuce and its impact on roots

Allocation of selenium (Se) in lettuce and its impact on root morphology were studied to better understand the growth responses of plants to added Se. Lettuce was grown in vermiculite under controlled growing conditions for seven weeks, and the allocation in the shoots and roots of selenate added in increasing dosages (0, 1, 10, 100, 500 and 1000 µg Se per 3.5-litre pot) as well as morphological variables of the roots were determined. The intermediate additions of 100 and 500 µg Se per pot seemed to produce the highest biomasses, although this was nearly masked by large scatter in the data. The Se contents both in roots and shoots increased roughly proportionally to the amount of Se added. However, at small additions Se was preferentially allocated to roots, whereas at larger additions the contents in roots and shoots (mg kg-1 dry matter) were roughly equal. Se treatments did not change the morphology of hypocotyls. On the contrary, the specific length and area of basal and lateral roots were smallest at intermediate Se additions, whereas the specific volume was largest at the largest Se addition. These effects of Se on root morphology were, however, not unambiguously related to plant growth. As the Se contents in roots increased, the roots grew thicker and the specific volume of lateral roots increased in agreement with a hypothesis of increased endogenous ethylene production

Quality of the ryegrass and lettuce yields as affected by selenium fertilization

The effect of Se-fertilization on the chemical composition and anti-oxidative properties of ryegrass and lettuce was studied in a pot experiment. The addition of Se enhanced its relative incorporation in soluble and insoluble proteins and diminished it in free amino acids. It also affected the anti-oxidative systems of the plants. The glutathione peroxidase (GSH-Px) activity found in both plant species increased with increasing Se-fertilization, whereas the superoxide dismutase (SOD) activity as well as the concentration of vitamin E decreased. This may indicate that the synthesis of SOD and vitamin E was reduced because the requirement of these anti-oxidants was diminished by antioxidative function of Se

Association of antioxidative enzymes with the synergistic effect of selenium and UV irradiation in enhancing plant growth

Seleeni (Se) on ihmisille ja eläimille välttämätön alkuaine, jonka tiedetään mm. puolustavan soluja UV(B)-säteilyn aiheuttamia vaurioita vastaan. Vallitsevan käsityksen mukaan korkeammat kasvit eivät tarvitse Se:ä, vaan pikemminkin ovat sille varsin arkoja. Äskettäin on kuitenkin osoitettu, että sopivan alhaisina pitoisuuksina Se pystyy suojaamaan myös kasveja UV-säteilyn aiheuttamalta hapetusstressiltä ja jopa edistämään säteilyä saaneiden kasvien kasvua. Tässä tutkimuksessa selvitettiin Se:n vaikutuksia antioksidatiivisiin entsyymeihin, jotka mahdollisesti liittyvät havaittuun synergismiin. Kasvihuoneesssa toteutetussa kokeessa kasvatettiin raiheinää ja salaattia maassa, johon oli lisätty Se:ä 0,1 mg tai 1.0 mg kg-1 (H2SeO4:nä) tai jätetty ilman Se-lisäystä. Puolet koekasveista kasvoi normaaleissa valaistusolosuhteissa, puolet altistettiin 1-3 minuutin episodeina annetulle UV-säteilylle. Kaksi ja neljä viikkoa kasvaneista kasveista mitattiin lipidien hapettumista määrittämällä tiobarbituurihapporeaktiivisten aineiden pitoisuudet (TBARS). Lisäksi niistä määritettiin glutationiperoksidaasin (GSH-Px), superoksididismutaasin (SOD), katalaasin (CAT), glutationi- S-transferaasin (GST) ja askorbaattireduktaasin (APX) aktiivisuudet. Ilman Se-lisäystä UV-säteilytys pienensi salaattisatoa (22%), mutta ei vaikuttanut raiheinän kasvuun. Pienempi Se-lisäys toimi antioksidatiivisesti ja vähensi kummassakin kasvissa valaistusolosuhteista riippumatta lipidien hapettumista (TBARS pieneni). Yhdessä UV:n kanssa Se-lisäys edisti molempien kasvien kasvua. Ainakin osittain tämä positiivinen synergistinen vaikutus liittyi lisääntyneeseen GSH-Px:n ja CAT:n aktiivisuuteen, mutta APX reagoi negatiivisesti sekä Se-lisäykseen että UV-säteilyyn. Muiden tutkittujen entsyymien yhteys havaittuun synergismiin näytti olevan kasvilajikohtaista: raiheinässä se liittyi GST:n aktiivisuuden lisääntymiseen kummassakin kasvuvaiheessa, sen sijaan nuoressa salaatissa nousi SOD. Suurempi Se-lisäys oli toksinen ja pienensi kuiva-ainesatoja. Mielenkiintoista oli kuitenkin havaita, että UV-säteilylle altistuneissa kasveissa toksisuus lieveni samalla kun CAT nousi raiheinässä ja SOD salaatissa.Selenium (Se) is able to defend human and animal cells against UV(B) stress. Higher plants are generally considered not to require Se but to have a low tolerance to it. However, recently it has been demonstrated that Se is able to protect also plants against UV-induced oxidative stress and even to promote the growth of plants subjected to high-energy light. In the present study the effects of Se on antioxidative enzymes possibly associated with this synergistic effect were investigated. Ryegrass and lettuce were grown in soil supplemented with Se at 0, 0.1 or 1.0 mg kg-1 under normal light or subjected to UV episodes. Lipid peroxidation and the changes of antioxidative enzymes were measured at two growing stages. The positive synergistic effect of the lower Se dosage and UV was found to be at least partly associated with the antioxidative role of Se through increased glutathione peroxidase (GSH-Px) and catalase (CAT) activity, whereas ascorbate peroxidase (APX) responded negatively to both factors. The contribution of the other enzymes studied seemed to be plant-specific: glutathione S-transferase (GST) increased in both ryegrass assays and superoxide dismutase (SOD) in the first lettuce assay. At the higher addition level Se acted as a pro-oxidant and diminished fresh weight yields. UV irradiation alleviated the toxicity coincidently with increase of CAT in ryegrass and SOD in lettuce.vokSeleenin ja UV-säteilyn synergistinen kasvua edistävä vaikutus ja siihen liittyvät antioksidatiiviset entsyymit kasveiss

