Effect of silicon on the growth of solution-cultured cucumber plant

Abstract

Cucumber plants were solution-cultured with and without silicon. Both silicon-free and silicon-supplied (100 ppm SiO₂) plants grew normally in the earlier growth stage. In the flowering stage, however, the newly developed leaves (8th or 9th leaves) of silicon-free plants showed malformations such as curling, whereas no abnormal symptoms were observed in leaves developing subsequently. In severe cases, the silicon-free plants began to dry up from the lower-leaves upwards. The growth and yield of silicon-free plants were markedly inferior to those of silicon-supplied plants. The pollen fertility of silicon-free plants was lower than that of silicon-supplied plants. Disease symptoms of powdery mildew were observed on al1leaves of silicon-free plants; however, no such symptoms were observed in leaves of silicon-supplied (100 ppm SiO₂) plants. The silicon content of leaves and plant growth increased, proportionally to the silicon concentration in the solutions, while disease symptoms of powdery mildew decreased. These results suggest that the growth response of the cucumber plant to Si deficiency is partly similar to that of the tomato plant and also to that of the rice plant.