Manganese Toxicity in Sugarcane Plantlets Grown on Acidic Soils of Southern China

Ratoon sugarcane plantlets in southern China have suffered a serious chlorosis problem in recent years. To reveal the causes of chlorosis, plant nutrition in chlorotic sugarcane plantlets and the role of manganese (Mn) in this condition were investigated. The study results showed that the pH of soils growing chlorotic plantlets ranged from 3.74 to 4.84. The symptoms of chlorosis were similar to those of iron (Fe) deficiency while the chlorotic and non-chlorotic plantlets contained similar amount of Fe. Chlorotic plantlets had 6.4-times more Mn in their leaf tissues compared to the control plants. There was a significantly positive correlation between Mn concentration in the leaves and the exchangeable Mn concentration in the soils. Moreover, leaf Mn concentration was related to both seasonal changes in leaf chlorophyll concentration and to the occurrence of chlorosis. Basal stalks of mature sugarcanes contained up to 564.36 mg·kg^-1 DW Mn. Excess Mn in the parent stalks resulted in a depress of chlorophyll concentration in the leaves of sugarcanes as indicated by lower chlorophyll concentration in the leaves of plantlets emerged from basal stalks. Ratoon sugarcane plantlets were susceptible to chlorosis due to high Mn accumulation in their leaves (456.90–1626.95 mg·kg^-1 DW), while in planted canes chlorosis did not occur because of low Mn accumulation (94.64–313.41mg·kg^-1 DW). On the other hand, active Fe content in chlorotic plantlets (3.39 mg kg^-1 FW) was only equivalent to 28.2% of the concentration found in the control. These results indicate that chlorosis in ratoon sugarcane plantlets results from excessive Mn accumulated in parent stalks of planted cane sugarcanes grown on excessive Mn acidic soils, while active Fe deficiency in plantlets may play a secondary role in the chlorosis.     

Photooxidative Damage in Young Leaves of Declining Grapevine: Does It Result from a New and Possibly Viroid-Related Disease?

Leaves of chlorotic plants of Vitis vinifera were investigatedfor physiological and ultrastructural disorders by comparingthem with leaves of apparently healthy plants from a vineyard,where infection with Hop Stunt Viroid F (HSVdg) and GrapevineYellow Speckle Viroid I (GYSVdl) was widespread. In affectedplants, chlorosis was much stronger in young and developingthan in old and fully expanded leaves. Chemical analyses failedto reveal mineral deficiencies. The quantum yield of photosynthesiswas decreased in chlorotic leaves. A decrease in the numberof PSI reaction centers was also observed. Persisting photoinhibitionoccurred only in leaves of affected plants. The redox stateof cellular and extracellular ascorbate and increased levelsof glutathione indicated oxidative stress in affected plants.Ultrastructural analysis revealed both swelling and loss ofthylakoids even in young chlorotic leaves and other pathologicalchanges. Symptoms were similar to those normally observed onlyin old senescing leaves. However, chlorotic leaves showed unexpectedlyhigh protein levels, though aging is known to lead to proteindegradation. (Received April 30, 1996; Accepted October 14, 1996)     

Iron availability in plant tissues-iron chlorosis on calcareous soils

The article describes factors and processes which lead to Fe chlorosis (lime chlorosis) in plants grown on calcareous soils. Such soils may contain high HCO₃ ^- concentrations in their soil solution, they are characterized by a high pH, and they rather tend to accumulate nitrate than ammonium because due to the high pH level ammonium nitrogen is rapidly nitrified and/or even may escape in form of volatile NH₃. Hence in these soils plant roots may be exposed to high nitrate and high bicarbonate concentrations. Both anion species are involved in the induction of Fe chlorosis.Physiological processes involved in Fe chlorosis occur in the roots and in the leaves. Even on calcareous soils and even in plants with chlorosis the Fe concentration in the roots is several times higher than the Fe concentration in the leaves. This shows that the Fe availability in the soil is not the critical process leading to chlorosis but rather the Fe uptake from the root apoplast into the cytosol of root cells. This situation applies to dicots as well as to monocots. Iron transport across the plasmamembrane is initiated by Fe^III reduction brought about by a plasmalemma located Fe^III reductase. Its activity is pH dependent and at alkaline pH supposed to be much depressed. Bicarbonate present in the root apoplast will neutralize the protons pumped out of the cytosol and together with nitrate which is taken up by a H⁺/nitrate cotransport high pH levels are provided which hamper or even block the Fe^III reduction.Frequently chlorotic leaves have higher Fe concentrations than green ones which phenomenon shows that chlorosis on calcareous soils is not only related to Fe uptake by roots and Fe translocation from the roots to the upper plant parts but also dependent on the efficiency of Fe in the leaves. It is hypothesized that also in the leaves Fe^III reduction and Fe uptake from the apoplast into the cytosol is affected by nitrate and bicarbonate in an analogous way as this is the case in the roots. This assumption was confirmed by the highly significant negative correlation between the leaf apoplast pH and the degree of iron chlorosis measured as leaf chlorophyll concentration. Depressing leaf apoplast pH by simply spraying chlorotic leaves with an acid led to a regreening of the leaves.     

