Half-strength Hoagland's Solution Research Articles

Physiological and biochemical responses of rice to polyethylene glycol

Effects of water deficit induced by polyethylene glycol (PEG-6000) on rice grown in half strength Hoagland solution was studied in the present investigation. Impacts of different water stress (10, 20 and 30% PEG) on some physiological and biochemical characteristics were determined in this investigation. Results showed that water stress significantly affected most physiological and biochemical characteristics. The increasing water stress declined the root and shoot length and fresh and dry weights of root and shoot. An increase in water stress also resulted in reduction of relative water content, leaf pigments and protein content. Upon dehydration, an incline in reducing and total sugar and proline content were evident in the root and shoot of rice. Water-deficit stress resulted in higher superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities but as the severity of the water stress increased, the SOD activity decreased. These crucial characteristics would be expected to be utilized as screening techniques for water stress tolerance to the future development of new variety. Bangladesh J. Bot. 52(4): 897-905, 2023 (December)

Trehalose Induced regulations in Physio-biochemical attributes of Helianthus annus under Lead stress

Heavy metal is a substantially severe abiotic environmental stress that is rising in many regions of the world. Current climate change circumstances and rapid industrialization increased heavy metal accumulation in soil and water. Overall, worldwide agricultural production decreased. Trehalose, a well-known plant growth regulator, is crucial in plants' responses to a variety of abiotic conditions. The Morpho-physiological and biochemical parameters were analyzed in hydroponic research to identify the possible role of trehalose in alleviating heavy metal lead acetate stress in sunflower (Helianthus annuus L.) crops. In the sole and mixed form, two Pb(C2H3O2)2 (Control and 30 micron) and one trehalose (50 M L-1) levels were used, and a half-strength Hoagland solution was used as a nutritional medium. The current study found that heavy metal stress had a significant negative impact on plant growth (root and shoot length), fresh and dry biomass, and plant water relations, as well as poor plant water relations, membrane stability, chlorophyll content, and antioxidant enzyme activities such as superoxide dismutase (SOD), peroxide (POD), ascorbate peroxide (APX), and catalase (CAT). MDA and H2O2 are the stress markers reduced by the application of trehalose. Exogenous treatment of trehalose, on the other hand, significantly mitigates the detrimental effects of metal toxicity by altering plant physiology, enhancing water relations, and providing robust antioxidant defense against heavy metal lead acetate stress. The findings of this study provide a new dimension to scientists' understanding of the beneficial usage of trehalose in plant science and offer up new research opportunities.

Yield performance, mineral profile, and nitrate content in a selection of seventeen microgreen species.

Originally regarded as garnish greens, microgreens are increasingly valued for their nutritional profile, including their mineral content. A study was conducted under controlled environmental conditions utilizing a selection of seventeen microgreen species belonging to seven different botanical families to investigate the genetic variation of macro- and micro-minerals and nitrate (NO3 -) content. Plants were grown in a soilless system using a natural fiber mat as the substrate. After germination, microgreens were fertigated with a modified half-strength Hoagland solution prepared using deionized water and without adding microelements. At harvest (10 to 19 days after sowing, based on the species), yield components were measured and dry tissue samples were analyzed for the concentration of total nitrogen (N), NO3 -, P, K, Ca, Mg, S, Na, Fe, Zn, Mn, Cu, and B. Genotypic variations were observed for all of the examined parameters. Nitrogen and K were the principal macronutrients accounting for 38.4% and 33.8% of the total macro-minerals concentration, respectively, followed in order by Ca, P, S, and Mg. Except for sunflower (Helianthus annuus L.), all the tested species accumulated high (1,000-2,500 mg kg-1 FW) or very high (>2,500 mg kg-1 FW) NO3 - levels. Eight of the studied species had a K concentration above 300 mg 100 g-1 FW and could be considered as a good dietary source of K. On the other hand, scallion (Allium fistulosum L.), red cabbage (Brassica oleracea L. var. capitata), amaranth (Amaranthus tricolor L.), and Genovese basil (Ocinum basilicum L.) microgreens were a good source of Ca. Among micro-minerals, the most abundant was Fe followed by Zn, Mn, B, and Cu. Sunflower, scallion, and shiso (Perilla frutescens (L.) Britton) were a good source of Cu. Moreover, sunflower was a good source of Zn, whereas none of the other species examined could be considered a good source of Fe and Zn, suggesting that supplementary fertilization may be required to biofortify microgreens with essential microminerals. In conclusion, the tested microgreens can be a good source of minerals showing a high potential to address different dietary needs; however, their yield potential and mineral profile are largely determined by the genotype.

