Boron foliar fertilization of soybean and lychee: Effects of side of application and formulation adjuvants

Experiments to assess the rate of absorption and translocation of foliar‐applied, isotopically labeled boric acid (BA) were carried out with lychee (Litchi chinensis Sonn.) and soybean (Glycine max [L.] Merr.) plants. Boron (B) absorption and translocation within the plant, one week after treatment, was investigated after adding to the boric acid (BA solutions 0.5 mM CaCl₂ and/or 50 or 500 mM sorbitol). The contribution of stomata to the absorption process was assessed by applying the solutions either to the adaxial or to the abaxial leaf side. Both plant species differed greatly in total absorption rates. The adaxial leaf surface (lacking stomata) of lychee leaves was nearly impermeable, while the stomatous abaxial surface was permeable to BA solutions. In this species, no translocation of ¹⁰B to other leaf parts and no effect of adjuvants in increasing ¹⁰B absorption were recorded. In contrast, ¹⁰B was absorbed both by adaxial and abaxial leaf surfaces of soybean leaves. Boron concentrations measured in treated soybean leaves were sixfold higher after application to the abaxial as compared to the adaxial leaf surface. The addition of adjuvants significantly enhanced the rate of ¹⁰B absorption, but not its translocation within the plant. Treatments containing 500 mM sorbitol led to increased ¹⁰B absorption and enhanced acropetal ¹⁰B movement, whereas adding only 50 mM sorbitol had no significant effect. Application of 0.5 mM CaCl₂ in combination with 500 mM sorbitol decreased the rate of ¹⁰B absorption, compared to the performance of 500 mM sorbitol alone. Basipetal ¹⁰B translocation was very limited. A distinct effect of B‐sorbitol complexes on B translocation apart from the pure adjuvant effect could not be discerned in this investigation.     

Time course study on the mobility and pattern of distribution of foliar‐applied boron in peaches

One‐year‐old Red Haven’ peach (Prunus Persica) trees grown in pots in the greenhouse were used to study the time course mobility and pattern of distribution of boron (B). Enriched‐¹⁰B boric acid solution was evenly spread onto the abaxial side of the fifth leaf (numbered acropetally). After harvesting at different time intervals, selected plant parts were analyzed for ¹⁰B using an ICP‐MASS spectrometer. The results showed that within 4 hours, B could be taken up and translocated bidirectionally to all plant parts, except for the fine roots. Treated leaf, green stem, and fine root were the tissues having high ¹⁰B concentrations in comparison to the other tissues. The highest ¹⁰B concentrations in the fed leaf, green stem, and fine root were reached in 12 hours, at the 4th week, and in 72 hours, respectively. The total ¹⁰B absorbed averaged 0.3% of the total ¹⁰B applied, with the highest total percent recovery of 0.43%, which was reached in 72 hours. The total amount of ¹⁰B exported from the fed leaf was more than 50% of the ¹⁰B absorbed. A comparison of the ¹⁰B/¹¹B ratio and the ¹⁰B content was used as the parameter of B movement. The method of data expression is also discussed.     

设施栽培油桃对叶面施15N的吸收、分配特性研究

以设施栽培的5年生早红珠油桃/山毛桃为试材,应用15N示踪技术研究油桃叶片对15N-尿素的吸收及运转特性。结果表明,叶片施用15N-尿素标记叶吸收主要发生在叶片涂抹15N-尿素后6.h内,平均吸收速率为0.204mg/(g.h);标记叶中15N吸收量24.h达到最高,新梢和梢顶嫩叶15N含量在施用15N-尿素48.h达到最高,下部叶15N含量很低,没有明显的峰;处理168.h各器官中15N含量为标记叶梢顶嫩叶新梢下部叶;试验结束时分配势Ndff(即各器官N含量来自化肥N所占的百分率)为标记叶中最高,然后依次为梢顶嫩叶、新梢、下部叶。这说明氮素迅速被吸收并运到嫩梢和嫩叶中,从而促进这些新生器官的形态建造,可起到以N增C的作用。不同叶面处理的试验还表明,正面和背面全部涂抹的叶片15N含量最高,只涂抹叶片背面次之,涂抹正面最低。设施栽培油桃叶片可迅速吸收尿素,其吸收量早晨明显优于中午和下午,因此设施油桃栽培管理中于早晨进行叶面施尿素,且正反面兼顾,N素的吸收利用效果最好。     

