Nutrient Solution pH Research Articles

Effect of Nutrient Solution pH on the Growth and Quality of Lactuca sativa Grown in a Static Hydroponic System

Lettuce is an easy-to-grow and nutrient-rich leafy vegetable. It grows well using a static hydroponic system, which saves space and is easy to maintain. However, understanding pH’s impact on lettuce growth in static hydroponic systems is limited. Hence, this study was conducted to determine the effect of pH nutrient solution on the growth performance and eating quality of lettuce grown in a static hydroponic system. Lettuce was grown in pH 5.2, 6.2, and 7.2 nutrient solutions. Its growth performance was collected weekly, including plant height, root length, number of leaves, leaf area, leaf chlorophyll content, total dry weight, and total moisture content. The harvested lettuce was analyzed for firmness, soluble solids concentration, titratable acidity, pH, and ascorbic acid content by the fourth week after transplanting. The plant height, root length, number of leaves, leaf area, and total dry weight of lettuce were affected by the interaction between nutrient solution pH and weeks after transplanting. By the third week after transplanting, lettuce grown in pH 6.2 was 11.12 and 18.67% taller than those grown in pH 7.2 and 5.2 nutrient solutions, respectively. By the fourth week after transplanting, the firmness of lettuce grown in pH 6.2 was significantly higher than those grown in pH 5.2 and 7.2 nutrient solutions by 2.34 and 7.32%, respectively. It is concluded that lettuce should be grown in a pH 6.2 nutrient solution when using a static hydroponic system.

Effects of LED treatments on the growth and nutritional content of lettuce (Lactuca sativa) in a hydroponic vertical farming system

Introduction: LED-integrated hydroponic vertical farming system (HVFS) may address food security challenges arising from urbanisation, while antioxidants in vegetables may prevent cardiovascular disease. This study aimed to explore the LED effects on yield, antioxidant properties, and vitamin C content in Butterhead lettuce (BL) and Italian lettuce (IL). Methods: Three LED combinations were used: 77% red, 14% green, and 9% blue lights (77R:14G:9B); 7% red, 41% green, and 52% blue lights (7R:41G:52B); and 25% red, 67% green, and 8% blue lights (25R:67G:8B). The concentration and pH of nutrient solution in HVFS ranged from 0.878-2.061ppm and 6.0-6.6, respectively, with a 12:12 light-dark cycle. Chlorophyll and anthocyanin contents were measured using chlorophyll and anthocyanin meters, respectively. Total phenolic and vitamin C content were measured using Folin-Ciocalteu colorimetric assay. Total flavonoid and antioxidant activity were determined through aluminium chloride colorimetric assay and 2,2-diphenyl-1-picrylhydrazyl (DPPH) colorimetric assay, respectively. Completely randomised design was adapted with three replications. Results: BL exhibited greater yield, anthocyanin and chlorophyll contents, while IL had higher vitamin C content. Significantly (p<0.001) higher yields were produced under 77R:14G:9B and 25R:67G:8B. Significantly higher phenolic (p<0.001) and flavonoid (p=0.003) contents were produced under 25R:67G:8B. Vitamin C was significantly (p=0.037) higher under 25R:67G:8B than 7R:41G:52B. Conclusion: LED treatment with higher proportion of red light generated greater yield, whereas higher proportion of green light gave higher phenolic, flavonoids, and vitamin C accumulation. This study provided preliminary data on boosting crop yield and phytochemical contents, which may improve food self-production and population health.

