Auxin is a growth type of this substance; it regulates plant growth, especially in stems
... any of a group of hormones that 
regulate plant growth, particularly by stimulating cell elongation in stems and... [DOC] [TLE] AuxinCytokinin Interaction Regulates Meristem Development - NCBI [PAR] Feb 28, 2011 ... Plant hormones regulate many aspects of plant growth and .... of the polar axis 
and the formation of two types of meristems in the embryo.