Effects of O, O-diisopropyl-S-benzyl thiophosphate(IBP) on the Seedling Growth of Rice : I. Inhibition of the mesocotyl growth

[摘要] IBP (O, O-diisopropyl-S-benzyl thiophosphate) is known as a fungicide. However, in practice, some farmers are believing that IBP has also a preventive effect to lodging. Here we report the findings obtained by laboratory experiments that IBP inhibits the stem growth of intact ricc seedlings in darkness. Rice sceds, Oryza sativa L. cv. Hatishail (indica type), Milyang 23 (indica xjaponica type) and Sasanishiki (japonica type) were used as materials. Seeds were sterilized and placed on culture medium in a test tube (25 X 60 mm). The medium contained 2 ml of water or various concentrations of IBP and/or some other growth regulators. The tubes were kept in darkness or in light condition for l0-12 days at 30-32°C. Results of the tests are as follows: 1. As shown in Fig. 1, the mesocotyls of Hatishail elongated about 110 mm or more in a water alone (0 ppm) under darkness. However, the mesocotyl elongation was markedly depressed by an application of each growth retardant and IBP. The degree of inhibition by IBP (●) was greater than those with B995 (□) or CCC (△), but lesser extent than those with ancymidol (▲) or RH531 (○). In this case, the shoot length was also decreased by an application of the growth retardant, but IBP at 2.5-40 ppm caused the stimulation of shoot growth. When 2.5-40 ppm IBP was applied to the seedlings of Milyang 23 under darkness, marked inhibition of growth of mesocotyls and first internodes occured with the concomitant increase of growth of coleoptiles, first leaves, second leaves and seminal roots. 2. The second internodes seems to be little affected by an application of IBP, whenever the treatment started from 1 to 6 days after immersion under darkness. 3. When IBP at 2.5-160 ppm was applied with GA3 or ABA to the seedlings of japonica rice, it depressed the stimulative effect on the mesocotylgrowth of both chemicals under dark condition. Under light condition, however, 2.5∼40 ppm IBP did not cause a notable inhibition of growth of the second leaf sheaths when it was applied alone, or with GA3 or ABA. It may suggest that IBP affect independent-ly with GA3 or ABA to the stem elongation of ricc seedlings grown under darkness.

[学科分类] 农业科学（综合）