Influence of potassium and manganese on growth and uptake of magnesium by soybeans (Glycine max (L.) Merr. cv. Bragg)

Summary Soybean (Glycine max (L) Merr. cv. Bragg) seedlings were grown in nutrient solutions to evaluate the response to manganese nutrition as affected by potassium supply. In solutions containing 275 M manganese, increasing the solution concentration of potassium from 1 mM to 10 mM alleviated symptoms of manganese toxicity, decreased manganese concentrations in the leaves and increased dry matter yields of the plants. The reduction in manganese toxicity was brought about by a reduced rate of root absorption of manganese at high potassium supply levels.Increasing the supply of either potassium or manganese decreased the leaf concentration of magnesium although there were no apparent symptoms of magnesium deficiency in any treatment. The reduced concentration of magnesium in the leaves was due to effects of potassium and manganese on the rate of root absorption of magnesium.Under manganese deficiency conditions, growth was reduced and manganese concentrations in plant parts were very low; there was no effect of potassium supply when manganese was absent from the nutrient solution.     

Manganese deficiency of sugar beet in organic soils

Summary The manganese content of sugar beet grown in pots of organic soils taken from fields where crops regularly show symptoms of manganese deficiency, and the effects on it of foliar sprays of manganous sulphate and of manganous oxide or manganese silicate frit applied to the soil, of changing the soil pH, air-drying the soil, and growing the plants either in the glasshouse or outside were determined. All the manganese treatments increased the concentration of manganese in the plants and decreased deficiency symptoms, but increased the dry matter yield only slightly. Increasing the pH by liming greatly increased symptoms and decreased the manganese concentration in the dry matter; air-drying the soil before cropping had the opposite effect. Plants grown in pots of the same soil in the glasshouse or outdoors showed similar symptoms and had similar manganese content.The concentration of manganese in the leaves was related to the percentage of plants with deficiency symptoms and to the concentration of active soil manganese. Leaves usually had symptoms when the concentration of manganese in the dried leaves was less than 30 ppm, and always had severe symptoms when they contained less than 15 ppm Mn. The soil analyses suggest that sugar beet grown in organic soil with pH greater than 7.0 and containing less than 40 ppm active soil manganese is likely to show deficiency symptoms.     

Integrated effect of irrigation frequency and phosphorus level on lettuce: P uptake, root growth and yield

The objective of the present research was to assess the effects of fertigation frequency on plant phosphorus and water uptake. Special attention was given to root measurement in order to elucidate the mechanism that relates the fertigation frequency to P uptake and plant growth. Lettuce (Lactuca sativa L., cv. Iceberg) grown in pots filled with quartz sand was chosen as a test plant. The experiment comprised six treatments, with two concentrations of P in irrigation water (0.2 mM and 1.0 mM), and three daily fertigation frequencies (one, four and ten). It was found that high irrigation frequency induced a significant increase in plant-P concentration at low solution-P concentration, whereas at high P concentration the effect of irrigation frequency was insignificant. Increasing the irrigation frequency significantly enhanced the transpiration flux so that the transpiration flux of plants under low irrigation-P level at 10 daily irrigation events was similar to that of plants under high solution-P. The increases with irrigation frequency of P concentration in lettuce organs and of P influx to the roots, at the low P level, were attributed to the elimination of the depletion zone at the root-soil interface by the supply of fresh nutrient solution, and the enhancement of P uptake. The higher P uptake resulted from higher convective flux of dissolved P from the substrate solution to the root surface owing to the higher average moisture content associated with frequent irrigation. The only significant correlation revealed by multiple stepwise regressions relating nutrient concentrations in the plant to yield was that between plant-P concentration and the yield. On the basis of a quadratic regression, 97% of the dry weight variation could be explained by differences in P uptake, indicating that the main effect of fertigation frequency was related to an improvement in P mobilization and uptake. Thus, frequent irrigations may compensate for P shortage.     

Mineral nutrient disorders of root crops of the Pacific: Preliminary observations on sweet potato (Ipomoea batatas)

Solution culture was used to characterise deficiencies or toxicities of several essential elements in Ipomoea batatas cv. Wanmun, and to define the critical concentrations of these elements in young mature leaves during vegetative growth. Tentative critical concentrations for deficiency, expressed on the basis of dry weight of leaf blade, were: nitrogen 3.8%, phosphorus 0.17%, potassium 2.4%, magnesium 0.12%, manganese 20g/g and zinc 10g/g. For manganese and zinc toxicities it was possible only to designate the range within which the critical concentration occurred. Visible symptoms are briefly described.     

