José Lavres Junior

Perfilhamento, área foliar e sistema radicular do capim-Mombaça submetido a combinações de doses de nitrogênio e potássio

An experiment was carried out in a greenhouse from November 2000 to February 2001 with the objective of evaluating the effects of nitrogen (N) and potassium (K) rates on tillering, leaf area, total root length, total root surface, specific root length and specific root surface of Panicum maximum Jacq. cv. Mombaca. The forage grass was grown in nutrient solution using ground quartz as substrate. The experimental arrange used was an incomplete 5² factorial of N and K and the 13 combinations between N and K were obtained according to design points of the modified central composite nonrotatable design that was set in a randomized block design, with four replications. Plants were harvested twice. The first harvest was at 36 days after transplanting and the second at 29 days after the first harvest. Following the second harvest, the roots were separated from ground quartz, collected and also washed. Results showed that N x K interaction was significant for leaf area at both harvest, for plant tillering at the second harvest, and for total root length and total root surface. Tillering was significantly affected by N and K rates at the first harvest. Specific root length and specific root surface was significantly influenced by the supply of N as well as by K rates.

Diagnose nutricional de nitrogênio no capim-aruana em condições controladas

SUMMARY : NITROGEN NUTRITIONAL STATUS IN ARUANA GRASS IN ACONTROLLED ENVIRONMENT Aruana grass ( Panicum maximum cv. Aruana) is well adapted to pastures, especiallythose grazed by sheeps, but knowledge on mineral nutrition of this grass is scant. In orderto evaluate the nutritional status of this forage in relation to nitrogen, Aruana grass wasgrown in a nutrient solution with N six rates (14; 112; 210; 294; 378 and 462 mg L -1 ). Theexperiment was carried out in a greenhouse in the Spring, from October to December 2000.Each experimental unit consisted of one pot with ground quartz as substrate. Plants wereharvested twice. The first harvest occurred 35 days after transplanting to the pots, whilethe second one was 28 days after the first harvest. Right after the second harvest the rootswere separated from the substrate and collected. Visual symptoms of N deficiency appearedon the 10 th day after seedling transplanting. Results showed significant effects of N rateson N concentration and N distribution in the plant parts, on nitrate reductase activity aswell as the SPAD values. At the first harvest, SPAD values ranged from 32.0 to 52.6 andfrom 25.1 to 42.1 at the second harvest, respectively, from the lowest to the highest N rate.The critical levels of N concentration and SPAD values determined in the recently expandedleaf blades were, respectively, 28.4 g kg

Deficiências de macronutrientes no estado nutricional da mamoneira cultivar Iris

The objectives of this work were to evaluate the effect of macronutrient deficiencies on growth and on nutritional status of castor beans ( Ricinus communis L.), and to obtain the symptoms of the lack of N, P, K, Ca, Mg and S. Nutrient solutions containing all macronutrients and those from which one of these elements was omitted were the treatments used. The following determinations were made: chlorophyll (indirectly), nitrate reductase activity, NO 3 - -N, H2PO4 - -P and K + , both on soluble fractions, and by spot tests. Deficiencies of N, Ca, S and Mg were the most limiting for dry matter production, followed in decreasing order by those of K and P. The highest concentrations of macronutrients were measured in roots and lower leaf blades. Critical levels of N and Ca in the upper leaf blades and of Mg in lower petioles were respectively, 46.7, 13.8, 6.5 g kg -1 . Deficiencies affected chlorophyll meter readings. Nitrate reductase activity was correlated with chlorophyll readings. Soluble contents of N, P and K in the leaves were lower in plants deficient in the respective element. The same was found when spot tests were applied on the leaf sap.

Photosynthesis, Chlorophylls, and SPAD Readings in Coffee Leaves in Relation to Nitrogen Supply

The export of nitrogen (N) from senescent plant parts is important for the efficient use of this macronutrient. The objective of this study was to establish correlations among the photosynthetic pigment content, total N, and the photosynthetic variables with the SPAD‐502 readings in Coffea arabica leaves. Correlations were established among the chlorophyll content, N content, and chlorophyll a and b with SPAD‐502 readings taken on coffee leaves at different months. The results show that all variables decreased with time. However, correlation increased linearly with N doses. Total chlorophyll presented a direct linear correlation with readings of the portable chlorophyll meter. The SPAD readings have shown to be a good tool to diagnose the integrity of the photosynthetic system in coffee leaves. Thus, the portable chlorophyll SPAD‐502 instrument can be used to evaluate the N status and can also help to evaluate the photosynthetic process in coffee plants.

