Induction of plant defense responses by Ocimum gratissimum L. (Lamiaceae) leaf extracts

Aqueous extracts of the leaves of Ocimum gratissimum at 10, 25, 40 and 50% (w/v) concentrations induced the production of phytoalexins in soybean cotyledons and sorghum mesocotyls. The aqueous extracts also induced systemic resistance in cucumber to Colletotrichum lagenarium, reflected by reduction in disease incidence and an increase in chitinase production. Modes of action and the existence of possible elicitors of defense response in O. gratissimum leaf extracts are discussed.

Eucalyptus ESTs involved in mechanisms against plant pathogens and environmental stresses

Eucalypt plantation has high economical importance in Brazil; however, it has been attacked by various pathogens under different environmental stress conditions. Disease resistance and survival under unfavorable environmental conditions have revealed that the eucalypt has developed highly efficient defense systems. Here we show the results of the Eucalyptus ESTs Genome Project (FORESTs). Using the expressed sequence tags (ESTs) obtained by the Project, contigs of similar sequences from each cDNA library induced and not induced by stress agents were formed, and cDNA sequences similar to other already known molecules, such as plant-signaling molecules, phytoalexins, lignin biosynthesis pathways, PR-proteins and putative genes corresponding to enzymes involved in the detoxification of reactive oxygen species, were identified. We also present general considerations about the mechanisms of Eucalyptus defense against biotic and abiotic stresses. These data are of extreme importance for future eucalypt breeding programs aimed at developing plants with enhanced resistance against pathogens and environmental stresses.

Nematicidal effect of volatile organic compounds (VOCs) on the plant-parasitic nematode Meloidogyne javanica

Previous studies have demonstrated that volatile organic compounds (VOCs), produced by the yeast Saccharomyces cerevisiae, were able to inhibit the development of phytopathogenic fungi. In this context, the nematicidal potential of the synthetic mixture of VOCs, constituted of alcohols and esters, was evaluated for the control of the root-knot nematode Meloidogyne javanica, which causes losses to crops of high economic value. The fumigation of substrate containing second-stage juveniles with VOCs exhibited nematicidal effect higher than 30% for the lowest concentration tested (33.3 µL g-1 substrate), whereas at 66.6 and 133.3 µL g-1 substrate, the nematode mortality was 100%. The present results stimulate other studies on VOCs for nematode management.

Effect of light intensity and growth substratum on plant development and production of secondary metabolites in Cordia curassavica (Jacq.) Roem. & Schult

Cordia curassavica (Jacq.) Roem. & Schult. (Boraginaceae), also referred to as Cordia verbenacea DC, has been traditionally used for medicinal purposes. This study was driven to verify the behavior of the species in similar conditions to its natural environment, such as high light intensity and sandbank soil, and in conditions of low light intensity and fertilized substratum (dystroferric red nitosoil plus earthworm humus). The growth of the plant, the income of leaf crude extracts and, in the alcoholic extract, the number of substances found in thin layer cromatography and the toxicity of the substratum was observed. The results indicated that the growth of the root biomass, stem and leaves in discharge or lower light intensity was similar, but smaller in sandbank soil than in fertilized soil. The relative income of extracts in ether of petroleum and alcohol was larger in high light intensity and fertilized substratum. The light intensity and the substratum type didn't affect the number of substances detected in the alcoholic extract or the toxicity of this extract. Stains corresponding to the rosmarinic acid were only evidenced in some samples of the alcoholic extract, not allowing the verification of the effect of the treatments about its production.

Effects of global climate changes on geographical distribution patterns of economically important plant species in cerrado

Different climate models, modeling methods and carbon emission scenarios were used in this paper to evaluate the effects of future climate changes on geographical distribution of species of economic and cultural importance across the Cerrado biome. As the results of several studies have shown, there are still many uncertainties associated with these projections, although bioclimatic models are still widely used and effective method to evaluate the consequences for biodiversity of these climate changes. In this article, it was found that 90% of these uncertainties are related to methods of modeling, although, regardless of the uncertainties, the results revealed that the studied species will reduce about 78% of their geographic distribution in Cerrado. For an effective work on the conservation of these species, many studies still need to be carried out, although it is already possible to observe that climate change will have a strong influence on the pattern of distribution of these species.

Does the edge effect influence plant community structure in a tropical dry forest?

Edge effects are considered a key factor in regulating the structure of plant communities in different ecosystems. However, regardless to few studies, edge influence does not seem to be decisive in semiarid regions such as the Brazilian tropical dry forest known as Caatinga but this issue remains inconclusive. The present study tests the null hypothesis that the plant community of shrubs and trees does not change in its structure due to edge effects. Twenty-four plots (20 x 20 m) were set up in a fragment of Caatinga, in which 12 plots were in the forest edges and 12 plots were inside the fragment. Tree richness, abundance and species composition did not differ between edge and interior plots. The results of this study are in agreement with the pattern previously found for semiarid environments and contrasts with previous results obtained in different environments such as Rainforests, Savanna and Forest of Araucaria, which indicate abrupt differences between the border and interior of the plant communities in these ecosystems, and suggest that the community of woody plants of the Caatinga is not ecologically affected by the presence of edges.