Photosynthetic carbon fixation in iron-chlorotic and recovered green sugarcane leaves

Summary Sugarcane var. Co 740 is grown in various parts of Maharashtra (India) and is susceptible to chlorosis due to physiological non-utilization of iron. The physiological disorder is seen over a large area and it results in poor yield. Low sucrose yield can be recovered by foliar sprays of ferrous sulphate. The nonchlorotic and chlorotic leaves were used for the photosynthetic studies. The leaves after ferrous sulphate treatment show an increase in total chlorophyll contents and at the same time show an improved chlorophylla to chlorophyllb ratio which is affected in the chlorotic ones. The recovered green leaves have higher uptake of nitrogen, phosphorus, potassium and iron.¹⁴CO₂ fixation studies for short- and long-term experiments reveal that recovered green leaves can synthesize malate more efficiently and also utilize it for sucrose synthesis more rapidly than in the chlorotic ones. On the contrary more amino acids, reducing sugars and sugar phosphates are synthesized in the chlorotic leaves. There is also an accumulation of citrate, glutamate, and tartrate in the chlorotic leaves. Our results indicate that sucrose synthesis is disturbed in the chlorotic leaves and can be corected byfolia: sprays of ferrous sulphate.     

The effect of soil moisture on the tolerance of Lupinus pilosus genotypes to a calcareous soil

Commercial narrow-leafed lupins (Lupinus angustifolius L.) grown on calcareous soils commonly display chlorotic symptoms resembling Fe deficiency. The severity of chlorosis increases with concurrent increases in soil moisture content. Our research has indicated that the rough-seeded lupin species, Lupinus pilosus Murr., has a range of adaptation to calcareous soils, from tolerant to intolerant. A pot experiment was conducted comparing a tolerant, a moderately tolerant and a moderately intolerant genotype of L. pilosus. Plants were grown for 35 days in a calcareous soil (50% CaCO₃) at three moisture contents (80%, 100% and 120% of field capacity); the growth was compared with that on a fertile black cracking clay control soil at 70% of field capacity. Visual chlorosis score, chlorophyll meter readings, number of leaves and shoot dry weights were recorded at 14, 21, 28 and 35 days after sowing. Concentrations of chlorophyll, active Fe and nutrients in the youngest fully expanded leaves were also measured. Results showed that increased soil moisture increased the severity of chlorotic symptoms (increased chlorosis score) in all genotypes. The tolerant genotype showed significantly less symptoms than other genotypes at all moisture contents. All genotypes were able to recover from chlorosis symptoms at 80% moisture in the calcareous soil. Chlorosis score negatively correlated with chlorophyll meter readings, chlorophyll concentration and foliar active and total Fe, and Mn concentrations. Visual chlorosis score appeared to be a cost effective, accurate and efficient method enabling classification of the tolerance of genotypes. The chlorotic symptoms were likely to be due to HCO₃ ^- induced nutrient deficiencies or a direct effect of HCO₃ ^- on chlorophyll synthesis. This study indicates that the most probable mechanism of tolerance is related to an ability to prevent uptake of HCO₃ ^- or efficiently sequester it once inside the root which prevents increases in internal pH and transport to the shoots.     

Ethylene-Induced Chlorosis in the Pathogenesis of Bipolaris sorokiniana Leaf Spot of Poa pratensis

Endogenous ethylene of Poa pratensis leaves infected by Bipolaris sorokiniana was evaluated as a factor in leaf chlorosis during pathogenesis. Detectable increases in endogenous ethylene of leaves of intact plants under normal ambient pressure occurred 12 hours after inoculation and was maximum at 48 hours; from 48 to 96 hours the ethylene progressively decreased. Necrotic lesions surrounded by chlorotic halos occurred on infected leaves between 24 and 48 hours. Midvein chlorosis interconnecting individual lesions and complete chlorosis of all tissues not directly affected by the lesions occurred between 72 and 96 hours, after maximum production of ethylene at 48 hours. The chlorophyll loss in infected leaves by 96 hours was 44% compared with controls.

