Abstract
Bush snap bean cv. Torukatto was used to investigate the effects of root zone temperatures (RZTs) and N-K levels on the growth, abscissions of flowers and pods, pod production and mineral contents. The effects of RZTs were more pronounced than N-K supply on the vegetative as well as reproductive performance in this cultivar. RZTs at 20, 25 and 30°C enhanced plant growth while 35°C RZT reduced it producing plants with less vegetative growth of vine, greener leaves and smaller leaf area. Moreover, photosynthetic activity tended to increase with an increase in RZT up to 30°C in combination with either of the N-K levels. Higher number of pods was obtained from plants grown with 20, 25 and 30°C RZT. Increased total-N, Ca and Mg contents were observed in leaf blades while P was higher in the pods and K was similar in both organs. The results suggest that maintaining the root zone temperature within the range of 20 to 30°C may act more effective for growth performance regardless of N-K supply in the nutrient solution. High RZT of 35°C has an adverse effect on root growth that can lead to the death of root tissues.
