Activities of Iron‐Containing Enzymes in Leaves of Two Tomato Genotypes Differing in Their Resistance to Fe Chlorosis

Abstract

Two tomato (Lycopersicon esculentum Mill., cvs. Pakmor and Target) genotypes differing in resistance to iron (Fe) deficiency were grown in nutrient solution under controlled environmental conditions over 50 days to study the relationships between severity of leaf chlorosis, total concentration of Fe, and activities of Fe‐containing enzymes in leaves. The activities of Fe‐containing enzymes ascorbate peroxidase, catalase, and guaiacol peroxidase, and additionaly the activity of glutathione reductase, an enzyme that does not contain Fe, were measured. Plants were supplied with 2 × 10^?7 M (Fe deficient) and 10^?4 M (Fe sufficient) FeEDTA, respectively. Leaf chlorosis appeared more rapidly and severely in Target (Fe deficiency senstive genotype) than Pakmor (Fe deficiency resistant genotype). On day 50, Pakmor had 2‐fold more chlorophyll than Target under Fe deficiency, while at adequate supply of Fe the two genotypes were very similar in chlorophyll concentration. Despite distinct differences in development of leaf chlorosis and chlorophyll concentrations, Pakmor and Target were very similar in concentrations of total Fe under Fe deficiency. In contrast to Fe concentration, activities of Fe‐containing enzymes were closely related to the severity of leaf chlorosis. The Fe‐containing enzymes studied, especially catalase, showed a close relationship with the concentration of chlorophyll and thus differential sensitivity of tomato genotypes to Fe deficiency. Glutathione reductase did not show relationship between Fe deficiency chlorosis and enzyme activity. The results confirm that measurement of Fe‐containing enzymes in leaves is more reliable than the total concentration of Fe for characterization of Fe nutritional status of plants and for assessing genotypical differences in resistance to Fe deficiency. It appears that Fe deficiency‐resistant genotype contains more physiologically available Fe in tissues than the genotype with high sensitivity to Fe deficiency.     

Influence of Gyttja on Shoot Growth and Shoot Concentrations of Zinc and Boron of Wheat Cultivars Grown on Zinc‐Deficient and Boron‐Toxic Soil

Abstract

Greenhouse experiments were carried out to study the influence of gyttja, a sedimentary peat, on the shoot dry weight and shoot concentrations of zinc (Zn) and boron (B) in one bread wheat (Triticum aestivum L., cv. Bezostaja) and one durum wheat (Triticum durum L., cv. Kiziltan) cultivar. Plants were grown in a Zn‐deficient (DTPA‐Zn: 0.09 mg kg^?1 soil) and B‐toxic soil (CaCl₂/mannitol‐extractable B: 10.5 mg kg^?1 soil) with (+Zn = 5 mg Zn kg^?1 soil) and without (?Zn = 0) Zn supply for 55 days. Gyttja containing 545 g kg^?1 organic matter was applied to the soil at the rates of 0, 1, 2.5, 5, and 10% (w/w). When Zn and gyttja were not added, plants showed leaf symptoms of Zn deficiency and B toxicity, and had a reduced growth. With increased rates of gyttja application, shoot growth of both cultivars was significantly enhanced under Zn deficiency, but not at sufficient supply of Zn. The adverse effects of Zn deficiency and B toxicity on shoot dry matter production became very minimal at the highest rate of gyttja application. Increases in gyttja application significantly enhanced shoot concentrations of Zn in plants grown without addition of inorganic Zn. In Zn‐sufficient plants, the gyttja application up to 5% (w/w) did not affect Zn concentration in shoots, but at the highest rate of gyttja application there was a clear decrease in shoot Zn concentration. Irrespective of Zn supply, the gyttja application strongly decreased shoot concentration of B in plants, particularly in durum wheat. For example, in Zn‐deficient Kiziltan shoot concentration of B was reduced from 385 mg kg^?1 to 214 mg kg^?1 with an increased gyttja application. The results obtained indicate that gyttja is a useful organic material improving Zn nutrition of plants in Zn‐deficient soils and alleviating adverse effects of B toxicity on plant growth. The beneficial effects of gyttja on plant growth in the Zn‐deficient and B‐toxic soil were discussed in terms of increases in plant available concentration of Zn in soil and reduction of B uptake due to formation of tightly bound complexes of B with gyttja.     

