Concentration In Nutrient Solution Research Articles

The response of barley to salinity stress differs between hydroponic and soil systems

Many studies on salinity stress assume that responses in hydroponics mimic those in soil. However, interactions between the soil solution and the soil matrix can affect responses to salinity stress. This study compared responses to salinity in hydroponics and soil, using two varieties of barley (Hordeum vulgare L.). The responses to salinity caused by high concentrations of Na+ and Cl– were compared to assess any consistent differences between hydroponics and soil associated with a cation and an anion that contribute to salinity stress. Concentrated nutrient solutions were also used to assess the effects of osmotic stress. The effects of salinity differed between the hydroponic and soil systems. Differences between barley cultivars in growth, tissue moisture content and ionic composition were not apparent in hydroponics, whereas significant differences occurred in soil. Growth reductions were greater under hydroponics than in soil at similar electrical conductivity values, and the uptake of Na+ and Cl– was also greater. The relative importance of ion exclusion and osmotic stress varied. In soil, ion exclusion tended to be more important at low to moderate levels of stress (EC at field capacity up to 10 dS m–1) but osmotic stress became more important at higher stress levels. High external concentrations of Cl– had similar adverse effects as high concentrations of Na+, suggesting that Cl– toxicity may reduce growth. Fundamental differences in salinity responses appeared between soil and solution culture, and the importance of the different mechanisms of damage varies according to the severity and duration of the salt stress.

Variation for tolerance to high concentration of ferrous iron (Fe2+) in Australian hexaploid wheat

High concentration of reduced iron (Fe2+) in waterlogged acid soils is a constraint for growing wheat in high rainfall (waterlogged-prone) areas of Western Australia. Growing crop genotypes tolerant to high Fe2+ concentrations may be desirable in such situations, but there is no knowledge about the extent of variability in Fe2+ tolerance in the wheat germplasm. A bioassay for tolerance to high concentrations of iron in wheat was developed and optimised using Siete Cerros (Fe-tolerant) and BH1146 (Fe-intolerant) as control genotypes and a range of FeSO4 concentrations (36, 313, 625, 1250, 1875, 2500 and 3125 μM Fe2+) in nutrient solution in a controlled-temperature environment. Increasing external concentration of iron decreased both shoot and root dry weight, increased shoot iron concentration and intensified the development of toxicity symptoms to a greater degree in intolerant BH1146 as compared to tolerant Siete Cerros. Increased iron supply negatively affected uptake of Ca (r = −0.41) and Mg (r = −0.40). The tolerant genotype Siete Cerros showed an improved avoidance/exclusion of high external concentration of Fe2+ compared with intolerant BH1146. The genotypic discrimination based on relative root dry weight and the development of toxicity symptoms was most pronounced at 625 μM Fe2+. This concentration was chosen for screening of 20 bread wheat and one durum genotype chosen from a preliminary screening of 94 Australian wheat genotypes. A relatively narrow but significant variation (22–38%) in terms of relative root dry weight under Fe2+ toxicity was observed among Australian advanced breeding lines and varieties. The presence of genotypic variation for Fe2+ tolerance across and within the Australian breeding programs could be exploited in a deliberate selection process to enhance Fe2+ tolerance in wheat. Durum wheat (Arrivato) and several Australian wheat varieties and advanced lines in this study were as tolerant to Fe2+ toxicity as Siete Cerros, a variety representing common parentage of iron-tolerant genotypes.

EFFECT OF NUTRITION SOLUTION CONCENTRATION DURING SEEDLING PREPARATION PERIOD ON SEEDLING QUALITY, YIELD AND FRUIT QUALITY IN WATERMELON (Citrullus lanatus)

We studied the effect of different concentration of nutrient solution(1NPK, 2NPK, 4NPK, 6NPK) at seedling preparation stage on seedlinggrowth fruit quality and yield of watermelon.As result, we found that the nutrient solution had remarkable effecton seedling survival ratio, whereas the better treatments were 2NPK and4NPK.