Morpho-physiological effects of irrigation with saline water in ex vitro plants of Juglans regia ‘Sorrento’

Soil salinization is a global problem limiting growth and economical yield in fruit species including walnut. Knowledge of the response of varieties and cultivars to salinity can represent an important contribution to future walnut plantation in areas affected by soil salinization. Juglans regia ‘Sorrento’ is a commercially important Italian variety. The present work aimed to explore the morpho-physiological response to NaCl-induced stress in ‘Sorrento’ plants using clonally propagated ex vitro plantlets to reduce the impact of genetic variation. Ex vitro acclimatized plants were exposed to salinity conditions by irrigating pot soil with half-strength Hoagland solution containing 100 mM NaCl for 20 days. Salt-induced effects on plant growth, chlorophyll and carotenoid content, osmolality, membrane injury and on activities of antioxidant enzymes catalase and guaiacol peroxidase (G-POD) in leaves were evaluated. Morphological and growth parameters were not significantly altered by salt stress with respect to the control. Slight differences in leaf necrosis and absence of injury in the membranes, stable content of photosynthetic pigments, and an increase in G-POD activity were also found in salt-treated plants. These results collectively suggest that ‘Sorrento’ has potential for the cultivation in salinized environments.

Exogenous abscisic acid (ABA) and jasmonate (JA) promote metabolic regulation in Jacarandá-Pardo (Machaerium villosum Vog.) seedlings under PEG-induced water deficit

Plant hormones are essential in regulating plant responses to water deficit. However, there is little information on their effects on the growth of Cerrado plants under water deficit. This study aimed to investigate how exogenous abscisic acid (ABA) and jasmonic acid (JA), used separately, can minimize the effects of induced water deficit by polyethylene glycol (PEG-6000) in Machaerium villosum seedlings. The experiment had four treatments: 1) control: half-strength Hoagland's nutrient solution; (2) PEG-water deficit: Hoagland's solution supplemented with PEG (−1.0 MPa); (3) PEG-water deficit + 100 μM ABA; and (4) PEG-water deficit + 100 μM JA. Seedlings of M. villosum were collected separately at 0, 3, 7, and 14 days after treatment. At the end of 14 days, the relative water content (RWC) substantially decreased by 29.69% in the PEG treatment, followed by 14.59 and 13.83% in the PEG+ABA and PEG+JA treatments, respectively. The PSII photochemistry quantum yield (Fv/Fm) differed significantly between control and PEG treatments at seven days. Oxidative stress was detected after three days of water deficit. The superoxide anion (O₂⁻) content gradually increased in the PEG and PEG + ABA treatments, while the PEG + JA treatment interacted positively with the suppression of O₂⁻ production. Hydrogen peroxide (H2O2) production increased by 132.2 and 66.2% at seven days and 277.4 and 131.3% at 14 days in the PEG and PEG + ABA treatments, respectively. Metabolic profiling analysis showed that ABA and JA affected common water deficit-induced metabolic pathways. PEG and PEG + ABA treatments accumulated carbohydrates and some amino acids responsible for osmotic adjustment and energy production. Conversely, the PEG + JA treatment accumulated caffeic acid, vanillic acid, and quinic acid related to secondary metabolism, antioxidant compounds, and fatty acids, important membrane repair agents.

