Effect of Plant Growth Regulator on Root Activity of Tomato in Long-termSoilless Cultivation Effect of Plant Growth Regulator on Root Activity of Tomato in Long-termSoilless Cultivation Application Effect of Piggery Biogas Slurry on the Soilless Culture of Swamp Cabbage Studies on seed germination and soilless cultivation of Schizonepeta tenuifolia Preliminary Study on Soilless Cultivation Techniques of Panax quinquefolium L.