Some cesium and potassium salts increase the water permeability of astomatous isolated plant cuticles

Salts were applied as aqueous solution to the outer surfaces of astomatous isolated cuticles, and the water was allowed to evaporate. Effects of salt residues on the surfaces of cuticles on water permeability of cuticles were measured at 25°C. A surface dose of 0.2 mol m^–2 Cs₂CO₃ and K₂CO₃ increased the water permeability of pear leaf cuticles by factors of 9.9 and 3.9, respectively. Na₂CO₃ was barely effective, and Li₂CO₃ as well as (NH₄)₂CO₃ had no influence on water permeability. Potassium applied as sulfate, nitrate, or chloride had no effect on the water permeability of pear leaf cuticles, while K⁺ salts of weak acids (0.2 mol m^–2) were effective, as they increased water permeability by factors of 5.4 (K⁺‐acetate), 3.9 (K₂CO₃), and 2.0 (K₂HPO₄), respectively. Sensitivity of Idesia polycarpa leaf cuticles to treatment with K₂CO₃ at 0.2 mol m^–2 was greatest as water permeability was increased 35‐fold, while the water permeability of cuticles from other species tested (astomatous leaf cuticles from Hedera helix, Citrus aurantium, Prunus laurocerasus, Pyrus communis, and Populus canescens; fruit cuticles from Capsicum annuum and Lycopersicon esculentum) increased only by factors ranging from 1.7 to 3.9. Data are discussed in relation to swelling and ion‐exchange properties of cuticles.     

Silicon Decreases Transpiration Rate and Conductance from Stomata of Maize Plants

ABSTRACT

To characterize the effect of silicon (Si) on decreasing transpiration rate in maize (Zea mays L.) plants, the transpiration rate and conductance from both leaves and cuticula of maize plants were measured directly. Plants were grown in nutrient solutions with and without Si under both normal water conditions and drought stress [20% polyethylene glycol (PEG) concentration in nutrient solution] treatments. Silicon application of 2 mmol L^?1 significantly decreased transpiration rate and conductance for both adaxial and abaxial leaf surface, but had no effect on transpiration rate and conductance from the cuticle. These results indicate that the role of Si in decreasing transpiration rate must be largely attributed to the reduction in transpiration rate from stomata rather than cuticula. Stomatal structure, element deposition, and stomatal density on both adaxial and abaxial leaf surfaces were observed with scanning electron microscopy (SEM) and a light microscope. Results showed that changes in neither stomatal morphology nor stomatal density could explain the role of Si in decreasing stomatal transpiration of maize plants. Silicon application with H₄SiO₄ significantly increased Si concentration in shoots and roots of maize plants. Silicon concentration in shoots of maize plants was higher than in roots, whether or not Si was applied. Silicon deposits in cell walls of the leaf epidermis were mostly in the form of polymerized SiO₂.     

Phosphorus status of paddy soils from the central region of the Mekong River in Laos

Microorganisms colonizing the leaf sheaths of rice plants placed in a waterlogged paddy field were studied using a scanning electron microscope. Decomposition was faster on the adaxial side than on the abaxial side of the leaf sheaths. The veins and trichomes were highly resistant to microbial decomposition throughout the waterlogged period of rice growth. The decomposition and disintegration of leaf sheaths markedly progressed from the third month (from July) after the placement in the paddy field. Microbial colonization was gradual in the first month after the placement of leaf sheaths in the field. One of the common first colonizers had a terminal endospore (Clostridium dissolvens-like microorganisms). Microbial colonization proceeded actively in the second month, and microbiota became diversified. Microbial colonization on the adaxial surface was more than that on the abaxial surface. Respective microorganisms colonized the surfaces separately from each others in this period. They grew mainly on the thin membrane that covered the epidermal layer. Microbial colonies spread all over the abaxial and adaxial surfaces, and there was no significant difference in the degree of colonization between the abaxial surface and the adaxial surface in the third month (in July). Although separate colonization of the respective microorganisms was common, the co-existence of different microorganisms within a colony was also observed. The thin membrane that covered the epidermal layer and the epidermis seemed to be the main substrate during this period. Co-existence of different microorganisms was a common occurrence in colony formation, and organic debris and remaining tissues of leaf sheaths were assumed to be the major substrates in August. These findings on microbial colonization were well correlated with the findings on the degree of decomposition.     