Similarity of nutrient uptake and root dimensions of Engelmann spruce and subalpine fir at two contrasting sites in Colorado

Nutrient uptake capacity is an important parameter in modeling nutrient uptake by plants. Researchers commonly assume that uptake capacity measured for a species can be used across sites. We tested this assumption by measuring the nutrient uptake capacity of intact roots of Engelmann spruce ( Picea engelmanni Parry) and subalpine fir ( Abies lasiocarpa (Hook.) Nutt.) at Loch Vale Watershed and Fraser Experimental Forest in the Rocky Mountains of central Colorado. Roots still attached to the tree were exposed to one of three concentrations of nutrient solutions for time periods ranging from 1 to 96 h, and solutions were analyzed for ammonium, nitrate, calcium, magnesium, and potassium. Surprisingly, the two species were indistinguishable in nutrient uptake within site for all nutrients ( P > 0.25), but uptake rates differed by site. In general, nutrient uptake was higher at Fraser ( P = 0.01, 0.15, 0.03, and 0.18 for NH 4 +, NO 3 −, Ca 2+, and K +, respectively), which is west of the Continental Divide and has lower atmospheric deposition of N than Loch Vale. Mean uptake rates by site for ambient solution concentrations were 0.12 μ mol N H 4 + g fwt − 1 h − 1 , 0.02 μ mol N O 3 − g fwt − 1 h − 1 , 0.21 μ mol C a 2+ g fwt − 1 h − 1 , and 0.01 μ mol M g 2+ g fwt − 1 h − 1 at Loch Vale, and 0.21 μ mol N H 4 + g fwt − 1 h − 1 , 0.04 μ mol N O 3 − g fwt − 1 h − 1 , 0.51 μ mol C a 2+ g fwt − 1 h − 1 , and 0.07 μ mol M g 2+ g fwt − 1 h − 1 at Fraser. The importance of site conditions in determining uptake capacity should not be overlooked when parameterizing nutrient uptake models. We also characterized the root morphology of these two species and compared them to other tree species we have measured at various sites in the northeastern USA. Engelmann spruce and subalpine fir were indistinguishable in specific root length and diameter distribution, while most of the other 10 species had statistically distinct diameter distributions across five diameter classes < 2 mm. Based on specific root length, subalpine fir and Engelmann spruce had significantly coarser roots than red pine ( Pinus resinosa Soland), yellow birch ( Betula allegheniensis Britt.), sugar maple ( Acer saccharum Marsh.), chestnut oak ( Quercus prinus L.), black cherry ( Prunus serotina Ehrh.), and red spruce ( Picea rubens Sarg.). White oak ( Quercus alba L.), balsam fir ( Abies balsamea (L.) Mill.), American beech ( Fagus grandifolia Ehrh.) and loblolly pine ( Pinus taeda L.) were intermediate in SRL (indistinguishable from Engelmann spruce and subalpine fir by ANOVA). Species that differ more in physiology and morphology than the two species we compared would likely show dissimilar uptake characteristics even at the same site.

Nutrient solution concentration and growing season affect yield and quality of Lactuca sativa L. var. acephala in floating raft culture

AbstractBACKGROUND: There is growing interest among consumers in baby leaf vegetables, mostly requested for mixed salads, both as fresh market products and ready‐to‐use vegetables. Fertilisation is one of the most practical and effective ways of controlling and improving the yield and nutritional quality of crops for human consumption. The optimal fertiliser concentration for baby leaf vegetables depends on the environmental conditions. The aim of the present work was to determine the effects of nutrient solution concentration (2, 18, 34, 50 or 66 mequiv L−1) during two consecutive growing seasons (spring and summer) on the yield and leaf quality of Lactuca sativa L. var. acephala grown in a floating system.RESULTS: Marketable fresh yield, total dry biomass, leaf area index, macroelement (N, P, K and Mg) concentrations and nitrate and total chlorophyll contents increased in response to an increase in nutrient solution concentration, while the opposite trend was observed for root/shoot ratio and glucose, fructose, starch, total carbohydrate and protein contents. Plants grown in the spring season exhibited lower yield and growth (total dry biomass and leaf area index) but higher leaf quality (higher carbohydrate content and lower nitrate content) than those grown in the summer season.CONCLUSION: The use of nutrient solution concentrations of 37 and 44 mequiv L−1 for the spring and summer seasons respectively could be adopted in the present conditions to improve marketable fresh yield and leaf mineral content, but with a slight reduction in some nutritional parameters. Copyright © 2009 Society of Chemical Industry

THE EFFECTS OF N CONCENTRATION IN PRE-TRANSPLANT NUTRIENT SOLUTION ON THE N USE EFFICIENCY AND DRY MASS PARTITIONING OF VEGETABLE SOLANACEAE SEEDLINGS

ISHS IV Balkan Symposium on Vegetables and Potatoes THE EFFECTS OF N CONCENTRATION IN PRE-TRANSPLANT NUTRIENT SOLUTION ON THE N USE EFFICIENCY AND DRY MASS PARTITIONING OF VEGETABLE SOLANACEAE SEEDLINGS

