Growth of Trees

[IM Chol Hong]

I am making computer animation of the growth of trees in forest. 
I am wondering about following point.
Do the growth of trees(or any plants) show hysteresis ?
It means that when the growth rate of a tree approaches 0 
(because of the limit of sunlight), the growth rate jumps down to 
some value at some amount of sunlight and in turn, when the growth
rate approches 0 (because of the increase of sunlight), the growth 
rate jumps up to some value at some amount of sunlight greater than
one in the case that the grwoth rate decreases (needs more sunlight 
to recover). 
If this happens, what is the casue of this phenomenon ? 
Any help will be appreciated.
Thanks in advance.
--
Im Cholhong
chim at is.s.u-tokyo.ac.jp