Hydroponic Nutrient Solution Research Articles

Influence of Cow Dung Extract Complemented with Nutrient Solution on the Growth Performance of Lettuce (Lactuca sativa L)

Limited studies have focused on plant growth performance using organic-based solutions complemented with mineral elements in a hydroponic system. Thus, this study aimed to investigate the growth performance of lettuce (Lactuca sativa L.) as influenced by cow dung extract combined with a hydroponic nutrient solution. Treatments considered as four different levels of aerated cow dung extracts (C), viz., C1 = 50 g l-1, C2 =100 g l-1, C3 =150 g l-1 and C4 =200 g l-1 and four strengths of standard nutrient solution (S), viz, S1 = 30% of standard nutrient solution, S2 = 40% of standard nutrient solution, S3 = 50% of standard nutrient solution and S4 = 60% of standard nutrient solution. The experiment was carried out using a deep flow technique in a semi-greenhouse. Various growth and physiological parameters were measured in this experiment. The obtained data were subjected to statistical analysis with 4 replicates by analysis of variance (ANOVA) using SPSS. In the case of growth parameters, the tallest plant (23.54 cm), maximum number of leaves per plant (17.01) broadest leaf (13.32 cm), and the highest fresh weight (112.05 g/plant) were recorded from C3 while the lowest in C1. For hydroponic nutrient solution, the tallest plant (23.13 cm), the maximum number of leaves per plant (16.66), the widest leaf breath (14.17 cm), and the highest fresh weight (116.0 g/plant) were recorded from S4 while the lowest in S1. On the other hand, physiological traits viz. leaf area, net assimilation ratio, and relative growth rate were statistically higher in C3 and lowest in C1. In the nutrient solution, all physiological parameters were highest in S4 and the lowest in S1. In the case of the interaction effect, the highest fresh weight and almost all the parameters were found best in C3S4 and the lowest in C1S1. Therefore, the analysis showed that in terms of growth promotion properties hydroponic nutrient solution along with cow dung extract had a substantial impact and C3S4 was the most preferable treatment combination. Based on these findings, in a hydroponic system, an inorganic nutrient solution combined with organic liquid fertilizer derived from cow dung extract (as an alternative nutrient source) requires further improvements to achieve optimal growth and yield.

A two-step approach to recycling hydroponics waste nutrient solutions using fertiliser drawn forward osmosis and chemical precipitation

Hydroponic waste nutrient solutions (HWNS) present significant environmental and economic challenges due to their high phosphorus content and potential for eutrophication. Addressing these issues requires innovative approaches that mitigate environmental impacts and recover valuable resources. This study introduces a novel two-step approach that combines Fertiliser Drawn Forward Osmosis (FDFO) and chemical precipitation to recycle HWNS effectively.In the first phase, FDFO was employed to concentrate HWNS using a commercial hydroponic fertiliser as the draw solution. This process resulted in a diluted fertiliser solution (potentially suitable for reuse in hydroponics irrigation) and a concentrated HWNS rich in phosphorus. The concentrated HWNS was then subjected to chemical precipitation in the second phase, where phosphorus was recovered as calcium phosphate by adding sodium hydroxide at an optimised pH of 9.5.Bench-scale experiments demonstrated a 93% water recovery rate using FDFO and an impressive 99.5% phosphorus removal efficiency through chemical precipitation. These results indicate that the combined FDFO and chemical precipitation processes effectively recover water and phosphorus from HWNS and reduce reliance on synthetic fertilisers and freshwater in hydroponic systems.The findings of this study demonstrate that the two-step approach not only enhances water and phosphorus recovery but also improves the efficiency of the chemical precipitation process by achieving higher recovery rates resulting in more sustainable hydroponic systems.