Genotypic variation in partitioning of dry matter and manganese between source and sink organs of rice under manganese stress

Key message

Genetic variability in dry matter and manganese partitioning between source and sink organs was the key mechanism for Mn efficient rice genotypes to cope with Mn stress.

Abstract

Considerable differences exist among cereal genotypes to cope manganese (Mn) deficiency, but the underlying mechanisms are poorly understood. Minimal information regarding partitioning and/or remobilization of dry matter and Mn between source and sink organs exists in rice genotypes differing in Mn efficiency. The present study was aimed to assess the growth dynamics in terms of dry matter and Mn remobilization in the whole plant (leaves and tillers as source and panicles and grains as sink) during the grain development in diverse rice genotypes. The efficient genotypes accumulated higher dry matter than inefficient genotypes under low Mn level. The translocation index i.e., uptake in grain/total uptake was 0.11 in efficient genotype (PR 116) and 0.04 in inefficient genotypes (PR 111). The efficient genotype had higher grain Mn utilization efficiency of 0.71 in comparison to 0.48 of inefficient genotype indicating that in efficient genotype, Mn in grain produces more dry matter than inefficient genotypes. The efficient genotypes also had higher flag leaf area and nitrate reductase activity. The source of efficient genotypes contributed to a greater extent to developing sink but further mobilization to grain was hindered by panicle. The panicle of inefficient genotypes had higher per cent of Mn uptake than efficient genotypes indicating that Mn was least mobilized from panicle to grain in inefficient genotypes. The lower per cent uptake of Mn in efficient genotypes indicated that Mn was mobilized from panicle to developing grain and this led to higher Mn translocation index in grain of efficient genotypes. The uptake partitioning revealed that source of all genotypes mobilized the Mn towards the sink to almost same extent but it was the panicle where highest per cent uptake per plant was in inefficient genotypes and lowest in efficient genotypes. The lowest per cent uptake in panicle of efficient genotypes revealed that it supported developing grain to have highest translocation index.     

The reduction in zinc concentration of wheat grain upon increased phosphorus-fertilization and its mitigation by foliar zinc application

Background and aims

Malnutrition resulting from zinc (Zn) and iron (Fe) deficiency has become a global issue. Excessive phosphorus (P) application may aggravate this issue due to the interactions of P and micronutrients in soil crop. Crop grain micronutrients associated with P applications and the increase of grain Zn by Zn fertilization were field-evaluated.

Methods

A field experiment with wheat was conducted to quantify the effect of P applications on grain micronutrient quality during two cropping seasons. The effect of foliar Zn applications on grain Zn quality with varied P applications was tested in 2011.

Results

Phosphorus applications decreased grain Zn concentration by 17–56%, while grain levels of Fe, manganese (Mn) and copper (Cu) either remained the same or increased. Although P applications increased grain yield, they restricted the accumulation of shoot Zn, but enhanced the accumulation of shoot Fe, Cu and especially Mn. In 2011, foliar Zn application restored the grain Zn to levels occurring without P and Zn application, and consequently reduced the grain P/Zn molar ratio by 19–53% than that without Zn application.

Conclusions

Foliar Zn application may be needed to achieve both favorable yield and grain Zn quality of wheat in production areas where soil P is building up.     

The effect of iron supply on the yield and composition of leaves of tomato plants

Summary This paper describes a factorial experiment which was designed to elucidate the effect of total iron supply and rate of iron supply on the yield of tomato plants. Information was also obtained on the effect of iron supply and leaf age on the concentration of a number of nutrient elements in the leaf tissue.Increasing the total iron supply increases the yield, and the iron concentration in the leaves, while the manganese, phosphorus, sodium, calcium and magnesium decrease in concentration. The young leaves have a lower concentration of iron, manganese, potassium, sodium, calcium and magnesium than the older leaves, while the reverse is true of nitrogen and phosphorus. A slow rate of iron supply decreases the yield and sodium concentration in the leaves but increases the manganese and phosphorus concentrations.Interaction between total iron supply and leaf position affects the manganese, potassium, calcium and magnesium concentrations in the leaves, while the interaction between total-iron level and rate of iron supply affects the phosphorus and calcium concentration in the leaves.     

