adding vertical tropism to cordate curve and a curve control.

below is the part related to curve control. to create the cordate curve, I use 12 curves, the ones connected with the petiole (base of the leave). those curves are growing like branches with a little vertical tropism to make them curvy (in nature, it is not a tropism...).

also each curves have a different length. their lengths are controlled like below. 

I am not sure to be clear, so here is the 3dxml.