Phosphorus protects against cadmium-induced phytotoxicity by stimulating plasma membrane H+-ATPase activity

Proper plant nutrition can be an effective strategy to alleviate the phytotoxicity and damaging effects of Cd stress on plants and to avoid its entry into the food chain. This study aimed to investigate effects of phosphorus concentrations, and pH levels in the nutrient solution on Cd uptake, growth, photosynthetic characters, total phytochelatins (PCs), and plasma membrane ATPase activity of sugar beet (Beta vulgaris L.) plants grown in sand culture. Two successive experimental studies were carried out under controlled conditions. In the first study, 10-day-old sugar beet seedlings were irrigated with a half-strength Hoagland and Arnon nutrient solution, adjusted to different pH (3.5, 5.0, 6.0, 7.0, or 8.0), and containing 0, 0.15, or 0.30 mg Cd L−1 as CdCl2. In the second study, 10-day-old sugar beet seedlings were irrigated with the same nutrient solution (pH 6), but combined with different phosphorus concentrations (0, 10, 25 and 50 µg P ml−1 as KH2PO4) and Cd levels (0, 0.15, and 0.30 mg Cd L−1 as CdCl2). The first study revealed that pH had a strong influence on Cd uptake by sugar beet roots. Cd stress significantly decreased sugar beet growth and Mg2+-ATPase activity, whereas it increased total phytochelatins (PCs). Second study indicated an antagonistic effect between P and Cd. Furthermore, phosphorus had the potential to stimulate Mg2+-ATPase activity and synthesis of photosynthetic pigments and to promote growth of sugar beet seedlings. Cadmium induced phytotoxicity in sugar beet seedlings can be alleviated by a proper pH and phosphorus nutrition.

Effect of polypropylene microplastics on seed germination and nutrient uptake of tomato and cherry tomato plants

Although microplastic (MP) pollution in farmland increased, the effect of MPs on plant growth was not clearly explained. Therefore, the object of the study was to evaluate the effect of polypropylene microplastics (PP-MPs) on plant germination, growth, and nutrient uptake under hydroponic conditions. The effect of PP-MPs on seed germination, shoot and root length, and nutrient uptake were assessed using tomato (Solanum lycopersicum L.) and cherry tomato (Solanum lycopersicum var. cerasiforme) seeds grown in half-strength Hoagland solution. The results showed that PP-MPs did not significantly affect seed germination, but positively affected the shoot and root elongation. In cherry tomato, the root elongation was significantly increased by 34%. Microplastics also affected nutrient uptake by plants, however, the effect varied depending on elements and plant species. The Cu concentration was substantially increased in tomato shoot while it decreased in cherry tomato root. Nitrogen uptake decreased in MP treated plants compared to the control and phosphorus uptake was significantly decreased in the shoot of cherry tomato. However, the root-to-shoot translocation rate of most macro nutrients decreased following exposure to PP-MPs indicating that long-term exposure to MPs may lead to a nutritional imbalance in plants.

Iso-osmotic calcium nitrate and sodium chloride stresses have differential effects on growth and photosynthetic capacity in tomato

Calcium nitrate [Ca(NO3)2] and sodium chloride (NaCl) are among the main salts used in cultivation and present in salinized soil, respectively. These salts at high levels would reduce photosynthetic capacity and eventually cause a reduction in tomato growth. To better understand the growth disruption caused by Ca(NO3)2 salt (from the fertilizer) and the other predominant salt NaCl in salinized soils, tomato plants were grown in half-strength Hoagland's nutrient solution with three treatments. Through 7 days of salt stress and later 7 days of recovery, we investigated tomato seedling growth, nonstructural carbohydrates accumulation, antioxidant capacity, photosynthetic gas exchange, and chlorophyll fluorescence parameters. We found that Ca(NO3)2 and NaCl stresses increased the levels of nonstructural carbohydrates, reactive oxygen species (ROS), and various antioxidant enzyme activities in tomatoes while lowering foliar photosynthetic capacity. Under iso-osmotic salt stress conditions, the disruption of photosynthesis by NaCl was greater than that brought about by the Ca(NO3)2 treatment, which was attributed to Na+ accumulation. Interestingly, Na+ increased the levels of nonstructural carbohydrates and disrupted the feedback inhibition of photosynthesis. In addition, Na+ inhibited the activities of antioxidant enzymes, leading to more ROS production that would disrupt the processes within various photosynthetic apparatus. Our study further revealed that foliar nonstructural carbohydrates played an important role in delaying the onset of photoinhibition and rapid recovery of photosystem damage after Na+stress.