Fluorescence and reflectance characteristics of manganese deficient soybean leaves: Effects of leaf age and choice of leaflet

Leaf reflectance and fluorescence characteristics of soybean (Glycine max cv Bragg) are influenced strongly by Mn availability. This report evaluates the effects of leaflet choice, leaf age, and leaf nodal position on several spectral characteristics. Leaves were obtained from soybeans grown hydroponically under controlled environmental conditions with wide differences in Mn supply. The ratio of constant yield fluorescence (F_o) to variable yield fluorescence (F_v), the ratios of reflectance at 750 nm to 550 nm and that at 650 nm to 550 nm, the position of the "red edge" near 700 nm, and an index of leaf "yellowness" were measured periodically. Increasing leaf age caused increases in the "red edge" and in both reflectance ratios. Leaf "yellowness" and the fluorescence ratio F_o/F_v decreased with leaf age and increased with leaf nodal position, primarily in Mn deficient leaves. Effects arising from leaf choice were smaller than those caused by Mn deficiency.     

High fertigation frequency: the effects on uptake of nutrients, water and plant growth

The objective of the present research was to explore the effects of combined irrigation and fertilization (fertigation) frequency on growth, yield and uptake of water and nutritional elements by plants. Lettuce (Lactuca sativa L., cv. Iceberg) was used as the model plant. Two experiments were conducted in a screen-house: compound fertilizer at a constant N:P:K ratio at different concentrations was used in the first, while in the second the concentration of P varied solely while the concentration of the other nutritional elements was kept constant. The lettuce was planted in pots filled with perlite and irrigated daily with a constant volume of nutrient solution at different frequencies. The major finding in the two experiments was that high fertigation frequency induced a significant increase in yield, mainly at low nutrients concentration level. Yield improvement was primarily related to enhancement of nutrient uptake, especially P. It was suggested that the yield reduction obtained at low frequency resulted from nutrient deficiency, rather than water shortage, and that high irrigation frequency can compensate for nutrient deficiency. Frequent fertigation improved the uptake of nutrients through two main mechanisms: continuous replenishment of nutrients in the depletion zone at the vicinity of root interface and enhanced transport of dissolved nutrients by mass flow, due to the higher averaged water content in the medium. As such, an increase in fertigation frequency enables to reduce the concentrations of immobile elements such as P, K and trace metals in irrigation water, and to lessen the environment pollution by discharge.     

The suppression of salinity-associated oxygen radicals production, in pepper (Capsicum annuum) fruit, by manganese, zinc and calcium in relation to its sensitivity to blossom-end rot

We investigated the possibility that oxidative stress contributes to blossom-end rot (BER) initiation in bell pepper ( Capsicum annuum L.) grown under high salinity. Pepper plants (cv. Mazurka, Rijk Zwaan, the Netherlands) were grown in a greenhouse and irrigated with nutrient solution made up with either desalinated water (control — rising from E.C. 1.9 to 2.4 dS m⁻¹) or saline water (salinity – rising from E.C. 3.2 to 7.0 dS m⁻¹). Irrigation was by a circulation system. BER symptoms were observed throughout the experiment but were highly enhanced in the salinity–grown plants during the spring and summer. The fruit calcium concentration was not affected by salinity, but manganese concentrations in both leaves and fruits were significantly reduced under these conditions. Under salinity there was an enhancement of apoplast reactive oxygen species (ROS) production, which was partly a result of increase in NAD(P)H oxidase activity in the pericarp of pepper fruit at the stage that it was most sensitive to BER. Apoplast ROS production and extracted NAD(P)H oxidase activity were inhibited by manganese, zinc and to a lesser extent by calcium. These cations also negated the enhancement of ROS production caused by incubation of fruit pericarp discs in NaCl solutions. Manganese, zinc and calcium also inhibited NAD(P)H oxidase activity, extracted following their infiltration into fruit pericarp discs. The results suggest that generation and scavenging of oxygen free radicals in the apoplast may contribute to the appearance of BER symptoms in pepper fruits under saline conditions. It is suggested that manganese may serve as antioxidant in pepper fruit and that manganese addition to peppers grown under salinity may alleviate BER symptoms in the fruits.     