Quantification of fine root responses to selenium toxicity

Research NoteJuurten kasvua voivat rajoittaa maan fysikaaliset tekijät, kuten vedenpuute ja suuri mekaaninen vastus. Myös kemialliset tekijät, kuten eräiden mikroravinteiden korkeat pitoisuudet, voivat heikentää juurten kasvuedellytyksiä. Seleeni (Se) on ihmiselle ja eläimille välttämätön alkuaine, joka on kuitenkin myrkyllinen jo verraten pieninä pitoisuuksina. Suomessa moniravinteisiin lannoitteisiin on vuodesta 1984 lähtien lisätty seleeniä rehun ja ruoan ravitsemuksellisen arvon parantamiseksi. Viljelykasvien ei ole katsottu välttämättä tarvitsevan seleeniä, mutta myös kasvien on vastikään havaittu hyötyvän pienestä seleenilisästä. Suuret lisäykset ovat selvästi haitallisia ja rajoittavat kasvin kasvua. Seleenin myrkytysoireiden ilmenemistä juurissa tutkittiin astiakokeessa, jossa salaattia ja raiheinää kasvatettiin melko suurilla, nousevilla seleenimäärillä (0, 0,1 ja 1,0 mg kg-1) lannoitetussa hiekkamaassa. Vertailusalaatin (Se ei lisätty) juuret tulivat vanhetessaan paksummiksi, kun taas niiden ominaispituus, -pinta-ala ja -tilavuus pienenivät. Suuri seleenilisäys aiheutti nuoren salaatin juurissa samanlaisia muutoksia kuin vanheneminen vertailusalaatissa. Kasvin vanhetessa seleenilannoituksen vaikutukset pienenivät tai muuttuivat vastakkaisiksi. Raiheinän juuret eivät reagoineet seleenin lisäykseen yhtä herkästi kuin salaatin juuret, mutta suurin seleenilisäys vähensi juurten kuivamassaa.The morphological changes of lettuce and ryegrass roots in response to Se toxicity were quantified by image analysis. Based on the assumption that soil stresses increase endogenous ethylene production in plants, changes indicating higher construction costs for roots, such as decreased specific root length, were expected. As lettuce roots in soil without Se addition (control) became older, their width increased whereas their specific length, specific surface area and specific volume decreased. In younger lettuce, large Se additions induced changes resembling those identified in the control plant upon senescence. In older plants, Se fertilisation reversed these changes or made them smaller. Ryegrass roots were not as sensitive to added Se as lettuce roots; a lower dosage stimulated root growth but a higher one reduced it.vokSeleenin myrkytysoireet juuriss