Nutrient Management of Brahmi (Bacopa monnieri L.) Cultivars in Soil and Comparison with Hydroponically Grown Plants for Better Herbage Yield

A field experiment was conducted during kharif season of 2019-20 at Department of Agriculture, Khalsa College, Amritsar. It consisted of 10 treatment combinations which included two cultivars (CIM-Jagriti and Subodhak) and five nutrient management, viz. Vermicompost 10 t ha-1, FYM 20 t ha-1, Vermicompost 5 t ha-1+ FYM 10 t ha-1, Recommended dose of NPK fertilizers 100: 60: 50 kg ha-1 and Hydroponics (half-strength Hoagland solution). The results revealed that cv. Subodhak had produced more yield than cv. CIM-Jagriti but bacoside-A content was higher in the latter (16 percent higher). Among nutrient management, Brahmi grown in hydroponics (half-strength Hoagland solution) had significantly higher growth and yield attributes (viz. main shoot length, number of shoots, number of leaves, leaf area, fresh and dry weight) while FYM 20 t ha-1 recorded lowest growth and yield. Additionally, hydroponically grown brahmi had 7.5 percent more bacoside-A content than soil grown brahmi.

NITROGEN AND PHOSPHOROUS EFFECTS ON GROWTH OF Stevia rebaudiana Bertoni UNDER LIGHT EMITTING DIODE (LED)

Studies on planting of Stevia rebaudiana, an important industrial crop that provides non-caloric sweeteners for the beverage sector, is lacking in an indoor controlled environment. In the present study, using a nutrient film technique, nitrogen (N) and phosphorous (P) levels needed for S. rebaudiana were determined. The plants were grown under light emitting diodes (LED) at 16h/8h light/darkness photoperiod in an air-conditioned laboratory. The results obtained indicated that in terms of growth performance and leaf production, the half strength Hoagland solution, where N was 100 mg L-1 and P was 15 mg L-1 , enabled the optimum gain in this crop. The results have implications for economic purposes

Sand Particle Size and Phosphorus Amount Affect Rhizophagus irregularis Spore Production Using In Vitro Propagated Spore as a Starter Inoculum in Rhizosphere of Maize (Zea mays) Plantlets.

Microbial inoculants, particularly arbuscular mycorrhizal (AM) fungi, have great potential for sustainable crop management. In this study, monoxenic culture of indigenous R. irregularis was developed and used as a tool to determine the minimum phosphorus (P) level for maximum spore production under the in vitro conditions. This type of starter AM fungal inoculum was then applied to an in vivo substrate-based mass-cultivation system. Spore production, colonization rate, and plant growth were examined in maize (Zea mays L.) plant inoculated with the monoxenic culture of R. irregularis in sand graded by particle size with varying P levels in nutrient treatments. In the in vitro culture, the growth medium supplemented with 20 µM P generated the maximum number of spores (400 spores/mL media) of R. irregularis. In the in vivo system, the highest sporulation (≈500 spores g−1 sand) occurred when we added a half-strength Hoagland solution (20 µM P) in the sand with particle size between 500 µm and 710 µm and omitted P after seven weeks. However, the highest colonization occurred when we added a half-strength Hoagland solution in the sand with particle sizes between 710 µm and 1000 µm and omitted P after seven weeks. This study suggests that substrate particle size and P reduction and regulation might have a strong influence on the maximization of sporulation and colonization of R. irregularis in sand substrate-based culture.

Improvement of tomato salt tolerance by the regulation of photosynthetic performance and antioxidant enzyme capacity under a low red to far-red light ratio

The red light (R) to far-red light (FR) ratio (R:FR) regulates plant responses to salt stress, but the regulation mechanism is still unclear. In this study, tomato seedlings were grown under half-strength Hoagland solution with or without 150 mM NaCl at two different R:FR ratios (7.4 and 0.8). The photosynthetic capacity, antioxidant enzyme activities, and the phenotypes at chloroplast ultrastructure and whole plant levels were investigated. The results showed that low R:FR significantly alleviated the damage of tomato seedlings from salt stress. On day 4, 8, and 12 at low R:FR, the maximum photochemical quantum yields (Fv/Fm) of photosystem II (PSII) were increased by 4.53%, 3.89%, and 16.49%, respectively; the net photosynthetic rates (Pn) of leaves were increased by 16.21%, 90.81%, and 118.00%, respectively. Low R:FR enhanced the integrity and stability of the chloroplast structure of salinity-treated plants through maintaining the high activities of antioxidant enzymes and mitigated the degradation rate of photosynthetic pigments caused by reactive oxygen species (ROS) under salt stress. The photosynthesis, antioxidant enzyme-related gene expression, and transcriptome sequencing analysis of tomato seedlings under different treatments were also investigated. Low R:FR promoted the de novo synthesis of D1 protein via triggering psbA expression, and upregulated the transcripts of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) related genes. Meanwhile, the transcriptome analysis confirmed the positive function of low R:FR on enhancing tomato salinity stress tolerance from the regulation of photosynthesis and ROS scavenging systems.

