Effect of 2,4-D sub-dose on the initial development of common bean crop

ABSTRACT - The adoption of cultures tolerant to auxin mimics can increase the occurrence of drift of these herbicides, interfering in the development of naturally sensitive cultures, such as beans. The aim of this study was to evaluate the germination and initial development of bean seedlings, using sub-doses of the herbicide 2,4-D. The design of experiment I was completely randomized, with eight treatments and four replications, except for germination, with eight replications. The seeds were sowed in 100 mL of water with concentrations of 0.0; 1.12; 2.14; 4.18; 8.37; 16.75; 33.50 and 67.00 g a.e. L-1 of 2,4-D. Germination, length, seedling fresh and dry mass and electrical conductivity were evaluated. The design of experiment II was completely randomized with five treatments and four replications. The beans were sowed in sand and then sprayed at concentrations of 0.0; 8.37; 16.75; 33.50 and 67.00 g e.a. L-1 of 2,4-D. Seed emergence, injury, fresh and dry shoot mass were evaluated. According to the regression analysis, there was a reduction in germination, regardless of the concentration used, as well as the seedling length. Seeds sown in this solution presented impaired root system and development, tending to mortality. Electrical conductivity increased as herbicide concentrations increased, indicating lower physiological potential of seeds. In experiment II, increasing 2,4-D concentrations reduced emergence and increased injury to bean plants. It is concluded that the sub-doses of the 2,4-D herbicide negatively affect the germination and initial development of bean seedlings.

摘要：种植对生长素类似物具有耐受性的作物，会加剧此类除草剂的飘移问题，进而干扰菜豆等天然敏感作物的生长发育。本研究旨在通过使用除草剂2,4-D的亚剂量，评估菜豆幼苗的萌发与初始生长发育情况。试验一采用完全随机设计，设置8个处理组与4次重复，仅萌发指标设置8次重复。将种子播种于100mL水中，设置2,4-D的浓度梯度为0.0、1.12、2.14、4.18、8.37、16.75、33.50及67.00 g酸当量·L⁻¹，测定指标包括萌发率、幼苗长度、鲜重、干重以及电导率。试验二同样采用完全随机设计，设置5个处理组与4次重复：将菜豆种子播种于砂床中，随后喷施浓度分别为0.0、8.37、16.75、33.50及67.00 g酸当量·L⁻¹的2,4-D药液，测定指标包括出苗率、药害症状以及地上部鲜重与干重。回归分析结果显示，无论施用何种浓度的2,4-D，菜豆的萌发率与幼苗长度均出现下降；在该药液中播种的种子，其根系与生长发育均受到损害，且死亡率呈上升趋势。电导率随除草剂浓度升高而上升，表明种子的生理潜力下降。试验二结果表明，2,4-D浓度升高会降低菜豆的出苗率并加剧植株药害程度。综上可知，除草剂2,4-D的亚剂量会对菜豆幼苗的萌发与初始生长发育产生负面影响。