Influence of potassium nutrition and the nitrate ammonium ratio on the putrescine and spermidine contents in banana vitroplants

Potassium (K) is required in high doses by the banana (Musa sp.) plant and interacts with other nutrient elements in which banana tissues are maintained under in vitro condition as a consequence modifications in the plant metabolism take place mainly in nitrogen (N) compounds, such as proteins, amino acids, and secondary compounds. When K is present in concentrations lower than that required, diamines such as putrescine and poliamines are formed. This metabolic disorder can also be correlated with the presence of different inorganic N forms, such as nitrate (NO3) and ammonium (NH4), and the ratios between both ions as well. In order to follow the physiological performance of the interrelationships, K/putrescine and of the NO3/NH4 ratio in the tissue of banana vitroplantlets, shoot apex of two banana cvs. Nanica and Prata Ana were maintained in modified MS medium in the presence of six different doses of K: 5, 10, 15, 20, 25, and 30 mM. After the period of tissue proliferation the cultures were transferred to rooting media containing the same different K doses. Dry matter, K, putrescine, and spermidine contents and their accumulation were determined in the shoots and roots of the vitroplantlets and in the shoot apex of the explant donor cultivar as well as the corresponding values for the whole vitroplantlets calculated. The data were statistically analyzed. The contents and accumulations of putrescine and spermidine in banana tissues were enhanced as K concentration decreased in the medium: four times (0.19% of the dry matter) for cv. Nanica and eight times (0.25% of the dry matter) for cv. Prata Ana. This behavior was not only related to the K depletion but to the NO3/NH4 ratio as well.

Structural and functional characteristics of selected soft wheat starches

Starches from eight soft wheat samples (two parent lines and six offspring) were isolated; relationships between their structures and properties were examined. Branch chain-length distributions of amylopectins were determined by using high-performance anion exchange chromatography equipped with an amyloglucosidase reactor and a pulsed amperometric detector (HPAEC-ENZ-PAD). Results showed that the average chain length of the eight samples varied at DP 25.6-26.9. Starch samples of lines 02, 60, 63, 95, and 114 consisted of amylopectins with more long chains (DP greater than or equal to 37) and longer average chain length (DP 26.2-26.9) than that of other samples. These starch samples of longer branch chain length displayed higher gelatinization temperatures (55.3-56.5degreesC) than that of other samples (54.4-54.9degreesC) and higher peak viscosity (110-131 RVU) and lower pasting temperature (86.3-87.6degreesC) than others (83-100 RVU and 88.2-88.9degreesC, respectively). The M-w of amylopectins, determined by using high-performance size exclusion chromatography equipped with multiangle laser-light scattering and refractive index detectors (HPSEC-MALLS-RI), were similar for all samples (6.17 x 10(8) to 6.97 x 10(8)). There were no significant differences in amylose and phosphorus contents between samples. These results indicated that physical properties of wheat starch were affected by the branch-chain length of amylopectin.

The effects of soil fumigation on the growth and mineral nutrition of weeds and crops

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Uso de trigo orgânico na alimentação de juvenis de tilápia do Nilo

Embora a produção de peixes em sistema orgânico seja crescente no mundo, no Brasil, ainda há poucos estudos sobre esta prática. Este trabalho objetivou avaliar a utilização de trigo orgânico, em substituição ao milho orgânico, na dieta de juvenis de tilápia do Nilo. Foram utilizados 200 juvenis (5,24 ± 0,13 g; 6,91 ± 0,40 cm), distribuídos em 20 hapas experimentais (0,15 m³ de volume útil), em tanque de concreto com capacidade para 25,0 m³ de água, com sistema de aeração constante, em delineamento experimental inteiramente casualizado. Foram elaboradas cinco dietas contendo farelo de trigo orgânico (0,0 g kg-1; 50,0 g kg-1; 100,0 g kg-1; 150,0 g kg-1; e 200,0 g kg-1) e o arraçoamento foi realizado quatro vezes ao dia (08:00h, 11:00h, 14:00h e 17:00h). Foram avaliados a massa final, comprimento total, taxa de sobrevivência, ganho de peso diário, fator de condição de Fulton, gordura visceral, índice hepatossomático, índice viscerossomático e a composição centesimal da carcaça dos peixes (teores de umidade, proteína, lipídio e cinza). Os níveis de inclusão de farelo de trigo orgânico não afetaram as variáveis analisadas. O trigo orgânico pode ser incluído na dieta de juvenis de tilápia do Nilo até o limite de 200,0 g kg-1, sem causar qualquer problema produtivo.