Effect of nitrogen, phosphorus and potassium deficiencies on some morphological and physiological properties and nutrient uptake by two almond rootstocks

Abstract A soilless culture and completely randomised two-factorial experiment was carried out to investigate the effect of nitrogen (N), phosphorus (P) and potassium (K) deficiencies on macronutrient uptake and to determine some characteristics of Prunus dulcis L. (bitter almond: BA) and Prunus scoparia L. (Alook: AL) seedlings. Seedlings in pots containing perlite were irrigated with half-strength, N-, P- and K-free Hoagland solutions for 12 wk. Results showed that N deficiency decreased the N and Ca levels and increased the K concentration in the shoots of both rootstocks. Phosphorus deficiency decreased N and P concentrations of both seedlings, as well as the Ca and Mg concentrations of BA seedlings. Potassium deficiency decreased the K concentration of the BA seedlings and decreased N, K and Ca concentrations of the AL seedlings. In the BA seedlings, only the fresh weight of the shoot decreased under the P deficiency condition; the other morphological traits of shoots in this genotype and none of the traits in the AL seedlings were affected by P deficiency. Furthermore, both the rootstocks can maintain their optimal growth even at very low concentration of K; this shows that both rootstocks consume K in a luxurious way. Under nutrient-deficient conditions, the AL seedling has greater ability to maintain the N concentration or uptake it more than the BA seedling. The N P and K deficiency conditions disturbed the electron transfer cycle of photosystem II in the AL leaves and caused a response. Most root traits of the AL seedling were not changed under nutrient deficiency, and this indicates a high tolerance of the AL roots compared to the BA roots or lower demand in this genotype for these elements. The characteristics of P. scoparia seedlings were less affected by the deficiency of these three elements, and therefore, P. scoparia rootstock is preferred to BA for weak and non-fertile soils.

Effects of Nitrogen and Water Deficiency on Agronomic Properties, Root Characteristics and Expression of Related Genes in Soybean

Drought and insufficient nutrient supply are the main limiting factors for field crop production; therefore, the present study aimed to investigate the responses of four registered soybean varieties to limited nitrogen (N) supply in combination with drought stress. Plants were grown in tubes filled with silica sand, under open-air conditions. Water shortage was initiated at the three-leaf stage by providing 50% of water, and N deficiency was obtained by reducing the N content of the half-strength Hoagland solution by 50%. N deficiency did not influence the grain yield, while it significantly increased the root dry biomass in Boglár and Pannónia Kincse. Compared with nitrogen supply, the effects of the water shortage were dominant in root development. The expression levels of the investigated genes also showed genotypic variations. The expression of the Inducible nitrate reductase1 gene increased under N-deficient conditions in Boglár and decreased in Pannónia Kincse under drought conditions. The expression level of the aldehyde dehydrogenase gene and abscisic acid 8’-hydroxylase 3 increased under combined stress conditions. Summarising the agronomic and physiological characteristics, Boglár and Sinara were sensitive to drought, Bagera was sensitive to N deficiency but produced the highest yield under limited watering in each nitrogen treatment, while Pannónia Kincse was tolerant to nitrogen deficiency under well-watered conditions.

