Herbicidas inibidores da ACCase em plantas de Cenchrus echinatus em estresse hídrico

This project aimed to relate the efficiency of control of ACCase inhibiting herbicides applied post-emergence in Cenchrus echinatus under different soil water contents. The experiments were conducted in a greenhouse, with the application of three different herbicides (fluazifop-p-butyl, haloxyfop-methyl and sethoxydim + oil Assist) and the experimental design for each herbicide was completely randomized design with four replications, consisting a 3 x 4 factorial, with the combination of water management strategies (-0.03, -0.07 and -1.5 MPa) and four doses of these products (100, 50, 25 and 0% of the recommended dose). Herbicide application was made at vegetative stage of 2-3 tillers. The water management strategies were initiated in the development stage of two leaves, replacing the water until the soil reaches the potential of -0.01 MPa, when it came to severe pre-determined for each water management. The physiological parameters evaluated were: photosynthetic rate, stomatal conductance, transpiration, leaf temperature and plant dry matter. The visual assessments of phytotoxicity were performed at 7, 14, 21 and 28 days after application. The efficiency of these herbicides was influenced by soil management and water lowest in plants grown in the minimal potential of water in the soil of -1.5 MPa. All the herbicides were unsatisfactory controls in applications late (2-3 tiller plants).

Influence of soil water potential in the action of herbicides on goosegrass (Eleusine indica (L) Gaertn)

Currently, the use of herbicides is essential in a practical and common in agricultural areas, but efficiency of these herbicides can be compromised when applied on plants that thrive in water deficit conditions, due to low uptake and translocation of the product. Therefore, the aim of this study was to compare the efficiency of control ACCase inhibiting herbicides applied post-emergence in plants of Eleusine indica under different soil water contents. The experiment was conducted in a greenhouse and the experimental design was completely randomized design with four replications, consisting of a 9x4 factorial, with the combination of three soil water potentials (-0.03, -0.07 and -1.5 MPa) three herbicides (fluazifop-p -butyl, haloxyfop-methyl and sethoxydim + oil) and four doses (0, 25, 50, and 100 % of the recommended dose). Herbicide application was made in plants in vegetative stage 2-3 tillers. The soil water potential was initiated in the development stage of two leaves, and the water was supplemented until the soil reaches the potential of -0.01 MPa, when it came to minimum pre-determined for each water management. The physiological parameters evaluated were: photosynthetic rate, stomatal conductance, transpiration leaf temperature and plant dry mass. The visual assessments of phytotoxicity were performed at 7 and 14 days after application. The herbicides behaved in different ways according to the used water management. In severe water stress conditions (soil moisture at 8%) only fluazifop-p-butyl herbicide achieved satisfactory control (> 90%) in E. indica plants.

Effect of temperature, leaf wetness, and rainfall on the production of Guignardia citricarpa ascospores and on back spot severity on sweet orange

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of temperature and leaf wetness duration on infection of sweet oranges by Asiatic citrus canker

Asiatic citrus canker, caused by Xanthomonas smithii ssp. citri, formerly X. axonopodis pv. citri, is one of the most serious phytosanitary problems in Brazilian citrus crops. Experiments were conducted under controlled conditions to assess the influence of temperature and leaf wetness duration on infection and subsequent symptom development of citrus canker in sweet orange cvs Hamlin, Natal, Pera and Valencia. The quantified variables were incubation period, disease incidence, disease severity, mean lesion density and mean lesion size at temperatures of 12, 15, 20, 25, 30, 35, 40 and 42 degrees C, and leaf wetness durations of 0, 4, 8, 12, 16, 20 and 24 h. Symptoms did not develop at 42 degrees C. A generalized beta function showed a good fit to the temperature data, severity being highest in the range 30-35 degrees C. The relationship between citrus canker severity and leaf wetness duration was explained by a monomolecular model, with the greatest severity occurring at 24 h of leaf wetness, with 4 h of wetness being the minimum duration sufficient to cause 100% incidence at optimal temperatures of 25-35 degrees C. Mean lesion density behaved similarly to disease severity in relation to temperature variation and leaf wetness duration. A combined monomolecular-beta generalized model fitted disease severity, mean lesion density or lesion size as a function of both temperature and duration of leaf wetness. The estimated minimum and maximum temperatures for the occurrence of disease were 12 degrees C and 40 degrees C, respectively.

