Verbal fluency development across childhood: normative data from brazilian–portuguese speakers and underlying cognitive processes

Objective: Verbal fluency (VF) tasks are widely used to investigate children’s lexical knowledge and executive functions skills. Consistency of measurement of the strategic retrieval components is still an issue and performance of Brazilian–Portuguese speaking children are currently not available. A cross-sectional study investigated the effects of age, school type (public × private) and the influence of language, memory and inhibitory control on VF. Method: We assessed 414 Brazilian children, aged 6–12, in the number of words produced and both clustering and switching components, with two measures of VF: letter (LVF) and semantic (SVF). Results: Analysis of the number of words produced showed a significant increase between 6–8-year-olds, 9–10-year-olds and 11–12-yearolds in SVF, while in LVF, the differences were significant only in the later age group. In SVF, the numbers of clusters and switches increased with age, whereas in LVF, the number of switches increased in all age groups, but clusters increased only in the older group. Structural equation model analyses showed that oral and written language, verbal memory and inhibitory control are associated with VF performance and IQ, while age mediated VF performance. Conclusions: The results indicate a different development pattern between LVF and SVF in the number of words produced and in clustering and switching, with the latter predicting VF performance in words produced. VF development is shown to depend on language, memory and inhibitory control. Our results have important implications to clinical neuropsychology

Verbal fluency development across childhood: normative data from brazilian–portuguese speakers and underlying cognitive processes

Objective: Verbal fluency (VF) tasks are widely used to investigate children’s lexical knowledge and executive functions skills. Consistency of measurement of the strategic retrieval components is still an issue and performance of Brazilian–Portuguese speaking children are currently not available. A cross-sectional study investigated the effects of age, school type (public × private) and the influence of language, memory and inhibitory control on VF. Method: We assessed 414 Brazilian children, aged 6–12, in the number of words produced and both clustering and switching components, with two measures of VF: letter (LVF) and semantic (SVF). Results: Analysis of the number of words produced showed a significant increase between 6–8-year-olds, 9–10-year-olds and 11–12-yearolds in SVF, while in LVF, the differences were significant only in the later age group. In SVF, the numbers of clusters and switches increased with age, whereas in LVF, the number of switches increased in all age groups, but clusters increased only in the older group. Structural equation model analyses showed that oral and written language, verbal memory and inhibitory control are associated with VF performance and IQ, while age mediated VF performance. Conclusions: The results indicate a different development pattern between LVF and SVF in the number of words produced and in clustering and switching, with the latter predicting VF performance in words produced. VF development is shown to depend on language, memory and inhibitory control. Our results have important implications to clinical neuropsychology

Humic substances trigger plant immune responses

Abstract Background Huanglongbing (HLB) is a devastating citrus disease. Before callose deposition, the bacterial infection causes oxidative stress, starting cell damage. Humic substances are among the most efficient antioxidants found in nature. Furthermore, it is also previously reported that humic substances can induce a phenylpropanoid metabolism contributing to the production of antimicrobial compounds. It has been noted by technicians and growers in the Brazil's main citrus belt that orchards continuously treated with humic substances can live well with the symptoms of HLB. Methods We treated two young citrus orchards (Citrus sinensis cultivars Baía and Pera)  with soluble humic substances (HS) isolated from peat either combined or not with a plant growth-promoting bacteria consortium. The activity of key enzymes related to the response against biotic stresses, such as peroxidase (POX), β-1,3-glucanase (PR) and phenylalanine ammonia-lyase (PAL), as well as the differential transcription level of target genes linked to plant stress response by qRT-PCR was monitored for six months. Results No differences were obtained between sole humic substances and their application combined with plant growth-promoting bacteria, indicating that the microbial consortium had no modulatory effect on HS-treated plants. The treatments promoted the activities of POX, PAL and β-1,3-glucanase, which remained significantly higher concerning the control throughout the evaluation period. In addition, treatments positively regulated the transcription levels of CsPR-7, CsPR-3 and CsPR-11 genes. The experimental data were qualitatively similar to those found in commercial orange orchards treated continuously for 12 and 6 years with humic substances, where the activity and transcription levels were also more significant than for untreated plants. Conclusion Our results indicate that humic substances can trigger immune-mediated responses in plants and they can be used as a natural chemical priming agent to mitigate disease symptoms and contribute to more resilient citrus cultivation. Graphical Abstrac

Humic and fulvic acids as biostimulants in horticulture

Maintaining food production for a growing world population without compromising natural resources for future generations represents one of the greatest challenges for agricultural science, even compared with the green revolution in the 20th century. The intensification of agriculture has now reached a critical point whereby the negative impacts derived from this activity are now resulting in irreversible global climate change and loss in many ecosystem services. New approaches to help promote sustainable intensification are therefore required. One potential solution to help in this transition is the use of plant biostimulants based on humic substances. In this review we define humic substances in a horticultural context. Their effects on nutrient uptake and plant metabolism are then discussed and a general schematic model of plant-humic responses is presented. The review also highlights the relationship between the chemical properties of humified matter and its bioactivity with specific reference to the promotion of lateral root growth. Finally, we summarize and critically evaluate experimental data related to the overall effect of humic substances applied to horticultural crops. Current evidence suggests that the biostimulant effects of humic substances are characterized by both structural and physiological changes in roots and shoots related to nutrient uptake, assimilation and distribution (nutrient use efficiency traits). In addition, they can induce shifts in plant primary and secondary metabolism related to abiotic stress tolerance which collectively modulate plant growth as well as promoting fitness. In conclusion, the exogenous application of humic substances within agronomic systems can be used to aid the development of sustainable intensification. As most humic substances used in agriculture are currently derived from non-renewable resources like coal and peat, the promotion of this technology also requires the development of new sustainable sources of humic products (e.g. organic wastes)

Phosphorus speciation and high-affinity transporters are influenced by humic substances

Phosphorus (P) is a limiting factor for plant growth, especially in highly weathered tropical soils. Plants have several mechanisms to overcome low P availability in soil, such as humic substances, that reduce phosphate (Pi) adsorption on oxide surfaces and enhance soil P availability. However, the direct influence of humic substances on Pi transporters in root cells or the distribution of P species in leaves remains unclear. Tomato seedlings were grown in a sand–vermiculite mixture with low or high P concentrations (10 or 100 mg kg–1 KH2PO4, respectively) and humic acids (0 or 48 mg C L–1) isolated from vermicompost. Plant responses were evaluated in the fifth week by measuring root and shoot weights and P concentration, and differential expression in the roots of the high-affinity Pi transporter genes LePT1 and LePT2. In addition, the distribution of P species in the leaves was assessed using 31P-NMR. Humic acids increased the root biomass and changed the distribution of P species in the leaves. Inorganic phosphate was the major compound in plants supplied with a high P concentration, whereas in plants supplied with a low P concentration, Pi was only identified in plants not treated with humic acids. Glycerophosphodiester and phosphorylcholine accumulated in plants treated with humic acid, indicating a modified metabolic pathway for economical P consumption at low P concentrations. High transcript accumulation of LePT2 was observed in roots treated with humic acids at both P concentrations. Our results show that humic substances are strategically involved in plant adaptation to P availability