Foliar absorption of nickel: Determination of its cuticular behavior using isolated cuticles

The sorption and penetration of ⁶³Ni at the cuticular level were investigated using enzymatically isolated tomato fruit cuticles. The high values of the partition coefficients determined by immersing cuticular material in a nickel chloride solution indicated that Ni was well retained by cuticular constituents. They were assayed by both direct and indirect methods and increased more than twofold between 1 and 6 days revealing that equilibration between the cuticular material and the bathing solution proceeds very slowly. Ni concentrations at 6 days were about 1,000 times higher in cuticles than in the immersion solution. No significant difference appeared between the immersion with buffer (pH : 8) and without buffer (pH: 6.5). Only 3.2% of sorbed ⁶³Ni was removed by successive rinses in water. The remainder of the radioactivity appeared to be ionically bound to negatively charged exchange sites on the cuticle since 99% of bound ⁶³Ni could be exchanged by rinsing with IN HC1. The cuticular permeability coefficient (P) and the diffusion coefficient (D) determined under self‐diffusion conditions at pH 8, were 1.6 x 10^‐8 cm.8^‐l and 37.4 x 10^‐12 cm².s^‐1 respectively. High variability was noted between cuticles isolated from the same fruit sample. By comparison the permeability coefficient of ⁴⁵Ca at pH 8 was 16 times higher than for Ni.

The agronomical and ecotoxicological implications of these results are considered.     

Boron uptake by peach leaf slices

The objective of this study was to determine if plasma‐lemma transport is a limiting step for boron (B) uptake by peach leaf. Only about 0.3% of the B applied could be absorbed by peach (Prunus persica L. Batsch) leaves when enriched ¹⁰B‐boric acid was used as a tracer.

Boron uptake increased proportionally to the external B concentration in the range of 1 mM to 20 mM. The highest B content was found in the 20 mM treatment. Boron uptake was rapid for the initial 6 to 8 hours, but it then slowed down steadily until the end of the experiment. A linear correlation between the external B concentration and leaf B content was obtained (y =‐8.98 + 46.1×, R² = 0.999). pH had a profound effect on B uptake by peach leaf slices with pH 7 and 8 had the highest B absorption.

Boron uptake was strongly dependent on temperature over the 2°C to 40°C range. Peach leaf slices had the highest B absorption at 40°C. B uptake decreased sharply when the temperature dropped to 2°C. Adenosine Triphosphate (ATP) increased B uptake significantly in the range from 1 to 2 mM. ATP concentrations higher or lower than this range did not affect B uptake. Diethylstilbestrol (DES) and 2,6 ‐ Diiodo ‐4‐ nitrophenol (DNP) both inhibited B uptake with DNP the more effective inhibitor than DES. It is suggested that plasmalemma transport is not the rate limiting step in B absorption by peach leaves. Boron uptake by peach leaf slices involves both an active and a passive process with the active uptake as a major component.     

Micromorphological and anatomical alterations caused by simulated acid rain in Restinga plants: Eugenia uniflora and Clusia hilariana

Eugenia uniflora and Clusia hilariana seedlings were submitted to simulated acid rain, pH 3, for 40 days. The degree of visible injury and the anatomical and micromorphological alterations were determined 24 hours after the last simulation. E. uniflora presented a higher degree of leaf necrosis. The adaxial epidermis and part of the palisade parenchyma of the entire leaf blade were affected and hypertrophy, hyperplasia and cicatrization tissue differentiation occurred. Erosion and morphological modification of the epicuticular wax and alterations in the epidermis were detected on the upper and lower leaf surfaces. Stomata with deformed ostioles and rupture of the stomatal ledge were observed. C. hilariana presented necrosis in leaf margin and in abaxial leaf surface, showing collapsed cells or with plasmolized aspect, cicatrization tissue, epicuticular wax alterations, occasional leaf perforations, irregular arrangement of adaxial epidermis cells and twisted subsidiary cells. The structural alterations indicated a greater susceptibility of E. uniflora to acid rain. he lower sensibility of C. hilariana can be related with the anatomical characteristics as: thick cuticle with evident cuticular flanges, three layers of hypodermis and mesophyll more thick and compact.     