Improved morphological and yield responses of green lettuce (Lactuca sativa L.) grown with seaweed extract as a hydroponic nutrient solution

Sargassum polycystum is among the seaweed species in the Philippines that are considered coastal waste after drifting on the shorelines. Although there has been a report on the potential of S. polycystum as a biostimulant for certain crops, its utilization as a hydroponic nutrient solution is not yet thoroughly analyzed. Thus, a study utilizes various ratios of S. polycystum seaweed extract (SE) mixed with commercial hydroponic nutrient solution (CHNS) to the growth and yield of green leaf lettuce grown under the Kratky method of hydroponic system. Treatments are 100% CHNS and percentage replacements of CHNS with SE (25%, 50%, and 75%, respectively). The result shows a 10.53% increase in lettuce plant height grown under 25% and 50% SE compared to 100% CHNS. A similar result is also observed in the lettuce leaf width (14.29%), leaf length (7.14%), and plant weight (22.41%). Regarding root length, replacing 50% SE resulted in longer root length (44.83%) and more leaves (10%) compared to lettuce plants grown under 100% CHNS. However, replacement of SE beyond 50% is detrimental to leaf length and comparable to all growth and yield parameters with 100% CHNS. Regarding the return on investment, 50% SE replacement has the highest return of 98.62% compared to 100% CHNS, with 49.87% only for a projected six cropping cycles. Hence, a 50% replacement of CHNS with SE from its recommended rate can be suggested for more profitable production of green leaf lettuce under a hydroponic system.

Assessing the Capabilities of UV-NIR Spectroscopy for Predicting Macronutrients in Hydroponic Solutions with Single-Task and Multi-Task Learning

Macronutrients, including nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S), are the most basic nutrient elements in the solution for the hydroponic system. However, the current management of hydroponic nutrient solutions usually depends on EC and pH sensors due to the lack of accurate specific macronutrient sensing equipment, which easily leads to nutritional imbalance for the cultivated plant. In this study, the UV-NIR absorption spectroscopy (200–1100 nm) was used to predict six macronutrients in hydroponic solutions; two kinds of single-task learning algorithms, including partial least squares (PLS) and least absolute shrinkage and selection operator (LASSO), and two kinds of multi-task learning algorithms, including dirty multi-task learning (DMTL) and robust multi-task learning (RMTL), were investigated to develop prediction models and assess capabilities of UV-NIR. The results showed that N and Ca could be quantitatively predicted by UV-NIR with the ratio of performance to deviation (RPD) more than 2, K could be qualitatively predicted (1.4 < RPD < 2), and P, Mg, and S could not be successfully predicted (RPD < 1.4); the RMTL algorithm outperformed others for predicting K and Ca benefit from the underlying task relationships with N; and predicting P, Mg, and S were identified as irrelevant (outlier) tasks. Our study provides a potential approach for predicting several macronutrients in hydroponic solutions with UV-NIR, especially using RMTL to improve model prediction ability.

A real-time on-site precision nutrient monitoring system for hydroponic cultivation utilizing LIBS

Indoor hydroponic farming is an advanced cultivation technique with diverse sustainability benefits, such as facilitating local produce, minimizing transportation costs and emissions, and enabling year-round crop cultivation. To optimize crop growth for enhanced yield, improved crop quality, and reduced environmental footprint, precise monitoring and replenishment of essential nutrients within hydroponic systems is crucial. Current methods employed in most commercial farms for online nutrient supply monitoring is limited to pH and conductivity measurements. These techniques can only offer an indication of the overall change in the complex nutrient mixture and lack the capability to precisely identify the specific nutrient or quantify the nutrient content. Most of the existing techniques for measuring individual nutrient levels are expensive and invasive, necessitating sample preparation, frequent recalibration, and skilled personnel for operation. In this context, we propose and demonstrate a real-time, on-site monitoring system for the precise analysis of hydroponic nutrient supply based on laser-induced breakdown spectroscopy (LIBS). We also discuss the system design considerations, parametric optimizations, limit of detection (LOD), and limit of quantitation (LOQ) of key nutrient components such as potassium (K), sodium (Na), calcium (Ca), and magnesium (Mg), using the proposed approach. The detection range of the developed LIBS-based monitoring system can encompass the typical concentration range observed in hydroponic nutrient solutions used at agricultural farms. This technique offers rapid online monitoring of individual nutrient components, providing precise, real-time analysis and the potential to enable comprehensive automation capabilities for current and future hydroponic farms.Graphical abstract

Efficiency of zinc in alleviating cadmium toxicity in hydroponically grown lettuce (Lactuca sativa L. cv. Ferdos)