TRACE-ELEMENT TOXICITIES IN OAT PLANTS

Excessive amounts of nickel, cobalt, chromium, copper, zinc, manganese, molybdenum and aluminium in nutrient solutions supplied to oat plants in sand culture produce ( a ) chlorosis and ( b ) other symptoms specific to the element involved. The specific symptoms are distinct for each metal, although those of cobalt and nickel might be confused.
The toxic effects of nickel, cobalt, copper, zinc, manganese and molybdenum are associated with high concentrations of the element in the leaf tissue, but this is not always so with chromium and aluminium.
The toxic effects of nickel, chromium, copper and molybdenum are associated with a reduced nitrogen content of the plant. Nickel, cobalt, chromium, zinc and manganese increase the concentration of phosphorus in the tissue whilst aluminium decreases it, probably to a deficiency level.
Aluminium reduces the intensity of toxic symptoms produced by nickel—probably by reducing the uptake of nickel and phosphorus. Copper effectively reduces the leaf necrosis produced by nickel, but not the nickel content of the leaf tissue; it is suggested that one factor in nickel toxicity may be inhibition of one or more functions of copper. The other elements slightly increase chlorosis and some increase necrosis.
The order of activitjl of the elements in producing chlorosis is found to be Ni>Cu>Co>Cr>Zn>Mo>Mn. This order, which is related to that giving yield reduction and is similar to the order of stability of metal complexes, is discussed in relation to induced iron deficiency.     

Iron deficiency in peach trees: effects on leaf chlorophyll and nutrient concentrations in flowers and leaves

The effects of iron deficiency on the leaf chlorophyll concentrations and on the macro- (N, P, K, Ca and Mg) and micro-nutrient (Fe, Mn, Zn and Cu) composition of flowers (at full bloom) and leaves (60 and 120 days after full bloom) of field-grown peach (Prunus persica L. Batsch) trees were investigated. Flowers and leaves were taken and analysed from fifty individual trees. Our data indicate that large decreases in leaf chlorophyll concentration were found at the beginning of the season in control trees, possibly associated to a dilution effect by leaf growth, that were later followed by leaf chlorophyll concentration increases. Leaf Fe chlorosis apparently results from two different processes, the dilution of leaf Chl caused by growth and the subsequent inability to produce and/or stabilize new Chl molecules in the thylakoid membrane. Iron chlorosis did not change the seasonal change patterns of any of the nutrients studied. In Fe-deficient trees the K concentration and the K/Ca ratio were high not only in leaves but also in flowers, indicating that this is a characteristic of Fe-deficient plant tissue in the whole fruit tree growing season. Flower Fe concentrations were well correlated with the degree of chlorosis developed later in the season by the trees, suggesting that flower analysis could be used for the prognosis of Fe deficiency in peach.     

Influence of Varied Phosphorus Supply on Growth and Xylem Sap Cytokinin Level of Sycamore (Platanus occidentalis L.) Seedlings

Effects of varying levels of phosphorus (P) on sycamore (Platanus occidentalis L.) growth and on the endogenous cytokinin levels in the xylem sap were tested. The seedlings were grown in aerated nutrient solutions in the greenhouse. Photoperiod was held constant at 16 hours. Four P concentrations, 0.02, 0.10, 0.50, and 2 mm, were used. There were no P deficiency symptoms even at the lowest P concentration. The maximum growth occurred in seedlings grown in 0.10 mm P. The greatest dry matter yield as well as stem height, stem diameter, and leaf area were produced at 0.10 or 0.50 mm P. The amount of cytokinin in xylem sap for each harvest during P nutrition followed closely the dry matter values, stem height, stem diameter, and leaf area.     

Manganese and iron interactions on their uptake and distribution in soybean (Glycine max (L.) Merr.)

Summary The uptake and distribution of iron and manganese were studied in a manganese-sensitive soybean cultivar (‘Bragg’) grown over a range of supply levels of these nutrients in solution culture. At high (90 and 275 μM) manganese levels, increasing the iron concentration in solution from 2 to 100 μM partially overcame the effects of manganese toxicity. Interactions between manganese and iron occurred for dry matter yields, rate of Mn absorption by the roots, and the proportions of manganese and iron transported to the tops. No interaction was observed for the rate of root absorption of iron. The percentage distribution of manganese in the plant top increased with increasing iron, despite a reduced rate of Mn uptake. On the other hand, iron uptake was independent of solution Mn concentration and increased with increasing solution Fe. Also more iron was retained in the roots at high Mn and/or Fe levels in solution. Concentrations of manganese and iron in roots, stems and individual leaves were affected independently by the manganese and iron supplyi.e. without any interaction occurring between the two elements. In general, the concentration in a plant part was related directly to the solution concentration. Symptoms resembling iron deficiency correlated poorly with leaf Fe concentrations whereas high levels of manganese were found in leaves displaying Mn toxicity symptoms.     

