Cleusa Pereira Cabral

Evaluation of Nutritional Status of the Cotton Plant with Respect to Nitrogen

Abstract Cotton plants, Gossypium hirsutum L. cv. Antares, were grown in nutrient solution, under three levels of nitrogen (N) supply, in order to assess their effects on growth and yield, and to evaluate the N status by the following methods: visual symptoms, changes in the leaf ultrastructure, direct and indirect determinations of leaf chlorophyll (SPAD readings); NO3-N in the petiole both, by spot test in vivo and by quantitative determination; total N in the leaf blade and nitrate reductase activity (NO3 R) in the same; total N in the seeds. Low N level in the solution drastically reduced vegetative growth components, number of bolls and seed cotton and fiber yields. Nitrogen deficiency caused yellowing of the leaves beginning in the older ones. The main changes in the ultrastructure of the N deficient leaves were the disruption of the chloroplast membrane and the accumulation of starch granules and lipid globules. The semiquantitative assessment of nitrate in the petiole was unable to differentiate between the upper levels of nitrogen supply, this being also the case for seed N. Nitrogen status was well correlated both with the quantitative determination of NO3-N and with the NO3 R activity. Both direct and indirect determinations of leaf chlorophyll (SPAD readings) were able to reflect the N status, showing significant correlation with yield.

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.

Efeitos do manganês sobre a soja cultivada em solo de Cerrado do Triângulo Mineiro

Manganese deficiency in soybean [Glycine max (L.) Merrill) and in other crops could be due to its low levels in the soil, or to its unavailability induced by liming. The objective of this research was to verify the soybean mineral composition in relation to Mn availability. An experiment was carried out in a greenhouse, using soil from Patrocinio, MG, Brazil, where the cultivated coffee shows symptoms of Mn deficiency. Mn was applied at the rates of zero, 10, 50 and 100 mg kg with an additional treatment of 0.6% of foliar applied Mn and two rates of lime, namely: zero and 2.7 t ha. Mn concentration in the plant tissue was increased with the rate of lime application; liming, however, caused a Mn reduction. It must be pointed out that the lowest Mn level in the leaves was 84 mg kg, at the zero rate of Mn with lime. Mn ratio caused an increase both in dry matter and grain yield either in the presence and absence of lime. Liming did not induce any symptom of Mn deficiency in the leaves. Leaf applied Mn was efficient to raise and maintain soybean yield.

Cadmium availability and accumulation by lettuce and rice

Among the toxic elements, Cd has received considerable attention in view of its association with a number of human health problems. The objectives of this study were to evaluate the Cd availability and accumulation in soil, transfer rate and toxicity in lettuce and rice plants grown in a Cd-contaminated Typic Hapludox. Two simultaneous greenhouse experiments with lettuce and rice test plants were conducted in a randomized complete block design with four replications. The treatments consisted of four Cd rates (CdCl2), 0.0; 1.3; 3.0 and 6.0 mg kg-1, based on the guidelines recommended by the Environmental Agency of the State of Sao Paulo, Brazil (Cetesb). Higher Cd rates increased extractable Cd (using Mehlich-3, Mehlich-1 and DTPA chemical extractants) and decreased lettuce and rice dry matter yields. However, no visual toxicity symptoms were observed in plants. Mehlich-1, Mehlich-3 and DTPA extractants were effective in predicting soil Cd availability as well as the Cd concentration and accumulation in plant parts. Cadmium concentration in rice remained below the threshold for human consumption established by Brazilian legislation. On the other hand, lettuce Cd concentration in edible parts exceeded the acceptable limit.

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).

Influência do boro e do manganês no crescimento e na composição mineral de mudas de goiabeira

