The idea of a plant being able to conduct photosynthesis during freezing temperatures was a novel idea to me. The researchers in this article wanted to see how lingonberries were able to recover to a photosynthetic state during periods of mild temperature during winter months. They tested temperature, photoperiod, and preceding frost for effects on the lingonberry, and what they discovered surprised me. Extreme cold slowed down the recovery, however the berries were able to come back and maintain photosynthesis even at freezing temperatures. These berries amaze me! The more I learn, the more I realize I don’t know. Check out their findings in the article listed below. CM Fairbanks
Saarinen, T., R. Lundell, and H. Hänninen. 2011. Recovery of photosynthetic capacity in Vaccinium vitis-idaea during mild spells in winter. Plant Ecol 212:1429-1440
This link with nice photos of different growth stages of a blueberry plant. What I find interesting is the different cold tolerances of the different stages, which as mentioned in this class, is an important consideration when predicting fruit production from our plants. For example, flower bud swell can tolerate 10-15F, while flower bud break is tolerant to about 20F, full bloom to 28F and petal fall (while fruit is developing) only 32F. This shows how vulnerable late developmental stages can be and how a cold snap late in the season could be detrimental to the fruit crop.
Note that this site talks about highbush blueberries and not our native bog blueberry, Vaccinium uliginosum, in Interior Alaska. I need to do more searching to find the critical temperatures for V. uliginosum! However, I think that these photos of bud stages and listed critical temps are helpful reminders that not all stages or parts of a plant have the same temperature tolerances. The plant is growing, developing and changing and as managers, one would need to be attentive to these changes.
I was inspired by the time-lapse strawberry video and started searching for more. I could watch these all day long. Here is another great one for a pear that was created by Neil Bromhall: https://www.youtube.com/watch?v=4ttRgMj7PdQ
Being in Biology right now we are learning about proteins so I looked into the proteins that keep plants from freezing in harsh Alaskan winters. I found an article titled “Antifreeze proteins enable plants to survive in freezing conditions” by RAVI GUPTA and RENU DESWAL. I was intrigued by the fact that this article came out of India, where I imagine they do not get cold weather like maybe a northern European country, where I would expect an article like this to come from. The article goes into depth of how the proteins impede the hydrogen bonds of the water molecules so that they cannot bond and form ice crystals.
“Overwintering plants secrete antifreeze proteins to provide freezing tolerance. These proteins bind to and inhibit the growth of ice crystals that are formed in the apoplast [conduit for water transport in plants where water moves through the cell walls without going through the inner cell membrane] during subzero temperatures. Antifreeze activity has been detected in more than 60 plants and antifreeze proteins have been detected in 15 of these, including gymnosperms, dicots and monocots.
The main function of antifreeze proteins is inhibition of ice crystal growth rather than the lowering of freezing temperatures. Antifreeze activity with higher Thermal hysteresis also exists in plants. Calcium and hormones like ethylene and jasmonic acid have been shown to regulate plant antifreeze activity. Plant antifreeze proteins may have evolved nearly 36 million years ago”.
Gupta, R. and R. Deswal. 2014. Antifreeze proteins enable plants to survive in freezing conditions.J Biosci.