NUTRITIONAL DIAGNOSIS AND CORRECTION OF SHOOT DIEBACK OF RED BAYBERRY (MYRICA RUBRA SIEB. ET ZUCA)

Shoot dieback characterized by leaflet, rosette shoots, and dieback of shoot tips is one of the most important problems in red bayberry production in south China. However, the causes of shoot dieback have not been determined. The results of leaf analysis and correction experiment showed that leaf boron (B) concentrations were highly correlated with leaf area (P < 0.01), spring shoot length (P < 0.01), and spring shoot numbers sprouting from one old shoot (P < 0.05). Foliar application of B at 2.0 g L^–1 of borax was more effective on correcting shoot dieback than foliar application of Zn at 2.0 g L^–1 of zinc sulfate and of molybdenum (Mo) at 2.0 g L^–1 of ammonium molybdate. Boron application increased fruit yields by 1.23–2.15 times compared with the control. Shoot dieback resulted mainly from B deficiency in the red bayberry trees.     

Response of Chickpea Cultivars to Application of Boron in Boron‐Deficient Calcareous Soils

Abstract

This study was conducted to investigate the effects of four boron (B) doses (control, 0 kg B ha^?1; B₁, 1 kg B ha^?1; B₂, 3 kg B ha^?1; and B₃, 6 kg B ha^?1) in soils deficient in available B (0.19 mg B kg^?1) and lime (CaCO₃) content (20.7%) on yield and some yield components of five chickpea (Cicer arietinum L.) genotypes, namely Akçin‐91, Population, Gökçe, ?zmir‐92, and Menemen‐92 in central Anatolian Turkey in the 2002 and 2003 growing seasons. Plant height, pods per plant, grain yield, protein content, protein yield, thousand seed weight, and leaf B concentration were measured. Grain yields in all genotypes (except for Gökçe) were significantly increased by 1 kg ha^?1 B application. Application of 1 kg ha^?1 B increased the yield by an average of 5%. Genotypes studied showed significant variations with respect to their responses to additional B. Akçin‐91 gave the highest grain yield (1704.8 kg ha^?1) at 3 kg B ha^?1, whereas Population, ?zmir‐92, and Menemen‐92 yielded best (1468.2 kg ha^?1, 1483.0 kg ha^?1, and 1484.7 kg ha^?1, respectively) at 1 kg B ha^?1. Interestingly, Gökçe reached to the highest level of grain yield (1827.1 kg ha^?1) at the control. Gökçe was a B deficiency B tolerance genotype. The other genotypes appeared to have high sensitivity to B deficiency. This study showed that B deficiency could result in significant yield losses in chickpea under the experimental conditions tested. Thus, B contents of soils for the cultivation of chickpea should be analyzed in advance to avoid yield losses.     

Responses of fees used for revegetation of desert areas to iron deficiency stress

We investigated the responses to iron deficiency of four major tree species, Prosopis cineraria (local name: Ghaf), Acacia tortilis (Samar), Zizyphus spina-christi (Sidr), and Leptadenia pyrotechnica (Markh), used for revegetation of desert areas in the United Arab Emirates (UAE). The responses to iron deficiency differed among the tree species. Ghaf, Samar, and Sidr decreased the nutrient solution pH in response to iron deficiency. Markh and iron-deficient Sidr did not release protons in the CaCl₂ solution. The Fe reducing capacity of the roots of Ghaf, Samar, and Sidr was significantly enhanced by iron deficiency, whereas a smaller increase in the reducing activity of the roots of Markh was observed. In all the tree species, the amount of reductant released from iron-deficient plants was higher than that from iron-sufficient ones. Markh released a small amount of reductant under irondeficient conditions. In the present study, the reductant released by all the trees was caffeic acid. Acidification treatment enhanced the amount of reductant released irrespective of iron treatments in Ghaf, Samar, and Sidr but had no effect on the amount of reductant released in iron-deficient Markh. The activity of p-coumarate hydroxylase was higher in Sidr and Ghaf than in the other trees. This activity decreased in iron-deficient Samar. Ghaf, Samar, and Sidr showed a high capacity to lower the pH of the nutrient solution, and Ghaf markedly enhanced the effectiveness of all the examined mechanisms, while Markh showed a lower ability compared to the other tree species.     

