To explore whether or not the supernatant is able to inhibit rice pollen tube elongation, pollen grains were first treated for 6 min in the germination solution, the germinated pollen grains were selected and the pollen tube length was recorded (Figure 3(c)). At the same time, some of the selected pollen grains were kept in the germination solution, and others were treated withthe supernatant mixture (5 volumes of the supernatant and 1 volume of germination solution), the length of pollen tube was recorded after incubation in the solutions for 9 min. The pollen tube continued to elongate when pollen grains were kept in the germination solution (Figure 3(d)), whereas pollen
tube elongation was completely inhibited if the germinated pollens were kept in the supernatant mixture (Figure 3(e)).