Urea retention and uptake by avocado and apple leaves

Solution retention by avocado (Persea americana cv. Fuerte) and apple (Mallus domestica Burkh. cv. Anna) leaves was measured by weight gain of detached leaves after dipping them in solutions of two surfactants and by analysis of various concentrations of urea retained at zero time on surfaces of attached leaves. Linear regression equations were calulated, relating leaf area and retention of solution. The slope of the equation represents the retention of solution on the leaf surface, and its intercept represents the value retained on the leaf margin. Solution retained on leaf surface was 2.5–2.6 and 5.4–6.4 mg/cm² for ‘old’ avocado and apple leaves, respectively. Retention on the serrated leaf margin of the apple was greater than on the smooth margin of the avocado. The abaxial leaf surfaces retained approximately 62% and 83% of the total solution retained by the avocado and the apple leaves, respectively.

The rate of urea uptake was proportional to the applied concentration and reached in avocado 65–85% within 2–5 days and over 90% in apple within 2 days. The rate of urea uptake by avocado was similar on ‘Young’ and ‘old’ leaves, similar from either Triton X‐100 or L‐77 surfactants, and similar through abaxial and adaxial surfaces. The nitrogen enrichment from foliar application of urea was related to retention and threshold of phytotoxicity rather than to rate of uptake. Older leaves of avocado showed some phytoxicity to 4% urea. Young leaves were damaged by repeated 2% application and flowers by 0.5–1.0%.

The actual nitrogen enrichment in avocado, which could be predicted accurately from measurement of urea retention, was 43% following three successive applications of 3% urea in 12 days.     

Effects of copper,zinc, and sulfur application to peach trees on coastal plain soil

Abstract

Expanded use of sulfur (S)‐free fertilizers and copper (Cu)‐free fungicides is likely to increase plant deficiencies of these essential elements. Zinc (Zn) deficiency occurs more frequently. An effective and reliable means of correcting Zn deficiency in peach trees remains to be documented in Texas. This study was designed to evaluate S, Cu, and Zn treatments on peach trees. Fifteen treatments consisting of combinations of five rates each of S, Cu, and Zn were evaluated using a central‐composite, rotatable design. Each treatment was replicated four times. Sulfur and Cu treatments were applied in January. Zinc treatments were foliar‐applied in March, April, and May. Responses were linear between applied Zn and leaf Zn, applied S and leaf S, and applied S and leaf area. A positive correlation between leaf Cu and leaf N was found. A preliminary study in the greenhouse revealed that both the 12.5 and 25 ppm Cu treatments were toxic. In a succeeding study, no statistical differences among Cu treatments from 0 to 10 mg/kg were found.     

Quantitative methods for estimating foliar uptake of zinc from suspension‐based Zn chemicals

The present study developed methods for quantifying foliar Zn uptake from suspension‐based Zn chemicals of low solubility, which were ZnO (particle size: 0.15^–1.34 μm) and a newly synthesized Zn hydroxide nitrate crystal (Zn‐HNC) (50^–100 nm thickness and 0.2^–1 μm lateral dimension). Recently matured leaves of citrus (Citrus aurantium L. cv. Valencia), capsicum (Capsicum annume L. cv. Giant Bell), and/or tomato (Solanum lycopersicum L. cv. Roma) were in vitro–treated with microdroplets (5 μL per droplet) of Zn‐HNC‐ and ZnO‐suspension solutions on the adaxial surface and incubated under controlled conditions for up to 72 h. Leaf‐washing protocols were compared, including: dilute ethanol (3%), dilute nitric acid (2%), and their combination. The methods for quantifying Zn uptake were: (1) whole‐leaf loading by which droplets of the Zn suspension solutions were loaded onto central regions of both left and right sides of leaf blades and (2) half‐leaf loading by which soluble‐Zn (ZnSO₄) droplets were loaded onto only one side of leaf blades while the other was used as the background Zn control. Foliar‐surface characteristics of the plant species affected the effectiveness of the washing methods. The dilute nitric acid (2%; ± 3% ethanol) was required to remove residue particles of the ZnO and Zn‐HNC suspensions from foliar surfaces of capsicum and tomato (highly trichomatic), but the residue Zn chemicals on citrus leaves (nontrichomatic and highly waxy) were similarly and effectively removed by the three washing methods. For quantifying Zn uptake by the leaves, the half‐leaf loading method showed its advantages over the whole‐leaf loading method, because it did not stringently require similar background Zn concentrations in the control and treated leaves at the start and had little risks of secondary absorption of soluble Zn in the washing solution.     