Effect of supplied phytosiderophore on 59Fe absorption and translocation in Fe-deficient barley grown hydroponically in low phosphorus media

Abstract

Hydroponically grown barley plants (Hordeum vulgare L. cv. Minorimugi) under iron-deficient (–Fe) and high phosphorus (P) conditions (500 µmol L^?1) showed Fe chlorosis and lower growth compared with plants grown in –Fe and low P conditions (50, 5 and 0.5 µmol L^?1). To understand the physiological role of P in regulating the growth of plants in –Fe medium, we carried out an Fe feeding experiment using four P levels (500, 50, 5 and 0.5 µmol L^?1) and phytosiderophores (PS), mugineic acid. Our results suggest that plants grown in a high P medium had higher absorption activity of ⁵⁹Fe compared with plants grown in low P media, irrespective of the presence or absence of added PS. Translocation of ⁵⁹Fe from roots to shoots was not affected by the P level. The relative translocation rate of ⁵⁹Fe increased with decreasing levels of P in the medium. In general, the addition of PS enhanced the absorption of ⁵⁹Fe and its translocation. Taken together these results suggest that the lower relative translocation rate of Fe in high P plants may be induced by the physiological inactivation of Fe in the roots, and the higher absorption activity of Fe in high P conditions possibly results from the response of barley plants to Fe deficiency.     

Effects of Nitric Oxide on Iron-Deficiency Stress Alleviation of Peanut

The aim of this research was to study the role of nitric oxide (NO) in alleviating iron deficiency induced chlorosis of peanut (Arachis hypogaea L.). For this study, sodium nitroprusside (SNP) was used to supply NO for hydroponic peanut plants. After 18 days, the peanut seedlings growing without iron exhibited significant leaf interveinal chlorosis, and this iron-deficiency induced symptom was completely prevented by NO. An increased content of chlorophyll and active iron was observed in NO-treated young leaves, suggesting an improvement of iron availability in plants. In addition, the improved rhizosphere acidification and increased secretion of organic acids by root in NO-treated plants suggesting that NO is effective in modulating iron uptake and transport inside the peanut plants. Furthermore, NO treatment alleviated the increased accumulation of superoxide anion (O₂^??) and malondialdehyde (MDA), and modulated the antioxidant enzymes. However, the SNP with a prior sunlight treatment that does not release NO had no significant effect on the chlorophyll levels in iron-deficient plants. Therefore, these results support a physiological action of NO on the availability, uptake and transport of iron in the plant.     

Boron Absorption and Translocation in Apple Rootstocks Under Conditions of Low Medium Boron

Abstract

The purpose of the experiment was to examine the differences in rates of boron (B) absorption and translocation to above‐ground plant parts by selected apple rootstocks under conditions of low medium B. The study was performed under greenhouse conditions on P22, P60, P14, M.26, and M.9 rootstocks grown for 180 days in pots filled with perlite and supplied with Hoagland's nutrient solution at 5 µmol B L^?1. The first B deficiency symptoms appeared on the youngest leaves of P22, P60, and P14 after 86–95 days of growth, whereas on M.9 and M.26 after 130–145 days. Boron deficiency signs on leaves were less severe on M.26 and M.9 than on the other ones. The M.9 and M.26 rootstocks produced more biomass and had higher total B concentrations in root, stem, and leaf tissues and also higher cell wall B status of root and leaves compared to those of P22, P14, and P60. Rates of absorption and B translocation to above‐ground plant parts were higher for M.9 and M.26 than for the other ones. These results indicate that on soils with high risk of B deficiency, apple trees should be grafted on M.9 or M.26.     

Root and Leaf Ferric Chelate Reductase Activity in Pond Apple and Soursop

Abstract

Root and leaf ferric chelate reductase (FCR) activity in Annona glabra L. (pond apple), native to subtropical wetland habitats and Annona muricata L. (soursop), native to nonwetland tropical habitats, was determined under iron (Fe)-sufficient and Fe-deficient conditions. One-year-old seedlings of each species were grown with 2, 22.5, or 45 µM Fe in a nutrient solution. The degree of tolerance of Fe deficiency was evaluated by determining root and leaf FCR activity, leaf chlorophyll index, Fe concentration in recently mature leaves, and plant growth. Root FCR activity was generally lower in soursop than in pond apple. Eighty days after plants were put in nutrient solutions, leaf FCR activity of each species was lower in plants grown with low Fe concentrations (2 µM) than in plants grown with high (22.5 or 45 µM) Fe concentrations in the nutrient solution. Leaves of pond apple grown without Fe became chlorotic within 6 weeks. The Fe level in the nutrient solution had no effect on fresh and dry weights of soursop. Lack of Fe decreased the leaf chlorophyll index and Fe concentration in recently matured leaves less in soursop than in pond apple. The rapid development of leaf chlorosis in low Fe conditions and low root and leaf FCR activities of pond apple are probably related to its native origin in wetland areas, where there is sufficient soluble Fe for adequate plant growth and development. The higher leaf FCR activity and slower growth rate of soursop compared to pond apple may explain why soursop did not exhibit leaf chlorosis even under low Fe conditions.     