IoT-Based Smart Vertical Hydroponic System for Chili Plant

Agriculture serves as the primary source of food for the global population, playing a critical role in meeting the nutritional needs of people worldwide. With the projected population reaching 9.7 billion by 2050, ensuring an adequate and sustainable food supply becomes increasingly challenging. Hydroponics, a technique that cultivates plants without soil by delivering mineral nutrients through water, offers a potential solution. Hydroponics requires only 10% of the space and 90% less water compared to conventional farming, enabling year-round production of nearly organic food. Vertical hydroponic systems, which arrange plants in stacked or suspended layers, optimize the use of vertical space and are particularly suitable for indoor and urban agriculture where land is limited. However, these systems require regular maintenance and monitoring, including managing nutrient solution balance, pH levels, water quality, and lighting conditions. This complexity can pose challenges for growers lacking time, resources, or technical expertise. To address these issues and ensure sustainability, an automated monitoring method is proposed for vertical hydroponic farming. This project aims to develop a system that automates the checking and maintenance of nutrient levels in the vertical farming process, monitoring factors such as Electrical Conductivity (EC), pH, liquid level, and water temperature. The integration of automation technologies in vertical hydroponics enhances precision, efficiency, and productivity by reducing labour requirements, optimizing resource utilization, and granting growers greater control over the growing environment. These advancements result in healthier plants, higher yields, and more sustainable agricultural practices.

Development of a Hydroponic Growing Protocol for Vegetative Strawberry Production

Hydroponic growing systems are advantageous for nutrient studies in which root data are important because they alleviate the laborious and time-consuming task of washing roots to remove soilless substrate particulates from them. However, the growing system should be optimized for the crop of interest. Our overall objective was to develop a protocol for hydroponic strawberry (Fragaria ×ananassa) production that provided growth equal to or better than soilless substrate. Plants were initially grown in perlite, sand, deep water culture (DWC), or a peat-based soilless substrate. Aboveground plant growth in DWC was similar to that of plants grown in the peat-based substrate and required minimal effort to harvest the entire root system. However, the pH of the DWC nutrient solution decreased to 4.0 ± 0.1 (mean ± SE) when plants were provided a modified strawberry (Yamazaki) nutrient solution with a ratio of nitrate (NO3−) to ammonium (NH4+) of 80:20. As a result, a subsequent trial was conducted to evaluate the buffering capacity of nutrient solutions with NO3− to NH4+ ratios of 0:100, 20:80, 50:50, 60:40, 80:20, or 100:0, with the addition of potassium bicarbonate (KHCO3). Up to 2.6 mM KHCO3 did not provide adequate buffering in nutrient solutions containing NH4+ (0:100 to 80:20 treatments), and nutrient solution pH decreased by ∼1.5 units every 2 to 3 days. The 100% NO3− nutrient solution, however, maintained a stable pH of 5.9 ± 0.1 when buffered with 0.8 mM KHCO3. Finally, 2(N-Morpholino)ethanesulfonic acid (MES) was evaluated as a potential buffering agent for DWC strawberry production. Plants were grown in a nutrient solution with a 60:40 ratio of NO3−:NH4+. The buffering capacity of the nutrient solution increased as the MES concentration supplied increased from 1 to 5 mM, and the 5 mM MES treatment maintained a pH of 5.6 ± 0.2. In summary, strawberry plants can successfully be grown hydroponically in DWC, provided that nutrient solution pH is adequately managed. The addition of MES buffer provided better pH stability than KHCO3.

Influence of different levels of pH of nutrient solution & TDS of micronutrients mixture on vegetative growth, flowering and fruit setting of strawberry (Fragaria x ananassa L.) grown in Aeroponics system

Influence of different levels of pH of nutrient solution & TDS of micronutrients mixture on vegetative growth, flowering and fruit setting of strawberry (Fragaria x ananassa L.) grown in Aeroponics system

Bicarbonate used as a buffer for controling nutrient solution pH value during the growth of hydroponic lettuce

Bicarbonate used as a buffer for controling nutrient solution pH value during the growth of hydroponic lettuce

Morphological and Physiological Mechanism of Activating Insoluble Inorganic Phosphorus of Different Peanut (Arachis hypogaea L.) Varieties under Low Phosphorus