Biofiltration of Air Contaminated by Styrene Vapors on Inorganic Filtering Media: An Experimental Study

This paper presents a study on the biofiltration of styrene by using two inorganic filtering materials. The effects of styrene inlet load and nitrogen concentration present in the nutrient solution on biofilter performance were studied. The styrene inlet concentration was varied from 65 to 1115 parts per million by volume (ppmv), whereas the contaminated airflow rate was fixed at 1 m3/hr. The nitrogen concentration in nutrient solution was varied from 1 to 4 gN/L. The maximum elimination capacity obtained was 105 g/m3-hr, which corresponded to a removal efficiency of 80% for a styrene inlet load of 130 g/m3-hr. This study shows that the nitrogen content in the nutrient solution affects the removal rate of styrene, with an optimal nitrogen concentration of 3 gN/L. The performance comparison between two different inorganic bed types was undertaken and a comparative study on biofiltration of two aromatic compounds, styrene and toluene, is also presented.

Potencial de Cajanus cajan e Crotalaria spectabilis parafitorremediação: absorção de arsênio e respostas antioxidativas

Neste estudo, avaliaram-se os efeitos tóxicos do arsênio (As) sobre o crescimento e atividade de enzimas antioxidativas dismutase do superóxido (SOD), catalase (CAT), peroxidases (POX), peroxidase do ascorbato peroxidase (APX) e glutationa redutase (GR) em plantas de Cajanus cajan e Crotalaria spectabili. Plantas das duas espécies foram expostas a diferentes concentrações de As, em solução nutritiva de Hoagland, pH 6,5. A taxa de crescimento relativo (TCR) das duas espécies reduziu-se com o aumento da concentração de As na solução nutritiva, sendo de forma mais intensa em C. cajan. A concentração de As na solução capaz de reduzir em 50% a TCR de C. cajan foi de 0,93 mg L-1, enquanto em C. spectabilis foi de 4,80 mg L-1. As duas espécies apresentaram reduzida translocação de As para a parte aérea, sendo em raízes de C. spectabilis observada a maior concentração desse elemento. C. cajan exposto ao As teve as atividades das enzimas CAT, POX e APX reduzidas, ao contrário do que ocorreu em C. spectabilis. Esta espécie, quando submetida ao As, apresentou incremento na atividade de todas as enzimas avaliadas. A maior tolerância ao As observada em C. spectabilis pode estar relacionada à maior capacidade em reter o As nas raízes e à indução das enzimas SOD, CAT, POX, APX e GR. Dessa forma, C. spectabilis é uma espécie com potencial para utilização em programas de revegetação de áreas contaminadas com As.

The Influence of Drip Irrigation or Subirrigation on Zucchini Squash Grown in Closed-loop Substrate Culture with High and Low Nutrient Solution Concentrations

Zucchini plants (Cucurbita pepo L. cultivar Afrodite) were grown during a summer–fall season in closed-soilless systems using a mixture peat–pumice to evaluate the effects of irrigation system (drip irrigation and subirrigation) and nutrient solution concentration (half = 1 dS·m−1 and full = 2 dS·m−1) in terms of substrate electrical conductivity (ECs) using the dilution 1:1.5 media:water method, growth, yield, leaf mineral composition, fruit quality, and mineral solution composition. At the end of the cultural cycle, the highest ECs at the upper (0 to 7.5 cm) and lower (7.5 to 15.0 cm) layers were recorded with subirrigation using a full nutrient solution concentration. The highest plant growth, yield, and leaf macroelements concentration (nitrogen, phosphorus, and potassium) were recorded in both irrigation systems using a full-strength solution, followed by drip irrigation, and finally by subirrigation treatment using a half-strength nutrient solution. Fruit yield, fruit mineral composition (phosphorus, potassium, calcium, and magnesium), and leaf macroelements concentration (nitrogen, phosphorus, potassium, and magnesium) were substantially reduced when the concentrations of macronutrients in the feed solution were lowered to 50% of control. Using half-nutrient solution concentration, the marketable yield reduction was more pronounced with subirrigation (58%) than with drip irrigation (42%). The variation of the macronutrient and EC in the solution during the growing cycle was less pronounced in the subirrigation than with the drip irrigation system, which represents an important aspect for the simplification of the closed-loop management of the nutrient solution.

