COMPARATIVE-STUDY OF PLANT-GROWTH HORMONE (HERBICIDE) TOXICITY IN VARIOUS BIOLOGICAL SUBJECTS

Due to their widespread distribution and toxic nature, herbicides may have a serious impact on the environment and exert adverse effects on associated organisms. The present study was conducted to determine the acute toxicological effects of some plant growth hormones used as her bicides on four biological subjects and compare the subjects' sensitiv ity to individual testing substances. The herbicides 4-(indol-3-yl)ace tic acid C10H9O2N (IAA), N6-(beta 2-isopenfenyl)adenosine (pi-indolylp ropionic acid) C11H11O2N (IPA), 2,4-dichlorophenoxyacetic acid C8H6O3C l2 (2,4-D), 4-chloro-2-methylphenoxyacetic acid C9H9O3Cl (MCPA), and 1 ,napthylacetic acid C12H10O2 (NAA) were tested and the following biolo gical subjects were used: Daphnia magna, Tubifex tubifex, Scenedesmus quadricauda, and seeds of Sinapis alba. For S. alba, the influence of herbicides on seed germination (G) and root growth inhibition (I) was observed. For T. tubifex, the tests lasted 96 hr, for D. magna 48 hr, for S. quadricauda 20 days, and for S. alba 72 hr. The rank order of t oxicity of herbicides used for T. tubifex was NAA > IAA > IPA > 2,4-D > MCPA; for D. magna. NAA > IAA > IPA > MCPA > 2,4-D; for S. quadricau da, IAA, IPA > NAA > MCPA > 2,4-D; for S. alba seed germination, NAA > IPA > 2,4-D > MCPA > IAA; and for root growth inhibition. NAA > 2,4-D > MCPA > IAA > IPA. When the sensitivity of tested organisms to indiv idual herbicides was studied from LC(50) and EC(50) values, the follow ing rank orders of sensitivity were obtained: for IAA, it was S. alba (I), S. quadricauda > T. tubifex, D. magna > S. alba (G); for 2,4-D, i t was S. alba (I) > S. guadvicauda > T. tubifex = S. alba (G) 1 D. mag na; for MCPA, it was S. alba (I) > S.quadricauda > T. tubifex = D. mag na = S. alba (G); for IPA, it was S. alba (I) > T. tubifex > S. quadri cauda > D. magna = S. alba (G); and for NAA, it was S. a[ba (I) > S. q uaduicauda > T. tubifex > S. alba (G) > D. magna. (C) 1994 Academic Pr ess, Inc.