Mefenpyr-diethyl action on fenoxaprop-p-ethyl detoxification in wheat varieties

Protetores ou safeners protegem culturas contra a injúria de herbicidas. O propósito deste estudo foi investigar a suscetibilidade diferencial de cinco variedades de trigo (Triticum aestivum) ao herbicida fenoxaprop-p-ethyl e o efeito do protetor mefenpyr-diethyl na minimização da injúria do herbicida e sobre o conteúdo de lipídios. As variedades BRS 49, CD 104, CEP 24, IAPAR 78 e Rubi foram pulverizadas com fenoxaprop-p-ethyl (69 g ha-1), fenoxaprop-p-ethyl + mefenpyr‑diethyl (69 g + 18,75 g ha¹) ou mefenpyr-diethyl (18,75 g ha¹). A injúria das plantas foi avaliada visualmente aos 7 e 14 dias após o tratamento (DAT). A atividade da glutationa S-transferase (GST) foi analisada na parte aérea aos 7 DAT, e o conteúdo de lipídios, aos 14 DAT. As variedades CEP 24, IAPAR 78 e Rubi foram mais tolerantes ao fenoxaprop-p-ethyl do que a BRS 49, e a variedade CD 104 rapidamente se recuperou dos sintomas de intoxicação produzidos pelo herbicida. Mefenpyr-diethyl preveniu a injúria da cultura pelo herbicida. A atividade da GST não foi correlacionada diretamente com a desintoxicação do fenoxaprop-p-ethyl. Contudo, o conteúdo de lipídios esteve relacionado à suscetibilidade de trigo ao tratamento de fenoxaprop-p-ethyl.

Effect of high and low molecular weight glutenin subunits, and subunits of gliadin on physicochemical parameters of different wheat genotypes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

WHEAT CULTIVARS: RESPONSE TO IRRIGATION and SOWING DATES

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Resistance inducing agents on the biology and probing behaviour of the greenbug in wheat

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Liming in the transition to no-till under a wheat-soybean rotation

Soil and subsoil aluminium toxicity has been one of the main limiting factors for soybean and wheat yields in tropical soils. Usually liming is the most effective way to deal with soil acidity and Al toxicity, but in no-till systems the soil is not disturbed making it impossible to incorporate lime in the arable layer, and lime has been usually applied on the soil surface. In this paper soybean and wheat responses to lime applied on the soil surface and/or incorporated in the soil arable layer were evaluated during the transition from conventional tillage to a no-till system. The experiment was conducted for 3 years in Parana, Brazil, using a wheat-soybean rotation. Lime rates ranging from 0.0 to 9.0 t ha(-1) were incorporated down to 20 cm and 4.5 t ha(-1) were spread or not on the soil surface. Soil samples were taken down to 60 cm, 39 months after the first lime application. Soil chemical characteristics were affected by lime application down to 60 cm deep in the profile. Soybean responded to lime irrespective of application method, but the highest accumulated yield was obtained when lime was incorporated into the arable layer. For wheat, the more sensitive the cultivar, the greater was the response to lime. During the introduction of a no-till system, lime must be incorporated into the arable layer when the wheat cultivar is Al-sensitive. (C) 2007 Elsevier B.V. All rights reserved.

ROOT-GROWTH AND MINERAL-NUTRITION OF CORN HYBRIDS AS AFFECTED BY PHOSPHORUS AND LIME

The effects of triple superphosphate (TS) and liming on macronutrient accumulation and root growth of Pioneer 3072 and Cargill 505 com hybrids were studied. Com plants were grown up to 30 days in pots with 7 L of a dark red Latosol sandy loam (Haplortox). Lime was applied to raise base saturation to 30, 50, and 70%, in two levels of phosphorus (P) fertilization with TS (0 and 200 ppm P). There was an increase in root surface due to lime only in pots without TS, with no effects on plant growth or nutrition. Both com hybrids responded to P fertilization, but Pioneer yielded more dry matter than Cargill. The roots of Cargill were thicker and, when in TS presence, were longer and had a larger surface than Pioneer. There was an increase in macronutrient uptake in the P fertilized pots. Pioneer required more nutrients and showed a higher efficiency in acquiring and utilizing the nutrients from the soil. A higher response of Pioneer in dry matter and nutrient acquisition was more related to the physiological efficiency than to root morphology.

