The aim of this study was to evaluate the anesthesia induction and recovery times of sub-adult and post-larvae white shrimp (Litopenaeus vannamei) that were treated with eugenol and the essential oils (EOs) from Lippia alba and Aloysia triphylla. Oxidative stress parameters in the hemolymph of this species were also analyzed. The concentrations of eugenol, A. triphylla EO and L. alba EO recommended for anesthesia were 200, 300 and 750 μL L(-1) for sub-adults and 175, 300 and 500 μL L(-1) for post-larvae, respectively. The concentrations studied during the transport of sub-adults were between 20 and 50 μL L(-1) eugenol, 20-30 μL L(-1)A. triphylla EO and 50 μL L(-1)L. alba EO. For post-larvae, the optimal concentrations for transport were 20 μL L(-1) eugenol and between 20 and 50 μL L(-1)A. triphylla EO. The white shrimp sub-adults that were exposed to A. triphylla EO (20 μL L(-1)) showed increases in their total antioxidant capacities (150%), catalase (70%) and glutathione-S-transferase (615%) activity after 6 h. L. alba EO (50 μL L(-1)) and eugenol (20 μL L(-1)) also increased GST activity (1292 and 1315%) after 6 h, and eugenol (20 μL L(-1)) decreased the total antioxidant capacity (100%). Moreover, concentrations above 30 μL L(-1) for the EOs of A. triphylla and L. alba and 20 μL L(-1) eugenol were effective at inducing anesthesia and improving the antioxidant system against reactive oxygen species (ROS) after 6 h.

Plant diseases cause losses of approximately 16% globally. Thus, management measures must be implemented to mitigate losses and guarantee food production. In addition to traditional management measures, induced resistance and biological control have gained ground in agriculture due to their enormous potential. Endophytic fungi internally colonize plant tissues and have the potential to act as control agents, such as biological agents or elicitors in the process of induced resistance and in attenuating abiotic stresses. In this review, we list the mode of action of this group of microorganisms which can act in controlling plant diseases and describe several examples in which endophytes were able to reduce the damage caused by pathogens and adverse conditions. This is due to their arsenal of molecules generated during the interaction by which they form a kind of biological shield in the plant. Furthermore, considering that endophytic fungi can be an important tool in managing for biotic and abiotic stresses due to the large amount of biologically active substances produced, bioprospecting this class of microorganisms is tending to increase and generate valuable products for agriculture.

Responses to anaesthesia with essential oil (EO) of Aloysia triphylla (135 and 180 mg L−1) and tricaine methanesulfonate (MS222) (150 and 300 mg L−1) were assessed in silver catfish. Exposure to the anaesthetics elicited a stress response in the species. In the case of MS222, it was displayed as a release of cortisol into bloodstream, elevation in hematocrit and plasma ion loss. The EO presented cortisol‐blocking properties, but increased haematocrit and disturbances of hydromineral balance were observed. Liver antioxidant/oxidant status of EO and MS222‐anaesthetized silver catfish was also estimated. The synthetic anaesthetic induced lipoperoxidation, notwithstanding increased catalase contents, whereas the naturally occurring product was capable of preventing the formation of lipid peroxides, possibly due to combined actions of catalase and glutathione‐S‐transferase. Anaesthetic efficacy was also tested via induction and recovery times. Overall, the promising results obtained for the physiological parameters of the EO‐treated fish counterbalanced the slight prolonged induction time observed for 180 mg L−1. As for 135 mg L−1, both induction and recovery times were lengthy; despite that, the EO was able to promote oxidative protection and mitigate stress. None of the MS222 concentrations prompted such responses concomitantly.

