Basically, it wasn't the cold temps that did the major damage. It was the extreme change in temperature drop that happened in such a short timespan. Plants can survive the low temps, but they normally have time to prepare physiologically. In this rare circumstance, they didn't have time to prepare. The sudden wilting/yellowing was mostly caused by water actually freezing inside the cell walls and bursting the plant's walls.
Grasses like wheats and oats ought to rebound OK. Annual clovers and brassicas are going to have a much harder time rebounding, and its possible they won't. Perennial clovers with a well established root system (not planted this fall) should be OK as their roots should still be alive.
As far as what we can do... Some dry fertilizer applications may help once we get rain and warm weather (most of state just had). Since plant tissue is dead (the yellow/wilt), foliar applications are about useless.
