RECOVERY OF AN OXISOL DEGRADED BY THE CONSTRUCTION OF A HYDROELECTRIC POWER PLANT

ABSTRACT The removal of thick layers of soil under native scrubland (Cerrado) on the right bank of the Paraná River in Selvíria (State of Mato Grosso do Sul, Brazil) for construction of the Ilha Solteira Hydroelectric Power Plant caused environmental damage, affecting the revegetation process of the stripped soil. Over the years, various kinds of land use and management systems have been tried, and the aim of this study was to assess the effects of these attempts to restore the structural quality of the soil. The experiment was conducted considering five treatments and thirty replications. The following treatments were applied: stripped soil without anthropic intervention and total absence of plant cover; stripped soil treated with sewage sludge and planted to eucalyptus and grass a year ago; stripped soil developing natural secondary vegetation (capoeira) since 1969; pastureland since 1978, replacing the native vegetation; and soil under native vegetation (Cerrado). In the 0.00-0.20 m layer, the soil was chemically characterized for each experimental treatment. A 30-point sampling grid was used to assess soil porosity and bulk density, and to assess aggregate stability in terms of mean weight diameter (MWD) and geometric mean diameter (GMD). Aggregate stability was also determined using simulated rainfall. The results show that using sewage sludge incorporated with a rotary hoe improved the chemical fertility of the soil and produced more uniform soil pore size distribution. Leaving the land to develop secondary vegetation or turning it over to pastureland produced an intermediate level of structural soil quality, and these two treatments produced similar results. Stripped soil without anthropic intervention was of the lowest quality, with the lowest values for cation exchange capacity (CEC) and macroporosity, as well as the highest values of soil bulk density and percentage of aggregates with diameter size <0.50 mm, corroborated by its lower organic matter content. However, the percentage of larger aggregates was higher in the native vegetation treatment, which boosted MWD and GMD values. Therefore, assessment of some land use and management systems show that even decades after their implementation to mitigate the degenerative effects resulting from the installation of the Hydroelectric Plant, more efficient approaches are still required to recover the structural quality of the soil.

Plant architecture of Paspalum vaginatum schwartz modified by nitrate and ammonium nutrition

Paspalum vaginatum Schwartz plants were grown under greenhouse conditions in a continuous-flow hydroponic culture, containing NO3- or NH4+or NH4NO3 as nitrogen source. After 30 days, the size of aerial biomass and root system decreased significantly when plants were supplied with NH4+as exclusive nitrogen source. Compared to NO3- treatment, reducing and non-reducing sugars were decreasing together with a significant increase in amino acids content. NH4+-nutrition caused tillers to grow toward an orthogravitropic position (average angle of 68° with respect to the horizontal), and with NO3--nutrition, tillers tended to become diagravitropic (average angle of 23°). With NH4NO3 all the parameters measured had values in between those of the other two sources. Thus, the morphologic differences among plants growing in NO3- or NH4+ nutrition confirm the hypothesis that nitrogen source determines the growth habit of tillers in P. vaginatum by modulating the endogenous levels of reducing-non-reducing sugars.

Characterization for plant height and flowering date in the biological species oat

The use of wild oat races in artificial hybridization with cultivated oat (Avena sativa L.) has been used as a way of increasing the variability. This work aimed to identify the variability for plant height and flowering date of groups of cultivated oat genotypes, wild introductions of A. fatua L. and segregating populations of natural crosses between A. sativa and A. fatua. Wide genetic variability was observed for both traits in the groups and between them. The wild group of A. fatua L. showed high plants with early maturity, but in the segregating group there was reduced plant height and early maturity. The wild introductions of A. fatua L. studied in this work can be used in oat breeding programs to increase genetic variability by transferring specific characters into the cultivated germ plasm.