The Translocation and Redistribution of Manganese in Avena

⁵⁴Mn present in the first two leaves of oat seedlings subsequentlydeprived of manganese was later redistributed to leaves 4 and5. ⁵⁴Mn was found in leaves 3 and 4 even when the roots of seedlingswere excised immediately after exposure to ⁵⁴Mn, but more wasdetected if the roots were left intact. ⁵⁴Mn applied as a drop to the 4th leaf of manganese-deficientoat plants was concentrated in the stem and translocated primarilyto the youngest developing leaf or to the grain if present.⁵⁴Mn was readily detected in the roots but almost none was translocatedto the first three leaves. More ⁵⁴Mn was translocated in 96hrs. than 24, but little or no more was translocated in 192hrs. Plants which were given 0.5 p.p.m. stable manganese until theyreached the 4th leaf stage, and were then exposed to ⁵⁴Mn, showeda fairly uniform distribution of ⁵⁴Mn throughout the plant.There was relatively slight concentration at active growth centres. It is concluded that physiologically significant redistributionof manganese occurs in the oat plant.     

Leaf anatomy and chloroplast ultrastructure of Mn-deficient orange plants

Leaf samples of Mn-deficient and Mn-sufficient (control) ‘Navelate’ orange plants grown in a greenhouse were taken to investigate the effects of Mn deficiency in leaf structure and chloroplast ultrastructure. Total leaf chlorophyll concentration was significantly lower in Mn-deficient plants than in control ones. Entire lamina thickness was not altered due to Mn deficiency. However, Mn deficiency resulted in disorganization of mesophyll cells, mainly of palisade parenchyma cells. The number of mesophyll chloroplasts per cellular area and their length were both affected negatively. The membranous system of chloroplasts was also disorganized. The percentages of starch grains and plastoglobuli per chloroplast of Mn-deficient leaves were significantly greater than those of control leaves.     

Micronutrient Deficiency Influences Plant Growth and Activities of Superoxide Dismutases in Narrow-leafed Lupins

The effect of copper (Cu), zinc (Zn) or manganese (Mn) deficiencyon the growth and activity of superoxide dismutase (SOD) formswas investigated in seedlings of narrow-leafed lupins (LupinusangustifoliusL.). Plants grown without Zn developed Zn deficiencysymptoms 24 d after sowing (DAS), and those grown without Mnshowed Mn deficiency symptoms 31 DAS. However, plants grownwithout Cu did not show visible leaf symptoms. Shoot dry weightwas decreased by Zn and Mn deficiency 24 DAS, and by Cu deficiency31 DAS. Soluble protein concentration was reduced considerablyby Zn deficiency 24 DAS, but was not affected by Cu deficiencyuntil 31 DAS. In contrast, soluble protein concentration inMn-deficient plants was higher than in control plants 31 DAS.Shoot concentration of micronutrients which were not suppliedto plants decreased significantly, with a simultaneous increasein concentration of one or more of the other nutrients analysed.The activities of total SOD, MnSOD and Cu/ZnSOD on a fresh weightbasis declined drastically in -Cu and -Zn plants 24 DAS. Onthe contrary, the activities of total SOD and Cu/ZnSOD on eithera fresh weight or soluble protein basis increased markedly in-Mn plants 24 DAS, and MnSOD activity increased significantlyin these plants 31 DAS. It was concluded that micronutrientdeficiency (Cu, Zn or Mn) altered the activities of SOD formsdepending on the kind and severity of the deficiency stress.Manipulation of the capacity of plants to tolerate oxidativestress may influence their capacity to tolerate micronutrientdeficiency.Copyright 1999 Annals of Botany Company. Copper,Lupinus angustifolius, manganese, deficiency, superoxide dismutase, zinc.     

Influence of Phosphorus on Gas Exchange and Plant Growth of Two Morphologically Distinct Types of Capsicum Annuum

