Studies on Chemicals Effective for Breaking Seed-dormancy and for Killing Dormant Seed of Barnyardgrass (Echinochloa Crus-galli Beauv. var. oryzicola Ohwi) : 2. Factors influencing the activity of effective chemicals in the soaking treatment

[摘要] Six chemicals, which were found effective in the previous report, were examined in various conditions of the soaking treatment in order to make clear the factors influencing their activity. The results were as follows; 1. Soaking of the domant seeds in 500 ppm emulsion of NIP for 5 days or in 1, 000 ppm for 3 days at 30°C respectively broke the dormancy sufficiently. More breaking was observed at the higher concentration of the chemical or higher temperature, with the longer soaking period, or in cases in which degree of dormancy of tested-seeds was weaker. When the activity of the chemical was too high, most of the seeds lost viability. 2. Emulsion of 1-thiocyanato-2, 3-dibromopropane (U-1), 1, 3-dithiocyanato-2-bromopropane (U-2), 1-isothiocyanato-2-bromopropene (U-3) and 1-thiocyanato-2-bromopopene (U-4) showed remarkable activity in breaking dormancy. The seeds lost viability when the activity of these chemicals was too high. The order of activity of these chemicals was as follows; U-1≤U-2《U-4≒U-3. In order to break the dormancy almost completely, barnyardrass seeds had to be soaked for 2 to 4 days in 500 ppm solution of U-1 or U-2, and for 2 days in 100 ppm or for 4 days in 50 ppm of U-3 or U-4 at 30°C, respectively. 3. The dormant seeds were killed by a soaking treatment in 1, 000 ppm solution of DNBP (amine salt) for 3 days at 30°C. The activity was markedly decreased at the temperature below 20°C. 4. The solvents themselves used for the formulation of these chemicals showed some activity in breaking dormancy, though, in general, it was a limited one. The activity of chemicals, however, varied according to the formulating method of chemicals such as kind of solvent used. The formulating method, therefore, was assumed to have such effects on the activity of the chemicals possibly through affecting their permeability into barnyardgrass seeds. 5. In the screening of effective chemicals for breaking the seed-dormancy or killing the seed by means of the soaking treatment, degree of dormancy of tested seeds and formulating method of the chemicals as well as temperature and duration of the treatment were considered to be important factors. Even in testing chemicals which aim to break the seed-dormancy, it was may be pointed out that not only the number of awakened seeds but also that of killed seeds should be counted.

[学科分类] 农业科学（综合）