Knop's Solution Research Articles

The nitrogen deficiency influence on the growth and development of spring two-nuclear barley varieties grown under photoculture conditions

The purpose of the research is to study, the effect of N deficiency in irrigation solutions on the structural and functional characteristics of spring barley (Hordeum vulgare L.), the Oplot variety under controlled environmental conditions, in comparison with the structural and functional characteristics of Takmak barley, which has been the standard in all variety testing sites of the Krasnoyarsk Territory since 2022. The plants were grown under light culture conditions using hydroponics on expanded clay with constant environmental conditions at a photoperiod day/night of 17h / 7h, respectively. The basis for the preparation of irrigation solutions was Knop solution (control) and a solution in which, in order to reduce the concentration of N-NO3, the salt content was changed 2 times so as not to change the concentration of other macronutrients. A comparison of the rate of absorption of macronutrients by barley plants of the Oplot and Takmak varieties, depending on the composition of the irrigation solution, shows a higher demand of the barley of the Oplot variety for the presence of mineral nutrition elements in the irrigation solution in comparison with the barley of the Takmak variety. The deficiency of N in the irrigation solution led to a decrease in total tillering by about 2.5 times, but productive tillering in the barley of the Oplot variety decreased to a greater extent than in the barley of the Takmak variety. When growing on Knop solution the barley of the Oplot variety showed higher productivity than the barley of the Takmak variety. When grown on solutions with a deficiency of N, the grain yield of the barley of the Oplot variety decreased by 2.8 times, and in the barley of the Takmak variety, the differences between the control and experimental variants were unreliable. The barley of the Takmak variety showed higher resistance to N deficiency in the irrigation solution, thereby showing higher plasticity compared to the barley of the Oplot variety.

Biochemical Responses to the Long-Term Impact of Copper Sulfate (CuSO4) in Tobacco Plants.

Metabolic changes under stress are often studied in short-term experiments, revealing rapid responses in gene expression, enzyme activity, and the amount of antioxidants. In a long-term experiment, it is possible to identify adaptive changes in both primary and secondary metabolism. In this study, we characterized the physiological state of tobacco plants and assessed the amount and spectrum of phenolic compounds and the lignification of axial organs under excess copper stress in a long-term experiment (40 days). Plants were treated with 100 and 300 μM CuSO4, as well as a control (Knop solution). Copper accumulation, the size and anatomical structure of organs, stress markers, and the activity of antioxidant enzymes were studied. Lignin content was determined with the cysteine-assisted sulfuric method (CASA), and the metabolite profile and phenolic spectrum were determined with UHPLC-MS and thin-layer chromatography (TLC). Cu2+ mainly accumulated in the roots and, to a lesser extent, in the shoots. Copper sulfate (100 μM) slightly stimulated stem and leaf growth. A higher concentration (300 μM) caused oxidative stress; H2O2 content, superoxide dismutase (SOD), and guaiacol peroxidase (GPOX) activity increased in roots, and malondialdehyde (MDA) increased in all organs. The deposition of lignin increased in the roots and stems compared with the control. The content of free phenolics, which could be used as substrates for lignification, declined. The proportions of ferulic, cinnamic, and p-coumaric acids in the hydrolysate of bound phenolics were higher, and they tended toward additional lignification. The metabolic profile changed in both roots and stems at both concentrations, and changed in leaves only at a concentration of 300 μM. Thus, changes in the phenolic spectrum and the enhanced lignification of cell walls in the metaxylem of axial (root and stem) organs in tobacco can be considered important metabolic responses to stress caused by excess CuSO4.

