DYNAMIC MANAGEMENT OF ROOT EXPOSURE TO AIR ABOVE THE NUTRIENT FLUID SURFACE FOR PRODUCTION OF TOMATO (LYCOPERSICON ESCULENTUM MILL.) TRANSPLANTS

A new cultivation method was designed in which the seedling beds are gradually raised above the nutrient fluid, increasing the amount of roots exposed to air as the roots grow. The growth and morphological characteristics of roots of tomato (Lycopersicon esculentum Mill.) seedlings resulting from root exposure to air were studied. During the initial 3-day adaptation period after transplanting, the bed heights were fixed at 0.5, 2.5, and 5.0 cm (treatments F0.5, F2.5, and F5.0, respectively) above the surface of the nutrient fluid. For F2.5 and F5.0, the root hairs and lateral roots exposed to the air died away, resulting in barren primary roots above the fluid surface. Next, half of the planting plates in each treatment were gradually raised from their initial heights in increments of 2.4 mm per day over a period of 17 days (treatments R0.5, R2.5, and R5.0). The seedlings in R0.5 had many more lateral roots, root hairs, and greater total volume of roots than those in other treatments. These results suggest that the new method of dynamic management of root exposure to air can be used to replace solid growth media culture for production of young tomato transplants. For commercial applications, it may be more feasible to control the amount of root exposure to air by adjusting the nutrient fluid level instead of the seedling bed height.