Análise de crescimento do capim-marandu submetido a doses de nitrogênio

This research was conducted with the objective of determining growth of Brachiaria brizantha (A. Rich.) Stapf. cv. Marandu under nitrogen (N) rates (28, 112, 210, 294 and 378 mg/L, where N-NO3- : N-NH4+ of 70%:30% proportion was kept constant) and growth ages (21, 28, 35, 42, 49 and 56 days after seedling emergence). The experiment was carried out in greenhouse conditions, with nutrient solution and using ground quartz as substrate. The experimental design used was a complete randomized block design, with treatments arranged in a 5x6 factorial, with four replications. Nitrogen rates and growth ages interaction was significant for all growth attributes of Marandugrass, except for the mean net assimilation rate (NAR). The results showed that the maximum values for the relative growth rate (RGR) and absolute growth rate (AGR) were 0.25 g/g.day and that was observed at 28 days with N rate at 378 mg/L, and 3.68 g/day at 56 days associated to N rate at 378 mg/L, respectively. At 21 days of growth, occurred maximum values of 2.16 dm2/g at the highest N rate for leaf area ratio (LAR), of 0.48 g/g with N rate at 294 mg/L for leaf weight ratio (LWR), and of 5.14 dm2/g for specific leaf area (SLA) at N rate of 378 mg/L.

Changes in the ultrastructure of soybean cultivars in response to manganese supply in solution culture

The deleterious effects of Mn stress on many species have been studied, mainly concerning biochemical, physiological and growth parameters of plants. However, there are few studies relating the anatomical and ultrastructural changes in response to manganese (Mn) nutritional disorders, This study examined the leaf ultrastructure of Mn-inefficient (IAC-15, Santa Rosa) and Mn-efficient (IAC-Foscarin 31) soybean (Glycine max L.) genotypes in response to three rates of Mn (0.5, 2 and 200 µmol L-1) in the nutrient solution. Symptoms of Mn deficiency developed 12 days after transplanting in IAC-15 and Santa Rosa, followed by IAC-Foscarin 31 on the 15th day. Only IAC-15 and Santa Rosa leaves showed symptoms of Mn toxicity. The Mn concentration in leaves ranged from 8.6 (deficiency) to 886.3 mg kg-1 d.w. (toxicity). There were no changes either in stomata length or stomata number per unit of leaf surface. Cytoplasm disorganization was observed in IAC-15 under Mn-excess. In this case, the cytoplasm was amorphous, densely stained and extensively disorganized, with increased vacuolation. Mn effects were not found in mitochondria and nucleus in any of the genotypes tested. Under all Mn concentrations, many lipid globules were observed in the IAC15 chloroplasts. There was an increase in the number of plastids as well as in the size of starch grains within IAC-Foscarin 31 chloroplasts as Mn concentration in the nutrient solution increased. Genotypes had marked differences in the ultrastructure organization, mainly in leaf chloroplasts grown under conditions of both Mn deficiency and toxicity (the most sensitive genotype was IAC-15).

Faixas normais de nutrientes em cana-de-açúcar pelos métodos ChM, DRIS e CND e nível crítico pela distribuição normal reduzida

There are several interpretation methods for foliar nutrient analysis, and the critical level or nutrient sufficient range described in the literature are the most commonly used. However, an inclusion of methods that determine the normal nutrient ranges for specific regions (sites) can increase the efficiency of interpretation. The objective of this study was to compare normal nutrient ranges for sugarcane cultivation, determined by the methods ChM (Mathematical Chance), DRIS (Integrated System of Diagnosis and Recommendation) and CND (Compositional Nutrient Diagnosis), and the Critical Level, by the method of reduced normal distribution. The study was carried out based on data of foliar nutrient contents and crop yield, from commercial sugarcane fields in Campos de Goytacazes, State of Rio de Janeiro. By the ChM method, sufficiency ranges for N, Ca, S, and Mn were similar to those determined by DRIS and CND, while for P, K, Mg, Cu, and Zn the values obtained by ChM were higher. In general, the use of ChM, DRIS and CND in commercial sugarcane fields reduced the amplitude of the normal nutrient ranges, compared with the values obtained by the critical level and sufficiency range methods.