Thinning effect on plant growth of pruned eucalypt clone

A pruned stand of eucalypt clone underwent five thinning treatments with the removal of different proportion of the planted trees, at different ages: a) 0% - unthinned, b) 35% at 55 months, c) 35% at 81 months, d) 70% at 81 months, removing sprouts in the thinned plant stumps and, e) 70% at 81 months, without coppice sprouts removal. By the age of 141 months, the Weibull distribution showed higher number of trees in the smallest diameter classes for the unthinned treatment. The 70% thinning, with thinned coppice sprouts removal, presented higher number of individuals in the largest diameter classes. Height and yield were the smallest with the removal of 70% of the trees at 81 months, maintaining coppice sprouts. The afterthinning periodic annual increment was greater by thinning 35% of the trees at 55 months resulting in greater number of trees in the largest diameter classes as compared to the other treatments. Yield was higher for the unthinned treatment. The results of this study indicated that thinning 70% of the trees at the age of 81 months, with coppice sprout removal, could be recommended to obtain trees of larger diameter for multiproduct.

PLANT GROWTH-PROMOTING MICROBIAL INOCULANT FOR Schizolobium parahyba pv. parahyba

ABSTRACTSchizolobium parahyba pv. amazonicum (Huber ex Ducke) Barneby (paricá) occurs naturally in the Amazon and is significant commercial importance due to its rapid growth and excellent performance on cropping systems. The aim of this paper was to evaluate a microbial inoculants such as arbuscular mycorrhiza fungi (AMF) and Rhizobium sp. that promote plant growth. The inocula was 10 g of root colonized and spores of Glomus clarum and/or 1 mL of cell suspension (107 CFU/mL) of Rhizobium sp. and/or 100 g of chemical fertilizer NPK 20-05-20 per planting hole. The experimental design was complete randomized blocks with five replications and eight treatments (n = 800). Plant height, stem diameter and plant survival were measured. The results were tested for normality and homogeneity of variances and analyzed by ANOVA and Tukey test (p < 0.05). Rhizobium sp and AM fungi showed no effect on plant growth. Environmental factors probably influenced the effectiveness of symbiosis of both microorganisms and plant growth. The chemical fertilizer increased S. parahyba growth. During the first 120 days plants suffered with drought and frost, and at 180 days plants inoculated with microorganism plus chemical fertilizer showed higher survival when compared with control. The results showed that the microbial inoculants used showed an important role on plant survival after high stress conditions, but not in plant growth. Also was concluded that the planting time should be between November to December to avoid the presence of young plants during winter time that is dry and cold.

Quali/quantitative characterization of biogas produced in batch digesters supplied with six distinct substrates

The present research was carried out at the DER/FCAV, São Paulo State University - Brazil, with the purpose of analyzing the quantity and quality of biogas produced by six types of substrates. The substrates used in the anaerobic digestion were characterized as: 1- Litter of broiler (LB); 2- Grinded broiler litter (GBL); 3- Broiler litter with wood shavings (BLWS); 4- Grinded broiler litter with wood shavings (GBLWS); 5- Broiler litter with peanut hulls (BLPH); 6- Grinded broiler litter with peanut hull (GBLPH). It was concluded from the collected data that: the (GBL) substrate showed a superior biogas accumulated production in relation to the other substrates, while the BLWS presented an inferior accumulated production; the grinded substrates showed higher quantities of accumulated biogas in relation to the non-grinded substrates, except for GBLPH, with 20.9 m³ inferior than BLPH; the period of maximum biogas production started from 45 to 60 days, declining after 120 days; at 57 days after filling up the digesters the biogas produced had levels of CH4 superior than 53%, and from 99 days all of them produced biogas with levels of CH4 superior than 70%; LB and GBL presented higher concentrations of CH4 in the biogas.

Estimation of transpiration of the 'Valencia' orange young plant using thermal dissipation probe method

Most studies on measures of transpiration of plants, especially woody fruit, relies on methods of heat supply in the trunk. This study aimed to calibrate the Thermal Dissipation Probe Method (TDP) to estimate the transpiration, study the effects of natural thermal gradients and determine the relation between outside diameter and area of xylem in 'Valencia' orange young plants. TDP were installed in 40 orange plants of 15 months old, planted in boxes of 500 L, in a greenhouse. It was tested the correction of the natural thermal differences (DTN) for the estimation based on two unheated probes. The area of the conductive section was related to the outside diameter of the stem by means of polynomial regression. The equation for estimation of sap flow was calibrated having as standard lysimeter measures of a representative plant. The angular coefficient of the equation for estimating sap flow was adjusted by minimizing the absolute deviation between the sap flow and daily transpiration measured by lysimeter. Based on these results, it was concluded that the method of TDP, adjusting the original calibration and correction of the DTN, was effective in transpiration assessment.

