Question

what are characteristic of trees growing in cold areas ?​

Answer 1

Answer:

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Explanation:

Gradual low temperature constraints affect the growth process (meristems) long before they affect photosynthetic carbon gain. Hence, plants growing in cold climates are commonly not carbon limited.

Answer 2

Answer:

Explanation:

cold-adapted genotype must, first of all, resist local low temperature extremes, so all plants found in cold climates have gone through that selection filter. Freezing resistance is the number one sieve that species must pass through to live in cold climates. The spectrum of freezing resistance reflects the spectrum of life conditions, and no plant can be found in this planet's periodically cold regions that is not resistant to the local low temperature extremes. This is not the place to review the knowledge on freezing resistance physiology (see 6, 7). In brief, freezing resistance in plants has little to do with antifreeze solutes. From physical chemistry, we know that 1 molar solution depresses the freezing point by 1.8 K only. Since the cells of most organisms are operating at or slightly below a 1 molar cell sap concentration, such a marginal gain in freezing point depression would require at least doubling concentration. Thus, the actual processes involved are water extraction from the cell through extracellular ice formation that requires a fluid outer cell membrane at low temperature, protective compounds such as certain sugars and proteins to safeguard membranes, and enzymes against damage during dehydration. For all this to work, the onset of extracellular ice formation must not be delayed, so that the flow of water out of the cell can keep pace with cooling. Surviving extremely low temperatures is the evolutionary outcome of cell membrane properties and certain cell sap constituents. Finally, freezing resistance is not constant for a given plant, but it varies, driven by internal controls (seasonality) and by short-term acclimation, all deeply rooted in evolution (phylogeny). In addition, some tropical alpine taxa have been found to perform what is called leaf super-cooling, which is retaining water in a gel-like metastable state below freezing point (to avoid nucleation). When the super-cooling capacity is exhausted around -12°C, tissues freeze immediately and are dead. There is evidence that the xylem water of trees of cold regions can super-cool down to -40°C (for a review, see 8).