In vivo polyploidy induction of Phalaenopsis amabilis in a bubble bioreactor system using colchicine

Abstract Phalaenopsis amabilis Blume var. grandiflora Bateman is economically important as cut and pot flower. Polyploidy is considered as a valuable tool in improvement and evolution of ornamental plants. Protocorm-like bodies (PLBs) of P. amabilis were cultured on Murashige and Skoog medium containing 0.20 mg L-1 IBA together with 2.00 mg L-1 KIN and 1.00 g L-1 activated charcoal and grown for a period of five months. Fully-developed plantlets from in vitro grown PLBs were immersed in a bubble reactor filled with half-strength Hoagland solution containing the antimitotic agent colchicine (0.05%, 0.10% and 0.15%, w/v) for 72 h with a few drops (1 mL of 0.1%) of octylphenoxypolyethoxyethanol or Nonidet (P-40) as a surfactant. Plantlets were aerated to prevent hypoxia. Colchicine-treated and untreated plantlets were transferred to pots for a period of 60 days. Tetraploidy was successfully induced by 0.15% colchicine. Polyploidy levels were firstly detected using flow cytometry and then confirmed by cytological and morphological observations. The chromosome number was 2n = 2x = 38 in diploids and 2n = 4x = 76 in tetraploid. Incubation of plantlets in liquid medium containing 0.15% colchicine induced the maximum recovered tetraploids with minimum frequency of survival (50%). The tetraploid plants were more compact and exhibited round and thick leaves with darker green color than diploids. Stomata size in tetraploids were larger with less density than diploids. Chloroplast number in guard cells of tetraploids was about two times more than that of control. These results indicate that induction of tetraploids are a reliable and powerful tool for generation of novel phenotypes with ornamental and horticultural value for genetic improvement and breeding. Produced tetraploids in current study have potential in the ornamental/floriculture trade.

Arbuscular mycorrhizal fungi improve growth, essential oil, secondary metabolism, and yield of tobacco (Nicotiana tabacum L.) under drought stress conditions.

Drought is a major environmental threat limiting worldwide crop production. Drought stress affects the tobacco quality and yield; therefore, the current research studies were undertaken to investigate the effectiveness of arbuscular mycorrhizal fungi (AMF) under drought stress on morphological and biochemical attributes of tobacco (Nicotiana tabacum L. variety Yunyan 87). AMF-inoculated and AMF-non-inoculated plants were maintained in a greenhouse and irrigated with a half-strength Hoagland solution (100 mL pot-1) once a week. At harvesting, the plant height, number of leaves, fresh and dry weights, mycorrhizal colonization, and concentration of leaf photosynthetic pigments and photosynthetic rate were measured. Data were statistically analyzed by ANOVA and the principal component (PCA) analyses. The effect of root colonization significantly increased biomass production and essential oil accumulation. Results showed that drought at mild and severe stressed levels significantly affected tobacco growth by decreasing plant height, biomass, and a number of leaves. However, inoculation of AMF considerably increased plant height, fresh and dry weights, chlorophyll (a, b), total chlorophyll, and carotenoid content by 43.84, 40.87 and 49.76, 185.29, 325.60, 173.12, and 211.49%, respectively. Compared with non-inoculated plants, AMF inoculation significantly enhanced the essential oil yield and the uptake of nitrogen, phosphorus, and potassium with the increase of 257.36, 102.71, and 90.76, 62.32, and 84.51%, respectively, in mild drought + AMF-treated plants. Similarly, the antioxidant enzymatic activity, glomalin-related soil protein (GRSP), and accumulation of phenols and flavonoids and osmolytes content were also significantly improved in inoculated plants under drought stress. Additionally, AMF inoculation significantly upregulated the lipoxygenase (LOX) and phenylalanine ammonia-lyase (PAL) enzymes by 197 and 298.44% under drought conditions. These findings depicted that the symbiotic association of AMF improved the overall growth pattern and secondary metabolism in tobacco plants under severe drought stress conditions and may be used as an approaching source of important drugs in the field of pharmacology.

Simultaneous removal of arsenic, fluoride, and manganese from synthetic wastewater by Vetiveria zizanioides.

