Avaliação de crescimento inicial da especie Swietenia macrophylla king – Paulo Ernani Ramalho (Mogno Brasileiro) sob exposição de pesticidas

Abstract

The uncontrolled use of pesticides in regions close to native forests can cause effects not only on target organisms, causing effects on non-target organisms, forests, whether in the tropics or in temperate areas, have great importance for the environment, economy and the human imagination. In this context, we used a native Amazonian species Swietenia macrophylla king (Mahogany), with a common occurrence in southern Pará. The present work aims to verify the effects caused by the exposure of different concentrations of 2,4-D and atrazine pesticides on seedlings of S. macrophylla after 30 days of growth. A completely randomized experimental design was carried out in containers using a substrate composed of a 1:1 (v/v) mixture of commercial soil and washed sand. Applications of concentrations were carried out 30 days after seed germination and the effect of the toxicant was verified for 30 days. At the end of the test period, a dose-response curve was prepared and the EC50 value was calculated. Four concentrations calculated in μl/cm² were tested according to the indications provided on the product label in the following proportions: 1/2, 1, 2x, 4x the recommended concentration. In plants, the stem length, collar diameter, dry mass of the area and dry mass of the root were measured. The 2,4-D results: through the dose-response calculation, an EC50 value =0.034 µl/cm², in the analyzed variables, only the dry mass of the part area in the dose (4x) showed a significant difference in relation to the control. Therefore, it is necessary to carry out more ecotoxicological tests with longer intervals of time to more pertinently verify the action of the pesticide on mahogany plants. Atrazine: in relation to the morphometry of the seeds, they showed variations in length from 9.11 mm to 31.45 mm (average of 19.42 ± 4.17 mm), in width from 1.03 mm to 13.21 mm (average of 9 .74 ± 2.31 mm), and in thickness from 1.18 mm to 5.12 mm (average of 3.36 ± 0.65 mm). The dose-response curve determined the EC50 value = 0.028 µl/cm². The dry mass variables showed significant differences compared to the control, showing that atrazine had a negative effect on plant growth. Therefore, it is necessary to carry out ecotoxicological tests to measure how these substances affect the reproduction and development of different forest species.