To reduce the application of phosphorus fertilizer and improve phosphorus efficiency in peanut (Arachis hypogaea L.) production, six peanut varieties with different phosphorus activation efficiencies were selected, and the root morphology, physiological indexes, and types and content of organic acids secreted were measured via a hydroponic experiment for 20 days. We analyzed the difference in calcium phosphate activation between peanut seedlings cultivated under low-phosphorus (LP, 0.01 mmol/L KH2PO4) and normal phosphorus (NP, 0.6 mmol/L KH2PO4) conditions and explored the physiological mechanisms of different peanut varieties on the activation efficiency of insoluble inorganic phosphorus. The results showed that under LP conditions, the root length, root surface area, root volume, root tip number, and root activity of the efficient P activation varieties were 18.31%, 17.50%, 15.23%, 20.00%, and 50.90% higher than those of the inefficient P activation varieties respectively. The reduction range of the nutrient solution pH of the high-efficiency varieties was 74.48% higher than that of the low-efficiency varieties under LP conditions. The total amount of organic acid secreted by the efficient P activation varieties increased by 236.07% on average under LP conditions compared with that under NP conditions. In comparison, the average increase in inefficient P activation varieties was only 16.36%. Under low P stress, the peanut varieties with high-efficiency P activation could increase the activation of insoluble inorganic P in the environment mainly by changing the root architecture and increasing the root-shoot ratio, root activity, and root proton and organic acid secretion.

Rhizospheric Precipitation of Manganese by Phosphate: A Novel Strategy to Enhance Mn Tolerance in the Hyperaccumulator Phytolacca americana.

Manganese (Mn) exclusion in the Mn hyperaccumulator pokeweed (Phytolacca americana L.) was investigated. Hydroponic experiments were carried out to observe the responses of pokeweeds continually exposed to high levels of Mn. In this study, crystals were observed to appear firstly on the root hair, and soon after, more crystals appeared on the root surface, and crystals of Mn phosphate were observed to appear on the root surface in a time sequence negatively correlated with the number of leaves treated with 5 mM Mn. Crystals were identified via phase analysis of X-ray diffraction and element analysis, and these white insoluble crystals were identified using XRD to be Mn phosphate, with the molecular formula (Mn,Fe)3(PO4)2·4H2O. The nutrient solution pH increased from 4.5 to about 5.6 before the crystals appeared. Mn phosphate crystals appeared in all solutions except those without phosphate and emerged earlier in the solutions containing no Fe. Compared with control group, pokeweed accumulated much more Mn in the leaves when treated without phosphate or Fe. The present study suggests that pokeweed can exclude Mn by means of rhizosphere precipitation by phosphate to form Mn phosphate crystals that accumulate on the root surface. Although the detailed mechanism requires further investigation, this study provides the first direct evidence of a novel strategy to inhibit Mn uptake in the roots of a hyperaccumulator in a P-enriched environment.

Relationships of Water Quality Parameters for Hydroponic Production of Kale (Brassica oleracea) with In-Ground Passive Cooling System

Greenhouses in Philippines are encountering high ambient air temperature problem. Along with this, the water quality directly affects the growth, development and yield of hydroponically grown plants. This study was conceptualized through the principle of cooling the nutrient solution that will effectively regulate plant’s growth and yield with relatively low investment and easier management. One of the essential elements of a functional hydroponics system is water quality monitoring, hence this study utilized a monitoring system for water quality parameters. Nutrient solution was closely monitored to maintain and ensure that nutrient levels are not too low to inhibit growth and not too high to be potentially toxic. The study was conducted to develop a monitoring system for environmental and water quality parameters of in-ground passive cooling system for hydroponic production of kale. Specifically, the study aimed to determine the relationships of water quality parameters such as pH, EC, TDS, and temperature for kale production, compare the performance of an in-ground passive cooling system (IGPCS) and without cooling system (Control) on hydroponically grown kale, and to evaluate the water productivity of the in-ground passive cooling system. This study utilized both in-ground passive cooling system (IGPCS) and control (without cooling system) to compare its performance based on the growth and yield of the kale, and to determine the water productivity of utilizing IGPCS. In addition, water quality parameter such as pH, EC, TDS, and temperature were closely monitored using the installed monitoring system, and relationships of these water quality parameters were established. The gathered data were analyzed using trend analysis in Microsoft Excel, Analysis of variance (ANOVA) was computed in Completely Randomized Design (CRD) and comparison among means were compared using Least Significant Difference (LSD) Test at 5% level. Results revealed that EC and TDS of nutrient solution are inversely proportional to pH and temperature of nutrient solution, moreover EC and TDS are directly proportional, also with pH and temperature of nutrient solution. The performance of the IGPCS and without cooling system is comparable with growth and yield of kale in terms of leaf length, leaf width, number of leaves, weight and yield at harvest, but are significantly affected by the location of growing pipes where crops received less and ample amount of sunlight. Since the temperature of IGPCS was reduced up to 3°C, kale plants with cooling system uptake less water compared to without cooling system and results to higher productivity. Therefore, regulating one of the water quality parameters directly affects other water quality parameters, so relationships of these water quality parameters were established through close monitoring of water quality parameters using the monitoring system. Utilization of IGPCS reduced the temperature of the nutrient solution up to 3°C which gave higher yield (44.01 g/plant) than without cooling system (41.18 g/plant). Kale production in tropical areas can have higher yield using the in-ground passive cooling system that reduced water consumption, resulting to higher productivity.