Dois experimentos conduzidos em solucao nutritiva tiveram como objetivo avaliar os efeitos de doses de boro e de manganes no crescimento e na composicao mineral de folhas de mudas de goiabeira (Psidium guajava L.). No experimento com boro, foram testadas sete doses (0, 0,125, 0,25, 0,5, 1,0, 1,5 e 3,0 mg L-1). Pelos resultados, verificou-se que a necrose marginal e as manchas circulares purpuras e esparsas no limbo foliar foram os principais sintomas de toxidez apresentados, sendo esses associados com a dose maxima e com um teor foliar de 146 mg kg-1. Analises de tecidos foliares sem e com necroses mostraram teores de 92 e 720 mg kg-1, respectivamente. Somente a producao de materia seca de raizes e o teor foliar de fosforo e enxofre foram afetados significativamente pelas doses de B. Para o manganes, foram usadas sete doses (0, 0,5, 10, 20, 30, 40 e 50 mg L-1). A producao de materia seca total e os teores foliares de Ca, Mg e Fe foram afetados pelas doses de Mn. Os sintomas foliares de toxidez evidenciaram-se em salpicos adensados de minusculas pontuacoes escuras nas folhas velhas; folhas novas de dimensoes menores, cloroticas e com reticulado verde das nervuras; formacao de pontuacoes circulares castanhas espalhadas ou fundidas ao longo ou entre as nervuras.

Influência do alumínio no crescimento e na acumulação de nutrientes em mudas de goiabeira

Durante 110 dias, realizou-se um experimento em solucao nutritiva, para avaliar os efeitos do aluminio nas concentracoes de 0, 5, 10, 15, 20 e 25 mg L-1, em pH 4,0, sobre o crescimento de mudas de goiabeira, absorcao e acumulacao de macronutrientes e de Cu, Fe, Mn, Zn e Al. Os sintomas visuais de fitotoxidez, associados as doses 20 e 25 mg L-1 de Al, foram caracterizados pela menor altura das plantas, ausencia de ramificacao, menor diâmetro do caule e raizes mais escuras; as folhas apresentaram dimensoes menores e peciolos avermelhados. Em doses relativamente baixas, o aluminio promoveu resposta positiva de crescimento, porem, em doses altas, os teores de macronutrientes e de Fe, Mn e Zn nas folhas de diagnose (3o e 4o pares a partir do apice), bem como o conteudo mineral nas diversas partes da planta, foram influenciados pelas doses de aluminio. A fitotoxidez afetou, mais acentuadamente, os teores de P, Ca, Mg, Mn e Zn. Cerca de 95% do Al absorvido concentrou-se nas raizes.

Effects of Molybdenum, Nickel, and Nitrogen Sources on the Mineral Nutrition and Growth of Rice Plants

Upland rice plants, cultivar ‘IAC 202,’ were grown in nutrient solution until full tillering. Treatments consisted of ammonium nitrate (AN) or urea (UR) as nitrogen (N) source plus molybdenum (Mo) and/or nickel (Ni): AN + Mo + Ni, AN + Mo − Ni, AN − Mo + Ni, UR + Mo + Ni, UR + Mo − Ni, and UR − Mo + Ni. The experiment was carried out to better understand the effect of these treatments on dry‐matter yield, chlorophyll, net photosynthesis rate, nitrate (NO3 −‐N), total N, in vitro activities of urease and nitrate reductase (NR), and Mo and Ni concentrations. In UR‐grown plants, Mo and Ni addition increased yield of dry matter. Regardless of the N source, chlorophyll concentration and net photosynthesis rate were reduced when Mo or Ni were omitted, although not always significantly. The omission of either Mo or Ni led to a decrease in urease activity, independent of N source. Nitrate reductase activity increased in nutrient solutions without Mo, although NO3 −‐N increased. There was not a consistent variation in total N concentration. Molybdenum and Ni concentration in roots and shoots were influenced by their supply in the nutrient solution. Molybdenum concentration was not influenced by N sources, whereas Ni content in both root and shoots was greater in ammonium nitrate–grown plants. In conclusion, it can be hypothesized that there is a relationship between Mo and Ni acting on photosynthesis, although is an indirect one. This is the first evidence for a beneficial effect of Mo and Ni interaction on plant growth.

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).

Resposta do arroz em casa de vegetação a fontes de micronutrientes de diferentes granulometria e solubilidade

A granulometria e a solubilidade do fertilizante podem resultar em maior ou menor efeito da adubacao. O objetivo deste trabalho foi comparar o efeito de um produto comercial granulado e moido de micronutrientes, com uma mistura de igual composicao feita com materiais pro-analise. O delineamento experimental foi o inteiramente casualizado, utilizando tres produtos com micronutrientes e quatro doses de cada mistura (0, 14, 28 e 56 mg dm-3), com quatro repeticoes. A maior producao de graos e obtida com a aplicacao do produto comercial em po. A melhor correlacao entre os materiais e teor na planta ocorre em razao do zinco.