Tomato yield and potassium concentrations in soil and in plant petioles as affected by potassium fertirrigation

Tomato (Lycopersicon esculentum Mill.) cv. Santa Clara was grown on a silt clay soil with 46 mg dm-3 Mehlich 1 extractable K, to evaluate the effects of trickle-applied K rates on fruit yield and to establish K critical concentrations in soil and in plant petioles. Six potassium rates (0, 48, 119, 189, 259 and 400 kg ha-1 K) were applied in a randomized complete block design with four replications. Soil and plant K critical levels were determined at two plant growth stages (at the beginning of the second and fourth cluster flowering). Total, marketable and weighted yields increased with K rates, reaching their maximum of 86.4, 73.4, and 54.9 ton ha-1 at 198, 194, and 125 kg ha-1 K , respectively. At the first soil sampling date K critical concentrations in the soil associated with K rates for maximum marketable and weighted yields were 92 and 68 mg dm-3, respectively. Potassium critical concentrations in the dry matter of the petioles sampled by the beginning of the second and fourth cluster flowering time, associated with maximum weighted yield, were 10.30 and 7.30 dag kg-1, respectively.

Plant regeneration from protoplast of Brazilian citrus cultivars

A procedure is described to regenerate plants from protoplasts of Brazilian citrus cultivars, after isolation, fusion and culture. Protoplasts were isolated from embryogenic cell suspension cultures and from leaf mesophyll of seedlings germinated in vitro. The enzyme solution for protoplast isolation was composed of mannitol (0.7 M), CaCl2 (24.5 mM), NaH2PO4 (0.92 mM), MES (6.15 mM), cellulase (Onozuka RS - Yakult, 1%), macerase (Onozuka R10 - Yakult, 1%) and pectolyase Y-23 (Seishin, 0.2%). Protoplast culture in liquid medium after chemical fusion lead to the formation of callus colonies further adapted to solid medium. Somatic embryo formation occurred spontaneously after two subcultures, on modified MT medium supplemented with 500 mg/L of malt extract. Well defined embryos were germinated in modified MT medium with addition of GA3 (2.0 muM) and malt extract (500 mg/L). Plant regeneration was also achieved by adventitious shoots obtained through direct organogenesis of not well defined embryos in modified MT medium with addition of malt extract (500 mg/L), BAP (1.32 muM), NAA (1.07 muM) and coconut water (10 mL/L). Plantlets were transferred to root medium. Rooted plants were transferred to a greenhouse for further adaptation and development.

Potato crop growth as affected by nitrogen and plant density

Growth and development variables and dry matter characteristics were studied for cultivar Snowden of potato (Solanum tuberosum L.) to evaluate nitrogen and plant density influence. Disregarding ending of season plant stress, the average number of actives haulms per plant was five and it was not affected by plant spacing. However, seasonal and final number of active haulms per plant were increased at 200 kg/ha of nitrogen. Maximum stem elongation was reached quickly with double density and had the tendency to keep constant at the highest and lowest nitrogen levels after 70 days after planting. Specific stem mass defined as mass per unit stem length was established as an indirect measure of stem thickness and load capacity. Specific leaf mass position in plant was higher at upper stem leaves, increased as plant density increased and did not vary markedly over time throughout the season. The rate of leaf appearance increased drastically due to more branching caused by high nitrogen level, and increased above ground dry matter per plant. Canopy growth and development influenced main tuber yield components. The number of active tubers per haulm decreased after 60 days after planting showing that tuberization is reversible. Tuber growth functions were established allowing the estimate of dry biomass partitioning coefficients for each plant organ.

Rearing the southern green stink bug using an artificial dry diet and an artificial plant

Laboratory and greenhouse studies were conducted with an artificial dry diet to rear nymphs, and with an artificial plant as substrate for egg laying by the southern green stink bug, Nezara viridula (L.). The artificial diet was composed of: soybean protein (15 g); potato starch (7.5 g); dextrose (7.5 g); sucrose (2.5 g); cellulose (12.5 g); vitamin mixture (niacinamide 1 g, calcium pantothenate 1 g, thiamine 0.25 g, riboflavin 0.5 g, pyridoxine 0.25 g, folic acid 0.25 g, biotin 0.02 mL, vitamin B12 1 g - added to 1,000 mL of distilled water) (5.0 mL); soybean oil (20 mL); wheat germ (17.9 g); and water (30 mL). Nymphs showed normal feeding behavior when fed on the artificial diet. Nymphal development time was longer than or similar to that of nymphs fed on soybean pods. Total nymphal mortality was low (ca. 30%), both for nymphs reared on the artificial diet, and for nymphs fed on soybean pods. At adult emergence, fresh body weights were significantly (P<0.01) less on the artificial diet than on soybean pods. Despite the lower adult survivorship and fecundity on artificial plants than on soybean plants, it was demonstrated for the first time that a model simulating a natural plant, can be used as a substrate for egg mass laying, in conjunction with the artificial diet.