No abstract

The multicollinearity in path analysis was investigated in different scenarios. A biometrical approach identified the multicollinearity‐generating traits. Data derived from averages overestimated the correlation coefficients. The use of all sampled observations increased the accuracy in path analysis. A simple sample tracking method that reduces multicollinearity is proposed. Some data arrangement methods often used may mask correlation coefficients among explanatory traits, increasing multicollinearity in multiple regression analysis. This study was performed to determine if the harmful effects of multicollinearity might be reduced in the estimation of the X′X correlation matrix among explanatory traits. For this, data on 45 treatments (15 maize [Zea mays L.] hybrids sown in three places) were used. Three path analysis methods (traditional, with k inclusion, and traditional with trait exclusion) were tested in two scenarios: with X′X matrix estimated with all sampled observations (ASO, n = 900) and with the X′X matrix estimated with the average values of each plot (AVP, n = 180). The condition number (CN) was reduced from 3395 to 2004 when the matrix was estimated with all observations. On average, the factors that inflate the variance of regression coefficients were increased by 61% in the AVP scenario. The addition of the k coefficient reduced the CN to 85.40 and 51.17 for the ASO and AVP scenarios, respectively. Exclusion of multicollinearity‐generating traits was more effective in the ASO than the AVP scenario, resulting in CNs of 29.62 and 63.66, respectively. The largest coefficient of determination (0.977) and the smallest noise (0.150) were obtained in the ASO scenario after the exclusion of the multicollinearity‐generating traits. The use of all sampled observations does not mask the individual variances and reduces the magnitude of the correlations among explanatory traits in 90% of cases, improving the accuracy of biological studies involving path analysis.

No abstract

The objective of this study was to identify the possible involvement of the GABAergic system in the anesthetic effect of Lippia alba essential oil (EO). We propose a new animal model using silver catfish (Rhamdia quelen) exposed to an anesthetic bath to study the mechanism of action of EO. To observe the induction and potentiation of the anesthetic effect of EO, juvenile silver catfish (9.30 ± 1.85 g; 10.15 ± 0.95 cm; N = 6) were exposed to various concentrations of L. alba EO in the presence or absence of diazepam [an agonist of high-affinity binding sites for benzodiazepinic (BDZ) sites coupled to the GABAA receptor complex]. In another experiment, fish (N = 6) were initially anesthetized with the EO and then transferred to an anesthetic-free aquarium containing flumazenil (a selective antagonist of binding sites for BDZ coupled to the GABAA receptor complex) or water to assess recovery time from the anesthesia. In this case, flumazenil was used to observe the involvement of the GABA-BDZ receptor in the EO mechanism of action. The results showed that diazepam potentiates the anesthetic effect of EO at all concentrations tested. Fish exposed to diazepam and EO showed faster recovery from anesthesia when flumazenil was added to the recovery bath (12.0 ± 0.3 and 7.2 ± 0.7, respectively) than those exposed to water (9.2 ± 0.2 and 3.5 ± 0.3, respectively). In conclusion, the results demonstrated the involvement of the GABAergic system in the anesthetic effect of L. alba EO on silver catfish.

RESUMO -A produção de fitomassa é uma função da eficiência de conversão da radiação solar fotossinteticamente ativa interceptada em fotoassimilados, variando conforme as condições em que as plantas são cultivadas. Assim, este trabalho teve como objetivo quantificar a eficiência de conversão da radiação solar fotossinteticamente ativa interceptada em fitomassa -εb -de mudas de Eucalyptus grandis W. Hill ex Maiden (eucalipto) quando submetidas a diferentes tamanhos de tubetes e densidades de plantas. Para tanto, foi conduzido um experimento, em delineamento de blocos ao acaso, para estudar a produção de mudas em dois tamanhos de tubetes (pequeno e médio) e duas densidades de plantas na bandeja (alta com 100% de ocupação da bandeja e média com 50%), em que foram determinados a radiação fotossinteticamente ativa interceptada (RFAi), o índice de área foliar e a fitomassa seca total das mudas. O volume do tubete não interferiu nos valores de eficiência, mas, sim, a densidade de plantas, pois o índice de área foliar é quem determina tal valor. A εb foi de 7,33 g.MJ -1 em tubete médio e pequeno em densidade alta e de 3,26 g.MJ -1 em tubete médio e pequeno em densidade média.Palavras-chave: Ocupação da bandeja, Densidade de plantio e Radiação fotossinteticamente ativa. EFFICIENCY OF THE CONVERSION OF PHOTOSYNTHELICALLY ACTIVE RADIATION DRY BIOMASS IN EUCALYPTUS SEEDLINGS