Physiological and morphological characteristics of Phaseolus vulgaris L. grown in soil with picloram residues

e-ISSN 1983-4063 - www.agro.ufg.br/pat - Pesq. Agropec. Trop., Goiânia, v. 46, n. 3, p. 276-283, Jul./Sep. 2016 Physiological and morphological characteristics of Phaseolus vulgaris L. grown in soil with picloram residues1 Miguel Henrique Rosa Franco2, Vinícius Teixeira Lemos3, André Cabral França2, Nykolas Carvalho Schiavon2, Marco Túlio Gomes Albuquerque2, Ademílson de Oliveira Alecrim3, Leonardo D’Antonino4 ABSTRACT RESUMO Características fisiológicas e morfológicas de Phaseolus vulgaris L. cultivado em solo com resíduos de picloram The long lasting residual effect of some auxin herbicides depends on soil characteristics and may cause phytotoxicity on subsequent crops. Picloram is one of the main herbicides used in pastures, presenting a long lasting residual effect in the soil. This study aimed at determining the physiological and morphological characteristics of common bean plants grown in soil contaminated with picloram, under greenhouse conditions. A complete randomized blocks design, with treatments consisting of picloram doses (0 g ha-1, 7.5 g ha-1, 15 g ha-1, 30 g ha-1, 60 g ha-1 and 120 g ha-1 a.i.), with five replications, was used. Urochloa brizantha was sown in pots, and its height and shoot fresh and dry matter were evaluated. In the same pots, Phaseolus vulgaris was sown as a bio-indicator of picloram, and the following characteristics were measured: plant height, fresh and dry matter, phytotoxicity, leaf area, number of leaves per plant, maximum photosynthetic efficiency and relative electron transport rate. The phytoremediation process occurs in soil with picloram residues (up to 30 g ha-1) when covered by U. brizantha for 150 days. The common bean plants show a good potential as biological indicator of the presence of picloram residues in the soil. A longa persistência de alguns herbicidas auxínicos depende dos atributos do solo e pode causar intoxicação em cultivos em sucessão. O picloram é um dos principais herbicidas utilizados em pastagens, sendo que o mesmo apresenta período de meiavida longo no solo. Objetivou-se avaliar, em casa-de-vegetação, as características fisiológicas e morfológicas de plantas de feijão cultivadas em solo contaminado com picloram. O delineamento utilizado foi em blocos ao acaso, sendo os tratamentos compostos pela aplicação de picloram (0 g ha-1; 7,5 g ha-1; 15 g ha-1; 30 g ha-1; 60 g ha-1; e 120 g ha-1 i.a.), com cinco repetições. Urochloa brizantha foi semeada em vasos, avaliando-se a sua altura e matéria fresca e seca da parte aérea. Nos mesmos vasos, semeou-se feijão (Phaseolus vulgaris), como bioindicador do picloram, sendo avaliados a altura das plantas, matéria fresca e seca, fitotoxicidade, área foliar, número de folhas por planta, eficiência fotossintética máxima e taxa relativa de transporte de elétrons. Resíduos de picloram no solo (até 30 g ha-1) são fitorremediados pelo cultivo de U. brizantha por 150 dias. As plantas de feijão apresentam bom potencial como indicador biológico da presença de resíduos de picloram no solo. KEY-WORDS: Urochloa brizantha; auxin herbicides; soil contamination; phytoremediation. PALAVRAS-CHAVE: Urochloa brizantha; herbicidas auxínicos; contaminação do solo; fitorremediação. INTRODUCTION also reach groundwater through leaching and surface runoff (D’Antonino et al. 2009, Santos et al. 2010). Knowledge on adsorption, desorption, lifetime and leaching of herbicides is essential to identify eventual consequences of herbicide use for the environmental safety (Wyk & Reinhrdt 2001). Soil characteristics such as pH, mineralogy, organic matter and cation exchange capacity (at pH 7.0) may have a strong influence on control mechanisms of ionic herbicide destination in the soil (Costa et al. 2000, Rocha et al. 2000, Albuquerque et al. 2001). Brazil has recently become the largest consumer market of agrochemicals worldwide, and herbicides represent 45 % of the total consumption of such chemicals (SINDAG 2009). The increasing use of herbicides is a serious issue, due to its environmental contamination, especially in underground water (Celis et al. 2005). It is known that herbicides may negatively influence subsequent crops, due to its carryover effect, and 1. Manuscript received in Mar./2016 and accepted for publication in Sep./2016 (http://dx.doi.org/10.1590/1983-40632016v4640169). 2. Universidade Federal dos Vales do Jequitinhonha e Mucuri, Diamantina, MG, Brazil. E-mails: , , , . 3. Universidade Federal de Lavras, Lavras, MG, Brazil. E-mails: , . 4. Universidade Federal de Viçosa, Viçosa, MG, Brazil. E-mail: . Physiological and morphological characteristics of Phaseolus vulgaris L. grown in soil with picloram residues In Brazilian pastures, picloram is one of the main herbicides used to control broadleaf weeds that present selective characteristics to Poacea species (Santos et al. 2006). This herbicide has an average activity period of 20 to 300 days (Berisford et al. 2006, Santos et al. 2006) and, in some cases, may remain in the soil for 3 years after its application (Deubert & Corte-Real 1986, Santos et al. 2006). Picloram is an auxinic herbicide, i.e., that mimics auxin. Auxinic herbicides were introduced in agriculture in the 1940s, and were the first selective organic herbicides for weed control. They are still extensively used in rice, maize, wheat, sugarcane and pastures (Thill 2003). Among this group of herbicides, 2.4-D (2.4-dichlorophenoxyacetic acid) and picloram (4-amino-3.5.6-trichloro-2-pyridinecarboxylic acid) have the largest number of auxinic products registered for use in agriculture (Brasil 2013). These products are latifolicide mixtures. According to Silva et al. (2007), the 2.4-D herbicides cause poisoning in sensitive species such as soy, common bean, cotton and other dicots, when grown in areas where they are applied. Given the risk of crop phytotoxicity, it is important to remove this herbicide using simple, effective and economically viable techniques (Pires et al. 2003). The phytoremediation potential of some Poacea species can be explored to accelerate the degradation or immobilization of some toxic herbicide components in the environment. It is known that the association of plants with microbes may accelerate degradation of toxic molecules, reducing the soil contamination (Cunningham et al. 1996). The effectiveness of the method and the time required for remediation are directly related to the appropriate species selection for each type of toxic molecule, as well as soil and climatic condition (Santos et al. 2007a and 2007b). Some plant species have been studied for their picloram phytoremediation potential in soil and for reducing its residual activity. Various forage species, such as Eleusine coracana, brachiaria and Panicum maximum, have been used in picloram phytoremediation programs (Santos et al. 2006 and 2007b, Belo et al. 2007a and 2007b, Carmo et al. 2008a and 2008b, Pires et al. 2008). Santos et al. (2013) studied the sensitivity of three (...truncated)