BackgroundA study on photosynthetic and enzyme activity changes and mineral content in lettuce under cadmium stress has been conducted in a greenhouse, utilizing the modulated effect of zinc (Zn) application in the nutrient solution on lettuce. Zn is a micronutrient that plays an essential role in various critical plant processes. Accordingly, three concentrations of Zn (0.022, 5, and 10 mg L− 1) were applied to hydroponically grown lettuce (Lactuca sativa L. cv. Ferdos) under three concentrations of Cd toxicity (0, 2.5, and 5 mg L− 1).ResultsThe results showed that along with increasing concentrations of zinc in the nutrient solution, growth traits such as plant performance, chlorophyll index (SPAD), minimum fluorescence (F0), leaf zinc content (Zn), leaf and root iron (Fe) content, manganese (Mn), copper (Cu), and cadmium increased as well. The maximum amounts of chlorophyll a (33.9 mg g− 1FW), chlorophyll b (17.3 mg g− 1FW), carotenoids (10.7 mg g− 1FW), maximum fluorescence (Fm) (7.1), and variable fluorescence (Fv) (3.47) were observed in the treatment with Zn without Cd. Along with an increase in Cd concentration in the nutrient solution, the maximum amounts of leaf proline (5.93 mmol g− 1FW), malondialdehyde (MDA) (0.96 μm g− 1FW), hydrogen peroxide (H2O2) (22.1 μm g− 1FW), and superoxide dismutase (SOD) (90.3 Unit mg− 1 protein) were recorded in lettuce treated with 5 mg L− 1 of Cd without Zn. Additionally, the maximum activity of leaf guaiacol peroxidase (6.46 Unit mg− 1 protein) was obtained with the application of Cd at a 5 mg L− 1 concentration.ConclusionsIn general, an increase in Zn concentration in the nutrient solution decreased the absorption and toxicity of Cd in lettuce leaves, as demonstrated in most of the measured traits. These findings suggest that supplementing hydroponic nutrient solutions with zinc can mitigate the detrimental effects of cadmium toxicity on lettuce growth and physiological processes, offering a promising strategy to enhance crop productivity and food safety in cadmium-contaminated environments.

Application of 2-Iminoselenazolidin-4-Ones (ISeA) for Beta vulgaris L. and Brassica rapa L. Plants Se-Biofortification

Due to widespread selenium deficiency in food the aim of this study was to evaluate the effectiveness of a new Se(II)-containing organic chemical compound 2-iminoselenazolidin-4-ones (ISeA) in the form of a nanoscale associate (1–5 nm) solution for Swiss chard and komatsuna plants biofortification. Application of the chosen substance as a foliar treatment (2 mg·L−1) and as an additive to a hydroponic nutrient solution (10 mg·L−1) was performed. Both cultures had a high level of Se absorption, distribution and accumulation in leaves two or more times greater than in petioles. Se content in chard petioles (15 mg·L−1) when applying ISeA as a component of the nutrient solution exceeded the accumulation of Se during foliar treatment (9.6 mg·L−1) and the same trend in the komatsuna leaves was observed. When applying ISeA to the nutrient solution, an increase in komatsuna and chard biomass was seen at 36 and 68% and for leaf treatment by 21 and 45%, respectively. For komatsuna and chard an increase in the ratio of dry to fresh weight was also observed to be 27 and 26%, and for foliar treatment—0 and 16%, respectively. Treatments led to increase in chard plants height (7–17%), enlargement of leaves (19–42%), a rise in photosynthetic pigments (20–60%) and anthocyanin (2.9 and 2.2 times) concentration, and for komatsuna—the multiplication of leaves number (28%) and their surface area (27–29%) as well as a rise in the concentration of anthocyanin (1.0 and 1.6 times) with foliar treatment and nutrient solution enrichment.

