Leaf area estimation is an important biometrical trait for evaluating leaf development and plant growth in field and pot experiments. We developed a non-destructive model to estimate the leaf area (LA) of Vernonia ferruginea using the length (L) and width (W) leaf dimensions. ). Therefore, the linear regression "LA=0.463+0.676WL" provided the most accurate estimate of V. ferruginea leaf area. Validation of the selected model showed that the correlation between real measured leaf area and estimated leaf area was very high.Keywords: Asteraceae, cerrado, savanna, statistical model, validation. Modelo linear não-destrutivo para estimativa de área foliar de Vernonia ferruginea Less ResumoA estimativa de área foliar é um importante traço biométrico para avaliação do desenvolvimento foliar e do crescimento vegetal em experimentos de campo e casa-de-vegetação. Foi desenvolvido um modelo linear não destrutivo capaz de estimar a área foliar (AF) de Vernonia ferruginea usando o comprimento (C) e a largura (L) foliar. Diferentes combinações de equações lineares foram obtidas a partir de C, C 2 , L, L 2 , CL e C 2 L 2 . As regressões lineares usando o produto de dimensões CL foram mais eficientes para estimar a AF de V. ferruginea do que os modelos baseados em uma única dimensão (C, L, C 2 ou L 2 ). O modelo linear "AF = 0,463+0,676 CL" forneceu com maior precisão a AF de V. ferruginea em relação aos demais modelos testados. A validação do modelo selecionado revelou elevada correlação entre a área foliar real e a área foliar estimada pelo modelo.

Background and aims Acidic soil occupies 30% of the world's ice-free land, and exchangeable aluminum (Al) availability increases under these conditions, being toxic to many plant species. However, some plants accumulate Al without damage to their metabolism. Vochysia tucanorum is an Al-accumulating species endemic to the cerrado vegetation with acidic soils in South America. Here, we predict that it is a calcifuge species. Methods We assessed macro and micronutrient concentrations as well as Al accumulation, plant height and root length of potted plants grown on acidic and calcareous soil for 60 days. A LC-MS-based metabolite fingerprinting of plants on both conditions was also performed. Results Plants grown on acidic soil showed higher biomass and Al concentration in roots and shoots than those grown on calcareous soil. Despite the higher concentration of macronutrients on plants grown on calcareous soil, micronutrients concentration was similar between plants grown on these soils. Plants grown on the calcareous soil showed necrotic leaves. The metabolite fingerprinting indicated significant changes in the metabolism of phenolics and organic acids. Conclusions Due to the high Al accumulation in plants grown on acidic soil, and their inability to survive in calcareous soil, we conclude that V. tucanorum is an Alaccumulating species with calcifuge behavior.

Weed herbicide resistance has been a challenge in agriculture. The objective of this study was to detect sourgrass (Digitaria insularis (L.) Fedde) glyphosate-resistant plants and to evaluate the growth and polymorphism rate between the resistant and susceptible biotypes, as a subsidy for the integrated management of species. An experiment was conducted primarily for the detection of weed resistance using increasing doses of glyphosate to generate a dose-response curve. Then, an experiment consisting of eight treatments (destructives analysis of growth) and five replications was conducted to characterize and compare the phenological stages of each biotype. In addition to visual assessments, the dry weight and leaf area, absolute and relative growth rates, net assimilation rate and leaf area ratio of plants were determined. Finally, polymorphism among biotypes was determined using inter simple sequence repeat molecular markers. A resistant factor of 3.12 was found among the biotypes. The resistant biotype grew faster and was more robust than the susceptible biotype, arriving first to flowering. The resistant biotype was better adapted to light interception. The 25 inter simple sequence repeat molecular markers analysis showed a polymorphism rate of 56.6% among the analyzed biotypes.

O conhecimento da profundidade ideal de germinação de sementes de plantas daninhas é importante para o desenvolvimento de estratégias de manejo eficientes, seguras e econômicas. Com o objetivo de estudar a emergência de plântulas de Sida rhombifolia L. e Solanum viarum Dunal, em resposta à época (setembro de 2008 e janeiro de 2009) e às profundidades de semeadura (0, 1, 2, 3, 4 e 5 cm), foram realizados dois experimentos em casa de vegetação. Sida rhombifolia mostrou-se sensível às variações de temperatura, em decorrência das épocas de semeadura, e os maiores percentuais de emergência ocorreram nas profundidades entre 1 e 4 cm. Para S. viarum, observou-se forte influência da temperatura sobre a sua emergência, sendo, observado o máximo de emergência, nas profundidades de 1 a 5 cm e sua redução para as sementes locadas na superfície do solo.