Experimental modeling of the influence of mineral nutrition conditions on the plants of spring double

The purpose of the study: to identify the in uence of mineral nutrition conditions on morphogenesis and absorption of macronutrients by spring barley plants of two varieties in the period from germination to earing under controlled conditions of light culture. The objects of the study were plants of double-row barley of the Takmak variety and the Salome variety. The plants were grown by hydroponics on expanded clay under controlled environmental conditions. Four variants of nutrient solutions were prepared for watering plants: variant l (the control) - Knop solution of standard concentration; variant 2 - Knop solution was prepared with 50 % concentration from its standard concentration; variant 3 - solution was prepared on the basis of Knop solution, but with 50 % of N concentration from its standard concentration; variant 4 - solution was prepared on the basis of Knop solution, but with 25 % of P concentration from its standard concentration. As a result, variants 2 and 3 showed a decrease in total bushiness by more than 30 % compared to the control. The mass of plants in variants 2 and 3 turned out to be 50 % and 35 %, respectively, less than in the control. The decrease in plant mass was mainly due to a decrease in the mass of lateral shoots. The level of consumption of mineral elements, closely related to the composition of solutions, affected not so much the chemical composition of plant tissues as the amount of plant biomass, which manifested itself in high correlations between the consumption of mineral elements and the gross content of these elements in plants with rather weak links between consumption and the content of mineral elements in plants.

Copper, lead and zinc interactions during phytoextraction using Acer platanoides L.—a pot trial

Of the many environmental factors that modulate the phytoextraction of elements, little has been learnt about the role of metal interactions. The study aimed to show how different concentrations of Cu, Pb and Zn in the cultivation medium influenced the biomass, plant development and phytoextraction abilities of Acer platanoides L. seedlings. Additionally, the impact on the content and distribution of Ca, K, Mg and Na in plant parts was studied with an analysis of phenols. Plants treated with a mixture of two metals were characterised by lower biomass of leaves and higher major elements content jointly than those grown in the salt of one element. Leaves of A. platanoides cultivated in Pb5 + Zn1, Pb1 + Zn1 and Pb1 + Zn5 experimental systems were characterised by specific browning of their edges. The obtained results suggest higher toxicity to leaves of Pb and Zn present simultaneously in Knop solution than Cu and Pb or Cu and Zn, irrespective of the mutual ratio of the concentrations of these elements. Antagonism of Cu and Zn concerning Pb was clearly shown in whole plant biomass when one of these elements was in higher concentration (5 mmol L−1) in solution. In the lowest concentrations (1 mmol L−1), there was a synergism between Cu and Zn in plant roots. Plants exposed to Zn5, Cu1 + Pb5, Pb5 + Zn1 and Cu1 + Zn1 were characterised by higher total phenolic content than the rest plants. Both the presence and the concentration of other elements in the soil are significant factors that modulate element uptake, total phenolic content, and plant development.Graphical

Effects of different nutrient solutions on growth and flower quality of gerbera (Gerbera jamesonii) grown in hydroponic close system

The nutrient solution is the decisive factor for the growth and development of hydroponic plants. This study was conducted to determine the effect of five nutrient solutions, namely, Hoagland, Knop, Hydro Umat F, BKFAST, and Bio-Life, on the growth and development of gerbera (Gerbera jamesonii) in the hydroponic system. The results show that Hydro Umat F is the most suitable solution for planting gerbera in terms of plant height, number of leaves, leaf size, and root volume. In addition, the flower yield of the gerbera plants nourished on Hydro Umat F is also the highest, with 8.7 flowers per plant after five months in the hydroponic system. The flowers have a diameter of 9.8 cm and natural durability of 19.67 days. Meanwhile, gerbera plants stop growing after 15 days in the Bio-Life solution and 30 days in the Knop solution.

In Vitro Propagation, Genetic Assessment, and Medium-Term Conservation of the Coastal Endangered Species Tetraclinis articulata (Vahl) Masters (Cupressaceae) from Adult Trees.