The influence of temperature on oxygen consumption rates of workers of two leaf cutting ants, Atta laevigata (F. Smith, 1858) and Atta sexdens rubropilosa (Forel, 1908)

1. 1. The oxygen consumption in workers of two simpatric leaf cutting ants, Atta laevigata and Atta sexdens rubropilosa was measured at different temperatures. 2. 2. In the temperature range between 5-35°C, with 5°C increments, the respiratory rates increased with temperature, but the R-T curves of both ants showed neither a marked drop at the low end nor a break at the high end; except between 30 and 35°C. 3. 3. The respiratory rates of A. s. rubropilosa were higher than those of A. laevigata and in the midrange of temperatures, the rates of A. laevigata increased faster than those of A. s. rubropilosa. 4. 4. Q10 values did not indicate regions of compensation for temperature in both ants, but suggested that adjustments may occur at high temperatures (25-35°C), as expected for tropical ants. 5. 5. Temperature variations did not alter significantly the slope of the curve relating oxygen consumption and body weight in both species. © 1982.

Substrate and Temperature Effects on the Germination of Dypsis leptocheilos (Hodel) Beentje & J. Dransf. (Arecaceae) Seeds

Dypsis leptocheilos is highly valued as an ornamental palm. Its propagation is done by seeds; however, there is little information about this process. The objective of this work was to study the substrate and temperature effects on the germination of D. leptocheilos seeds. The experiments were carried out at FCAV/UNESP, Campus of Jaboticabal, São Paulo State, Brazil. In order to study the substrate effects, four treatments were arranged (coconut fiber, sand, vermiculite and Plantmax (R)) at 30 degrees C. For the temperature effects, six treatments were performed (temperature at laboratory conditions (21.5 degrees C and 72% RU), 25 degrees C, 30 degrees C, 35 degrees C, 20-30 degrees C and 25-35 degrees C), having the coconut fiber as the substrate. The experimental design was completely randomized, with four replicates of 25 disseminules per plot (seeds with attached endocarp). Water replacement was managed to maintain 100% of the retention capacity of the substrates. The germination tests were observed every two days, and conducted over 148 days for the substrate effects, and over 152 days for the temperature effects, when no more seed germination was noted. In order to determine the germination percentage (% G) and the Germination Speed Index (GSI), the seed was considered germinated when the germinative button appeared. At the end of the experiments, leaf area (cm(2)), root and shoot length (cm), root and shoot dry mass (g) were also obtained. Statistical analysis was performed and means were compared by the Tukey test. Germination rate and speed in coconut fiber was higher at 25 and 30 degrees C. However, when other substrates were tested at 30 degrees C, the highest germination percentage was observed in vermiculite, which also sustained better results for the seed germination and for the characteristics related to shoots and roots.

Cotton response to mepiquat chloride and temperature

Gibberellin inhibitor growth regulators are used for cotton (Gossypium hirsutum L.) canopy manipulation to avoid excess growth and yield losses. However, under temperatures below or over the optimum for cotton production the effect of mepiquat chloride (MC) has not always been significant. In this experiment, cotton plants were grown in growth chambers to study the response to MC as affected by temperature and to determine if an increase in dose could overcome the temperature effects. Mepiquat chloride was applied at rates of 0, 15 and 30 g ai ha-1 at the pinhead square stage. Plants were then grown under three temperature regimes: 25/15 °C, 32/22 °C, and 39/29 °C (day/night temperatures) for 51 days. Higher temperatures increased plant height, reproductive branches, fruit number, fruit abscission, and photosynthesis per unit area, but decreased leaf area and chlorophyll. The largest effect of MC on plant height was observed when the daily temperature was 32 °C, with nights of 22 °C, which was also best for plant growth. High temperatures not only decreased the effectiveness of MC on plant height control, but also caused lower dry matter and fruit number per plant. Low temperatures (25/15 ºC) decreased cotton growth and fruit retention, but a higher concentration of MC was required per unit of growth reduction as compared with 32/22 ºC. At high temperatures, the rate of MC to be applied must be disproportionately increased, because either plant growth is impaired by high temperature lessening the effect of MC, or degradation of MC within the plant is too rapid.

