increase of Al leaf content as a function of Al concentration in the nutrient solution. Plants grown in 1 mM Al showed a remarkable increase of K leaf content, net photosynthesis, stomatal conductance, and transpiration, while in 4 mM Al there were reductions of N, P, and K contents, gas exchange characteristics, and height. H. impetiginosus did not have mechanisms of avoidance, compartmentalization, or resistance to high Al concentrations. Indeed, this species showed a hormetic response, with low Al concentrations stimulating and high Al concentrations inhibiting plant responses.

Limited water availability in reforestation areas can compromise plant growth and development, especially for plants at early stages. In this context, the exogenous application of growth regulators, such as brassinosteroids (BRs), can be used to mitigate the negative effects of water restriction. The aim of this study was to evaluate the effect of the application of BRs (90% brassinolide + a brassinosteroid) on initial growth, gas exchange, leaf water potential and leaf anatomy in yellow Ipê (Handroanthus serratifolius), under water restriction conditions. Throughout the experimental period, plants were maintained in two different water regimes: WR1-plants maintained at 100% of the pot capacity; WR2-plants rehydrated with 50% of the evapotranspiration from the previous day. BRs were applied on three occasions during the experimental period, in five concentrations: C1, 0 g/L (application of distilled water); C2, 0.25 g/L; C3, 0.5 g/L; C4, 0.75 g/L; and C5, 1.00 g/L. The dry mass, root:shoot ratio, water status and leaf anatomy traits were evaluated at the end of the experimental period and were analysed in two-level factorial scheme (2WR  5BRs concentrations). The plant height, number of leaves, gas exchange and leaf chlorophyll content were evaluated four times during the experimental period and were analysed in a split-split-plot design (two WR  five BRs concentrations  four evaluation times). The differences between the means were evaluated by analysis of variance (ANOVA). Pairs of means were separated using the standard error of the difference between the means (SED) and the Fisher's protected least significant difference test (LSD) at p < .05. In addition, all variables were subjected to regression analysis, being the variables evaluated over time, analysed through a two-stage modelling approach. The results obtained indicate that the water deficit led to reductions in growth and gas exchange parameters, regardless of the exogenous application of the regulator; therefore, higher concentrations (C4 and C5) were the most harmful for the maintenance of metabolic and photosynthetic activity. The exogenous application of BRs in H. serratifolius plants attenuated the effects of water limitation on the leaf water potential, but was not able to mitigate for the negative effects in growth, gas exchange and leaf anatomy.

No abstract

This study aimed to determine the consumption of Planococcus citri (Risso, 1813) (Hemiptera: Pseudococcidae) nymphs and the predator:prey ratio required for high predatory efficacy and survival of Chrysoperla externa (Hagen, 1861) (Neuroptera: Chrysopidae) larvae under different densities of prey, reared in rose bushes. Consumption by first-, second-, and third-instar larvae of C. externa was assessed. The predatory efficiency and survival of the predator were calculated for larvae in the second instar under densities of 20, 40, 80, 120, and 160 nymphs of P. citri and predator:prey ratios of 1:5, 1:10, and 1:20. The assessments were performed after 24 and 48 hours of exposure between species. There was increasing consumption throughout the larval development of C. externa. The predator:prey ratios 1:5 and 1:10 were the most efficient for P. citri population reduction, but the 1:5 ratio led to lower survival of larvae than the 1:10 and 1:20 ratios. There was a positive correlation between C. externa larval density and cannibalism (ρ = 0.45) and a negative correlation between predator density and P. citri population density (ρ = -0.81). Third-instar larvae consume more P. citri nymphs than second-instar larvae. Second-instar larvae of this lacewing released at a 1:20 ratio caused total mortality of mealybug nymphs within 48 hours, regardless the density of P. citri, with high larvae survival of C. externa.

The predator Chrysoperla externa (Hagen, 1861) (Neuroptera: Chrysopidae) is a polyphagous species that has, among its wide range of acceptable prey, the aphid Macrosiphum rosae (Linnaeus, 1758) (Hemiptera: Aphididae), an important pest of rose plants. We assessed the consumption of nymphs and adults of M. rosae by C. externa larvae, the predatory efficiency, and larval survival under different predator:prey ratios, densities of aphids, and ages of aphids. The bioassays were performed at 25 ± 1°C and 70 ± 10% RH under a 12-hour photoperiod, with aphids taken from roses of the cultivar Avalanche. Consumption was assessed by making young aphids (2nd and 3rd instars) and more developed aphids (4th instar and adult) available throughout the larval stage of the predator. The predatory efficiency and survival were studied for second-instar larvae offered M. rosae nymphs at densities of 20, 40, 80, 120, and 160 using predator:prey ratios of 1:5, 1:10, and 1:20. The assessments were performed 24, 48, and 72 hours after putting the species together. All of the C. externa instars consumed younger than older aphids. Larvae in the third instar consumed 80% of the young aphids and 77% of the older aphids. The higher the predator:prey ratio and larval density, the higher the predatory efficiency and the lower the larval survival. The ratios 1:5 and 1:10 led to the elimination of younger and older aphid populations 72 hours into the interaction between species.