Tolerance to phosphorus stress was studied in Capsicum annuum L. Chile ancho cv. San Luis and bell pepper cv. Jupiter plants. Plants were fertilized weekly with Long-Ashton nutrient solution (LANS) modified to supply 0, 11, 22, 44, 66, or 88 g(P) m^-3 (P0, P11, P22, P44, P66, P88). Phosphorus stress occurred in both cultivars at P0 and P11, with reduced plant growth and development. At P0, the lowest percentage of total biomass was directed toward reproductive growth. The root/shoot ratio was greatest at P0, reflecting greater dry matter partitioning to the root system. Growth of ‘San Luis’ was more sensitive to phosphorus stress than ‘Jupiter’. A greater percentage of total biomass was directed towards reproductive growth in ‘Jupiter’ than ‘San Luis’. Increasing P nutrition elevated leaf tissue P in both cultivars with highest leaf tissue P at P88. There were no differences in tissue P between P0 and P11 ‘San Luis’ plants, whereas P0 ‘Jupiter’ plants had the lowest tissue P. Low P-plants generally had the highest tissue N and lowest S, Mn, and B. In both cultivars, gas exchange was lowest at P0, as indicated by reduced stomatal conductance (g_s) and net photosynthetic rate (P_N). Internal CO₂ concentration and leaf-to-air vapor pressure difference (VPD) were generally highest with P-stressed plants. Phosphorus use efficiency, as indicated by P_N per unit of leaf tissue P concentration (P_N/P), was highest at P11. Generally, no P treatments exceeded the gas exchange levels obtained by P44 (full strength LANS) plants. Both P_N and g_s declined during reproductive growth in ‘San Luis’, which fruits more rapidly than ‘Jupiter’, whereas no reduction in gas exchange occurred with ‘Jupiter’. This revised version was published online in September 2006 with corrections to the Cover Date.     

Experiments on effects of phosphorus on the manganese nutrition of plants

Summary Monocalcium phosphate (MCP), the salt of concentrated superphosphate, applied to a Buganda soil increased the amount of manganese taken up by ryegrass. To investigate the cause of this effect the derivatives of MCP hydrolysis, dicalcium phosphate (DCP) and triple-point solution (TPS) were separated and applied independently. Both derivatives, and a synthetic dicalcium phosphate dihydrate, increased the concentration of manganese in ryegrass showing that dissolution of soil manganese by TPS (pH 1.48) was not a unique cause.DCP derived by hydrolysis of MCP supplied little phosphorus to early crops of ryegrass but a larger proportion of its P was taken up by later crops; TPS supplied more of its P to earlier than to later crops. During 42 weeks the proportions of P taken up from DCP and TPS were similar to the proportions of phosphorus in these forms when MCP hydrolyzes.Phosphorus in DCP derived by hydrolysis of MCP was more available to ryegrass than phosphorus in a synthetic dicalcium phosphate dihydrate, showing that results may be misleading when synthetic materials are used to simulate the compounds that form from fertilizers in soil. re]19760401     

Enhancement of artemisinin concentration and yield in response to optimization of nitrogen and potassium supply to Artemisia annua

Background and Aims

The resurgence of malaria, particularly in the developing world, is considerable and exacerbated by the development of single-gene multi-drug resistances to chemicals such as chloroquinone. Drug therapies, as recommended by the World Health Organization, now include the use of antimalarial compounds derived from Artemisia annua – in particular, the use of artemisinin-based ingredients. Despite our limited knowledge of its mode of action or biosynthesis there is a need to secure a supply and enhance yields of artemisinin. The present study aims to determine how plant biomass can be enhanced while maximizing artemisinin concentration by understanding the plant''s nutritional requirements for nitrogen and potassium.

Methods

Experiments were carried out, the first with differing concentrations of nitrogen, at 6, 31, 56, 106, 206 or 306 mg L⁻¹ being applied, while the other differing in potassium concentration (51, 153 or 301 mg L⁻¹). Nutrients were supplied in irrigation water to plants in pots and after a growth period biomass production and leaf artemisinin concentration were measured. These data were used to determine optimal nutrient requirements for artemisinin yield.

Key Results

Nitrogen nutrition enhanced plant nitrogen concentration and biomass production successively up to 106 mg N L⁻¹ for biomass and 206 mg N L⁻¹ for leaf nitrogen; further increases in nitrogen had no influence. Artemisinin concentration in dried leaf material, measured by HPLC mass spectroscopy, was maximal at a nitrogen application of 106 mg L⁻¹, but declined at higher concentrations. Increasing potassium application from 51 to 153 mg L⁻¹ increased total plant biomass, but not at higher applications. Potassium application enhanced leaf potassium concentration, but there was no effect on leaf artemisinin concentration or leaf artemisinin yield.

Conclusions

Artemisinin concentration declined beyond an optimal point with increasing plant nitrogen concentration. Maximization of artemisinin yield (amount per plant) requires optimization of plant biomass via control of nitrogen nutrition.Key words: Artemisia, fertigation, malaria, nitrogen, nutrition, potassium