Studies On The Physiological And Metabolic Activities Of Some Crop Plants And Weeds In Response To Treatment With Certain Herbicides

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EL Hiweris, Sayeda Omer
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The effects of the two herbicides, fluometuron and diuron, on the germination of seeds, growth of roots and shoots, fresh and dry weights of roots, shoots and grains, and on respiration of a number of mono- and dicotyledonous crop and weed plant species were investigated. Various plants were first tested, of which the monocotyledonous crop plants, Sorghum vulgare, Triticum vulgare, the dicotyledonous crop plants, Arachis hypogaea, Dolichos lablab, Gossypium barbadense, Gossypium hirsutum. The monocotyledonous weed plants, Dinevra retroflexa, Echinochloa colonum and the dicotyledonous weeds Amaranthus graceazans, Ocimum bacilicum and Phyllanthus niruri were chosen for germination experiments. Floumeturon reduced the percentage of germination of mono- and dicotyledonous crop plants seeds investigated. Diuron caused more reduction of percentage germination of monocotyledonous crop plant seeds than fluometuron, but had no effect on seeds of the dicotyledonous crop plants, Arachis hypogaea and Dolichos lablab. However, the two herbicides had no effect on the percentage germination of seed of Gossypium barbadense namely Barakat and Tayeba. The percentage germination of seeds of Gossypium barbadense var. pima were however significantly reduced. For the weed plants investigated both herbicides generally stimulated germination of seeds at the low concentrations and reduced germination at the higher concentrations. Fluometuron, however, had no-significant effect on the germination of monocotyledonous weed seeds, but affected significantly germination of dicotyledonous weed seeds. Diuron, affected germination of both mono- and di-cotyledonous weed seeds with the exception of Echinochloa colonum, Amaranthus graceazans and Phyllanthus niruri. Both herbicides reduced the growth in length and the fresh and dry weights of roots and shoots of all plants tested, i.e. the crop plants Sorghum vulgare, Triticum vulgare, Dolichos lablab, Gossypium barbadense, and the weed Echinochloa colonum. The reduction was more in the roots lengths than shoots lengths, and in monocotyledonous crop plants than dicotyledonous crop plants. Diuron caused more reduction in all these parameters in Echinochloa colonum, than fluometuron. The fresh and dry weights of grains of all monocotyledonous plants treated with both herbicides were higher than those of controls. Respiration of roots tips of Sorghum vulgare, Gossypium barbadense and the weed Echinochloa colonum, measured as the amount of oxygen uptake and carbon dioxide output, was the amount of carbon dioxide produced by Sorghum vulgare root tips treated with fluometuron, which showed a significant reduction. For Gossypium barbadense root tips treated with diuron there was a slight increase in carbon dioxid produced during the first hour, after which the increase was non- significant.
herbicides, fluometuron, diuron