Development Of A Distance Education Experiment Set That Allows The Ratio Of Chemical Components In Hydroponic Farming Nutrient Liquid To Be Estimated By Artificial Intelligence

With the increase and development of electronic systems, especially with the advancement of artificial intelligence (AI) applications, AI has begun to meet many of humanity's needs. Due to the rapidly increasing human population and the decreasing availability of fertile land, the use of AI has become necessary in rapidly expanding soilless agriculture practices. One of the biggest challenges in soilless agriculture is the inability to accurately determine the chemical content of nutrient solutions in real-time. In this study, the results of inductively coupled plasma optical emission spectrometry (ICP-OES) and electrical conductivity (EC) were obtained for 300 hydroponic agriculture nutrient solutions containing different ratios of Mg, K, and P minerals. The obtained data were evaluated using artificial neural networks in Matlab® software, with ICP-OES results as inputs and EC results as outputs (3 inputs-1 output). The results were uploaded to the cloud system using Firebase, and an EC meter capable of communicating with the cloud was developed. The results of the produced EC meter were compared with the data in the cloud, and attempts were made to determine the element ratios in the nutrient solution content of 300 samples using artificial neural networks. The Pearson Correlation Constant (R) was found to be 0.860 for all data. According to the test results obtained with the produced system, the success rate of the artificial neural network in detecting the chemical composition of the nutrient solution ranged from 53.2% to 87.4% depending on the chemical ratios in the nutrient solution.

Development of a Greenhouse Wastewater Stream Utilization System for On-Site Microalgae-Based Biostimulant Production

The challenges to feed the world in 2050 are becoming more and more apparent. This calls for producing more with fewer inputs (most of them under scarcity), higher resource efficiency, minimum or zero effect on the environment, and higher sustainability. Therefore, increasing the circularity of production systems is highly significant for their sustainability. This study investigates the utilization of waste streams from greenhouse hydroponic drainage nutrient solutions for the cultivation of the microalgae Desmodesmus sp. The cultivation was done in an automatically controlled container-scale closed tubular Photo Bio-Reactor (PBR). The study included lab-scale open-pond system experiments and in situ container-scale experiments in the greenhouse wastewater system to assess biomass growth, optical density, nitrogen consumption, and the influence of enzymatic complexes on microalgae cell breakdown. A batch-harvesting process was followed, and the harvested microalgae biomass was pre-concentrated using FeCl3 as a flocculant that has demonstrated efficient sedimentation and biomass recovery. Following microalgae sedimentation, the produced biomass was used for biostimulant production by means of a biocatalysis process. The enzymatic complexes, “EnzProt”, “EnzCell”, and “EnzMix” were tested for cell breakdown, with “EnzMix” at a dosage of 10% showing the most promising results. The results demonstrate successful biomass production and nitrogen uptake in the lab-scale open-pond system, with promising upscaling results within container-scale cultivation. The findings contribute to a better assessment of the needs of Desmodesmus sp. culture and highlight the importance in optimizing culture conditions and enzymatic processes for the production of biostimulants.

Phosphorus recovery from hydroponics waste nutrient solution and its economic potential

Nutrient management, particularly phosphorus, is crucial for global food security due to its limited availability. This study investigates the extraction of phosphorus from hydroponic waste nutrient solutions (HWNS) using samples from various hydroponic farms. The results display elevated phosphorus levels, peaking at 70 mg/L and a median of 20 mg/L, in conjunction with a high median calcium concentration of 220 mg/L. This combination enhances the potential for efficient calcium phosphate precipitation. At a pH of 9.5, phosphorus removal reached consistently high levels, exceeding 94 % and achieving a median value of 97.6 %. The economic value of the recovered phosphorus was then compared to rock phosphates. Through chemical precipitation with micro-calcium phosphate, economic evaluations determined that to achieve production costs comparable to or below the market value of calcium phosphate, HWNS should contain a phosphorus concentration of at least 16 mg P/L and 12.4 mg P/L in the context of Australian and international markets, respectively.