Tetraclinis articulata (Vahl) Masters is an endangered tree growing in coastal and arid environments that is widely exploited by the timber and resin industry, among other applications. In this context, the use of in vitro techniques is highly encouraged for its propagation. We present a protocol for micropropagation using twigs from adult trees as a source of explants. The Schenk and Hildebrandt basal medium (SH) supplemented with 30 g L−1 sucrose, 6.5 g L−1 plant agar, 4.0 mg L−1 6-benzyladenine (BA), and 0.05 mg L−1 1-naphthaleneacetic acid (NAA) provided the optimum multiplication rate (90.48 ± 9.52 explants with basal shoots and 2.58 ± 0.29 basal shoots per explant). Application of activated charcoal (AC) or ½ Knop solution in a liquid overlay produced significantly longer shoots. Supplementation of solid media with indole-3-butyric acid (IBA) or NAA gave low rooting percentages (<17%). Addition of 0.9 g L−1 AC improved rooting (40%) but rooting performance was optimal (66.7%) after a pulse treatment consisting of 4 h immersion in liquid SH medium without growth regulators, followed by 8 weeks of cultivation. Rooted microplants were successfully acclimatized (93.33%) in a peat moss and vermiculite mixture (1:1 v/v ratio). The genetic stability of the in vitro regenerated plantlets was confirmed using the randomly amplified polymorphic DNA (RAPD) technique. Explant survival and growth remained higher than 90% after 28 weeks of cold storage at both 4 °C and 10 °C. The protocol presented here allows for largescale T. articulata production and could be applied for both ex situ conservation strategies and industrial purposes.

COMPLEX EFFECT OF CHROME AND SALINATION ON NITROGEN EXCHANGE IN PUMPKIN PLANTS

A specific character of physiological-biochemical stress responses of pumpkin plants to toxic effect of cadmium under conditions of salinity in the course of their long-term cross-adaptation was investigated. Cr and NaCl were added either alone or in combination in Knop solution along with non-treated controls. In 7- and 14- day plants, all the physiological processes studied (shoot and root growth, bioaccumulation of fresh and dry biomass by them and nitrogen-protein metabolism in different plant organs) were found to be more sensitive to inhibitory action of Cr excess than to NaCl effect. However, in 21-day plants, especially in their roots, a some activation of growth and biosynthetic processes was observed in the presence of combined Cr and NaCl treatments than at their lone application. All this indicates that an adaptation of plants to salinity is accompanied by a some reduction in toxic effect of Cr on growth and metabolism of plants

The effect of fullerene on the physiological and biochemical parameters of barley plants in hydroponic culture

The differences in the response to the action of fullerene of barley plants (Hordeum vulgare L., cultivar Yakub) grown in water culture (in distillated water or Knop’s nutrient solution) with the addition of fullerene C 60 (10 or 50 mg/l) were studied. The content of chlorophyll, flavonols, and nitrogen balance index (NBI) were evaluated in the 1st leaf during the growing. At the end of the experiment, the relative rate of water loss (RWL) by the leaves was determined, as well as the dry mass of the roots and shoots. The effect of fullerene on the physiological and biochemical parameters of barley plants depended on the concentration of these nanoparticles and the presence of nutrients in the cultivation medium. Under the action of 10 mg/l of fullerene, all investigated parameters were mainly maintained at the level of control values. At the same time, exposure to 50 mg/l of fullerene stimulated a decrease in the content of chlorophyll and flavonols in the first leaf, increased the relative loss of water by the leaves, and slowed down the growth of barley plants grown in water. When 50 mg/l of fullerene was added to the Knop solution, the chlorophyll content in the first leaf increased, the accumulation of flavonols practically did not change, and the NBI increase was more prolonged. In this case, the dry mass of shoots increased, and no significant changes in the relative loss of water by the leaves and root growth were noted. It is assumed that differences in the sensitivity of plants to fullerene during their growth in water and Knop’s nutrient solution are associated, on the one hand, with their anatomical, morphological, and physiological and biochemical characteristics, including the activity of detoxification mechanisms, and, on the other, with possible changes in physicochemical properties nanoparticles in a solution of salts, activation of the delivery of nutrients with the help of fullerene and the influence on the processes that cause the aging of the first leaf to slow down.