水稻叶片上下表面反射率差异及其与氮素状况的关系

在田间条件下测定了5个氮素水平处理的水稻叶片在分蘖、孕穗和抽穗期的上表面反射率和下表面反射率。结果表明:各生育期水稻叶片在可见光和近红外区域的下表面反射率均大于上表面反射率(绝对差值一般小于2%),上下表面反射率差值大小与供氮水平间无显著相关性,但在近红外区域这种差值随着生育期而降低。与上表面反射率相比,下表面反射率与叶片氮素和叶绿素含量间具有同样高的相关性,因此水稻下表面反射率也可用于估计叶片氮素和叶绿素含量。下表面中脉向外凸出及上下表皮细胞大小与排列的差异可能是引起水稻叶片上下表面反射差异的主要原因     

Effects of concentrated application of soil conditioners on soil–air permeability and absorption of nitrogen by young peach trees

ABSTRACT

To study the effects of concentrated application of two soil conditioners, two-year-old peach trees (Prunus persica L.‘Chunmei’) were selected to test the soil air permeability, ¹⁵N absorption and the growth of trees. The experiment comprised three treatments involved concentrated applying either polyacrylamide (treatment I) or Agri-SC (a proprietary soil conditioner, treatment II) at the bottom of each pit or neither of the two (treatment III). And then the whole pit was back-filled with soil. Neither digging a hole nor use of soil conditioners as the control (CK). The results showed that volumetric oxygen content in gases in 5–10 cm soil layer upon concentrated application layer was significantly higher in treatments I and II than that in CK. Soil volumetric water content upon concentrated application layer was higher in treatments I and II than that in CK. Compared with CK, no matter root activity, leaf area, leaf chlorophyll content, or leaf net photosynthesis rate in treatments I and II increased in August and October, which promoted the growth of new shoots and the stem. Compared with CK, the leaf superoxide dismutase activity increased 31.24%, 22.66% and 4.74%, Guaiacol peroxidase increased 21.88%, 13.25% and 3.39%, Catalase increased 11.80%, 7.92% and 1.24% respectively in treatments I, II and III in October. As a result, values of the total roots surface area, total root volume, number of root tips, dry matter accumulation, and organ nitrogen content were markedly higher in treatments I and II than that in CK. And the ¹⁵N utilization rate significantly increased 24.22% and 10.40% respectively in treatments I and II. The result suggested that concentrated application of soil conditioners formed a rhizosphere water storage and breathable layer that not only stores moisture but is also permeable to air. That, in turn, promotes plant growth, increases the nitrogen use efficiency.     

Effect of Boron Application on Yield,Quality, and Nutritional Status of Peach Cultivar Andross

During the cultivation period of 2005–2007, a project was carried out in the region of Eirinoupolis, prefecture of Imathia, Macedonia, northern Greece. The study investigated the application of boron (B) timing (flowering, fruit set, fruit growth) and method (soil and foliage) on the vegetative growth, fruit yield and quality, and nutritional status of the cling-stone peach variety Andross. The cultivar was grafted onto an 8-year-old rootstock GF 677. The results showed that the greatest marketable yield (135 kg tree^–1) was achieved in peach trees where B was applied on soil during the flowering stage in combination with a balanced nitrogen–phosphorus–potassium (NPK) basal application. Boron concentration in fruits of that treatment was increased in both cultivation years compared to most of the applied treatments. Foliar application of B at flowering, fruit set, and fruit growth, primarily in combination with foliar calcium (Ca) application, showed fruits to be less affected by cracking and Monilinia over all treatments. However, foliar application of Ca did not significantly promote leaf or fruit Ca concentration.     