Analysis of variance of primary data on plant growth analysis

Plant growth analysis presents difficulties related to statistical comparison of growth rates, and the analysis of variance of primary data could guide the interpretation of results. The objective of this work was to evaluate the analysis of variance of data from distinct harvests of an experiment, focusing especially on the homogeneity of variances and the choice of an adequate ANOVA model. Data from five experiments covering different crops and growth conditions were used. From the total number of variables, 19% were originally homoscedastic, 60% became homoscedastic after logarithmic transformation, and 21% remained heteroscedastic after transformation. Data transformation did not affect the F test in one experiment, whereas in the other experiments transformation modified the F test usually reducing the number of significant effects. Even when transformation has not altered the F test, mean comparisons led to divergent interpretations. The mixed ANOVA model, considering harvest as a random effect, reduced the number of significant effects of every factor which had the F test modified by this model. Examples illustrated that analysis of variance of primary variables provides a tool for identifying significant differences in growth rates. The analysis of variance imposes restrictions to experimental design thereby eliminating some advantages of the functional growth analysis.

Effects of plant population and nitrogen fertilizer on yield and efficiency of maize-bean intercropping

Nitrogen supply and plant population are basic parameters for cereal-legume intercropping. In order to study plant population and nitrogen fertilizer effects on yield and yield efficiency of maize-bean intercropping, a field experiment was established. Three bean plant populations and three nitrogen levels were used. Maize dry matter accumulation decreased with increases in bean plant population. Competitive effect of intercrop beans on maize yields was high at higher plant populations, being decreased by nitrogen fertilizer; application of 50 kg ha-1 N was very efficient in increasing maize cob yield. Intercropping significantly decreased harvest index of beans in all plant population and nitrogen fertilizer situations. The efficiency of intercropping, compared to sole cropping, was evidenced by the values obtained for Land Equivalent Ratio (LER) for biomass, cob and pod yields that increased with increases in bean plant populations and nitrogen fertilizer levels.

Spatial statistical analysis and selection of genotypes in plant breeding

The objective of this study was to evaluate the efficiency of spatial statistical analysis in the selection of genotypes in a plant breeding program and, particularly, to demonstrate the benefits of the approach when experimental observations are not spatially independent. The basic material of this study was a yield trial of soybean lines, with five check varieties (of fixed effect) and 110 test lines (of random effects), in an augmented block design. The spatial analysis used a random field linear model (RFML), with a covariance function estimated from the residuals of the analysis considering independent errors. Results showed a residual autocorrelation of significant magnitude and extension (range), which allowed a better discrimination among genotypes (increase of the power of statistical tests, reduction in the standard errors of estimates and predictors, and a greater amplitude of predictor values) when the spatial analysis was applied. Furthermore, the spatial analysis led to a different ranking of the genetic materials, in comparison with the non-spatial analysis, and a selection less influenced by local variation effects was obtained.

Plant growth and phosphorus uptake in mycorrhizal rangpur lime seedlings under different levels of phosphorus

The objective of this work was to evaluate the response of rangpur lime (Citrus limonia) to arbuscular mycorrhiza (Glomus intraradices), under P levels ranging from low to excessive. Plants were grown in three levels of soluble P (25, 200 and 1,000 mg kg-1), either inoculated with Glomus intraradices or left noninoculated, evaluated at 30, 60, 90, 120 and 150 days after transplanting (DAT). Total dry weight, shoot P concentration and specific P uptake by roots increased in mycorrhizal plants with the doses of 25 and 200 mg kg-1 P at 90 DAT. With 1,000 mg kg-1 P, mycorrhizal plants had a transient growth depression at 90 and 120 DAT, and nonmycorrhizal effects on P uptake at any harvesting period. Root colonization and total external mycelium correlated positively with shoot P concentration and total dry weight at the two lowest P levels. Although the highest P level decreased root colonization, it did not affect total external mycelium to the same extent. As a result, a P availability imbalance affected negatively the mycorrhizal symbiosis and, consequently, the plant growth.