Effect of Mikania glomerata (Asteraceae) leaf extract combined with anti-venom serum on experimental Crotalus durissus (Squamata: Viperidae) envenomation in rats

Crotalic envenomation represents the highest number of deaths when compared to other snakebite envenomations of medical interest. Crotalic venom has important characteristics such as neurotoxicity, myotoxicity, nephrotoxicity, and clotting and hemolytic action. We evaluated the clinical and laboratory aspects of Crotalus durissus terrificus experimental envenomation in Wistar rats treated with antivenom and the aqueous extract of the plant mikania glomerata. The animals were divided into three groups: Group C (control); Group VS-venom and antivenom; Group VSM-venom, antivenom and aqueous extract of M glomerata. Crotalic poison caused clinical and laboratory alterations in Wistar mice. Significant clinical alterations were: temperature decrease, edema in the venom inoculated member, sedation and a locomotion decrease in groups VS and VSM when compared with group C. A faster recovery from sedation was observed only for animals of group VSM when compared to VS. There was an increase in the number of leukocytes, neutrophils and creatine kinase in the VS and VSM groups, compared to group C. Wistar rats showed a high resistance to crotalic venom. Additional studies with different doses, time of treatment, different administration methods and histopathological and immunological studies are necessary to understand the action of M glomerata in crotalic accidents. Rev. Biol. Trop. 57 (4): 929-937. Epub 2009 December 01.

A model for optimal chemical control of leaf area damaged by fungi population - Parameter dependence

We present a model to study a fungi population submitted to chemical control, incorporating the fungicide application directly into the model. From that, we obtain an optimal control strategy that minimizes both the fungicide application (cost) and leaf area damaged by fungi population during the interval between the moment when the disease is detected (t = 0) and the time of harvest (t = t(f)). Initially, the parameters of the model are considered constant. Later, we consider the apparent infection rate depending on the time (and the temperature) and do some simulations to illustrate and to compare with the constant case.

Anti-nociceptive effects of Carpolobia lutea G. Don (Polygalaceae) leaf fractions in animal models

Leaves from Carpolobia lutea (Polygalaceae) were screened to establish the antiulcer ethnomedicinal claim and to quantitatively isolate, elucidate the active compounds by semi-preparative HPLC. The anti-nociceptive effects of Carpolobia lutea (CL) G. Don (Polygalaceae) organic leaf extracts were tested in experimental models in mice. The anti-nociceptive mechanism was determined using tail-flick test, acetic acid-induced abdominal constrictions, formalin-induced hind paw licking and the hot plate test. The fractions (ethanol, ethyl acetate, chloroform, n-hexane) and crude ethyl acetate extract of CL (770 mg/kg, i.p.) produced significant inhibitions of both phases of the formalin-induced pain in mice, a reduction in acetic acid-induced writhing as well as and an elevation of the pain threshold in the hot plate test in mice. The inhibitions were greater to those produced by indomethacin (5 mg/kg, i.p.). Ethyl acetate fraction revealed cinnamic and coumaric acids derivatives, which are described for the first time in literature. These cinnamalglucosides polyphenols characterised from CL may in part account for the pharmacological activities. These findings confirm its ethnomedical use in anti-inflammatory pain and in pains from gastric ulcer-associated symptoms. © 2011 Springer Basel AG.

Vertical variation in autumn leaf phenology of Fagus sylvatica L. in southern Germany

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)