Bicarbonate rather than high pH in growth medium induced Fe-deficiency chlorosis in dwarfing rootstock quince A (Cydonia oblonga Mill.) but did not impair Fe nutrition of vigorous rootstock Pyrus betulifolia.

Quince A (Cydonia oblonga Mill.), a typical dwarfing rootstock in pear cultivation, is susceptible to iron (Fe) deficiency in calcareous soils. The aim of this study was to compare the strategies in Fe uptake and utilization in dwarfing rootstock quince A (low Fe efficiency) versus a typical vigorous rootstock Pyrus betulifolia (PB) with high Fe efficiency. Quince A and PB were grown in nutrient solution (pH 6.3) for 4 weeks followed by three pH treatments: pH6.3, pH8.3a (adjusted with hydroxide) and pH8.3b (adjusted with bicarbonate). The Fe uptake and utilization indicators of the rootstocks were assessed at the onset of chlorosis symptoms (after 58 days of treatments). In contrast to PB, quince A exhibited Fe deficiency chlorosis under bicarbonate (pH8.3b). Bicarbonate stimulated the root proton secretion, inhibited root growth and ferric chelate reductase (FCR) activity in both PB and quince A, whereas high pH without bicarbonate (pH8.3a) stimulated only root proton release. Both species accumulated more Fe in roots under high pH treatments than under pH6.3, resulting in Fe sufficiency in leaves. Both high pH treatments increased the activity of leaf FCR in PB and quince A. However, extractable Fe(II) concentration in leaves was increased by high pH treatments in PB only. This study demonstrated that depressed Fe(III) reduction in leaves caused by bicarbonate rather than high pH explained Fe deficiency in quince A grown in bicarbonate-containing medium.

Nonlinear Adaptive Generalized Predictive Control for PH Model of Nutrient Solution in Plant Factory Based on ANFIS

A plant factory is typically considered to be an exceedingly advanced product management system characterized by higher crop yields and better quality control. The pH value of the nutrient solution is crucial for determining the health and productivity of crops. However, the nutrient solution process exhibits inherent complexity, such as parameters uncertainty, multi-disturbances, and strong nonlinearity. Therefore, the traditional control method cannot meet the necessary requirements. The main objective of this paper is to address the issues of parameter uncertainty, strong nonlinearity, and multiple disturbances in the regulation process of the nutrient solution while achieving accurate control of the nutrient solution pH in a plant factory. This is performed so that a dynamic model of a nutrient solution for pH is developed and a nonlinear adaptive controller is presented, which comprises a linear adaptive generalized predictive controller, a nonlinear adaptive generalized predictive controller, and a switching mechanism. The parameters of the controller are adjusted by generalized predictive control (GPC) laws. In this approach, an adaptive neuro-fuzzy inference system (ANFIS) is used to estimate the unmodeled dynamics to depress the influence of nonlinearity on the system. The experiments show that the mean errors and standard errors for gain-scheduling the proportional-integral-derivative (PID) control strategy are 0.1388 and 0.4784, respectively. The mean errors and standard errors for the nonlinear adaptive controller are 0.1046 and 0.3009, respectively. Simulation results indicate that the presented method can acquire a better control effect in the case of various complex situations. Therefore, by achieving precise control of the pH value, it is possible to provide a suitable growth environment for crops, promoting healthy crop growth and increasing crop yield.