Determination of iron chlorosis with extractable iron analysis in peach leaves

Iron (Fe) though indispensable for the biosynthesis of chlorophyll, but its total content in the plant was not associated with the occurrence of chlorosis. Iron, which is the ferrous‐iron (Fe²⁺) form—termed “active”; Fe— and extracted with weak acids and some chelating agents, has been closely related to Fe chlorosis. In this study, three different methods were tested in order to determine suitable methods for extractable‐Fe analysis in a Dixired peach cultivar. In the first two methods, o‐phenantroline (o‐Ph) and 1N hydrochloric acid (HCl) were used to extract Fe²⁺ from fresh leaves. In the third method, 1N HCl were used as an extractant on dried leaf samples. The relationship between chlorophyll content of the leaves and Fe extracted by the three methods, was statistically significant. Hydrochloric acid extraction with dried leaves which gave the highest significant correlation (r = 0.930) with chlorophyll content, can be used for the determination of Fe²⁺ ("active”; Fe) status in peach trees.     

Citrus leaf nutrient status: A critical evaluation of guidelines for optimal yield in Israel

Maintaining orchards with trees at optimal leaf nutrient concentrations is one of the key issues for maximizing yield. Experiments for evaluating and updating guidelines are very rare since they require several years of field experiments with mature fruit‐bearing trees. In the present paper, we first evaluated the Israeli guidelines for citrus by comparing them to the Israeli orchard leaf mineral status using a 10‐year leaf‐mineral database (results of 20 244 leaf analyses from commercial orchards all over Israel). Then, we created an updated guideline using a second database (the Israeli National Wastewater Effluent Irrigation Surveys database; INWEIS). This database summarizes yield and leaf mineral concentrations of commercial orchards from all over Israel. The data were collected from 122 orchards: 39 orchards of “Oroblanco” Pomelit (Citrus grandis), 33 orchards of “Michal” mandarin (C. reticulata), 30 orchards of “Star Ruby” grapefruit (C. paradise), and 20 orchards of “Shamouti” oranges (C. sinensis) over a 7‐year period. Based on the first database, there was a disagreement between recommendations and the leaf nutrient status (e.g., the Israeli Ministry of Agriculture recommendations were higher than orchard median values), which indicated that the growers and/or the recommendations need to be corrected. Based on the INWEIS database, a new guideline was set. It was found that the optimal leaf nutrient concentrations for grapefruit trees are 1.7% to 2.1% dry weight (DW) for N, 0.08% to 0.010% DW for P, 0.37% to 0.48% DW for K, and 0.33% to 0.45% DW for Mg. For orange trees, the optimal leaf nutrient concentrations are 1.9% to 2.3% DW for N, 0.11% to 0.14% DW for P, 0.80% to 1.00% DW for K, and 0.19% to 0.26% DW for Mg. For mandarin trees, the optimal leaf nutrient concentrations are 2.0% to 2.4% DW for N, 0.09% to 0.12% DW for P, 0.55% to 0.69% DW for K, and 0.19% to 0.26% DW for Mg. Maintaining leaf nutrient concentrations within these ranges will support maximal yields of 110 to 120 t ha^–1 for grapefruit, 65 to 70 t ha^–1 for orange, and 60 to 70 t ha^–1 for mandarin cultivars.     