Potentials of biogas production from young bulls manure fed with different diets

Physical and chemical characteristics of manure are modified by different animal production systems. In cattle feeding system for young bulls there is an inversion of the proportion between forage and concentrate. In other words, the animals receive a smaller amount of forage compared to the traditional system. These changes in the manure characteristics involve changes in the treatment systems. The aim of this study was to determine the potential production of biogas of batch digesters fed with manure from young bulls that received two diets containing different proportions between forage and concentrate, with or without inoculums and submitted to three levels of temperature (25, 35 and 40(0)C). The evaluated parameters were total solids (TS) and volatile solids (VS) reduction and biogas potentials production. The digesters fed with manure from animals that received the diet 2 (80%C + 20% R) showed the largest reductions of TS and VS. About the potentials of biogas production there was interaction between the factors diet and inoculums, but no effects of temperatures. The treatment content manure from animals fed with diet 2 without inoculums presented the greatest potential of biogas production per kg of TS added (0.2123 m³).

Potential of biogas production from swine manure supplemented with glycerine waste

In this study, was studied the biogas generation from swine manure, using residual glycerine supplementation. The biogas production by digestion occurred in the anaerobic batch system under mesophilic conditions (35°C), with a hydraulic retention time of 48 days. The experiment was performed with 48 samples divided into four groups, from these, one was kept as a control (without glycerin) and the other three groups were respectively supplemented with residual glycerine in the percentage of 3%, 6% and 9% of the total volume of the samples. The volume of biogas was controlled by an automated system for reading in laboratory scale and the quality of the biogas (CH4) measured from a specific sensor. The results showed that the residual glycerine has high potential for biogas production, with increases of 124.95%, 156.98% and 197.83% in the groups 3%, 6% and 9%, respectively, relative to the sample control. However, very high organic loads can compromise the process of digestion affecting the quality of the biogas generated in relation to methane.

Spraying systems and traveling speed in the deposit and spectrum of droplets in cotton plant

ABSTRACT Tractor traveling speed can influence the quality of spraying depending on the application technology used. This study aimed to evaluate the droplet spectrum, the deposition and uniformity of spray distribution with different spraying systems and traveling speeds of a self-propelled sprayer in two phenological stages of the cotton plant (B9 and F13). The experimental design was randomized blocks and treatments were three spraying techniques: common flat spray tips; tilted flat jet with air induction, at 120 L ha-1; and rotary atomizer disk, 20 L ha-1, combined with four traveling speeds: 12, 15, 18 and 25 km h-1, with four replications. Spraying deposition was evaluated for both leaf surfaces from the cotton plant apex and base (stage B9) and middle part of the plant (stage F13) with a cupric marker. A laser particle analyzer also assessed the droplet spectrum. The centrifugal power spray system produces more homogeneous droplet spectrum and increased penetration of droplets into the canopy in both phenological stages. Variation on the operating conditions necessary for increased traveling speed negatively influences the pattern of spraying deposits.

Rice seedling and plant development as affected by increasing rates of penoxsulam under controlled environments

Rice is a major staple in many countries. Weed control is one of the factors limiting higher rice yield. ALS (acetolactate synthase)-inhibiting herbicides are desirable weed control herbicides because of their high efficacy, low toxicity to mammalians, and low rates used. An important herbicide characteristic is high selectivity to the crop, since it facilitates fast crop establishment and greater crop advantage over the weeds. The objectives of this work were to study the effects of increasing rates of the ALS-inhibiting herbicide penoxsulam on seed integrity and germination, and seedling and plant development of rice cv. BRS Pelota under controlled laboratory and greenhouse conditions. The results showed that penoxsulam affected rice germination and seedling and plant growth at rates above 54 g a.i. ha-1, and that penoxsulam is safe for rice seedling development at the currently recommended rates.

Effect of plant row spacing and herbicide use on weed aboveground biomass and corn grain yield

The use of narrow plant spacing in corn (Zea mays) has been suggested as a technological alternative to obtain grain yield increases, due to a better use of resources. The regular pattern could diminish intraspecific competition while favoring interspecific competition with weeds. The objective of this study was to analyze the effect of corn row spacing on weed aboveground biomass and corn grain yield. Field experiments were conducted during 2002/2003 and 2003/2004 growing seasons. Three corn hybrids with two-row width (0.70 and 0.35 m) were tested. A greater photosynthetic photon flux density (PPFD) interception with a lower weed aboveground dry matter in narrow row arrangement was obtained. Corn grain yield was greater in the narrow row arrangement than in the wide row spacing. This increase in grain yield was related to a better resource use that allows for a reduced interspecific competition. The use of reduced spatial arrangement appeared to be an interesting alternative to increase both the grain yield potential and corn suppressive ability against weeds in corn dryland production systems.