The possibility of using of an aqueous extract from stevia (Stevia rebaudiana Bertoni) leaves as a biostimulant of plant growth in photoculture

Relevance. Plant growth biostimulants based on natural raw materials are ecologically safe and harmless to humans. Stevia (Stevia rebaudiana Bertoni) contains in its leaves sweet diterpene steviol glycosides, which are similar in structure and properties to gibberellins, as well as a number of other valuable biologically active compounds. Water extracts from stevia leaves are capable to accelerate growth, to increase the yield and quality of plants. However, further study and development of application technologies of the extracts for specific crops and different growing conditions are required. The purpouse of this work is to investigate the effect of an aqueous extract from stevia leaves on the yield and quality of lettuce and small radish under photoculture conditions. Materials and methods. The objects of the study were lettuce var. Typhoon and small radish var. Riesenbutter. The plants were grown in photoculture at the biopolygon of the FSBSI Agrophysical Research Institute (St. Petersburg) at an illumination of 10–20 klx, a temperature of 22–26°С (day) and 18–20°С (night). Watering was carried out with water, top-dressing was carried out with Knop's nutrient solution three times a week. Peat with mineral additives was used as a substrate. The original extract was prepared by extraction from stevia dry leaves powder with hot water (80°С) in a ratio of 1 g of leaves: 100 ml of water. Foliar treatment of plants was carried out twice at dilution of the original extract from stevia leaves 1:10, 1:50, and 1:100 (extract : water) at the rate of 0.20-0.25 ml / lettuce plant and 0.09-0.1 ml / radish plant; control plants were treated with water. The data were processed according to standard procedures using the Excel 2016 software. Results. Foliar treatment with an extract from stevia leaves did not significantly affect the size and weight of radish root crops, but increased the yield due to a decrease in the number of bolting plants. A significant decrease of bolting was observed in all treatment options (by 34-51%). When using a dilution of 1: 100, the yield of marketable root crops increased by 20% and the yield per sq. m. – by 25%. Foliar treatment with stevia extracts increased the mass of lettuce plants, as well as their biological value. The content of photosynthetic pigments, sugars, and vitamin C significantly increased, and a tendency towards a decrease in the content of nitrates was observed. According to data, we recommend for foliar treatment are dilutions of the original extract 1:50 and 1: 100. The effect of using of an extract from stevia leaves is similar in action to some biostimulants from plants with hormone-like properties, which determines the possibility of using it as a safe plant growth stimulant.

Time-dependent changes of arsenic and its selected forms in a hydroponic experiment with Quercus robur L.

Mutual transformations of particular As forms are dynamic. Therefore hydroponic experiments need to account for this variation. For this reason, the aim of the study was to determine the time-dependent changes of Astotal and selected forms of this metalloid (As(III), As(V), DMA or the sum of other organic forms) in modified Knop's solution and organs (root, low and high stem) of 2-year-old Quercus robur L. seedlings within a 33-day long hydroponic experiment. The results indicate the varying speed of As uptake and transport to aerial plant parts. A decrease in contents of As forms in organs of seedlings exposed to individual As forms varied, which indicates simultaneous transformations of As forms both in Knop's solution and plant organs. The obtained results indicate the need to analyse the main forms of As both in the nutrient solution and plant organs to assess the actual effectiveness of As phytoextraction by plants. It is necessary because, as demonstrated in this work, the addition of a specific As form does not mean that the capacity of a given plant relative to this form specifically is assessed. Capsule: The form of arsenic added to the medium undergoes dynamic changes affecting the phytoextraction of this metalloid in Quercus robur L. organs.

Effect of Landfill Leachate on the Growth Parameters in Two Selected Varieties of Fiber Hemp

The influence of landfill leachate on selected growth parameters in two varieties (‘Bialobrzeskie’ and ‘Monoica’) of hemp (Cannabis sativa L.) was studied to evaluate phytoremediation potential of these varieties. The plants were cultivated in hydroponic culture in Knop's nutrient solution. Landfill leachate was added to nutrient solution in concentrations of 10, 15, 20 and 40%, respectively. After 14 days of cultivation, selected parameters of above-ground organs and root system were determined in experimental plants, namely height of plants, dry weight of aerial parts, total leaf area, total length of the root system, dry weight of the root system and the content of photosynthetic pigments in leaves. The leachate application affected all the monitored parameters: the decrease in height of the plants, length of the root system, dry weight, total leaf area, and content of photosynthetic pigments were observed. While the 10% and 15% concentration of leachate often caused only a slight decrease in the monitored parameters, the 20% concentration dramatically affected all the observed characteristics. Concentration of 40% caused severe stunting and in some cases, even dying of experimental plants. The higher degree of tolerance in almost all parameters was observed in ‘Monoica’. This variety appears to be more suitable for landfill leachate treatment, but further research is needed, especially in terms of heavy metals accumulation in individual organs. According to our knowledge, this paper represents the first study on the use of hemp for treatment of landfill leachate.