Improving water productivity in the hydroponics with a plasma-nanobubble hybrid technology

Among new technologies aimed at improving water productivity, nanotechnology have been identified as effective means of enhancing the properties of agricultural water. Building on the synergy of plasma and nanobubbles, this study explored the combination of plasma electric discharge and nanocavitation as a novel approach for soilless cultivation. The study aimed to investigate the impact of this hybrid technology on hydroponics nutrient solution. Additionally, the study further aimed to assess the effect of both technologies individually, as well as various application periods, including 3, 9, and 15 min for hybrid technology use. The study employed the nutrient flow technique to hydroponically cultivate lettuce. The findings showed that the application of each technology individually did not significantly increase yield. However, the hybrid technology treatment for 9 min resulted in a significant yield increase of almost 60 %. This improvement can be attributed to the stability, solubility, and absorption of products resulting from plasma treatment, as well as the antimicrobial and anti-algae effects of both technologies. Additionally, an increase in flavonoid and potassium content and a decrease in iron were observed in plants grown under optimal treatment. Overall, this study demonstrated the potential for synergy between plasma and nanobubble techniques in hydroponic culture.

Growth response of mini-paprika ‘Raon red’ to different EC levels of supply nutrient solution in hydroponics using coir substrates

Growth response of mini-paprika ‘Raon red’ to different EC levels of supply nutrient solution in hydroponics using coir substrates

The responses of pepper plants to nitrogen form and dissolved oxygen concentration of nutrient solution in hydroponics

BackgroundThe presence of oxygen in the growth medium is absolutely essential for root development and the overall metabolic processes of plants. When plants do not have an adequate oxygen supply for respiration, they can experience a condition known as hypoxia. In order to investigate the impact of different nitrogen forms and varying oxygen levels in nutrient solutions on the growth, photosynthesis, and chlorophyll fluorescence parameters of bell pepper plants, a comprehensive study was conducted. The experiment was designed as a factorial experiment, considering two main factors: nitrogen forms (calcium nitrate and ammonium sulfate) with a fixed nitrogen concentration of 5 mM, and the oxygen levels of the nutrient solutions (ranging from 1.8 ± 0.2 to 5.3 ± 0.2 mg. L-1).ResultsThe study examined the effects of nitrogen (NH4+ and NO3−) application on various parameters of vegetative growth. The results demonstrated that the use of ammonium (NH4+) led to a reduction in the most measured parameters, including the fresh and dry mass of both the root and shoot, at low O2 concentrations of 1.8 ± 0.2; 2.6 ± 0.2 and 3.8 ± 0.2 mg. L-1. However, an interesting observation was made regarding the impact of oxygen levels on root growth in plants grown with nitrate (NO3−). Specifically, the highest levels of oxygen significantly increased root growth in NO3−-fed plants. Additionally, the application of NH4+ resulted in an increase in chlorophyll concentration in the leaves, particularly when combined with high oxygen levels in the nutrient solution. On the other hand, leaves of plants fed with NO3− exhibited higher photosynthetic rate (A), intrinsic water use efficiency (iWUE), and instantaneous carboxylation efficiency (A/Ci) compared to those fed with NH4+. Furthermore, it was found that NO3−-fed plants displayed the highest instantaneous carboxylation efficiency at oxygen levels of 3.8 and 5.3 mg. L-1, while the lowest efficiency was observed at oxygen levels of 1.8 and 2.6 mg. L-1. In contrast, NH4+-grown plants exhibited a higher maximal quantum yield of PSII photochemistry (Fv/Fm), as well as increased variable fluorescence (Fv) and maximum fluorescence (Fm), compared to NO3−-grown plants. Interestingly, the NO3−-fed plants showed an increase in Fv/Fm, Fv, and Fm with the elevation of oxygen concentration in the nutrient solution up to 5.3 mg. L-1.ConclusionThis study showed that, the growth and photosynthesis parameters in bell pepper plants are sensitive to oxygen stress in floating hydroponic culture. Therefore, the oxygen level in the nutrient solution must not be lower than 3.8 and 5.3 mg. L-1 in NH4+ and NO3− –supplied culture media or nutrient solutions, respectively.

Advantages of a novel in situ pH measurement for soilless media.

