Yesterday morning the NDAWN station near Eldred recorded a low of 19 degrees Fahrenheit while the NDAWN station near Stephen dipped as low as 13 degrees Fahrenheit. Luckily the blanket of snow ensured that soil temperatures were much milder and at a 4 inch depth the soil temperatures never dropped below 32 degrees Fahrenheit at either location. Nonetheless, I have heard a fair amount of worries about the viability of the seed that made it into ground last week and terms like imbibitional chilling were mentioned.
Imbibitional chilling is defined as the injury that results from the chilling effect that seeds may experience when they imbibe or absorb water. The mechanism of this imbibitional chilling injury in seeds is different from chilling or freezing injury of hydrated tissues. The result, however, is much the same as it can result in poor seedling establishment, stand losses, and therefor, ultimately, yield. Warm season species like corn and soybeans are more susceptible to this type of injury than wheat, barley or oats. Drowning out due to soils being above field capacity is also different from imbibiotional chilling as this is more related to an acute lack of oxygen that kills the embryo.
So the question is whether the recent weather is a treat to the crop that is already in the ground and possibly even emerged. First, small grains, including spring wheat, winter wheat, rye, barley or oats, that had emerged will likely not suffer much, if any. If the seed had germinated but not yet emerged you may see some stand reduction. These stand reductions are likely the result of drowning out rather than imbibitional chilling. The same is true if the seed was just in the imbibiotional phase of the germination process.
If you are worried about the viability seed or seedlings you can simply dig some seedlings or seeds up and place them in a moist to wet paper hand towel (preferably unbleached and undyed ones). Roll the paper towel up and place it at room temperature and ensure that the rolled-up paper towel can not dry out by placing in a coffee mug with some water in the bottom and putting an open Ziploc bag over the top of the rolled-up paper towel and coffee mug to avoid rapid dry-down. This will tell you whether the seed is still viable in 24 to 48 hours as the radicle and shoot will start to grow and elongate (further). If you place a second rolled-up paper towel with another sample in the fridge you also get an idea how vigorous the seed still as loss of vigor will show as very slow growing seedlings while more vigorous ones develop much faster.