Designs and model effects definitions in the initial stage of a plant breeding program

The objective of this work was to compare the relative efficiency of initial selection and genetic parameter estimation, using augmented blocks design (ABD), augmented blocks twice replicated design (DABD) and group of randomised block design experiments with common treatments (ERBCT), by simulations, considering fixed effect model and mixed model with regular treatment effects as random. For the simulations, eight different conditions (scenarios) were considered. From the 600 simulations in each scenario, the mean percentage selection coincidence, the Pearsons´s correlation estimates between adjusted means for the fixed effects model, and the heritability estimates for the mixed model were evaluated. DABD and ERBCT were very similar in their comparisons and slightly superior to ABD. Considering the initial stages of selection in a plant breeding program, ABD is a good alternative for selecting superior genotypes, although none of the designs had been effective to estimate heritability in all the different scenarios evaluated.

Somatic embryogenesis and in vitro plant regeneration from pejibaye adult plant leaf primordia

The aim of this work was to evaluate a protocol for plant regeneration by means of somatic embryos obtained from isolated adult pejibaye leaf primordia, and to describe histological origin of embryos and morphogenetic response. Explants were cultivated in modified MS medium. Mesophyll parenchymatous cells originated meristemoids (preembryonic complex formation) induced with 7.1 µM BAP in the first two subculture periods. After polarized structures with 12.9 µM NAA and 3.55 µM BAP were formed in the third subculture, somatic embryos developed and regenerated normal plants. The mesophyll parenchymatous cells display high capacity of direct response to the auxin and cytokinin.

Potato plant growth and macronutrient uptake as affected by soil tillage and irrigation systems

The objective of this study was to evaluate potato plant growth and macronutrient uptake, as affected by soil tillage methods, in sprinkle and drip irrigated experiments. Eight treatments were set: T1, no tillage, except for furrowing before planting; T2, one subsoiling (SS); T3, twice rotary hoeing (RH); T4, one disc plowing (DP) + twice disc harrow leveling (DL); T5, 1DP + 2DL + 1RH; T6, 1DP + 2DL + 2RH; T7, 1SS + T6; T8, one moldboard plowing (MP) + 2DL. Treatments were arranged in a randomized block design with four replications. In both irrigation systems, plants presented higher emergence velocity index (EVI), when the soil was not tillaged, and the EVI was inversely related to the maximum tuber dry mass production. In both experiments, a functional direct relationship was found between the leaf area index and maximum tuber dry mass yield. The growth of plant organs (tuber, leaf, stem and root) and the macronutrient (N, P, K, Ca and Mg) contents in potato plant responded positively to a deeper soil revolving caused by plowing, especially with moldboard plow.

Plant compounds insecticide activity against Coleoptera pests of stored products

The objective of this work was to screen plants with insecticide activity, in order to isolate, identify and assess the bioactivity of insecticide compounds present in these plants, against Coleoptera pests of stored products: Oryzaephilus surinamensis L. (Silvanidae), Rhyzopertha dominica F. (Bostrichidae) and Sitophilus zeamais Mots. (Curculionidae). The plant species used were: basil (Ocimum selloi Benth.), rue (Ruta graveolens L.), lion's ear (Leonotis nepetifolia (L.) R.Br.), jimson weed (Datura stramonium L.), baleeira herb (Cordia verbenacea L.), mint (Mentha piperita L.), wild balsam apple (Mormodica charantia L.), and billy goat weed or mentrasto (Ageratum conyzoides L.). The insecticide activity of hexane and ethanol extracts from those plants on R. dominica was evaluated. Among them, only hexane extract of A. conyzoides showed insecticide activity; the hexane extract of this species was successively fractionated by silica gel column chromatography, for isolation and purification of the active compounds. Compounds 5,6,7,8,3',4',5'-heptamethoxyflavone; 5,6,7,8,3'-pentamethoxy-4',5'-methilenedioxyflavone and coumarin were identified. However, only coumarin showed insecticide activity against three insect pests (LD50 from 2.72 to 39.71 mg g-1 a.i.). The increasing order of insects susceptibility to coumarin was R. dominica, S. zeamais and O. surinamensis.