Precise Management of Hydroponic Nutrient Solution pH: The Effects of Minor pH Changes and MES Buffer Molarity on Lettuce Physiological Properties

The precise management of the nutrient solution pH is substantial for optimizing the growth and yield of hydroponically cultivated crops. Nutrient solution pH affects the solubility and availability of essential nutrients; however, during hydroponic cultivation, the pH of nutrient solution fluctuates due to unbalanced ion absorption by plants. Nutrient solution pH fluctuations might be passively controlled using a supplementary buffering agent. Nutrient solution characteristics such as pH and buffering agent molarity must be addressed simultaneously. Therefore, in this study, we aimed to evaluate hydroponically cultivated lettuce’s physiological response to minor nutrient solution pH differences and the impact of supplementary buffering agent molarity on its growth, antioxidant activity, and mineral nutrient uptake. Green lettuce (Lactuca sativa (L.)) ‘Hugin’ was cultivated in deep water culture (DWC) hydroponics in a controlled environment replicating common vertical farming conditions, and nutrient solution pH impact within the range of 5.0–6.5 was evaluated every 0.5 pH unit. Initial nutrient solution buffer capacity was enhanced by adding MES (2-(N-morpholino) ethanesulfonic acid) at 0, 1, 3, and 5 mM concentrations. Results show that even small nutrient pH differences are reflected in plant physiological responses, indicating the significance of precise pH management. Even though dry weight accumulation is not affected by the pH 5.0–5.5 treatment, it increases root antioxidant response according to ABTS (2,2-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) radical scavenging activity. An initial nutrient solution buffer capacity increment with 3 mM of MES (2-(N-morpholino) ethanesulfonic acid) supplementary buffering agent resulted in a 17% yield increase compared to a nutrient solution without an additional buffering agent. MES buffer can provide adequate, passive, and precise nutrient solution pH control within the pH range of 6.0–6.5.

Optimizing Plant Growth and Crop Productivity through Hydroponics Technique for Sustainable Agriculture: A Review

A promising, economically viable and profitable form of cultivation is hydroponics. The findings of the present study indicate that the productivity as well as quality of different leafy vegetables and high valuable fruit crops (litchi etc) was significantly improved by adopting hydroponic techniques. The pH and EC of nutrient solution play an important role in this technique which directly affects the plant response. Article discusses how hydroponics can produce sustainable food while addressing issues such as climate change, lack of arable land and poor soil quality. The article highlights several hydroponic growing media and the importance of pH and dissolved solids (TDS) in a hydroponic fertilizer solution. The potential of hydroponics for Indian farmers and the need for education to facilitate their adoption is discussed at the end of the article. Presently the different substances are used to support plants, aerate them, promote maximum root growth and implement various hydroponic cultivation techniques. This paper also describes the different hydroponic techniques like nutrient film technique (NFT), deep water culture (DWC) and Ebb and flow etc and their mechanisms, applicability and advantages. Along with different hydroponics techniques the effectiveness of hydroponic growing media has also been investigated, with the best results obtained from nutrient film technique along with coconut peat as a growing media.

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.