Profile and concentration of the low molecular weight organic acids and phenolic compounds created by two-year-old Acer platanoides seedlings growing under different As forms

Two-year-old seedlings of Acer platanoides were cultivated during a three-month hydroponic experiment in modified Knop solution enriched with inorganic (As(III), As(V)) and organic (dimethylarsinic acid - DMA) arsenic forms at 0.06 mM, 0.6 mM and their combinations. The profile and content of low molecular weight organic acids (LMWOAs) and phenolic compounds were also determined in the rhizosphere, roots and leaves. Arsenic (As) treatment caused an elevated creation of the above mentioned metabolites, which was higher in leaves than in the rhizosphere or roots, and their overall content was correlated with the concentration of As in A. platanoides organs. The addition of all As forms strongly induced the exudation of citric and oxalic acids into the rhizosphere, while malonic, acetic, citric and malic acids were formed in the roots. The most differential profile of roots was confirmed for As(V) 0.06 mM (4-hydroxybenzoic (4-HBA), syringic, 2,5 dihydroxybenzoic (2,5-DHBA), caffeic, chlorogenic, ferulic, p-coumaric and sinapic acids and catechin). The obtained results indicate that the presence of particular As forms has a significant impact on the content and profile of exuded and created LMWOAs and phenolic compounds, and can also have a decisive influence on the activation of appropriate detoxification mechanisms.

PAH destruction in nitrogen deficient conditions by Pseudomonas putida strain BS3701

Two-year-old seedlings of Acer platanoides were cultivated during a three-month hydroponic experiment in modified Knop solution enriched with inorganic (As(III), As(V)) and organic (dimethylarsinic acid - DMA) arsenic forms at 0.06 mM, 0.6 mM and their combinations. The profile and content of low molecular weight organic acids (LMWOAs) and phenolic compounds were also determined in the rhizosphere, roots and leaves. Arsenic (As) treatment caused an elevated creation of the above mentioned metabolites, which was higher in leaves than in the rhizosphere or roots, and their overall content was correlated with the concentration of As in A. platanoides organs. The addition of all As forms strongly induced the exudation of citric and oxalic acids into the rhizosphere, while malonic, acetic, citric and malic acids were formed in the roots. The most differential profile of roots was confirmed for As(V) 0.06 mM (4-hydroxybenzoic (4-HBA), syringic, 2,5 dihydroxybenzoic (2,5-DHBA), caffeic, chlorogenic, ferulic, p-coumaric and sinapic acids and catechin). The obtained results indicate that the presence of particular As forms has a significant impact on the content and profile of exuded and created LMWOAs and phenolic compounds, and can also have a decisive influence on the activation of appropriate detoxification mechanisms.

Arsenic content in two-year-old Acer platanoides L. and Tilia cordata Miller seedlings growing under dimethylarsinic acid exposure\u2013model experiment

