system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:What makes a tree live on, while plants such as corn die off quickly?If a tree grows on and on without disturbance,is there a limit to its lifetime?
gpt
#Slow and steady vs. Fast and furious

The main difference is how each handles reproductive events. Reproduction is the most energy and resource consuming event any organism can live. 

Herbs (what you would call "plants") have chosen the strategy of tanking stressful environment as a seed or tubercule, gather resources during the favourable weather and use all their resources in a single reproductive event, this killing then because they don't have any more resources to keep themselves alive. 

On the other hand, trees have chosen the strategy to slowly gather resources, even during stressful conditions (like bad weather) and use only a fraction of their resources in each reproductive event, meaning they keep some resources to themselves, letting them stay alive. 

Neither strategy is inherently better than the other, they're just different ways of solving the same problem. 

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#How to live forever 

You might have seen that after cutting the main trunk of a tree, little branches grow back, ultimately making a new tree again. This is due a "stem cell like" property of trees, where they always retain their merismatic cells (the equivalent to stem cells in plants) after each growing event which grants trees with the ability to regrow or repair any organ. 

If met with theoretical ideal conditions (always good season, no predation, no competetition), you can argue that a tree can live forever. 

The next challenge comes from within the cells of the tree. Just like humans, trees have chromosomes (which are may bundles is compacted DNA), at their end they have a strand of DNA known as telomer. Each replication event of the cell shortens the telomer. When there's no more telomer left, the cell dies.  So, unless you have a way to repair that telomer loss, your days as a tree are counted. 

Some trees, like some types of pines, have the ability to repair that loss with an enzyme that "rebuilds" the telomer after some replication events, thus, granting the tree with eternal life. 

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#Could this actually happen? 

The dynamic nature of Earth and its ecosystems represents a huge challenge to any organism that aims for eternal life. 

You have catastrophic events that are cyclic, some unpredictable bad seasons, constant competition with other organisms like you, constant predation and parasitation, internal mistakes (trees can get cancer too!) and such. 

The oldest trees we know are around 5000 years old, although a whole lot of time, it's just a moment in the history of Earth.