Bromeliad-living spiders improve host plant nutrition and growth

Although bromeliads are believed to obtain nutrients from debris deposited by animals in their rosettes, there is little evidence to support this assumption. Using stable isotope methods, we found that the Neotropical jumping spider Psecas chapoda (Salticidae), which lives strictly associated with the terrestrial bromeliad Bromelia balansae, contributed 18% of the total nitrogen of its host plant in a greenhouse experiment. In a one-year field experiment, plants with spiders produced leaves 15% longer than plants from which the spiders were excluded. This is the first study to show nutrient provisioning in a spider-plant system. Because several animal species live strictly associated with bromeliad rosettes, this type of facultative mutualism involving the Bromeliaceac may be more common than previously thought.

Early development and nutrition of cover crop species as affected by soil compaction

A good cover crop should have a vigorous early development and a high potential for nutrient uptake that can be made available to the next crop. In tropical areas with relatively dry winters drought tolerance is also very important. An experiment was conducted to evaluate the early development and nutrition of six species used as cover crops as affected by sub-superficial compaction of the soil. The plants (oats, pigeon pea, pearl millet, black mucuna, grain sorghum, and blue lupin) were grown in pots filled with soil subjected to different subsurface compaction levels (bulk densities of 1.12, 1.16, and 1.60 mg m(-3)) for 39 days. The pots had an internal diameter of 10 cm and were 33.5 cm deep. Grasses were more sensitive to soil compaction than leguminous plants during the initial development. Irrespective of compaction rates, pearl millet and grain sorghum were more efficient in recycling nutrients. These two species proved to be more appropriate as cover crops in tropical regions with dry winters, especially if planted shortly before spring.

Root growth and cotton nutrition as affected by liming and soil compaction

Soil columns were produced by filling PVC tubes with a Dark Red Latosol (Acrortox, 22% of clay). A compacted layer was established at the depth of 15 cm in the columns. In the compacted layer, soil was packed to 1.13, 1.32, 1.48, and 1.82 Mg kg(-1), resulting in cone resistances of 0.18, 0.43, 1.20, and 2.50 MPa. Cotton was cropped for 30 days. Lime was applied to raise base saturation to 40, 52, and 67%. The highest base saturation caused a decrease in phosphorus (P) and zinc (Zn) concentrations in the plants. A decrease in root dry matter, length and surface area was also observed. This could be a consequence of lime induced Zn deficiency. Root growth was decreased in the compacted layer, and complete inhibition was noticed at 2.50 MPa. Once the roots got through the compacted layer, there was a growth recovery in the bottom layer of the pots. The increase in base saturation up 52% was effective in preventing a decrease in cotton root length at soil resistances to 1.20 MPa. Where the roots were shorter, there was an increase in nutrient uptake per unit of root surface area, which kept the plants well nourished, except for P.

Kinetics of zinc uptake and anatomy of roots and leaves of coffee trees as affected by zinc nutrition

Zinc (Zn) uptake kinetics and root and leaf anatomy were studied in coffee trees grown in nutrient solutions with or without Zn. Leaves and roots were sampled and cuts were made in the medium part of the leaves and in root tips and observed under an optical microscope. Plants grown without Zn showed an increase in root and in root stele diameter. There was also an increase in epidermis thickness and in the cross-sectional area of the cortex and stele due to Zn deficiency, but the diameter of xylem vessels was decreased. An increase in root cortex and stele diameter provided for an increased surface for nutrient uptake. Accordingly, C(min) was decreased from 13.8 to 3.4 mu mol L(-1) and V(max) increased from 0.50 to 2.1 mu mol cm(-2) h(-1) .