https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5130066/ According to the article, some adjustments might occur during early stages of growth, either reversible or irreversible. I believe it applied to all or most types of trees.
Trees respond to climate changes in 3 ways, evolutionary adaptation (through seeds), modification (during development), acclimation (internal chemical changes).
1) At least some of the off-springs of a certain hybrid citrus variety might adapt better to the cold climate than their hybrid parents. I did not mean the original ancestor like pure poncrius, but the immediate hybrid parents like citrange. For example, some of the citrange off-spring might adapt better than their parents in cold climate. Even Thomasville citangequat which mostly come true from seed might have experienced some adjustment to adapt better to colder climate than the original Thomasville citrangequat 100 years ago.
2) Some the adjustments were not reversible in its lifespan. Those adjustment we have been arguing about previously was the reversible adjustments which also calls acclimation (internal changes of chemicals to respond to climate change). I personally thought of leaving hybrid citrus seedlings in my plastic covered patio with no heat equipped to force those survivals to adjust themselves in their structure to respond to colder climate. Previously, most of us tried to over protected our seedlings in greenhouses with heaters which I believe might limit the seedling modification to adapt better to colder climate in its early growth stages.
It sounds pretty much similar to living beings. If someone grew up in a tropical climate region like the southern part of Florida, they might not tolerate to freezing weather as good as someone grew up in the north like Russia or Alaska. As the result, over many centuries, off-springs of the northern people inheriting the "evolutionary adaptation" from their ancestors and therefore tend to tolerate to freezing much better than someone from the south.