The sensitivity of germinating seeds of barley, winter wheat and spring one to synchrotron ultraviolet radiation is barley > winter wheat and spring one. But when dry seeds of the three crops are irradiated by 3.5~22 keV X-rays, the sequence of their sensitivity to radiation can be changed; for irradiation of 0.6~3 keV ultra soft X-rays, 0.40~0.90 of the seedlings of the first generation appear mutation of striped chlorophyll defect. This biological effect has never been found for irradiation of other rays.