Abstract
"Stairstep experiment" was used in the discrimination f allelopathy. This method is a sort of sand culture, connecting the pot with pipe so that root exudates of one plant can flow into another plant, in which they can recirculate along with the taking of nutrient solution. This method is one of the most advanced method for the discrimination of allelopathy, because we can diminish the competitions for light in the upper parts of the plant and for nutrients or water in root systems by this method. We assembled stairstep experiment apparatus and used it for the discrimination of allelopathy of tomato plant (Lycopersicum esculentum), whose interfering activity in the mixed planting by soil culture was already reported and inhibiting activities in the germination and growth test with tomato plant crude extracts were also demonstrated. The results showed that tomato plant cultivated in stairstep apparatus can no more inhibit the growth of cucumber plant. These results show that prominent growth-inhibiting effect of tomato plant in the mixed planting by soil culture was attributed to the interference other than allelopathy and could probably be ascribed to the competitions for light and nutrients. Though stairstep method is an advanced method for the discrimination of allelopathy by root exudates, it takes much effort but yields few data. So we developed a new system for the discrimination of allelopathy. This method is essentially a sand culture wherein the upper part of the two plants in the same pot is divided by a wall, through which light cannot penetrate, in order to separate the leaves of the plant and to make the light condition identical during growth in the rotary greenhouse. By these operations, we can discriminate between the competitions for light, water, nutrients and the chemical allelopathic interference. We call this method "rotary greenhouse method." By this method, we cultured some plants in the mixture, and found that tomato plant has no growth inhibition to other plants. These results supported the data obtained by stairstep method. The rotary greenhouse method may serve as another method for the discrimination of allelopathy.
