Abstract
1. Greenhouse tomato, cucumber and melon were grown in four temperature treatments (20°C, 24°C, 28°C and control) of nutrient solution in summer. The maximum air temperature in the greenhouse was over 35°C and the root temperature of the control reached 30-35°C in the daytime.
2. The cooling treatments decreased the rotting of root and increased the healthfulness of root.
3. Tomato showed the most notable effect of root cooling treatment. The growth of tomato was promoted and the yield of tomato increased in order of low of cooling temperature.
4. The cooling treatment of 20°C was too low for cucumber to achieve better growth and more yield.The treatment of 28°C was the best temperature for cucumber.
5. The effect of cooling treatment for melon was not recognized definitely on both the growth and the quality.