Subjecting inoculated leaves of intact plants to a controlled atmospheric-environmental system with an atmospheric pressure of 233 millibars and O₂ and CO₂ partial pressures adjusted to approximately that of normal ambient pressure during infection and disease development prevented most midvein chlorosis and complete chlorosis, but did not prevent necrotic lesion or chlorotic halo development. Under the hypobaric conditions, chlorophyll loss during disease development was reduced to 22% compared with controls at 96 hours. The observations suggest that ethylene may function late in pathogenesis of this host-pathogen interaction and is responsible for much of the chlorophyll loss after its maximum production at 48 hours.

     

Influence of Iron Chlorosis on Pigment and Protein Metabolism in Leaves of Nicotiana tabacum L

Experiments were conducted on Nicotiana tabacum, L. to study the relation in the grana among chlorophylls, carotenoids, and proteins. The effect of iron chlorosis on protein and pigment synthesis was studied at different stages of chlorosis using glycine-U-C¹⁴. Pigments were separated by thin layer chromatography.

Chlorophyll a, chlorophyll b, carotenoid, and protein contents of chloroplasts from chlorotic tissue were less than those of normal tissues. A 25% decrease in protein labeling and a 45% decrease in chlorophyll labeling was noted in deficient tissue compared to normal tissue even before chlorosis was perceptible. Both normal and iron deficient leaf discs which received iron in the incubation medium incorporated higher amounts of radioactive glycine into chlorophyll a and chlorophyll b at all stages of development than their respective counterparts not supplied with iron in the incubation medium. The presence of iron in the incubation medium reduced the amount of glycine incorporated into carotenes and xanthophylls, except where the tissue was severely chlorotic. This may be attributed to active competition for glycine between the iron-dependent- (chlorophyll) and iron-independent-(carotenoid) biosynthetic pathways. Incorporation of glycine into chloroplast pigments was lowest at severe chlorosis, probably due to a reduction in the overall enzyme activity.

     

Studies on rose mosaic disease in field-grown roses produced in the United Kingdom

Arabis mosaic virus (AMV) and prunus necrotic ringspot virus (PNRSV), separately or together, caused in field-grown roses the range of symptoms recognised as rose mosaic disease. PNRSV infection alone generally induced chlorotic line patterns, ring-spots or mottles in the leaves at some time during the growing season; AMV plus PNRSV normally caused chlorotic vein-banding. However, during prolonged periods of high temperatures (c. 21 °C or more) vein banding occurred in some roses infected only with PNRSV. Isolates of PNRSV from rose had particles which were similar in shape, protein mol. wt, density and sedimentation coefficients to previously described isolates of PNRSV from cherry, plum and rose; all were cherry serotypes. In graft-inoculated roses, apple serotypes of PNRSV induced stunting and chlorosis, puckering and distortion of leaves, which closely resembled symptoms associated with rose mosaic in the USA and chlorotic mottle rose mosaic in New Zealand. To avoid possible confusion in using the name rose mosaic it is suggested that the virus(es) present in roses should be named.     

Effect of selected soil factors on chlorosis of peanut plants grown in calcareous soils in Cyprus

In 1986 and 1987 surveys were conducted of 34 (1986) and 35 (1987) peanut (Arachis hypogaea L.) fields in which the plants showed various degrees of chlorosis. In the areas concerned, plant appearance was classified according to a chlorotic index and corresponding soil samples were taken and analysed for CaCO₃, pH, NO₃–N and DTPA-extractable Fe in 1986 and for CaCO₃, NO₃–N and active lime in 1987.Regression analyses showed that CaCO₃, active lime and NO₃–N were positively correlated, while DTPA-extractable Fe was negatively correlated, with the chlorosis problem. The critical levels above which plants were chlorotic were 20 to 25% CaCO₃ and 10% active lime. Plants began to be chlorotic when DTPA-extractable Fe was below 2.5 mg·kg^–1. The soil factors examined explained about 60% of the variability in plant chlorosis.     