Inhibition of iron-stress reactions in sunflower by bicarbonate

In pot culture experiments using a calcareous soil the growth rate of sunflowers was depressed by latent iron deficiency. Iron-stress reactions, reflected by enhanced uptake rate of Fe-59 after short-term supply of ⁵⁹FeEDDHA were observed under these conditions. These reactions, however, were delayed and much less distinct than those observed under latent iron deficiency in water culture experiments. Addition of MgCO₃ to this soil increased the iron deficiency of the plants and caused chlorosis, but prevented these iron-stress reactions. In contrast to the soil experiments, distinct iron-stress reactions could be observed with latent iron-deficiency in sand culture experiments in which varied amounts of inorganic Fe-III were supplied. These reactions were only observed, however, in absence of bicarbonate. Even 4 meq bicarbonate severely inhibited these iron-stress reactions which were almost totally inhibited at 10 meq bicarbonate. Bicarbonate depressed both short-term uptake of Fe-59 as well as total iron content of the leaves. There was no evidence for an additional “inactivation” of iron within the leaves due to bicarbonate treatment. Bicarbonate also strongly depressed the manganese content of the young leaves. The results demonstrate that the regulatory mechanism of so-called “iron-efficient” plant species like sunflower under iron-stress - increase in H⁺ efflux and reducing capacity of the roots and thus enhanced uptake of iron (and manganese) - is severely inhibited or even blocked by high bicarbonate concentrations. “Lime chlorosis”, caused by high bicarbonate concentrations on calcareous substrates is therefore also widespread in so-called “iron-efficient” species.     

Effect of Iron Deficiency on Gas Exchange and Catalase and Peroxidase Activity in Citrus

Abstract

The effects of iron (Fe) deficiency on catalase and peroxidase activity, net photosynthesis (Pn), stomatal conductance (g _s ), plant water relations, and specific leaf weight, were studied under greenhouse conditions in two sweet orange (C. sinensis) cultivars grafted on sour orange (Citrus aurantium) and Swingle citrumelo (C. paradisi × P. trifoliata). Iron deficiency caused by the absence of Fe in the Hoagland nutrient solution reduced significantly catalase and peroxidase activity, photosynthesis (Pn), osmotic potential (Ψ _π ), turgor potential (Ψ _p ), and specific leaf weight, but did not influence g _s and leaf water potential (Ψ _L ). Iron deficiency caused by increasing concentrations of bicarbonate supplied as NaHCO₃ (10 and 40 mM) in the nutrient solution reduced significantly g _s , Pn, and Ψ _p and increased Ψ _L and Ψ _π . Furthermore, remarkable differences were recorded between the various cultivars/rootstocks combinations.     

Effect of Calcium and Boron Sprays on Yield and Quality of “Elsanta” Strawberry

Abstract

The aim of the experiment was to examine the effects of foliar applications of calcium (Ca) and boron (B) on yield and fruit quality of “Elsanta” strawberries grown on a sandy loam soil with low status of available B. The study was conducted in 1999–2000 at a commercial strawberry plantation in Central Poland. Cold‐stored strawberries were planted in 1998 at a spacing of 0.25 × 0.8 m. The following treatments were applied: (i) five sprays of Ca as CaCl₂ at a rate of 1.5 kg Ca ha^?1 spray^?1 with addition of Tween 20 adjuvant at 0.1%; the first spray was performed at the petal fall stage and the next at 5‐day intervals; (ii) three sprays of B as Borvit material at a rate of 160 g B ha^?1 spray^?1 at the beginning of flowering and 5, and 10 days later; (iii) sprays of B and Ca as in the combination of (i) and (ii). Plants sprayed with water served as the control. Results showed that fruit and leaves from Ca‐treated plants had increased Ca concentrations. Sprays with B increased status of this microelement in fruit and leaf tissues. Treatments did not affect total and marketable fruit yield, mean berry weight, the number deformed fruit, soluble solids concentration and titratable acidity of fruit at harvest. Fruit sprayed with Ca or B plus Ca were firmer and more resistant to Botrytis rot at harvest and after 3 days of holding at 18°C compared to those of control plots. Moreover, sprays of Ca or B plus Ca increased soluble solids concentration and titratable acidity of fruit after 3 days of holding at room temperature. These results indicate that sprays of CaCl₂ with addition of Tween 20 should be recommended to improve quality and shelf‐life of strawberry fruit, particularly in proecological production where application of fungicides is restricted.     