Assessing Opportunities and Difficulties in Hydroponic Farming

Background: Hydroponics or water-culture-based agricultural systems are devoted to a reasonable prospect for future farming agriculture production. Especially in that region where the fertility of agricultural land is continuously going to there is a decline in groundwater level for irrigation. Hydroponics-based agriculture system realizes an admiring action towards an eco-friendly system and innovative technique to overcome challenges concerning food safety. Hydroponics is an advanced agriculture technique in which the plants grow without soil and without any pesticide use. It is used to grow plants, vegetables and shrubs on vertical as well as horizontal basis in the series and parallel. It could be applied via glass pots, clay pots, PVC pipes and useless plastic buckets and bottles. Methods: In the present study vegetables, flowering plants and shrubs were grown successfully by the use of mainly three techniques of hydroponics namely Kratky, Wick and DFT methods. This study was continued for two and half years (4th July 2020 to 21st March 2021 and December 2019 to April 2020) with controlled pH and TDS of the nutrient solution and conducted at different Indian climatic, weather and seasonal conditions at Markanda National College,Shahabad Markanda and at the researcher’s home. Several vegetables and plants were grown from Kratky, Wick and DFT hydroponics methods under continuous monitoring of pH and TDS of nutrient solutions. Result: During the conduction of this study of the growth of mustard, ladyfinger, spinach, marigold, daisy basil (Tulsi), cucumber, cauliflower, broccoli, tomatoes, peas, peppermint, coriander leaves plants in different sessions; some challenges and opportunities were discussed. The main objective of this research study is to spread awareness about novel types of advanced future agricultural techniques or farming among the farmers and masses, who have an interest in agriculture but cannot fulfill their ambitions towards agriculture farming due to scarcity of agricultural land. The results obtained from the growth of vegetable and plant through hydroponics methods province us to follow an idea to use of such agricultural techniques. We have grown several below said crops/vegetables two or three times and face several problems. It is an opportunity to overcome the world’s food scarcity at a large scale, if adopted by a large population all over the world.

Elevated CO2 concentration induces changes in plant growth, transcriptome, and antioxidant activity in fennel (Foeniculum vulgare Mill.).

Fennel (Foeniculum vulgare Mill.) is widely used to produce natural bio-materials. Elevated CO2 (eCO2) concentrations in the atmosphere improve the net photosynthesis of plants. The aim of the present study was to investigate distinct changes in fennel growth characteristics and phytonutrient contents under different CO2 concentrations. The effects of 400 and 800 ppm concentrations on plant growth and antioxidant activity were observed under hydroponics. Plant growth was improved by eCO2 concentrations. We also observed diverse changes in nutrient solution (pH, electrical conductivity, and dissolved oxygen) and environmental factors (temperature and humidity) in greenhouse under light or dark conditions. Electrical conductivity increased under dark and eCO2 conditions, whereas the pH decreased. Additionally, we performed transcriptome analysis and identified CO2-responsive differentially expressed genes. In the 800 ppm group, genes involved in photosynthesis and Karrikin response were upregulated whereas those involved in syncytium formation were downregulated. Four upregulated differentially expressed genes involved in flavonoid biosynthesis and total flavonoid content were relatively increased under the 800 ppm CO2 condition. In contrast, antioxidant activity, including total phenolic content, scavenging activity, ferric ion reducing antioxidant power, and reducing power were decreased in fennel under relatively high eCO2 concentrations. Moreover, different light intensities of 12 or 24 lx did not affect the growth and antioxidant activity of fennel, suggesting eCO2 has a stronger effect on plant improvement than light intensity. The results of the present study enhance our understanding of the positive effects of CO2 on the growth and antioxidant activity of fennel.

PH buffering of nutrient solutions with differing water quality in small-scale hydroponic systems

Nutrient solution pH and water quality are challenges faced by small-scale hydroponic growers. The objective was to evaluate the use of the pH buffer 2-(N-morpholino) ethanesulfonic acid (MES) as an initial dose to simplify pH management in small-scale hydroponic systems, and its effectiveness within the range of alkalinity that commonly occurs in irrigation water. Two experiments tested pH buffering capacity in response to acid-base titrations, and when growing compact tomatoes (Lycopersicon esculentum) over a nine-week cycle. MES was applied at 0 to 10 mM in water and nutrient solutions at five water qualities ranging from 4 to 295 mg.L−1 CaCO3 alkalinity. Solution buffering increased with addition of fertilizer, increasing doses of MES, and increasing water alkalinity. The MES decreased pH variability over time in all water qualities, without affecting plant growth or causing nutritional disorders. The pH of solutions without MES ranged from 4.5 to 8.0 over the growing cycle, whereas in 10 mM MES solutions it ranged from 5.7 to 7.0 for alkalinities 0 to 146 mg.L−1 CaCO3 and reached 7.6 for 295 mg.L−1 CaCO3. Titration of nutrient solutions after tomato growth indicates that MES acid-buffering capacity was partially consumed along the trial, which was probably the result of MES decomposition or interaction with acids and bases in solution. Results indicate that a single 10 mM MES application could be used by small-scale hydroponic growers to provide acceptable pH buffering for low to moderate alkalinity levels, but initial pH adjustment may be necessary and solution pH may still increase with high alkalinity.

