Nickel (Ni) toxicity has been reported to decrease productivity in soybean (Glycine max L.). However, soybean responses to Ni toxicity are not well understood. The aim of the present study was to describe Ni toxicity in soybean plants through physiological, nutritional, and ultrastructural analyses. Plants were grown in nutrient solution containing increasing Ni concentrations (0, 0.05, 0.1, 0.5, 10, and 20 μmol L −1), and nutritional, anatomical, physiological and biochemical features were determined. The results revealed previously unreported detrimental effects of Ni toxicity on soybean plants. CO 2 assimilation rates, stomatal conductance and transpiration decreased, resulting in lower biomass in soybean plants exposed to the highest Ni levels. Nitrate reductase activity increased with up to 0.05 μmol L −1 Ni and then decreased, indicating halted N-metabolism. Urease activity increased with increasing Ni availability in the nutrient solution, and peroxidase and superoxide dismutase activities were higher in plants grown at higher Ni levels. Leaf epidermal thickness (abaxial and adaxial), as well as root xylem and phloem diameter, decreased starting at 0.1 μmol L −1 Ni. Mean Ni concentrations varied from 77.5 to 17,797.4 mg kg −1 in roots and 2.3 to 16,774.5 mg kg −1 in shoots. Soybean plants exhibited symptoms of Ni toxicity starting at 0.1 μmol L −1 Ni, presenting mean shoot Ni concentration of 28.9 mg kg −1 , along with leaf water loss until complete drying. The results contribute to our understanding of several physiological, biochemical and histological mechanisms of Ni toxicity in soybean, which is still poorly understood.

Nickel (Ni) at low concentrations is an essential micronutrient for higher plants. Nickel is a cofactor of the enzyme urease and plays a critical role in the germination of seeds. This study aims to evaluate the effect of foliar Ni application on mineral nutrition status, urease activity and the physiological quality of soybean seeds. The study was conducted using different levels of Ni (0, 10, 20, 40, 60, 80 and 100 g ha -1 ) were applied in the presence or absence (0 or 75 g i.a. ha -1 ) of the fungicide pyraclostrobin. Leaf nitrogen concentrations showed a linear increase in response to Ni application irrespective of pyraclostrobin application. Foliar sulfur concentrations inversely proportional to Ni application in the absence of pyroclostrobin, but were proportional to Ni application when pyroclostrobin was also applied. Nickel application showed no effects on foliar concentrations of other macronutrients (P, K). Nickel concentrations in the leaves and seeds were proportional to nickel applications levels. There was a highly significant correlation between foliar Ni concentrations in the leaves and seed Ni levels (r = 0.99), indicating extensive translocation of Ni from leaf to seed. Urease activity increased proportionally up to 20 g ha -1 , with peak activity between 20 and 40 g ha -1 of Ni. Urease activity correlated highly with seed yield (r = 0.88) and pod number (r = 0.84). Seed germination and emergence rate increased proportionally with Ni application. However, when Ni was combined with pyraclostrobin, the germination percentage displayed a parabolic curve with an increase of germination up to 40 g ha -1 of Ni. The electrical conductivity for a maximum was between 40 and 60 g ha -1 of Ni. Nickel treatments had no significant effect on seedling length or seedling dry weight. Foliar application of Ni up to 20 g ha -1 in the presence or absence of pyraclostrobin was beneficial to soybean plants based on seed yield, mineral nutrition status and physiological quality of soybean seeds.

Nutritional deficiencies limit the growth of snap bean plants, therefore knowing the biological mechanisms involved in it is fundamental. This study is aimed to evaluate the damage caused by a deficiency of macronutrients in physiological variables that cause decreased growth and the appearance of visual symptoms in snap bean. Thus, we design a hydroponic system of snap bean cultivation in order to test the effect of macronutrient deficiencies in a controlled environment. The treatments consisted in evaluate the effects of lack of one macronutrient in time. To perform this, we used Hoagland and Arnon solution in its complete formulation (control) or without N, P; K; Mg, Ca or S in each treatment. Physiological, nutritional, and growth analyses were performed when visual deficiency symptoms of each omitted nutrient appeared. Thus, the omissions of N and P in the nutrient solution led to lower accumulations of all macronutrients in the shoot. And the K, Ca, Mg, and S omissions decreased the amounts of K, Ca, Mg, P, and S in the shoot of the snap bean plants when compared with the plants grown in the complete nutrient solution. With the lowest accumulation of macronutrients, the content of photosynthetic pigments and the photosynthetic rate were reduced, with harmful effects on plant growth. Thus, from the losses in dry matter production of the shoot, the order of limiting of macronutrients in bean plants was N < P < Ca < S < Mg < K, with a decrease of up to 86.2%, 80.1%, 51.2%, 46.5%, 25.6%, and 19.3%, respectively. The nitrogen deficiency is more evident, proven by symptoms such as chlorosis in the lower and upper third leaves and necrosis of the lower third leaves.

Cotton is a crop with a high economic value, usually sprayed with large amounts of pesticides to control pests and diseases. Ramularia spot is a foliar disease that cause early defoliation and can compromise cotton yield; however, there is a need of information about the interaction of cultivars and plant height as a tool to improve ramularia control and increase yield. The objective of this study was to evaluate the effects of the interaction between plant height, cultivar, and fungicides applied to the severity of the leaf spot and cotton yield. The experiment was carried on during the 2014/15 crop season in Chapadão do Sul, MS, Brazil. A randomized complete block design in a 2 × 3 × 3 factorial scheme was used, where the factors were plant heights (1 and 1.5 m), cultivar (FMT 701, FM 975, and FM 944) and type of fungicide (Negative control , FT1, and FT2). The fungicidal treatments consisted of sequential sprays of different fungicides, including the triazole, strobilurin, and carboxamide groups, recommended to farmers. The cultivar FM 975 showed greater ramularia spot progress curve when grown at 1 m height and without fungicide spray. The fungicides were efficient in reducing the severity of the ramularia spot and their use in shorter plants (1 m) increased yield. The cultivar FM 975 had the highest total yield.

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O experimento teve o intuito de estudar a qualidade fisiológica de sementes de soja utilizando extrato aquoso de Cyperus rotundus e biorreguladores sintéticos, sob diferentes métodos de hidratação. O estudo foi realizado na Universidade Estadual de Mato Grosso do Sul, Cassilândia-MS, utilizando o delineamento inteiramente casualizado, sendo realizado em duas etapas. Na primeira etapa avaliou-se o desempenho do extrato aquoso de C. rotundus a 3%, comparando-o com: testemunha (sem condicionamento); controle - água; Auxina (IBA) a 0,2%; Stimulate® a 0,2%; Nitrato de Cálcio Ca (NO3)2 a 0,2%. Na segunda etapa aferiu-se o melhor método de condicionamento, utilizando-se de extrato aquoso de C. rotundus 3%, em quatro processos de hidratação: testemunha, submersão, gerbox e entre papéis. Para ambas as etapas, foram realizadas as seguintes avaliações: germinação, índice de velocidade de germinação, condutividade elétrica, emergência das plântulas, índice de emergência, comprimento da parte aérea e das raízes. Em relação ao potencial fisiológico das sementes de soja não é recomendado a hidratação por imersão direta e tampouco o uso de agentes químicos. O fornecimento de extrato aquoso de C. rotundus L. a 3% na solução de hidratação das sementes pelo método de atmosfera umidade e entres folhas de papeis não interfere na germinação e emergência, todavia observa-se maior crescimento do sistema radicular da plântula.