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  • Author or Editor: Jenjira Chumpookam x
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Smoke-water is a chemical extract used to stimulate the germination of many plant species under cultivation. This study evaluated the efficacy of smoke-water on the seed germination and seedling growth of papaya (Carica papaya cv. Tainung No. 2). Smoke-water, prepared from dry rice straw (Oryza sativa) by burning and bubbling the smoke through water, was used for germination experiments, growth experiments, and anatomical structure changes of seeds. In the germination experiments, papaya seeds were soaked with different concentrations of smoke-water (0.1%, 0.2%, 1%, 2%, 3%, 4%, 5%, 7%, or 10%, v/v) for 24 h before planting. Low concentrations of smoke-water (0.1% or 0.2%, v/v) not only promoted the maximum rate of germination, but also shortened the germination time. Analysis of longitudinal sections of seeds treated with smoke-water concentrations of 0.1% or 0.2% v/v suggested that smoke-water could overcome water impermeability barriers, because it stimulated the seedcoat to rupture and allowed the radical to elongate and emerge faster. In the growth experiments, papaya seedlings were transplanted into peatmoss-filled pots that were saturated with different concentrations of smoke-water (0%, 1%, 2%, 3%, 4%, 5%, 7%, or 10%, v/v). Results showed that all growth parameters increased significantly compared with the control. In addition, smoke-water treatments consistently and significantly increased the percentage of nitrogen in roots and shoots and significantly increased the percentage of magnesium in shoots. In these experiments, smoke-water showed potent germination promotion at low concentrations and promoted multiple growth attributes such as chlorophyll content and seedling vigor index at all concentrations in papaya seedling production.

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The antifungal efficacy of smoke-water on damping-off caused by Pythium sp. was evaluated both in vitro and in vivo. Smoke-water was generated by burning plant material and bubbling the smoke through water; its effect on the morphology of Pythium sp. was investigated by scanning electron microscope (SEM). Mycelia growth and oospore production of the fungus were significantly inhibited when cultured on water agar amended with smoke-water at 0%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%. In growth chamber experiments with potted seedlings growing in peatmoss, papaya plants treated with smoke-water exhibited reduced symptoms of damping-off when compared with control plants treated with water. Furthermore, the pots treated with 1.5% or higher smoke-water did not show any symptoms of damping-off disease. Plant height significantly increased with treatment by higher concentrations of smoke-water. Maximum plant height was observed with treatment of 1% smoke-water or higher concentrations. One day after smoke-water application, SEM observations of the Pythium sp. revealed loss of structural integrity, abnormal degradation, deformation, abnormal lysis, cytoplasmic leakage, and hyphal slimming. This study showed that the addition of smoke-water to soil exerted significant disease suppression against Pythium sp., leading to improved growth of papaya seedlings.

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