Two-Layer Optimal Operation of AC–DC Hybrid Microgrid Considering Carbon Emissions Trading in Multiple Scenarios

To address the problem of low-carbon, optimal operation of AC–DC hybrid microgrids, a carbon trading mechanism is introduced and the impact of multiple uncertainties on system optimization is considered. Firstly, a two-layer model with the comprehensive economy of the hybrid microgrid as the upper layer and the respective optimal operation of the AC and DC sub-microgrids as the lower layer is established and the demand-side response is introduced, based on which the uncertainty of the scenery load is simulated using the multiscenario analysis method. Then, the baseline method is used to allocate carbon emission allowances to the system without compensation, and the actual carbon emissions of diesel engines, microcombustion engines, and fuel cells are considered to construct a hybrid microgrid. Finally, the model is solved using the CPLEX solver in conjunction with the calculation example, and the simulation verifies the effectiveness and feasibility of the proposed strategy in coordinating and optimizing the economy and low carbon of the system. The results show that when the carbon trading mechanism is considered, the carbon emission of the hybrid microgrid is reduced by 4.95%, the output power of the diesel generator is reduced by 5.14%, the output power of the fuel cell is reduced by 18.22%, but the electricity purchase from the power grid is increased by 38.91%. In addition, the influence degrees of the model considering the uncertainty of renewable energy and load are simulated. Furthermore, the impact of different electricity price models on optimal operation is evaluated, and the results show that electricity price will affect electricity purchase from the power grid and further affect carbon emissions

Comprehensive Control Strategy Considering Hybrid Energy Storage for Primary Frequency Modulation

The increase in the number of new energy sources connected to the grid has made it difficult for power systems to regulate frequencies. Although battery energy storage can alleviate this problem, battery cycle lives are short, so hybrid energy storage is introduced to assist grid frequency modulation. In this paper, a hybrid energy storage system composed of battery energy storage and super-capacitor energy storage systems was studied, and a comprehensive control strategy was proposed. Firstly, by setting the frequency dead zone of the energy storage to be smaller than that of the thermal power unit, the frequent action of the thermal power unit was avoided. Secondly, virtual inertial control and virtual droop control were effectively combined. Then, the state of charge of battery energy storage and super-capacitor energy storage was considered so that they could operate in harmony. Finally, a simulation model was built in MATLAB/SIMULINK, and case studies were conducted to verify the proposed control strategy. Results showed that the proposed control strategy could effectively reduce the frequency deviation of the power grid, and maintain the state of charge, reduce the number of operated batteries, and improve cycle life

Comprehensive Control Strategy Considering Hybrid Energy Storage for Primary Frequency Modulation

The increase in the number of new energy sources connected to the grid has made it difficult for power systems to regulate frequencies. Although battery energy storage can alleviate this problem, battery cycle lives are short, so hybrid energy storage is introduced to assist grid frequency modulation. In this paper, a hybrid energy storage system composed of battery energy storage and super-capacitor energy storage systems was studied, and a comprehensive control strategy was proposed. Firstly, by setting the frequency dead zone of the energy storage to be smaller than that of the thermal power unit, the frequent action of the thermal power unit was avoided. Secondly, virtual inertial control and virtual droop control were effectively combined. Then, the state of charge of battery energy storage and super-capacitor energy storage was considered so that they could operate in harmony. Finally, a simulation model was built in MATLAB/SIMULINK, and case studies were conducted to verify the proposed control strategy. Results showed that the proposed control strategy could effectively reduce the frequency deviation of the power grid, and maintain the state of charge, reduce the number of operated batteries, and improve cycle life

Quality of the ryegrass and lettuce yields as affected by selenium fertilization

Selostus: Seleenilannoituksen vaikutus raiheinän ja salaatin laatuu