Increasing media pH contribute to the absorption of boron via roots to promote the growth of citrus

Low pH is an important limiting factor for plant development in the south of China due to problems of acid red soil and boron (B) deficiency. Whereas, there is very limited information on the relationship between media pH and B distribution in plant, the physiological process changed by the interaction of pH and B in citrus growth also unclear. This experiment was conducted on trifoliate rootstock by employing two different concentrations of B (0 or 10 μM B) under three pH levels: pH 4, pH 5, and pH 6. Our results illustrate that low pH inhibite plant growth and cause oxidative stress in the roots, resulting in cell membrane injury. The increase of pH and B addition reduce the accumulation of ROS (O2.- and H2O2) by regulating the activity of Class Ⅲ peroxidases (CIII Prxs). Moreover, increased pH improves the internal circulation of B in plants and decrease the content of lignin and cellulose in cell wall (CW). In summary, our investigation demonstrated that the increase of pH in nutrient solution can accelerate the re-distribution of B by roots to promote citrus growth. The accumulation of B in roots can protect plants from the damage of ROS by regulating the activity of CIII Prxs as well as decrease the content of lignin and cellulose are to promotes roots elongation.

Iron Chelate Improves Rooting in Indole-3-Butyric Acid-Treated Rosemary (Rosmarinus officinalis) Stem Cuttings

Adventitious root formation in stem cuttings is affected by exogenous and endogenous factors. The study assessed the effect of Fe(III)-EDDHA (ethylenediamine-N,N-bis 2-hydroxyphenyl acetic acid) on the rooting of 4 indol-3-butyric acid (IBA)-treated hardwood cuttings of the aromatic and medicinal species Rosmarinus officinalis. Cuttings treated with 0, 1000, 2000 or 3000 mg L−1 IBA were placed in pots filled with sand:perlite mixture and irrigated daily with nutrient solution pH 5.8, containing 0, 5, 10 or 20 µM Fe(III)-EDDHA. Ten days later, the number of new emerging roots were recorded. After 20 days, leaf photosynthetic pigments and morphological traits, including root number, fresh (FW) and dry weight (DW), shoot FW and DW, mean length of the longest roots, number of new shoots and new growth in old shoots, were measured. Finally, plants were transplanted to pots filled with a sand:soil mixture and survival was measured after 10 days. Results indicate that Fe application promotes root emergence and improves root and shoot biomass, leaf photosynthetic pigment concentrations and survival percentage. This indicates that using low concentrations of Fe(III)-EDDHA (5–20 µM) in the growth medium could be a good management strategy to facilitate the production of vigorous R. officinalis plants from hardwood cuttings.

The Development of Hydroponic Nutrient Solutions Control Using Fuzzy and BPNN for Celery Plant

As the increasing number of human populations, most live in urban areas with limited farmlands. Hydroponic is one of the solutions to grow crops in urban areas. Electrical Conductivity (EC) and scale of acidity (pH) in the hydroponic nutrient solution are the important things to be controlled. Controlling EC and pH in hydroponic can increase the quantity and quality of the crop. This research suggested a new method to merge fuzzy and Backpropagation Neural Network (BPNN) to control nutrient solutions in a Nutrient Film Technique hydroponic, with sensors EC and pH as input. The training data of BPPN are obtained from the implementation of the fuzzy technique. Controlling nutrient solutions can use fuzzy methods, but it has a weakness: use greater power because sensors require continuous detection. By using BPNN method, sensors only detect once to perform the same control action. In this research, the outputs of both methods are the duration of pumps in active conditions to optimize the nutrient solution. Based on experiments, the best BPNN model has eight hidden layers with a learning rate of 0.8. The result accuracies which had been obtained by alkaline solution (pump A) was 90.77 %, 91.93% for acid solution (pump B), and 91.13% for nutrient fertilizer (pumps C and D). The result showed that the use of power for BPNN is less than fuzzy. The average total power used for BPNN method is 68.43% lower than the fuzzy method.