Transport of Foliar Applied Iron (59Fe) in Vicia faba

Abstract

Radioactively labeled iron (⁵⁹Fe) was used to study iron retranslocation from mature leaves of Broad bean (Vicia faba L. var. Scirocco). Our experiments offered the possibility to detect and quantify the translocation of foliar applied iron by imaging technique in combination with tissue analysis. ⁵⁹Fe labeled solution was placed as a droplet onto the leafs upper surface of intact plants. Distribution of ⁵⁹Fe was analyzed after 0.5 h up to 2 days. Iron was translocated acropetally (towards the tip of the treated leaf) as well as basipetally. Movement in the apical direction was predominant, amounting to about 65% of ⁵⁹Fe translocated from the application site. About 35% of ⁵⁹Fe were transported basipetally, corresponding to absolute amounts of 2.8–53.6 pmol h^?1. After 30 min, it was detectable in the petiole, which included a translocation of 20 mm basipetal from the application site. A mean of 15% of the iron retranslocated from a leaflet was detected in non‐treated leaflets of the same leaf. This iron was supposed to have been exchanged from the phloem into the xylem pathway, probably within the petiole. When the loading rate into the phloem was estimated on basis of the sum of retranslocated ⁵⁹Fe per time and per area of the leaf treated, a range of 0.031–2.21 pmol h^?1 mm^?2 (mean: 0.62 pmol h^?1 mm^?2) was obtained. This was not sufficient to meet an estimated demand for iron in the growing terminal bud, but could cover about 25% of it. In conclusion, average iron retranslocation from leaves of Fe‐sufficient plants was not large enough to meet the iron demand of the growing shoot. This was not due to a limitation in iron availability for transport, as an excess amount of iron was supplied which was not biologically bound, but a limitation due to transport facilities, probably in the phloem, seemed to be more likely in this case.     

Critical Levels of Boron in Soils for Cauliflower (Brassica oleracea Var. Botrytis)

Influence of boron (B) application to cauliflower (Brassica oleracea var. botrytis) was investigated in a pot experiment taking 15 Inceptisols with four levels of B. The critical levels of B for deficiency, adequacy and toxicity in soil and in cauliflower plant were also determined. Hot-calcium chloride (CaCl₂) extractable B in these soils varied from 0.33 to 0.78 mg kg^-1 and its content for deficiency to cauliflower was 0.48 mg kg^-1. Boron application significantly increased cauliflower yield, plant B concentration and uptake of B. The critical plant B concentrations for deficiency, sufficiency and toxicity varied with the growth stages and the values being 26, 31 and 48 mg kg^-1 at 50 days of growth and 17, 24 and 35.5 mg kg^-1 at harvest, respectively. The study also recommends application of fertilizer B at the rate 0.9–4.5 kg ha^-1 for optimum B nutrition to cauliflower in Inceptisols of the Gangetic plains of India.     

Iron fertilizers applied to calcareous soil on the growth of peanut in a pot experiment

A greenhouse pot experiment was conducted with peanuts (Arachis hypogaea L., Fabceae) to evaluate iron compound fertilizers for improving within-plant iron content and correcting chlorosis caused by iron deficiency. Peanuts were planted in containers with calcareous soil fertilized with three different granular iron nitrogen, phosphorus and potassium (NPK) fertilizers (ferrous sulphate (FeSO₄)–NPK, Fe–ethylendiamine di (o-hydroxyphenylacetic) (EDDHA)–NPK and Fe–citrate–NPK). Iron nutrition, plant biomass, seed yield and quality of peanuts were significantly affected by the application of Fe–citrate–NPK and Fe–EDDHA–NPK to the soil. Iron concentrations in tissues were significantly greater for plants grown with Fe–citrate–NPK and Fe–EDDHA–NPK. The active iron concentration in the youngest leaves of peanuts was linearly related to the leaf chlorophyll (via soil and plant analyzer development measurements) recorded 50 and 80 days after planting. However, no significant differences between Fe–citrate–NPK and Fe–EDDHA–NPK were observed. Despite the large amount of total iron bound and dry matter, FeSO₄–NPK was less effective than Fe–citrate–NPK and Fe–EDDHA–NPK to improve iron uptake. The results showed that application of Fe–citrate–NPK was as effective as application of Fe–EDDHA–NPK in remediating leaf iron chlorosis in peanut pot-grown in calcareous soil. The study suggested that Fe–citrate–NPK should be considered as a potential tool for correcting peanut iron deficiency in calcareous soil.     

