During an experiment involving the alternating O / X mode pump, the observation demonstrated that the high frequency enhanced ion line (HFIL) and plasma line (HFPL) did not immediately appear after the pump onset, but were delayed by a few seconds. By examining the initial behaviors of the ion line, plasma line and electron temperature, it is found that (1) the HFIL and HFPL are delayed not only in the X pump mode but also in the O pump mode; (2) the HFIL can not be observed until the electron temperature is enhanced. The analysis reveals that (1) the leakage of the X mode to the O mode pump can not be ignored; (2) the electron temperature and the spatiotemporal uncertainty may play an important role in the lack of the Bragg condition; (3) nevertheless, the absence of parametric decay instability can not be ruled out due to the spatiotemporal uncertainty.