Plant Adaptations to Cold

 

December was one of the colder months on record, and January has not been any great heat wave. With temperatures dropping into the 20’s or 30’s below, things are pretty inhospitable. It is at times like this that I can’t help but think about how all the plants and animals survive the winter cold.

Animals basically have three options when it comes to the winter cold: migrate, hibernate, or persevere. Those that persevere have adaptations to help them survive the cold, such as fat reserves, thick well insulating fur or feathers, and often times a den or nest. We humans are poorly adapted to the cold, but we’ll make it, thanks largely to human ingenuity. But it is the plants that really get my interest and curiosity during our cold winters.

Plants, of course don’t have fur or a burrow to help them keep warm, but they have less obvious adaptations to the winter cold. With few exceptions, plants in our area are dormant during our winters (conifers come to mind here, but I’ll save that for another time). However, dormant plants can still freeze. So how do these plants keep from freezing to death when the temperatures are well below zero?

Plant species obviously differ in their adaptation to low temperatures. That’s also true for populations of the same species as well as different tissues within the same plant. Those differences involve a myriad of factors including anatomical and physiological aspects.

It might surprise you, but it is not the cold temperatures, per se, that injures or kills plants. The damage is usually the result of ice formation within the cells which can cause fatal rips and tears. This has been illustrated through some experiments where non-hardy plant tissues have survived being slowly cooled or “supercooled” to temperatures of well over -100 C without ice crystals forming.

Plants become tolerant to subfreezing temperatures by a process called acclimation. The process is complex and not particularly well understood, but it apparently begins in late summer with the translocation of some organic compound(s) such as sugars or hormones. This translocation is thought to be initiated by shortening days and the cessation of growth. The first hard frost is also known to be a major factor. At any rate, the plants increasingly become more “hardy” or resistant to the potentially damaging effects of below freezing temperatures.

It really is amazing that these plants can survive exposure to such harsh conditions! So, the next time the temperature hits double digits below zero and you’re shivering in your heavy jacket, give a thought to the plants. Maybe it will even help you feel a bit warmer!

Chuck Lura

Natural North Dakota is supported by NDSU Central Grasslands Research Extension Center and Minot State University-Bottineau, and by the members of Prairie Public. Thanks to Sunny 101.9 in Bottineau for their recording services.

 



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