Alterações no ambiente luminoso provocam mudanças adaptativas nas plantas, na tentativa de manter o seu crescimento e desenvolvimento. Objetivou-se com esta revisão investigar e descrever o efeito do ambiente luminoso no crescimento e desenvolvimento de forrageiras de clima tropical em sistemas silvipastoris. A compreensão da influência do ambiente luminoso e, das mudanças biológicas que as diferentes intensidades do sombreamento podem causar nas forrageiras de clima tropical, possibilita fundamentar as alterações metabólicas das respostas das plantas na tentativa de se manterem persistentes em sistemas sombreados. A partir disso, entender quais são os níveis aceitáveis de radiação para que os sistemas de produção sombreados não entrem em colapso é fundamental para que tomadas de decisões sejam realizadas no tempo hábil do ciclo biológico das espécies vegetais. Em sistemas silvipastoris, a redução da luz incidente em forrageiras de clima tropical provoca alterações como aumento da área foliar específica, redução na densidade populacional de perfilhos e na relação raízes: parte aérea da planta. Cada espécie ou cultivar apresenta características adaptativas específicas ao sombreamento com a finalidade de aproveitar os recursos disponíveis em tecidos fotossintéticos e de suporte. No entanto, ainda assim o sombreamento intenso (>40%) afeta negativamente a produção forrageira de acordo com a variabilidade climática. Palavras-chave: adaptação morfofisiológica; fotossíntese; luz; plantas C4.   EFFECT OF THE LIGHT ENVIRONMENT IN TROPICAL CLIMATE FORAGES IN SILVOPASTORAL SYSTEMS   ABSTRACT:  Changes in the light environment cause adaptive changes in plants, to maintain their growth and development. The aim of this review is to investigate and describe the light environment effect on the growth and development of tropical forages in silvopastoral systems. The understanding of the influence of the light environment and the biological changes that different shading intensities can cause in tropical forages, makes it possible to substantiate the metabolic alterations of plant responses to remain persistent in shaded systems. From this, understanding what are the acceptable levels of radiation so that the systems do not collapse is essential for decision-making to be carried out in a timely manner in the plant's biological cycle. In silvopastoral systems, a light incidence reduction on tropical forages causes changes such as an increase in the leaf area index, reduction in the tiller population density, and shoot: root ratio. Each species or cultivar has adaptive characteristics specific to shading to take advantage of the resources available in photosynthetic and support tissue. However, even so, the intense shading (> 40%) negatively affects forage production according to climatic variability. Keywords: morphophysiological adaptation; photosynthesis; light; C4 plants.