Rhizosphere pH determines nutrient bioavailability, but this pH is difficult to measure. Standard pH tests require adding water to growth media. This dilutes hydrogen ion activity and increases pH. We used a novel, in situ, pointed-tip electrode to estimate rhizosphere pH without dilution. Measurements from this electrode matched a research-grade pH meter in hydroponic nutrient solutions. We then compared measurements from this electrode to saturated paste and pour-through methods in peat moss, coconut coir, and pine bark. The pointed-tip electrode was unable to accurately measure pH in the highly-porous pine bark media. Adding deionized water to the other media at container capacity using the saturated paste method resulted in a pH that was 0.59 ± 0.30 units higher than the initial in situ measurement at the top of the container. This increase aligns with established solution chemistry principles. Measurements of pH using the pour-through method were 0.38 ± 0.24 pH units higher than in situ measurements at the bottom of the container. We conclude that in situ pH measurements are not subject to dilution and are thus more representative of the rhizosphere pH than the saturated paste and pour-through techniques.

Effects of Variable Electrical Conductivity Levels in Hydroponic Nutrient Solutions on Morphological and Physiochemical Characteristics of Cucumber Plants in Advanced Greenhouse Cultivation

Cucumber (Cucumus sativus L.) is a fruit of the Cucurbitaceae family that is refreshing, low in calories, and offers various health benefits due to its rich nutritional profile. However, high-tech hydroponic greenhouse production of cucumber is nutrient-intensive and requires efficient management of electrical conductivity (EC) in the growing medium. In this study, three different EC levels (1.3, 2.6, and 3.6 dS/m) were applied to the nutrient medium of hydroponically grown Lebanese and Continental varieties of cucumber. The experiment did not have a significant impact on the number of fruits (p=0.744, p=0.163) or leaves per plant (p=0.252, p=0.377) at varying EC levels. However, in the Continental variety, pH (0.001***) and osmolality (0.005**) were significantly different among the three varied EC levels. High EC levels in the nutrient medium resulted in reduced TSS, pH, and osmolality of the fruit juice. Although the plants grown in low EC conditions produced almost the same number of fruits and leaves per plant as those grown in optimal EC conditions (2.6 dS/m), the physio-chemical attributes of the cucumbers were of inferior quality.

Influence of Nutrient Solutions in an NGS® Soilless System on the Yield, Quality and Shelf Life of Fresh-Cut Commercial Mint at Different Harvest Times

The optimal fertilizer concentration for Mentha plants is contingent on the growing systems and harvest time, serving as operational solutions to control and enhance quality and yield. This study aimed to determine the effects of three macronutrients concentration in hydroponic nutrient solution (HNS) during three harvest times on the growth, quality, yield, and shelf life of three mint species (M. spicata L. var. viridis (MV); M. piperita L. (MP); M. spicata L. var. rubra (MR)) grown in a New Growing System (NGS®). Total dry matter (DM), nitrate (NO3−), phosphate (PO43−), and calcium carbonate (CaCO3) concentrations were increased with the addition of higher levels of nutrient fertilization in three species. When the ion concentration of the HNS was increased, total fresh yield decreased. The highest total bacterial count (TBC) was obtained in MR species in the three harvests in all the levels of HNS. The lowest browning potential (BP) and soluble o-quinone (So-Q) levels were observed at second harvest in the MR species with the application of one of the two HNS high in nitrogen (N). In conclusion, the combination of optimal HNS ion concentration and appropriate species is considered essential to obtain suitable yield, quality, and ensure shelf life of mint.

Hydroponic Nutrient Solution Temperature Impacts Tulane Virus Persistence over Time

Controlled environment agriculture (CEA), or indoor agriculture, encompasses non-traditional farming methods that occur inside climate-controlled structures (e.g., greenhouses, warehouses, high tunnels) allowing for year-round production of fresh produce such as leaf lettuce. However, recent outbreaks and recalls associated with hydroponically grown lettuce contaminated with human pathogens have raised concerns. Few studies exist on the food safety risks during hydroponic cultivation of leaf lettuce; thus, it is important to identify contributing risk factors and potential mitigation strategies to prevent foodborne transmission via hydroponically grown produce. In this study, the concentration of infectious Tulane virus (TV), a human norovirus surrogate, in hydroponic nutrient solution at 15 °C, 25 °C, 30 °C, and 37 °C was determined over a duration of 21 days to mimic the time from seedling to mature lettuce. The mean log PFU reduction for TV was 0.86, 1.80, 2.87, and ≥ 3.77 log10 at 15 °C, 25 °C, 30 °C, and 37 °C, respectively, at the end of the 21-day period. Similarly, average decimal reduction values (D-values) of TV at 15 °C, 25 °C, 30 °C, and 37 °C were 48.0, 11.3, 8.57, and 7.02 days, respectively. This study aids in the (i) identification of possible food safety risks associated with hydroponic systems specifically related to nutrient solution temperature and (ii) generation of data to perform risk assessments within CEA leaf lettuce operations to inform risk management strategies for the reduction of foodborne outbreaks, fresh produce recalls, and economic losses.