Response of Cotton and Wheat Cultivars to Soil-applied Boron in a Boron-deficient,Noncalcareous Typic Ustochrept

Field experiments were conducted to study the response of cotton genotypes (G. arboreum Bt cv. RCH 650 BGII; non-Bt cv. F 2228; G. herbaceum cv. FDK 124) and wheat and triticale genotypes (T. aestivum cv. PBW 622; T. durum cv. PDW 314; triticale cv. TL 2908) to direct and residual B application (0, 0.5, 1.0, and 2.0 kg B ha^?1 as borax) using a Typic Ustrochrept, neutral, noncalcareous, loamy sand and B-deficient soil. A significant response of 218 and 231 kg ha^?1 in seed cotton yield was recorded with an application of 1.0 kg B ha^?1 to cotton and 2.0 kg B ha^?1 to wheat. A significant response of 152 kg ha^?1 grain yield of wheat was observed with the application of 0.5 kg B ha^?1 to wheat, while no residual effect of B was observed when B was applied to cotton. On the basis of agronomic and B uptake efficiency, genotypes of cotton (RCH 650 BG II > FDK 124 > F 2228) and wheat (PDW 314> TL 2908> PBW 621) responded differentially to B application, thus indicating that yield of Bt cotton and durum wheat will be reduced more than the other cultivars under B deficiency.     

Leaf structure and chemical compositions are correlated with cotton boron efficiency

In this study, in order to investigate the boron (B) efficiency and response to changes in leaves structure and chemical compositions correlated with B efficiency, two different cotton genotypes including genotype 103 and genotype 122 were treated by B-deficiency (0 mg L^?1) or moderate B (0.2 mg L^?1). All the seedlings were grown in hydroponics situation with modified Hoagland and Arnon solution under greenhouse conditions for 6 weeks. The changes in chemical compositions and cell structure of leaves as a consequence of B deficiency were revealed by Fourier-transform infrared spectroscopy (FTIR), ¹³C nuclear magnetic resonance (¹³C-NMR) and transmission electron microscope (TEM). The results showed that the leaves of genotype 122 appeared crinkled and prolapsed having more obvious symptoms than genotype 103. Besides, the dry mass of every part was higher while B concentration was lower in genotype 103, indicating that genotype 103 was much tolerant to low B, which was related to higher B utilization efficiency of genotype 103 under B-deprived condition. In addition, B deficiency stunted the synthesis of proteins, carbohydrates, cellulose and lignin, which is noticed more seriously in leaves of genotype 122, and the structure and integrity of cells were significantly destroyed by B starvation. These results indicated that genotype 103 had higher B efficiency than genotype 122, and the changes in the chemical composition and cell structure might be either specific or adaptive responses to B efficiency.     

Comparison of Various Analysis Methods for Determination of Iron Chlorosis in Apple Trees

Abstract

The objective of this study was to compare iron (Fe) concentrations (mg kg^?1) of the leaves measured by different methods and to determine the most suitable method to be used in evaluation of iron chlorosis in apple trees. For this purpose, green and chlorotic leaves were collected from 76 apple orchards in 1998 and 1999. Iron concentrations (mg kg^?1) of dried leaf samples were measured with 4 different methods, 1 N HCl (Method 1), 0.1 N HCl (Method 2), 0.005 M DTPA (Method 3), and 1.5% o-phenanthroline (Method 4). Total Fe concentrations (mg kg^?1) of dried leaf samples were also analyzed. Total chlorophyll and peroxidase enzyme activity in fresh leaf samples were measured. The total chlorophyll, peroxidase enzyme activity, Fe concentrations (mg kg^?1) determined by Method 1, Method 3, Method 4, and total Fe concentrations (mg kg^?1) of green leaves were higher than those of chlorotic leaves. On the other hand, no significant difference was found between Fe concentrations (mg kg^?1) of green and chlorotic leaves, measured with Method 2. Significant relationship observed amongst chlorophyll concentrations, peroxidase enzyme activity, and Fe concentrations (mg kg^?1) of samples suggests that 1 N HCl method was the most suitable method amongst the methods used in this study for apple trees.     