Objetivou-se descrever a dinâmica diária da temperatura (Tar) e umidade relativa do ar (UR) em ambientes protegidos com diferentes telas poliefinas de sombreamento, na região de transição Cerrado-Amazônia do Mato Grosso; ademais, foram avaliados os usos de regressões de estimativa de Tar e UR nos ambientes sombreados com base nas mesmas variáveis medidas em pleno sol. As avaliações micrometeorológicas foram realizadas em viveiros florestais modulares suspensos, alinhados no sentido Leste-Oeste, entre junho de 2017 e abril de 2019, sob telas pretas com níveis crescentes de sombreamento (35, 50, 65 e 80%) e coloridas/espectrais (termorefletora, vermelha, azul e verde, todas com 50% de sombreamento). Os dados do monitoramento micrometeorológico foram agrupados em função das estações hídricas regionais (seca, seca-chuvosa, chuvosa e chuvosa-seca), com separação da base de dados por decêndios. Foram empregados 70 e 30% dos dados para geração e validação das regressões, em cada agrupamento de dados, respectivamente. Na avaliação do desempenho estatístico das regressões foram empregados os indicadores estatísticos: coeficiente de determinação (R2), erro absoluto médio (MBE), raiz quadrada do erro quadrático médio (RMSE) e índice de Willmott (d). Houve dinâmica similar de Tar e UR entre a condição de pleno sol e as telas poliefinas pretas e coloridas ao longo do dia e do ano; porém, com aumento expressivo nos valores médios da Tar e UR nesses ambientes protegidos. Os valores de R² foram satisfatórios, demonstrando que mais de 60% da variável dependente (Tar nas telas de sombreamento) está relacionada à variável independente (Tar na condição de pleno sol). O d variou de 0,96 a 0,99, indicando que as regressões de estimativas da Tar e UR ajustadas apresentam desempenho satisfatório para todas as estações hídricas regional nos ambientes sombreados. Palavras-chave: ambientes protegidos; micrometeorologia; indicadores estatísticos; transição Cerrado-Amazônia.   Dynamics and estimates of air temperature and relative humidity in nurseries protected with different shading   ABSTRACT: The objective was to describe the daily dynamics of temperature (Tar) and relative humidity (RH) in protected environments with different polyolefin shading screens in transition region of Cerrado-Amazonia of Mato Grosso; in addition, the uses regressions of estimation of Tar and RH in shaded environments based on the same variables measured in full sun were evaluated. Micrometeorological assessments were performed in suspended modules forest nurseries, aligned to the East-West direction, between June 2017 and April 2019, under black screens with increasing levels of shading (35, 50, 65 and 80%) and colored / spectral (thermo-reflector, red, blue and green, all with 50% shading). The data of the micrometeorological monitoring were grouped according to the regional water stations (dry, dry-rainy, rainy and rainy-dry), with separation of the database for ten years. 70 and 30% of the data were used to generation and validation the regressions, in each data group, respectively. In the Statistical performance evaluation of the regressions were used the statistical indicators: coefficient of determination (R2), the mean error (MBE), root mean square error (RMSE) and Willmott's index of adjustment (d). There was similar dynamic of Tar and UR between the condition of full sun and the black and colored polyolefin screens throughout the day and year; however, with a significant increase in the mean values of Tar and UR in these protected environments. The R² values were satisfactory, showing that more than 60% of the dependent variable (Tar in the shading screens) is related to the independent variable (Tar in full sun). The d ranged from 0.96 to 0.99, indicating that the adjusted regressions of Tar and UR present satisfactory performance for all regional water stations in shaded environments. Palavras-chave: protected environments; micrometeorology; statistical indicators; Cerrado-Amazônia transition.

Flame retardants are efficient in fighting wildfire; however, their environmental implications, especially regarding the vegetation, need to be clarified. This work aimed at assessing the effects of flame retardant on the initial growth of Schizolobium amazonicum. Treatments consisted in applying different flame retardant concentrations via substrate and leaf: Phos-Chek WD-881® (0, 3.00, 6.00, 8.00 and 10.00 mL L-1), Hold Fire® (0, 7.00, 9.00, 12.00 and 15.00 mL L-1) and water-retaining polymer Nutrigel® used as alternative retardant (0, 0.25, 0.50, 0.75 and 1.00 g L-1). Growth analyses were carried out to assess the effects of these substances (10 repetitions per treatment). The aliquot of 10.00 mL L-1 of Phos-Chek WD881 applied on the leaves led to an increase of 70% in leaf area and 15% in seedling height. The same Phos-Chek concentration favored height increase (32%) and total dry mass accumulation (33%) throughout time. The concentration of 15 mL L-1 of Hold Fire® applied on leaves, compromised 45% the accumulation of dry biomass in the seedling. Initially, 1.00 g L-1 of Nutrigel® applied via substrate led to an increase of 70% in leaf area, 29% in plant height, and 89% in leaf dry mass. Therefore, Phos-Chek applied on leaves favored shoot growth in S. amazonicum. Hold Fire® applied on leaves impaired biomass accumulation in seedlings. Nutrigel® applied on substrate does not cause long-lasting damage to the initial growth of S. amazonicum. The aliquot of 0.50 g L-1 administered via polymer leave had positive effect on seedling shoot.