Bioaccumulation of Microcystin-LR and Induced Physio-Biochemical Changes in Rice (Oryza sativa L.) at Vegetative Stage under Hydroponic Culture Conditions.

Irrigation with water containing a variety of microcystins (MCs) may pose a potential threat to the normal growth of agricultural plants. To investigate the phytotoxicity of MC-LR at environmental concentrations on rice (Oryza sativa L.), the characteristics of uptake and accumulation in plant tissues, as well as a series of key physio-biochemical process changes in leaves of rice seedlings, were measured at concentrations of 0.10, 1.0, 10.0, and 50.0 μg·L-1 in hydroponic nutrient solutions for 7, 15, 20, and 34 days. Results showed that MC-LR could be detected in rice leaves and roots in exposure groups; however, a significant accumulation trend of MC-LR in plants (BCF > 1) was only found in the 0.10 μg·L-1 group. The time-course study revealed a biphasic response of O2•- levels in rice leaves to the exposure of MC-LR, which could be attributed to the combined effects of the antioxidant system and detoxification reaction in rice. Exposure to 1.0-50.0 μg·L-1 MC-LR resulted in significant depletion of GSH and MDA contents in rice leaves at later exposure times (15-34 days). Low MC-LR concentrations promoted nitric oxide synthase (NOS) activity, whereas high concentrations inhibited NOS activity during the later exposure times. The reduced sucrose synthase (SS) activities in rice exposed to MC-LR for 34 days indicated a decrease in the carbon accumulation ability of plants, and therefore may be directly related to the inhibition of plant growth under MC exposure. These findings indicate that the normal physiological status would be disrupted in terrestrial plants, even under exposure to low concentrations of MC-LR.

Influence of Hydroponics Nutrient Solution on Quality of Selected Varieties of Potato Minitubers

Influence of Hydroponics Nutrient Solution on Quality of Selected Varieties of Potato Minitubers

Strong Invasive Mechanism of Wedelia trilobata via Growth and Physiological Traits under Nitrogen Stress Condition

Nitrogen (N) is one of the most crucial elements for plant growth. However, a deficiency of N affects plant growth and development. Wedelia trilobata is a notorious invasive plant species that exhibits superior tolerance to adapt to environmental stresses. Yet, research on the growth and antioxidant defensive system of invasive Wedelia under low N stress, which could contribute to understanding invasion mechanisms, is still limited. Therefore, this study aims to investigate and compare the tolerance capability of invasive and native Wedelia under low and normal N conditions. Native and invasive Wedelia species were grown in normal and low-N conditions using a hydroponic nutrient solution for 8 weeks to assess the photosynthetic parameters, antioxidant activity, and localization of reactive oxygen species (ROS). The growth and biomass of W. trilobata were significantly (p < 0.05) higher than W. chinensis under low N. The leaves of W. trilobata resulted in a significant increase in chlorophyll a, chlorophyll b, and total chlorophyll content by 40.2, 56.2, and 46%, respectively, compared with W. chinensis. W. trilobata significantly enhanced antioxidant defense systems through catalase, peroxidase, and superoxide dismutase by 18.6%, 20%, and 36.3%, respectively, providing a positive response to oxidative stress caused by low N. The PCA analysis showed that W. trilobata was 95.3% correlated with physiological traits by Dim1 (79.1%) and Dim2 (16.3%). This study provides positive feedback on W. trilobata with respect to its comprehensive invasion mechanism to improve agricultural systems via eco-friendly approaches in N deficit conditions, thereby contributing to the reclamation of barren land.