The presence of cacodylic acid (dimethylarsinic acid, DMA) can be an important factor in limiting the abilities of young tree seedlings to adapt to unfavorable environmental conditions. For this reason, the aim of the study was to estimate the influence of different DMA additions (from 0.01 to 0.6 mM) to modified Knop solution to arsenic (As) and selected forms of this metalloid (As(III), As(V), DMA) phytoextraction by two-year-old Acer platanoides L. and Tilia cordata Miller seedlings. Additionally, the biomass and other elements important in As transport in plants were analyzed. Seedlings of both tree species were able to grow in all experimental systems except the one with the highest DMA concentration (0.6 mM). Exposure of tree seedlings was related to a general decrease in plant biomass. Phytoextraction of As in roots, stems, and leaves increased with a rise of DMA concentration in solution to the highest content of As in A. platanoides and T. cordata roots growing under 0.3 mM (135 ± 13 and 116 ± 14 mg kg−1 dry weight). Arsenic was accumulated mainly in roots, thereby confirming bioconcentration factor values BCF > 1 for all tree seedlings treated with DMA. Exposure of plants to low DMA concentrations (0.01 and 0.03 mM) was related to the transport of this element to aboveground parts, while increased DMA concentration in other experimental systems led to the limitation of As transport to stems, as confirmed by translocation factor values TF < 1. Changes in many other elements such as boron, silicon, phosphorus, or sulfur concentration indicated the possible influence of DMA on the transport of As from roots to leaves. The obtained results show that DMA can be an important factor in modulating As phytoextraction in the studied tree species.

ẢNH HƯỞNG CỦA BA DUNG DỊCH DINH DƯỠNG HOAGLAND, TC MOBI, KNOP ĐẾN NĂNG SUẤT VÀ CHẤT LƯỢNG QUẢ CỦA CÂY CÀ CHUA CHANOKA F1 THỦY CANH

The nutrient solution is an important factor which directly affects the growth, yield, and quality of hydroponic crops. In this study, the effects of three common nutrient solutions, namely Hoagland, Knop and TC Mobi on the growth, yield, and fruit quality of tomato Chanoka F1 variety were evaluated. The results showed that the Hoagland solution had more positive influence on the growth, yield and fruit quality characteristics of tomato Chanoka F1 than the other two solutions. The plants grown in the Knop solution had the smallest yield and the poorest fruit quality. In addition, the nitrate content in the fruits was within the limit set by WHO for all of the three studied hydroponic solutions.

Development of human exometabolite deep mineralization method for closed ecosystems.

Methods of physicochemical further oxidation of hardly soluble sediment obtained from "wet combustion" of human exometabolites applied to space-purpose Bio Technological Life Support Systems (BTLLS) were studied. Most hardly dissoluble sediment containing Ca, P, Mg, and other essential plant nutrition elements were shown to dissolve in H2O2 and HNO3 aqueous media activated by alternating electric current. Dissolved additional mineral elements allowed (as demonstrated for lettuce) to increase the productivity of BTLLS phototrophic unit plants more than twice, which is comparable to their productivity on standard Knop solution with balanced chemical composition. Thus, dissolved mineral elements can be involved into BTLLS turnover process and increase its closure degree.

Effects of PAR intensity and NaCl concentration on growth of Salicornia europaea plants as relevant to artificial ecological systems

Effects of variable levels of photosynthetically active radiation (PAR) and NaCl concentrations, typical of closed ecological life support systems, on growth of Salicornia europaea L. plants, CO2 exchange, mineral composition, and the content of malondialdehyde (MDA) and photosynthetic pigments were investigated. The plants were grown for 25 days at different salinities of nutrient Knop solution (171, 342, and 513 mM NaCl) under two PAR levels (690 and 1150 μmol/(m2 s)). At PAR of 690 μmol/(m2 s), the plant productivity did not show significant changes at increasing salinities; at 1150 μmol/(m2 s), the maximal productivity was observed at NaCl concentrations of 171 and 342 mM. The increase in NaCl concentration from 171 to 513 mM in the nutrient solution led to a substantial increase in the relative Na content in aboveground organs at PAR level of 1150 μmol/(m2 s). The MDA content in aboveground organs by the end of the growth period was independent of PAR intensity. The content of photosynthetic pigments in the assimilatory tissue decreased with the increase in salinity from 342 to 513 mM NaCl at PAR level of 1150 μmol/(m2 s) but not at the lower irradiance. The combination of 1150 μmol/(m2 s) PAR intensity with the salinity as high as 342 mM NaCl was found to be the most effective for optimal productivity of S. europaea plants.