A new technique of plant analysis to resolve iron chlorosis

Summary Iron though indispensable for the biosynthesis of chlorophyll, its total content in the plant was not associated with the occurrence of chlorosis. In order to overcome this inconsistency a new technique of plant iron analysis has been developed. It consists of the determination of Fe²⁺, the fraction of iron involved in the synthesis of chlorophyll.The choice of 1–10 o-phenanthroline (o-Ph) as an extractant for Fe²⁺ was based on its remarkably higher stability constant for Fe²⁺ than Fe³⁺. On this basis, it could preferentially chelate Fe²⁺. The highly specific organce colour of the Fe²⁺-phenanthroline complex made possible the determination of Fe²⁺ by reading the transmittancy at 510 nm.The procedure involves extraction of 2 g of thoroughly washed, chopped, fresh plant by 20 ml of o-phenanthroline extractant (pH 3.0, conc. 1.5%). The plant samples treated with the extractant are allowed to stand for 16 hours and Fe²⁺ is determined in the filtrate by reading the transmittancy at 510 nm.In sharp contrast to total iron the green plants always contained more Fe²⁺ than chlorotic plants. The technique has been developed for rice but is expected to be successful for other crops also.     

Influence of dietary fibre on plasma and urinary levels of zearalenone and metabolites in swine

The genusAlternaria is responsible for different plant diseases such as tobacco brown spot, tomato blight, and citrus seedling chlorosis but can also be present during storage of grain. The objective of the present paper is to summarize the knowledge concerning regulation of secondary metabolism inAlternaria, particularA alternata (A tenuis). The paper mainly deals with regulation of polyketide biosynthesis, one of the major pathways leading to the biosynthesis of mycotoxins inAlternaria. The mostly studiedAlternaria mycotoxins are dibenzopyrones such as alternariol (AOH) and alternariol monomethyl ether (AME) and altenuene along with the tetramic acid tenuazonic acid. The biosynthesis ofAlternaria mycotoxins has been reviewed by Stinson (12). Most information is available for the biosynthesis of the polyketides AOH / AME while a few biosynthetic studies have been accomplished for tenuazonic acid (11).     

Effects of Some Growth Regulators on Young Iron Deficient Maize Plants

Young maize plants, grown hydroponically, were supplied with 1/10 the optimal amount of iron (0.75 mg dm^–3). Foliar treatments with solutions, containing N⁶-benzyladenine (BA), indole-3-acetic acid (IAA) or (2-chloroethyl)-trimethylammoniumchloride (CCC) were conducted after chlorosis had been well manifested. Changes in growth, chlorophyll content, rate of photosynthesis, catalase and peroxidase activities in leaves, and the contents of Fe, Cu, Zn, Mn, and P in leaves were recorded. Growth regulators improved (CCC, IAA) or aggravated (BA) the physiological state of chlorotic plants. Their effect might be explained by changes in Fe transport towards the leaves, by increased efficiency of Fe utilization, and by effects on plant metabolism not involving Fe.     

Development of plants from leaf discs of variegatedColeus and its relation to patterns of leaf chlorosis

Summary Leaf discs approximately 8 mm in diameter taken from green and from chlorotic areas of variegated leaves ofColeus were grown in light under sterile conditions in a mineral salt, sucrose, vitamin medium supplemented with auxin and cytokinin. Green shoots, which later formed roots, grew from both green and chlorotic discs in media containing suitable amounts of auxin and cytokinin. None developed in media supplemented with auxin alone or with cytokinin alone. Discs with young plants were transferred to soil. Plants that grew varied widely from those with no chlorosis to those with more chlorosis than the original variety from which the discs were taken. Plants grown from discs taken from green areas of leaves with chlorosis varied in patterns of chlorosis as much as those that grew from discs from chlorotic areas of leaves. This research was supported, in part, by The Conservation and Research Foundation.     

First Report of Tomato infectious chlorosis virus on Tomato in Bulgaria

Virus‐like chlorotic symptoms were observed on tomato plants, cv. Velocity, grown in a greenhouse, region of Plovdiv. Samples collected from the leaves with interveinal yellowing and with initial interveinal chlorosis were tested for virus presence. Only the samples collected from the upper leaves with slight interveinal chlorosis were positive for Tomato infectious chlorosis virus (TICV) in indirect ELISA. Further, RT‐PCR analysis with specific primers for Tomato chlorosis virus (ToCV) heat shock protein 70, for TICV heat shock protein 70 and for TICV minor capsid protein was positive for TICV in all tested samples. No signals were obtained with primers for ToCV. Phylogenetic analysis showed that the Bulgarian sequence of Hsp70 and a sequence of Greek isolate clustered together having the highest resampling score. Regarding CPm, the Bulgarian isolate was more relevant to the French isolate. The obtained results from phylogenetic analysis supported the idea of a close relationship between the Bulgarian and Greek isolates.     