Com o objetivo de avaliar a eficácia de herbicidas no controle de mucuna-preta conduziu-se quatro ensaios. Em pré-emergência foram utilizados os herbicidas amicarbazone (1225 g ha-1); tebuthiuron (900 g ha-1) e sulfentrazone (600 g ha-1) e em pós-emergência, além dos três herbicidas citados anteriormente, foram utilizados 2,4 D amina (670 g ha-1); atrazina (3250 g ha-1); carfentrazonaetílica (35 g ha-1) e mesotriona (132 g ha-1) aplicados isoladamente em pós-emergência em plantas em três diferentes estádios de desenvolvimento: Ensaio 1: duas folhas desdobradas (BBCH-12); Ensaio 2: sete gemas laterais visíveis (BBCH-27) e Ensaio 3: 50% do comprimento máximo alcançado (BBCH-35). O delineamento utilizado foi em blocos casualizados, com quatro repetições por tratamento. A variável avaliada (eficácia) foi submetida à análise de variância pelo teste F, e as médias, comparadas pelo teste de Tukey a 5% de probabilidade. Em pré-emergência, verificou-se que os herbicidas amicarbazone e tebuthiuron, proporcionaram 100% do controle das plantas de mucuna-preta. Na pós-emergência, o herbicida amicarbazone proporcionou controle de 100% em todos os estádios de desenvolvimentos; o mesmo resultado foi observado no tratamento com sulfentrazone e atrazine em plantas com duas folhas desdobradas (BBCH-12) e nos tratamentos com tebuthiuron e atrazine em plantas com sete gemas laterais visíveis (BBCH-27). Palavras-chave: controle químico, estádio de desenvolvimento, Mucuna aterrima Efficacy of herbicides solo in pre and post-emergence to control velvet bean

Weed interference can reduce chickpea growth and, therefore, productivity depending on the period of coexistence and the nutritional status of the crop, among other factors. A study was performed over two crop years to estimate the critical period of weed interference (CPWI) during chickpea production under three doses of nitrogen (N) fertilizer topdressing (0, 50, and 75 kg N ha-1). The experiments were conducted at 0, 7, 14, 21, 28, 35, 42, 56, 63, and 140 days after emergence (DAE) of chickpea/weed coexistence under two conditions: initially weed-free and initially weed-infested. The presence of weeds negatively affected chickpea production and reduced yields by 70% on average regardless of N rate, rendering the crop economically unfeasible. The CPWI ranged from 5 to 76 DAE and was not affected by N topdressing up to 75 kg N ha-1 in both crop years, assuming an acceptable production loss of 5%. Although the CPWI without fertilization (0 kg N ha-1) was similar to that when fertilized with 50 and 75 kg N ha-1 , the two topdressing doses increased chickpea productivity by 37% and 51%, on average, respectively.

Leaf area (LA) is commonly used to evaluate plant traits such as leaf development and plant growth, which depend on sunlight interception. However, methods for obtaining LA are destructive and require many leaf samples that might not be available. The use of linear equations to estimate LA without destructive procedures has been successfully used in crops and weeds studied in the field and in potted-plant experiments. In the Brazilian savanna (Cerrado), many studies still depend on destructive leaf sampling because equations would be specific for each species. We developed a non-destructive model to estimate LA of five Vochysiaceae species from the cerrado, as this family exclusively comprised Al-accumulating species. In this study, LA versus leaf length (L) and leaf width (W) was regressed, and the best-fitted model (LA = -2.133 ? 0.719 LW, R 2 = 0.99) was validated to estimate LA in Qualea cordata Spreng., Qualea grandiflora Mart., Salvertia convallariodora A. St.-Hil., Vochysia cinnamomea Pohl., and Vochysia tucanorum Mart. with precise accuracy. This model may help scientists with distinct interests in plants from this family.

Plant susceptibility to herbicides is related to several factors, including the environmental conditions under which the plants develop. Two experiments were carried out using Synedrellopsis grisebachii plants in two different developmental stages (vegetative and reproductive), with the goal of studying plant susceptibility to the herbicide, glyphosate, and the dependence of this susceptibility on light intensity (full sunlight and 70% shading), correlated with leaf anatomy. The experimental design for both experiments was completely randomized, with a 2 × 7 factorial scheme, with two light intensities and seven different doses of glyphosate (0D, 1/4D, 1/2D, D, 2D, 4D and 6D, where D is the recommended dose of 1800 g ae ha −1 ) as the factors and four replicates per treatment. The leaf anatomy was characterized with optical and scanning electron microscopy. The plants that were grown in full sunlight were more tolerant of glyphosate because of thickening of the adaxial epidermis, parenchyma and main vein structures, which required higher glyphosate doses for effective weed control. The plants that were in the reproductive stage were more tolerant of glyphosate, probably because of lower glyphosate absorption and translocation to the reproductive organs.