Endogenous auxins and branching of wheat roots gaining nutrients from isolated compartments

The auxin content in roots of hydroponically grown wheat (Triticum durum Desf.) plants was affected by imbalanced distribution of nutrients when the root medium fed to plants from isolated compartments. One day after the transfer of seedlings on the nutrient medium with uneven ion distribution, the IAA content in roots contacting concentrated nutrient solution became significantly higher than in roots bathed with a dilute solution. The IAA content reached the peak on the second day and remained steadily high later on. The lateral root primordia developed in these roots were more numerous; the largest difference in this parameter was observed in 1–2 days after the increase in root content of auxin. One day later, numerous lateral roots appeared on the parent roots contacting the concentrated nutrient solution. Thus, the increase in concentration of the nutrient solution bathing a part of root system raised the IAA content in the affected roots prior to the enhanced root branching. This hormonal response of plants might play an important role in changes of root growth rate and root branching, thereby improving plant nutrition.

Accumulation of arsenic and nutrients by castor bean plants grown on an As-enriched nutrient solution

Phytoextraction is a remediation technique that consists in using plants to remove contaminants from soils and water. This study evaluated arsenic (As) accumulation in Castor bean ( Ricinus communis cv. Guarany) grown in nutrient solution in order to assess its phytoextraction ability. Castor bean plants were grown under greenhouse conditions in pots containing a nutrient solution amended with increasing doses of As (0, 10, 50, 100, 250, 500 and 5000 μg L −1) in a completely randomized design with four replications. Shoot and roots dry matter production as well as arsenic and nutrient tissue concentrations were measured at the end of the experiment. The results showed that increasing As concentration in nutrient solution caused a decrease in shoot and root biomass but did not result in severe toxicity symptoms in castor bean growing under a range of As concentration from 0 to 5000 μg L −1. The As doses tested did not affect the accumulation of nutrients by castor bean. Although castor bean did not pose characteristics of a plant suitable for commercial phytoextraction, it could be useful for revegetation of As-contaminated areas while providing an additional income by oil production.

The influence of arsenic speciation (AsIII &amp; AsV) and concentration on the growth, uptake and translocation of arsenic in vegetable crops (silverbeet and amaranth): greenhouse study

We examined arsenic (As) uptake by vegetable crops (amaranth, Amaranthus gangeticus, and silverbeet, Beta vulgaris) as affected by As speciation (As(III) and As(V)) and their concentrations in nutrient solution. Amaranth and silverbeet were grown in a nutrient solution containing four levels of arsenate (As(V)): 0, 1, 5, and 25 mg As/l and three levels of arsenite (As(III)): 0, 5, 10 mg As/l. Both As(V) and As(III) are phytotoxic to these crops with the latter being five times more toxic. Amaranth treated with As(III) exhibited As toxicity symptoms within 48 h of exposure and was close to death within 1 week. However, As(V) treatment did not show clear toxicity symptoms other than wilting and yield reduction at the highest dose rate of 25 mg As(V)/l. The main mechanism used by vegetable crops to tolerate As(V) is probably avoidance-limiting As transport to shoots and increasing As accumulation in the root system. When As(V) was added to the nutrient solution, the uptake of As in shoots increased and, at the highest dose (25 mg As(V)/l), 60 microg As/g DW (3.6 mg/kg FW) accumulated in the edible portion, which exceeds the WHO recommended limit for food stuffs (2 mg/kg FW) as the water contents of the crops were 94%. It is therefore important to determine the nature of the As species and their bio-accessibility. Iron treatment with 0.5 mg NaFe(III)EDTA/l dose decreased silverbeet As uptake by 45% given its affinity to bind As at the root surface or root rhizosphere and so restrict As translocation to the shoots.

Nutrient Solution Prepared with Ozonated Water does not Damage Early Growth of Hydroponically Grown Tomatoes

Ozonated water as a water source for nutrient solution was investigated in hydroponically grown tomatoes. Nutrient solution was prepared by diluting concentrated nutrient solutions with ozonated water with dissolved ozone (DO3) concentrations of 0 to 10 mg L−1. Manganese concentration in the nutrient solution decreased with increasing DO3 concentrations. Initial growth of tomato plants supplied with nutrient solution prepared with ozonated water with a DO3 concentration of 1.5 mg L−1 was greater than that with a DO3 concentration of 0 mg L−1. These results indicate that ozonated water can be used as a disinfectant for source water in hydroponics during the early growth stage of tomatoes.

