Anatomical Changes on the Stem and Leaves of Solanum lycopersicum Caused by Different Concentrations of Picloram + 2,4-D, in Two Different Types of Soil

ABSTRACT: Contamination by herbicides with a prolonged effect on the soil can cause anatomical changes in sensitive plants. Thus, this study aimed at verifying the anatomical changes of tomato stem and leaves caused by different concentrations of picloram in two classes of soil from the Amazon region. The study was developed at UNEMAT, Alta Floresta - Mato Grosso state, in a CRD, in a 2 x 5 factorial arrangement, with four replications. A clayey Rhodic Hapludox (LVAw) and a sandy clay loam Typic Ustipsamments (RQo) were contaminated with 0, 1, 2, 3, and 4 L ha-1 of Tordon®, leaving the soil exposed to weathering. One-hundred and twenty days after the application of the herbicide, 10 tomato seeds were sown in samples of both soils. Thirty days after sowing, cross sections of stem and leaf were fixed in FAA50, immersed in methacrylate, cut into a rotary microtome and stained with toluidine blue. The thickness of stem and leaf tissues was analyzed. Data were submitted to analysis of variance and regression analysis by the statistical program Sisvar. The increase in the concentration of picloram caused an increase in the thickness of the leaf blade and in the vascular bundle of the leaf in both soils, with greater effect in the LVAw, where there was tissue disorganization, with irregular and quite collapsed lacunar parenchyma cells and large intercellular spaces. There was also an increase in the diameter of the cortex and in the vascular cylinder of the stem up to the concentration of 2 L ha-1, but in the RQo, plants had more flattened cells with conspicuous intercellular spaces. The anatomical structures of the leaf were more affected by this herbicide.