In integrated crop‐livestock‐forestry (ICLF) systems, an agroforestry model, the forestry component influences the distribution of photosynthetically active radiation (PAR) and alters grain productivity. The aim of this study was to evaluate the effects of systematic and selective thinning of eucalyptus stands on the productivity of soybean and maize grown. The randomized block‐designed experiment comprised three treatments, namely crops grown under full sunlight (CFS) and in ICLF plots subjected to systematic and selective thinning to leave single‐row (ICLFS) and triple‐row (ICLFT) tree configurations. Soybean and maize were planted in succession between the tree stands and PAR incidence/transmittance and crop productivities were evaluated in the north and south sun‐exposed faces of the plots during three cultivation cycles after thinning. In comparison with CFS, PAR transmittance in the ICLF systems decrease varied according to the time of day, period of the year, distance of the sampling position from the trees, the sun‐exposed area (north and south faces) and time after thinning. Soybean productivities in ICLFS were similar to those of CFS in the first and second crop cycles, but significantly lower (p < 0.05) in the third crop cycle. In the ICLFT system, soybean productivity was similar to that of CFS in the second crop cycle but significantly lower in the first and third crop cycles. With regard to the maize crop, productivities decreased in the order CSF > ICLFS > ICLFT in all cultivation cycles. Our results showed that PAR transmittance and soybean/maize productivities were positively influenced by thinning of eucalyptus stands, particularly in ICLFS system.

The occurrence of fires in agricultural areas grown with winter maize has become recurrent in the Central-West region of Brazil, since the harvest occurs in the dry season in the region. Fire retardants can be used as an indirect control of fire; they consisted of chemical products that can remain in the straws or on the soil after the fire extinction.  The objective of this work was to evaluate the effect of two short-term fire retardants (Phos-Chek WD881® and Hold Fire®) and a hydrogel (alternative fire retardant) on germination of rice (Oryza sativa), common bean (Phaseolus vulgaris), millet (Pennisetum glaucum), maize (Zea mays), and soybean (Glycine max) seeds. The control treatment consisted of only distilled water. The seed germination percentage and speed index, mean time for germination, and seedling growth (shoot and root length and dry weight) were evaluated. A completely randomized experimental design was used, with 4 replications per treatment; each experimental unit consisted of 100 seeds maintained in germination chambers (30 °C and photoperiod of 12 hours). The effects of the fire retardants and hygroscopic polymer on the seed germination and seedling initial growth were specific, and no significant effect caused by the variations in the concentrations of the fire retardants was found.

Objetivou-se avaliar os efeitos de retardantes de fogo de curta duração e de um polímero hidrorretentor sobre a emergência e crescimento inicial de Handroanthus ochraceus e Tabebuia roseoalba, em condições de ambiente protegido. Foram realizadas aplicações via substrato na semeadura e com intervalos quinzenais, dos seguintes retardantes de fogo e concentrações: Phos-Chek WD881® (0; 3,00; 6,00; 8,00; 10,00 mL L-1), Hold Fire® (0; 7,00; 9,00; 12,00; 15,00 mL L-1), e polímero hidrorretentor Nutrigel® (0, 0,25; 0,50; 0,75; 1,00 g L-1), em delineamento inteiramente casualizado, com 10 repetições por tratamento.  Nas concentrações iguais a 0, utilizou-se apenas água. A emergência das plântulas foi avaliada por meio do índice de velocidade de emergência, porcentagem e tempo médio de emergência. Realizaram-se análises de crescimento destrutivas aos 30, 45, 60, 90 e 120 dias após a semeadura (DAS), enquanto as análises de fluorescência da clorofila a foram realizadas em três plantas por tratamento, a partir de 60 DAS. As concentrações testadas de Phos-Chek WD881, Hold Fire e Nutrigel não influenciaram na emergência das plântulas das espécies Handroanthus ochraceus e Tabebuia roseoalba. Aplicações de Phos-Chek WD881 até 5,00mL L-1 propiciam efeitos positivos sobre o crescimento das duas espécies. Concentrações de Hold Fire até 8,00 mL L-1 favorecem o crescimento inicial de Tabebuia roseoalba. O crescimento em diâmetro de Handroanthus ochraceus apresenta resposta positiva a partir de 9,60 mL L-1 quando submetido ao retardante Hold Fire. O intervalo de 0,50 g L-1 a 0,88 g L-1do polímero hidrorretentor Nutrigel promove o crescimento em diâmetro das duas espécies. A fluorescência da clorofila a indica que ocorreu pleno funcionamento da etapa fotoquímica no processo fotossintético de Handroanthus ochraceus e Tabebuia roseoalba na presença dos retardantes de fogo e do polímero hidroretentor.