Investigation of biochemical function of selenium and its influence on the content of protein fractions and peroxidase activity in maize seedlings

The release of elemental selenium on the root surface of maize (Zea mays L., variety Krasnodarskii 29/AMV) seedlings observed in response to the addition of selenium-organic preparation DAFS-25 (diacetophenonyl selenide) to the nutrient Knop solution and accompanied by inhibition of growth of the roots was investigated. This process was completely suppressed after the addition of cysteine to the above solution containing 10–2 g/L DAFS-25, with the inhibiting effect was attenuated as well. In addition, DAFS-25 exerted impact on nitrogen exchange in the plants as judged by elevating the protein fraction of albumins in the roots almost by a factor of two due to at the expense of decreasing the content of glutelin, prolamine, and globulin fractions by 43, 25, and 26%, respectively. In the case of the action of DAFS-25 in combination with cysteine the quantitative composition of the above proteins very closely resembled that of the control plants indicating that cysteine behaves as antidote. It was found that DAFS-25 exerted a similar action on the content of albumins in the above-ground part of maize seedlings where this value drastically increased (by a factor of 4.5) on the background of total protein content elevation. In addition, this preparation at the highest concentration tested stimulated the activity of peroxidase in both the roots (by 63%) and the above-ground part of seedlings (by 112%). However, this effect of DAFS-25 was strongly inhibited after addition of cysteine to the nutrient solution. Evaluation of selenium content in the same parts of the control seedlings showed that they contain only a little amount of this element. The highest content of selenium in the above plant tissues was found after addition of DAFS-25 to the nutrient solution that provides evidence for its decomposition directly on the surface of the roots. Such an action of DAFS-25, like its impact on the peroxidase activity, was markedly attenuated in the presence of cysteine.

Efficiency of Zn phytoextraction, biomass yield and formation of low-molecular-weight organic acids in S × rubens – a hydroponic experiment

The aim of the study was to estimate Zn phytoextraction and changes in biomass of S × rubens growing in modified Knop's solution with different levels of Zn addition (0.5, 1.0, 2.5 and 5.0 mM). Obtained results were correlated with secretion of selected low-molecular-weight organic acids (LMWOAs) in the rhizosphere, roots and leaves. An increase in Zn concentration in Knop's solution resulted in Zn accumulation in roots, shoots and leaves. The highest accumulation was observed for plants growing in 5 mM Zn, at concentration levels 4741.36 ± 98.66, 1227.31 ± 16.57 and 2241.65 ± 34.90 mg kg−1 DW in roots, shoots and leaves, respectively. The bioaccumulation factor and the translocation factor for plants growing in 0.5, 1.0 and 2.5 mM Zn clearly indicate that this Salix taxon is an effective Zn accumulator. The general reduction of Salix biomass with an increase in Zn concentration in the solution was observed. In the rhizosphere, the total LMWOA concentration was almost 0.93 µmol kg−1 DM for control (Zn free) plants, while for 5.0 mM of Zn it was 4.9 µmol kg−1 DM. Increasing concentrations of acids were observed in roots (1.34 for the control and 5.57 µmol kg−1 DM for plants treated with 2.5 mM of Zn).

Assessment of the Suitability of Phytotoxkit Plastic Vertical Containers Compared with Petri Dishes for Standard Seedling Growth Tests

This study compares two cultivation methods (Petri dishes vs. Phytotoxkit containers; tap water vs. Knop's solution) for standard seedling growth tests. Seeds and young seedlings of Sinapis alba and Hordeum vulgare were used as study subjects and the adverse effect of Cd was assessed. Under testing conditions, only H. vulgare showed a significant decrease in seed germination in Petri dishes when tap water was used as the growth medium (70.8 % ± 46.4 %). No significant differences in IC50 values were found in either plant type for root growth between plants cultivated in Phytotoxkit containers and those cultivated in Petri dishes. The same findings were confirmed for shoot growth in H. vulgare, but not in S. alba. Suitability of Phytotoxkit containers over traditionally used Petri dishes for phytotoxicity determination was confirmed by higher correlation coefficients for all tests.