In the hydro-culture system, the growth vegetable crop was greatly influenced by the value of dissolved oxygen(DO). Effects of different levels of dissolved oxygen supply on growth and water flux in stems on seedling growth in hydro-culture were studied. And a system for measurement of water flow rate in a crop stem was the method of stem heat balance by the heat flux control. The amounts of dissolved oxygen in water were regulated in five grades.
The main results were as follows: The growth rate of seedling growth of tomato was generally influenced by the value of dissolved oxygen(DO), especially, the more the value of DO decreased, the more the formation of roots might interfere. The value of DO exerted a deep influence on sucking up of water in the stem, consequently, the transpiration flux was decreased. The measurement of transpiration flux is a very fair possibility of the growth evaluation in the seedling growth.