Phosphorus Fertilization Impacts on Corn Yield and Soil Fertility

Optimization of phosphorus (P) fertilization is important for balancing soil fertility especially in vertisol to support economic crop production. The objective of the study was to determine the impact of P fertilization (1998 to 2014) on crop yield and nutrient uptake, and soil fertility under continuous annually tilled corn (Zea mays L.)-wheat (Triticum aestivum L.) system in semi-arid Mediterranean conditions. The study was conducted on Arik clay (isohyperthermic, fine clay Typic Haploxerert) using randomized complete block design with four replications for each treatment at the research farm of the Dept. of Soil Science and Plant Nutrition, Çukurova University, Adana, Turkey. P fertilizer at 0, 50, 100, 200 kg P₂O₅ ha^?1 as triple superphosphate (TSP), respectively was applied a week before planting corn. Results showed that increasing P fertilization rates significantly decreased the number of mycorrhizal spores associated with corn roots. Similarly, a 10% decrease in corn root mycorrhizal colonization was observed with 200 kg P₂O₅ ha^?1 fertilization. In the control treatment, corn yield was 4.3 Mg ha^?1 as compared to 5.6, 5.7 and 6.1 Mg ha^?1 in 50, 100 and 200 kg of P₂O₅/ha, respectively. The relationship between P fertilization and relative yield showed that more than 95% of the corn yield was produced when P applied at 100 kg P₂O₅ ha^?1. While P fertilization significantly increased the leaf N, P, and K contents but decreased the leaf Zn, Fe and Mn contents, as compared with the control. However, P fertilization did not consistently affect the grain N and P contents. Both physiological efficiency- and agronomic efficiency of P fertilization have shown a significant non-linear increase than that of the control. Total organic C (TOC) and total N (TN) concentrations were more than 34 and 26% higher in 100 and 200 kg P₂O₅ ha^?1rates as compared with the control. Likewise, available P (AP), manganese (Mn) and zinc (Zn) concentrations increased with an increase in P fertilization rates. The AP, Mn and Zn contents significantly stratified by P fertilization. Our results suggested that 100 kg P₂O₅ ha^?1 is optimum to sustain Vertisol fertility for supporting economic corn production in the Mediterranean climates of Turkey.     

Growth Response and Selenium and Boron Distribution in Broccoli Varieties Irrigated with Poor Quality Water

Abstract

Selenium (Se), and boron (B), and salinity contamination of agricultural drainage water is potentially hazardous for water reuse strategies in central California. This greenhouse study assessed tolerance and Se, B, and chloride (Cl^?) accumulation in different varieties (Emerald City, Samurai, Greenbelt, Marathon) of broccoli (Brassica oleracea L.) irrigated with water of the following different qualities: (1) non‐saline [electrical conductivity (EC) of <1 dS m^?1]; (2) Cl^?/sulfate salinity of ～5 dS m^?1, 250 µg Se L^?1, and 5 mg B L^?1; and (3) non‐saline and 250 µg Se L^?1. One hundred and ten days after transplanting, plants were harvested and dry weight (DW) yields and plant accumulation of Se, B, and Cl^? was evaluated in floret, leaf, and stem. Irrespective of treatments floret yields from var. Samurai were the lowest among all varieties, while floret yields from var. Marathon was the only variety to exhibit some sensitivity to treatments. For all varieties, plant Se concentrations were greatest in the floret (up to 51 mg kg^?1 DW) irrespective of treatment, and B and Cl^? concentrations were greatest in the leaves; 110 mg B kg^?1 DW and 5.4% Cl^?, respectively. At post harvest, treatment 2 (with salinity, B, and Se) increased soil salinity to almost 6 dS m^?1, total Se concentrations to a high of 0.64 mg kg^?1 DW soil, and water soluble B concentrations to a high of 2.3 mg B L^?1; soluble Se concentrations were insignificant. The results indicate that var. Emerald City, Greenbelt, and Marathon should be considered as recipients of moderately saline effluent enriched with Se and B under field conditions.