Concentração da solução nutritiva no crescimento da planta, na produtividade e na qualidade de frutas do morangueiro

O objetivo do trabalho foi determinar o efeito da concentração da solução nutritiva no crescimento da planta, na produtividade e na qualidade das frutas do morangueiro cultivado em sistema fechado de cultivo sem solo. Os tratamentos consistiram de cinco soluções nutritivas com condutividades elétricas (CE) de 0,9; 1,8; 2,5; 3,2 e 3,8dS m-1 no delineamento experimental inteiramente casualizado, com três repetições. Foram determinados os seguintes parâmetros: a produtividade e a qualidade das frutas durante o período de produção e o crescimento da parte aérea e das raízes ao final do experimento. A produtividade, o tamanho das frutas e o crescimento da planta diminuíram com o aumento da concentração da solução nutritiva, enquanto a acidez titulável e o teor de sólidos solúveis totais aumentaram. A solução nutritiva com CE de 0,9dS m-1 reduz o crescimento da planta e maximiza a produtividade de frutas no cultivo sem solo do morangueiro, em sistema fechado.

N AND CA CONCENTRATION OF PRE TRANSPLANT NUTRIENT SOLUTION EFFECTS ON THE STAND ESTABLISHMENT RATE OF PEPPER (C. ANNUM. L) SEEDLINGS UNDER SALINE CONDITIONS

N AND CA CONCENTRATION OF PRE TRANSPLANT NUTRIENT SOLUTION EFFECTS ON THE STAND ESTABLISHMENT RATE OF PEPPER (C. ANNUM. L) SEEDLINGS UNDER SALINE CONDITIONS

DOSES DE NITROGÊNIO, FÓSFORO E POTÁSSIO NA NUTRIÇÃO DO PORTA-ENXERTO CÍTRICO DE LIMOEIRO 'CRAVO'

Neste trabalho avaliou-se o efeito da aplicação de diferentes doses de N, P e K sobre o estado nutricional do porta-enxerto cítrico limoeiro ‘Cravo’. O experimento foi realizado na Faculdade de Ciências Agrárias e Veterinárias – Unesp, sob delineamento experimental em blocos casualizados, em esquema fatorial 33 + 1, com três repetições. As doses padrões de N, P e K foram de 920 mg dm-3, 100 mg dm-3 e 790 mg dm-3, respectivamente. Para compor os tratamentos utilizou-se: D1 – metade da dose padrão, D2 – a dose padrão e D3­ o dobro da dose padrão, além da testemunha (sem adubação). Após a emergência das plântulas, as adubações foram realizadas via fertirrigação, aumentando a concentração dos nutrientes na solução de acordo com o crescimento das mudas. As adubações N e K, em cada unidade experimental, foram realizadas durante quinze semanas. Aos 120 dias após a emergência das plântulas foi realizada a avaliação dos teores de nutrientes na massa seca total e o acúmulo de N, P e K nas plantas. A dose de nitrogênio de 1.840 mg dm-3 proporcionou maior teor e acúmulo de N, para o intervalo de doses aplicado. A aplicação de P e K acima de 100 e 790 mg dm-3 não proporcionou aumento na absorção desses nutrientes, respectivamente.

Optimization of EC Values of Nutrient Solution for Tomato Fruits Quality in Hydroponics System Using Artificial Neural Network and Genetic Algorithms

Total soluble solids (TSS) and fruit fresh weight are two indicators to show the quality of tomato fruits. To gain high values of TSS and fruit fresh weight, it is important to consider the concentration of nutrient solution, which is commonly represented by Electrical Conductivity (EC) value. Generally, the increasing of EC value not only increases the number of TSS, but also decreases fruit fresh weight. Therefore, it is important to optimize the EC value for both indicators of quality of tomato fruits. The objective of this research is to optimize the EC value of nutrient solution on each generative stage using Artificial Neural Network ( ANN) a nd G enetic A lgorithms ( GA). A NN w as u sed t o i dentify t he relationship between different EC value treatments with TSS value and fruit fresh weight. GA was applied to determine the optimal EC value in generative growth, which is divided into three stages. Results showed that the optimal EC values in the flowering stage, the fruiting stage and the harvesting stage were 1.4 mS/cm, 10.2 mS/cm and 9.7 mS/cm, respectively.