‘Schattenmorelle’ Tart Cherry Response to Boron Fertilization

ABSTRACT

The objective of the experiment was to examine the effects of soil and foliar applications of boron (B) on tart cherry (Prunus cerasus L.) tree vigor, yield, and fruit quality. The study was conducted during 2003–2004 on mature ‘Schattenmorelle’ tart cherry trees grown at a commercial orchard in central Poland on coarse-textured soil with low B content. Trees were supplied with B as foliar sprays or via soil application. Foliar B sprays were performed: (1) in the spring, at the white bud stage, when 5%–10% of flowers were at full bloom, and 5 d after petal fall, at a rate of 0.2 kg B ha^?1 per each spray treatment; and (2) in the fall, approximately six weeks before the natural leaf fall, at a rate of 0.8 kg B ha^?1. Soil B application was made at the bud-break stage at a rate of 2 kg ha^?1. Trees untreated with B served as a control. Spring and fall B sprays increased flower B concentrations, but had no effect on summer leaf B status. Leaf B concentrations of trees with B supplied to the soil were higher than those of the control trees. However, soil B application had no influence on flower B level. Vigor and yield of tart cherry trees were not influenced by B fertilization. Also, mean fruit weight and titratable acidity of fruit did not differ among treatments. Fruit of trees with B supplied to the soil had higher soluble solids concentration (SSC) than those of the control plants. In conclusion, high yield of tart cherry can be obtained on soils with water-soluble B concentrations as low as 0.32 mg kg^?1. It is also postulated that at low soil-B availability, under conditions of low-light intensity during fruit ripening, soil-B application increases SSC in tart cherry fruit.     

Soil nutrient supply and biomass production in a mixed forest on a skeleton‐rich soil and an adjacent beech forest

In the natural forest communities of Central Europe, beech (Fagus sylvatica L.) predominates in the tree layer over a wide range of soil conditions. An exception with respect to the dominance of beech are skeleton‐rich soils such as screes where up to 10 broad‐leaved trees co‐exist. In such a Tilia‐Fagus‐Fraxinus‐Acer‐Ulmus forest and an adjacent mono‐specific beech forest we compared (1) soil nutrient pools and net nitrogen mineralization rates, (2) leaf nutrient levels, and (3) leaf litter production and stem increment rates in order to evaluate the relationship between soil conditions and tree species composition. In the mixed forest only a small quantity of fine earth was present (35 g l^—1) which was distributed in patches between basalt stones; whereas a significantly higher (P < 0.05) soil quantity (182 g l^—1) was found in the beech forest. In the soil patches of the mixed forest C and N concentrations and also concentrations of exchangeable nutrients (K, Ca, Mg) were significantly higher than in the beech forest. Net N mineralization rates on soil dry weight basis in the mixed forest exceeded those in the beech forest by a factor of 2.6. Due to differences in fine earth and stone contents, the volume related soil K pool and the N mineralization rate were lower in the mixed forest (52 kg N ha^—1 yr^—1, 0—10 cm depth) than in the beech forest (105 kg N ha^—1 yr^—1). The leaf N and K concentrations of the beech trees did not differ significantly between the stands, which suggests that plant nutrition was not impaired. In the mixed forest leaf litter fall (11 %) and the increment rate of stem basal area (52 %) were lower than in the beech forest. Thus, compared with the adjacent beech forest, the mixed forest stand was characterized by a low volume of patchy distributed nutrient‐rich soil, a lower volume related K pool and N mineralization rate, and low rates of stem increment. Together with other factors such as water availability these patterns may contribute to an explanation of the diverse tree species composition on Central European screes.     

Phytotoxicity and some interactions of the essential trace metals iron,manganese, molybdenum,zinc, copper,and boron

Abstract

The essential trace elements Fe, Mn, Zn, Cu, and B in high concentrations can produce phytotoxicities. Iron toxicity resulted from 5 × 10^‐4 M and 10^‐3 M FeSO₄, but not from equivalent amounts of FeEDDHA (ferric ethylenediamine di (o‐hydroxyphenylacetic acid) ). Leaf concentrations in bush beans of 465 μg Mn/g, 291 μg B/g, and 321 μg Zn/g all on the dry weight basis resulted in 27%, 45%, and 34% reduction in yields of leaves, respectively. Zinc was concentrated in roots while Mn and B concentrated in leaves. Solution concentrations of MnS0₄ of 10^‐3 and 10^‐2 M depressed leaf yields of bush beans by 63% and 83%, respectively, with 5140 and 10780 μg Mn/g dry weight of leaves. Copper concentrations were simultaneously increased and those of Ca were decreased. Bush bean plants grown in Yolo loam soil with 200 μg Cu/g soil had a depression in leaf yield of 26% (with 28. 8 μg Cu/g leaf); plants failed to grow with 500 μg Cu/g soil. A level of 10^‐3 M H₂MoO₄ was toxic to bush beans grown in solution culture. Leaves, stems, and roots, respectively, contained 710, and 1054, and 5920 μg Mo/g dry weight.