Influência genotípica na absorção e na toxidez de manganês em soja

Plant species and genotypes within species can differ widely in their tolerance to excess manganese (Mn) (Foy et al., 1988) or susceptibility to its deficiency (Graham, 1988) in the soil or other substrate in which they grow. Often these differences are hereditary (Broadley & White, 2005; Pittman, 2005). Although manganese (Mn) toxicity can be a common problem in tropical regions with acid soils, Mn deficiency in soybeans (Glycine max L.) grown in Brazilian Cerrado (savanna) has been recognized as a nutritional disorder frequently related to excessive liming (Tanaka et al., 1992). However, the variations in the concentrations of Mn in plants have been attributed either to genetic factors or to soil fertility conditions (Fageria, 2001). Plant species and genotypes within the same species can differ widely in the tolerance to high Mn (Foy et al., 1988) as well as in susceptibility to the deficiency when grown under conditions of low Mn availability (Graham, 1988). The mechanisms of tolerance to excess Mn have been associated with oxidation of the Mn in the roots, restricted absorption by the roots and translocation of the excess Mn to the leaves, as well as uniform distribution in the tissues, greater internal tolerance and interaction with other elements (mainly K, Ca, Mg, Fe and Si) and defense mechanisms against oxygen reactive species, such as activation of enzymes like ascorbate peroxidase, catalase, Mnsuperoxide dismutase and glutathione peroxidase (Demirevska-Kepova et al., 2004; Morita et al., 2006). On the other hand, better internal utilization or lower requirement, greater redistribution of Mn, increased rate of absorption, exudation of organic acids, acidification of the rhyzosphere and geometry of the root system have been reported as the main mechanisms responsible for lower susceptibility of Mn deficiency (Graham, 1988; Rengel, 1999). The harmful effects of both deficient and excessive Mn on many species have been studied, mainly considering the morphological and anatomical aspects of the ultrastructure and biochemical aspects of the aerial part, where the symptoms are manifested, particularly the leaves (Demirevska-Kepova et al., 2004; Papadakis et al., 2007a,b). However, there are few reports on anatomical and changes in the root ultrastructure in response to variations in the supply of Mn (McQuattie & Schier, 2000) and regarding the effect of genotype (Santandrea et al., 1998a,b; Izaguirre-Mayoral & Sinclair, 2005).

INFLUENCE OF NITROGEN FERTILIZATION ON NICKEL ACCUMULATION AND CHEMICAL COMPOSITION OF COFFEE PLANTS DURING FRUIT DEVELOPMENT

Nutritional and physiological significance of micronutrients in coffee plants, especially with regard to nickel (Ni) is still unknown. The dynamics of nitrogen (N), phosphorus (P), potassium (K) and Ni accumulation in coffee fruits, as well as their relationships with total soluble protein, amino acids, reducing sugars, and starch content during coffee fruit development (green, ripe, and dry fruits), were investigated. Coffee trees received three N fertilizer rates (0, 150, and 300 kg of N ha−1) as ammonium sulfate split into three applications per year. Nitrogen fertilization increased reducing sugars and starch concentrations in ripe fruits. In contrast, green fruits showed the highest amino acid and Ni concentrations. Fruit Ni concentration decreased in both green and ripe fruits as N rates increased; thus, indicating the possibility of either a N-associated dilution effect on Ni concentration or that Ni uptake by roots and/or transport to developing fruit was limiting. Plant nutritional status and fruit development stage influenced the coffee grain chemical composition. Furthermore, the variation in reducing sugars and starch content was more closely linked to the stage of fruit development than to N supply. A supposed relationship among the decreased of caffeine, starch, amino acids, and proteins with Ni content during green fruit development suggests a fundamental role for Ni in coffee fruit ripening. The interaction between N and Ni metabolism during fruit ripening might influence the chemical parameters involved in the coffee grain quality. This is the first report documenting changes in Ni concentrations of coffee fruit as a function of N fertilization rates and the development stage, but further research is needed to better understand the significance of N-Ni interaction in developing coffee fruit.

OPTIMUM RATIO OF CALCIUM AND BORON IN THE NUTRIENT SOLUTION OR IN CASTOR BEAN SHOOT FOR FRUIT YIELD AND SEED OIL CONTENT

Calcium (Ca) and boron (B) have been reported as the major macro- and micronutrient required for castor bean plant yield. The objective of this study was to determine the Ca:B ratios (in the growth media and plant tissue) for fruit yield and shoot dry weight of the castor bean (Ricinus communis L.), grown in a nutrient solution, and to evaluate Ca and B supply on concentration and total uptake of Ca, potassium (K), magnesium (Mg), and B, as well on the seed oil content. The treatments were arranged in a 3 × 3 factorial fashion, consisting of three rates of Ca (40, 80, and 160 mg L−1) and three of B (0.32, 0.96, and 1.60 mg L−1). Calcium and B rates increased the shoot and root dry weight and fruit yield at a Ca:B ratio in the nutrient solution of 166 and 100, respectively. Symptoms of B deficiency were observed in plants supplied with 0.32 mg B L−1, regardless of the Ca concentration in the nutrient solution. Plants which showed visual symptoms of Ca deficiency cultivated with 40 mg Ca L−1 presented concentration of Ca in plant tissue up to 10 g kg−1. The concentration and total Ca and B uptake increased with the rates of them. Notwithstanding, the shoot Ca accumulation was improved by B rates. In addition, there were no decreases in K and Mg uptake due to Ca rates. Furthermore, addition of 80 mg L−1 of Ca and 1.60 mg L−1 of B in the growth media increased the seed oil content. The Ca:B ratio in the diagnostic leaf associated with the highest plant dry weight (shoot and root) and fruit yield, was 500 (16 to 20 g kg−1 of Ca, and for 30 to 40 mg kg−1 of B).