The Influence of Fertilization on Greenhouse Tomatoes Cultivated in Peat Bags System

Important factors to be considered for growing tomatoes in order to obtain high and safety yield are variety, system of culture and fertilization. To establish how the fertilization managing can influence both yield and quality of greenhouse tomatoes grown on peat bags system, different doses and types of fertilization (basic and additional) were studied in this experiment. Two Dutch cultivars (Cronos F1 and Menhir F1) with high yield potential were used. Cronos F1 recorded the best early yield (5.87 kg·m -2 ) and Menhir F1 the best total yield (13.06 kg·m -2 ). Foliar fertilization, done with a high K ratio fertilizer (10:5:26), once weekly applied, determined distinct significant efficiencies of early yield and significant efficiencies of total yield. Vitamin C, acidity and total sugar content in the fruit increase with foliar fertilization. None of the nitrate or nitrite values over passed the accepted limits of permission for greenhouse tomatoes. Greenhouse tomatoes grown on peat bags system allows to increase early and total yield in comparison with conventional crop in soil. Because bags contain only a small volume of growth medium, they offer much lower water holding capacity and much lower buffering capacity than most soils regarding both major and minor elements. Therefore it is necessary to monitor continually the nutrient availability in the substrate and to adjust accordingly the composition of feed applied to it. The quantity of nutrients which should be applied also depends on the yield potential of the cultivar and growth conditions. Tomatoes need a continuous and steady supply of nutrients through additional fertilization throughout their life cycle because their vegetative and reproductive stages overlap. Since many experiments have not revealed real differences between the product quality of vegetables grown in soil or hydroponically (Schnitzler and Gruda, 2003) soilless culture in greenhouse may be an alternative to soil culture for high-value vegetable crops including tomatoes. Better tomato fruit quality can be obtained by fertilization measures such as an increase in the concentration of the nutrient solution, or a reduction of nitrate application rates. It is also necessary to adopt appropriate nutrient management practices (use of slow- release fertilizers, split applications, combining of radicular and foliar fertilization) which help to supply nutrients in adequate quantities to just meet crop demand and minimize losses, thus increasing the nutrient use efficiency. The objective of the present study was to evaluate two greenhouse tomato hybrids grown in bags on organic substrate (mostly composed from brown peat) in order to establish how fertilization managing can influence yield and chemical properties of fruit.

Effect of magnesium and potassium interaction on growth, nutrient uptake and related physiological characteristics of rice

摘要: 在温室条件下，采用液体培养方法研究了Mg、K相互作用对水稻生长、养分吸收以及有关生理特性的影响。结果表明，在低Mg浓度条件下，水稻植株干物质积累随K浓度增加而减少；在高Mg条件下水稻植株干物质积累随K浓度增加而相应增加。在低Mg条件下，高浓度K显著抑制植株对Mg、K、N和P的吸收；在高Mg浓度下，植株对Mg、K、N和P的吸收有促进作用。植株叶片叶绿素含量在低Mg条件下随K浓度增加而减少，在高Mg条件下K浓度增加对叶绿素含量无显著影响。叶片硝酸还原酶活性和可溶性蛋白质含量随Mg浓度增加而增加，而K浓度增加对叶片硝酸还原酶活性和可溶性蛋白质含量无明显影响。高Mg条件下的叶片可溶性糖和淀粉含量明显高于低Mg处理，并随K浓度增加而提高。Mg、K营养拈抗作用主要表现在低Mg高K浓度条件下抑制Mg的吸收。 关键词: Mg, / K相互作用 / 水稻 / 养分吸收 / 生理特性

Absorption of aqueous inorganic and organic silicon compounds by wheat and their effect on growth and powdery mildew control

Soluble silicon, absorbed in the form of silicic acid by plant roots, confers efficient protection against many diseases. However, owing to its low solubility, there is a practical limit to increasing silicic acid availability to plants in the field. For this reason, methyl silanols – mono-, di- and trimethyl silicic acid – the water-soluble degradation products of silicone polymer, were evaluated for their ability to protect against powdery mildew in wheat grown under peat-based and hydroponic conditions. X-ray microanalysis indicated that only the monomethyl derivative was absorbed and deposited by wheat plants. Inductively coupled plasma–optical emission spectrometry measurements of total plant Si content confirmed this observation and indicated that monomethyl silicic acid remained mostly in its soluble monomeric form in planta. Mono- and trimethyl silicic acid offered no protection against powdery mildew and, indeed, yielded higher levels of infection than the control. Unexpectedly, dimethyl silicic acid induced severe symptoms of phytotoxicity early into the experiments at nutrient solution concentrations as low as 0.1 mM. For their part, both mono- and trimethyl silicic acid also caused symptoms of phytotoxicity by the end of the experiments. Our findings would suggest that silanols cannot be considered as substitutes for silicic acid in plants. Moreover, application of silicone-contaminated waste or sewage sludge to agricultural land needs to be evaluated with considerable care.