Main aim of the present research is to explore the potential use of Vetiveria zizanioides L. for phytoremediation of arsenic, fluoride, and manganese simultaneously from synthetic wastewater in a batch scale floating platform unit. Half strength Hoagland's nutrient solution spiked with arsenic, fluoride, and manganese concentrations of 1, 20, and 10 mg/L, respectively has been used. The effects of pH and treatment time on simultaneous removal of arsenic, fluoride, and manganese have been performed. V. zizanioides has exhibited optimum growth at pH 8 and the removal of arsenic and fluoride is observed to be 59.6 and 38.1%, respectively. This plant has successfully removed all of the manganese (99.3%). The uptake of manganese is found to be faster than the arsenic and fluoride. The trend of arsenic, fluoride, and manganese accumulation in various parts of V. zizanioides is found as roots > stems > leaves. Result showed that the use of V. zizanioides would be appropriate to treat arsenic, fluoride, and manganese contaminated wastewater.

The applicability of anaerobically treated domestic wastewater as a nutrient medium in hydroponic lettuce cultivation: Nitrogen toxicity and health risk assessment.

The applicability of anaerobic effluent (AE) from an anaerobic membrane bioreactor (AnMBR) treating domestic wastewater as a nutrient medium was evaluated through hydroponic cultivation of lettuce. The growth of lettuce plants on AE media was significantly inhibited to 31-40% in height and 36-48% in number of leaves compared to that on half-strength Hoagland solution (HHS) as a control. The primary cause of inhibition was nitrite toxicity as induced by partial nitrification. Therefore, the nitrification of AE as a pre-treatment step was adopted to prevent the toxicity of nitrite. The heights of lettuce grown on nitrified anaerobic effluent (NAE) and nitrified anaerobic effluent with 96mg/L sulfate (NAES) were in the range of 11.4-11.5cm and was comparable to that on control solution (11.4cm). The potential health risk for heavy metals was insignificant based on health risk index (HRI<1) and targeted hazardous quotient (THQ<1). These results show that efficient crop production can be achieved with AE, but suitable pre-treatment steps should be followed.

Kinetic parameters related to nitrogen uptake efficiency of pear trees (Pyrus communis)

Genetic improvement programs for pear trees in Brazil are characterized by rootstock (hypobiotic) selection mainly considering physiological attributes such as vigor, breakage of dormancy, propagation easiness, and sanitary characteristics, such as resistance to pests and diseases. However, kinetic parameters that determine nutrient uptake efficiency are not usually considered as, for example, nitrogen (N) in forms of NO3− and NH4+. The objective of this study was to evaluate the kinetic parameters related to N uptake in pear selection '54′ and '971′ as additional criteria for rootstock selection. The plants were acclimatized in a half-strength Hoagland solution and tested to assess the depletion of the internal reserves at 15 and 30 days, in CaSO4 solution to evaluate the depletion period during 65 h. The selection '971′ showed more significant NO3− and NH4+ uptake efficiency, because presented higher Vmax values and Influx. The internal reserve depletion (IRD) period for the evaluated selections was 30 days in CaSO4 solution. The evaluation period of the depletion period to reach the Cmin for selections '971′ and '54′ was 64 and 65 h for NO3− respectively, and 65 h for NH4+. The selection '971′ had a higher affinity with the NO3− ion when correlated with the physiological parameters of minimum fluorescence (Fo) and electron transport rate (ETRm).

Foliar applications of spermidine improve foxtail millet seedling characteristics under salt stress

This study investigated the mitigating effects of spermidine (Spd) application on salinity-induced ion inbalance, physiological properties, and the expression of some genes in foxtail millet (Setaria italica L.). We observed 30-d-old seedlings maintained at a half-strength Hoagland solution (control), 1.0 % NaCl, 10, 20, and 40 μM Spd, and 10, 20, and 40 μM Spd + 1.0 % (m/v) NaCl for 14 d. The results show that salt stress significantly inhibited plant growth, and this was significantly ameliorated by Spd. The mass of the shoots and roots, content of chlorophyll a and chlorophyll b, root activity, and K+ content were higher whereas Na+ content, Na+/K+ ratio, relative electrolyte leakage, glutathione content, H2O2 content, activity of glutathione reductase (GR), and catalase (CAT) were lower after application of Spd in comparison with NaCl alone. The expression of GR, ascorbate peroxidase, CAT, and superoxide dismutase genes also significantly decreased in salt stressed plants with Spd. This study has proved the role of Spd in alleviating salt stress in foxtail millet and identified that 20 μM Spd was most effective.