Bicarbonate,the most important factor inducing iron chlorosis in vine grapes on calcareous soil

Summary In pot experiments grape vine was grown on a calcareous and on a non calcareous soil with a low and with a high water saturation. During the growing period soil solution samples were collected and analyzed for their pH and for HCO ₃ ⁻ , phosphate, Fe, and Ca. High water saturation resulted in a pH increase and in an increase of the HCO ₃ ⁻ concentration in both soils. The level in pH and HCO ₃ ⁻ , however, was much higher in the calcareous soil than in the non calcareous soil. The Fe concentration varied much throughout the experimental period, but there was no major differences between soils and water saturation treatments. The Ca concentration of the soil solution increased with time in the calcareous soil; for the non calcareous soil rather the reverse was true. The phosphate level in the soil solution of the non calcareous soil was about 10 times higher than in the calcareous soil. After 3 weeks growth all plants of the calcareous soil with the high water saturation showed first symptoms of Fe deficiency. These became more intense from day to day. Plants of the other treatments did not show any chlorotic symptoms. In the treatment with the chlorotic plants the HCO ₃ ⁻ concentration of the soil solution was the highest, the phosphate concentration the lowest from all treatments. It is therefore concluded that HCO ₃ ⁻ and not phosphate is the primary cause for lime induced Fe chlorosis. Despite the low phosphate concentration in the soil solution, the P concentration in the chlorotic leaves was more than twice as high as the P concentration in green leaves grown on the same soil. It is thus assumed that the high P content frequently found in chlorotic leaves is the result and not the cause for Fe chlorosis.     

Purification and properties of cassava green mottle, a previously undescribed virus from the Solomon Islands

A sap-transmissible virus obtained from cassava with a green mottle disease occurring at Choiseul, Solomon Islands, was transmitted to 30 species in 12 plant families and was readily seed-borne in Nicotiana clevelandii. In cassava plants infected by inoculation with sap, the first leaves to be infected systemically developed a mottle with some necrosis whereas leaves produced subsequently were symptomless but contained the virus. Most other species developed chlorotic or necrotic local lesions and systemic mottle or necrosis. This was followed, in several species, by production of small symptomless virus-containing leaves. The virus was cultured in N. clevelandii; Chenopodium quinoa was used for local-lesion assays. Leaf extracts from infected N. clevelandii were infective after dilution to 10–⁵ but usually not at 10–⁶, after heating for 10 min at 60°C but not at 65°C, and after storage at 20°C for at least 12 days. The virus has isometric particles of 26 nm diameter which sediment as three components, all containing a protein of mol. wt c. 53000. The two fastest sedimenting components respectively contain single-stranded RNA of mol. wt, estimated after glyoxylation, c. 2.9 × 10⁶ and 2.3 × 10⁶. Both RNA species are needed for infection of plants. In tests with antiserum prepared to purified virus particles, the virus was detected in cassava and N. clevelandii by gel-diffusion precipitin tests, by immunosorbent electron microscopy and by ELISA. Despite its similarity to nepoviruses, the virus did not react with antisera to 18 members of the group. It was named cassava green mottle virus and is considered to be a previously undescribed nepovirus.     

Nutritional Status of the Cauliflower Cultivar ‘Verona’ Grown with Omission of out Added Macronutrients

Knowledge of plant nutritional status allows an understanding of the physiological responses of plants to crop fertilization. A hydroponic experiment evaluated the symptoms of macronutrient deficiency in cauliflower ‘Verona’ and determined: a) the macronutrient contents of foliar tissues when visual symptoms were observed, b) macronutrients content of foliar and inflorescence tissues at harvest. The effect of nutrient deficiency on inflorescence mass was also evaluated. Nitrogen deficiency caused chlorosis followed by purple color in the old leaves, while P deficiency caused only chlorosis in old leaves. Chlorosis at the edge of old leaves progressing to the center of the leaves was observed with the omission of K, and after was observed necrosis in the chlorotic areas. Ca deficiency caused tip burn in new leaves, while Mg deficiency caused internerval chlorosis in old leaves. The omission of each macronutrient reduced inflorescence dry matter. This deleterious effect was larger for N, P, and K deficiencies, reducing inflorescence dry matter by 87, 49, and 42%, respectively. When the nutrient solutions without N, P, K, Ca, or Mg were supplied to cauliflower plants, the macronutrient contents at harvest were 8.8, 0.6, 3.5, 13.0, and 0.8 g kg^-1 in the foliar tissues and 27.3, 2.2, 21.6, 1.1, and 0.7 g kg^-1 in the inflorescence tissues, respectively.     

