Phytogrowth-inhibitory activities of sulfur-containing compounds. II. The inhibitory activities of thiosalicylic acid and dihydro-2(3H)-thiophenone-related compounds on plant growth.

Thiosalicylic acid (I) showed rather strong inhibitory activity on the growth of roots of all plants treated except Abelmoschus esculentus Moench at the concentration of 5.0 x 10(-4) M. This compound strongly inhibited the growth of the root of Echinochloa utilis Ohwi et Yabuno even at the low concentration of 5.0 x 10(-5) M. Dihydro-2(3H)-thiophenone (VII) also exhibited inhibitory activity on the growth of roots of all plants treated except Glycine max Merrill. Both compounds inhibited the germination of seeds of some plants at the concentration of 1.0 x 10(-3) M. In I-related compounds (I-V), methyl acetylthiosalicylate (IV) had the strongest inhibitory activity, while in VII-related compounds (VII-XI), 4-hydroxy-2(5H)-thiophenone (VIII) showed the most potent inhibitory activity. The amount of chlorophyll in the cotyledon of Brassica campestris L. subsp. rapa Hook. f. et Anders treated with all compounds except tetrahydrothiophene (XI) was lower than that of the control group.