They grow and develop all year. this gives them an advantage over other trees.
The two cells go into interphase, preparing to split apart again.
I think the answer is 90%. According to the recent National institute of Health, Microbes in the human body estimates that 90% of the cells in human body are bacterial, fungal, or otherwise non-human. Despite the arguments that bacteria enjoys a commensal relationship with the humans hosts, only a fraction of the human microbia has been characterized.