Properties of a resistance-breaking strain of potato virus X

During indexing of a potato germplasm collection from Bolivia, a strain of potato virus X (PVX), X_HB, which failed to cause local lesions in inoculated leaves of Gomphrena globosa was found in 7% of the clones. X_HB was transmitted by inoculation of sap to 56 species from 11 families out of 64 species from 12 families tested. It was best propagated in Nicotiana glutinosa or N. debneyi; Montia perfolia and Petunia hybrida were useful as local lesion hosts. Inoculated leaves of G. globosa plants kept at 10°, 14°, 18°, 22°, or 26 °C after inoculation were always infected symptomlessly. X_HB caused a mild mosaic, systemic chlorotic blotching or symptomless infection in 16 wild potato species and eight Andean potato cultivars, systemic necrotic symptoms in clone A6 and cultivar Mi Peru, and bright yellow leaf markings in cultivar Renacimiento. It caused necrotic local lesions in inoculated leaves of British potato cultivars with the PVX hypersensitivity gene Nb but then invaded the plants systemically without causing further necrosis; with gene Nx systemic invasion occurred but no necrotic symptoms developed. These reactions resemble those of PVX strain group four. X_HB differed from other known strains of PVX in readily infecting PVX-immune clones 44/1016/10, G. 4298.69 and USDA 41956, cultivars Saphir and Saco, and Solanum acaule PI 230554. X_HB had slightly flexuous filamentous particles with a normal length of 516 nm. It was transmitted readily by plant contact and it partially protected G. globosa leaves from infection with X_CP, a group two strain of PVX. Sap from infected N. glutinosa was infective after dilution to 10^--⁶ but not 10^--⁷ after 10 min at 75° but not 80 °C and after 1 yr at 20 °C. X_HB was readily purified from infected N. debneyi leaves by precipitation with polyethylene glycol followed by differential centrifugation. Microprecipitin tests showed that X_HB and X_CP are closely related serologically.     

Ursachen der Chlorosen an Mandarinen (Citrus Reticulata Blanco) der Ägäischen region

Zusammenfassung Im Gebiet von Gümüssu der Provinz Izmir (Türkei) wurden aus 20 repr?sentativen Mandarinenplantagen Blatt- und Bodenproben entnommen und auf Mikroelementgehalte untersucht. In den Bodenproben erfolgte au?erdem die Bestimmung der Textur, des pH-Wertes, des Gehaltes an Phosphat, Calciumkarbonat, Bikarbonat und Salz. Die Gehalte der Bl?tter an Eisen und anderen Mikroelementen ergaben keinen Aufschlu? über die Chloroseursache. Es bestanden auch keine gesicherten Korrelationen zwischen den NH₄-azetatl?slichen Mikroelementgehalten des Bodens und dem Auftreten der Chlorose. Eigentliche Ursache der Chlorose scheint das HCO₃ ⁻ zu sein, da sich, in der Mehrzahl der F?lle eine erh?hte Bikarbonat-Konzentration im Boden chloroseerkrankter Plantagen feststellen lie?. Aus den Ergebnissen wird geschlossen, da? in erster Linie die Verbesserung der Drainage und der Wasserführung als Ma?nahme zur Chlorosebek?mpfung in den untersuchten Plantagen erfolgen mu?. Fe- und Zn-Chelat-Spritzungen sind nur als vorl?ufige Ma?nahmen zu betrachten.

---

Summary To ascertain reasons for chlorosis in madarin orchards, microelement content in leaf and soil samples from 20 representative mandarine plantages in tne Izmir-region (Turkey) have been determined. In soil samples also texture, pH and content of P, CaCO₃, HCO₃ ⁻ and salt was analyzed. Fe-, Zn- and Mn-contents of leaves did not help to clarify the reason for chlorosis. There was also no significant correlation between the amount of ammoniumacetate soluble microelements in the soil and the appearence of chlorosis. HCO₃ ⁻ seems to be the main reason of chlorosis, because its content in most of the chlorotic plantages was raised. According to these results, improvement of the drainage system as the most important step in curing chlorosis is concluded. Spraying with Fe- and Zn-chelats are considered only as preliminary steps.