Bn. Nagorcka, THE REACTION-DIFFUSION (RD) THEORY OF WOOL (HAIR) FOLLICLE INITIATIONAND DEVELOPMENT .2. ORIGINAL SECONDARY FOLLICLES, Australian Journal of Agricultural Research, 46(2), 1995, pp. 357-378
In an accompanying paper it was shown that a spatial prepattern mechan
ism based on a biochemical reaction referred to as a reaction-diffusio
n (RD) system is able to account for many aspects of the initiation an
d development of primary (P) wool follicles. In this paper the same RD
system is applied to the initiation and development of original secon
dary (SO) follicles. Prepatterns are generated by solving the equation
s describing the reaction and diffusion of the chemical components of
the RD system in early stage follicles. It is demonstrated that the pr
epattern mechanism can account for the loss of a sweat gland causing a
change from P follicle initiation to SO follicle initiation. The RD s
ystem equations are also solved in the epidermis. The time sequence of
prepatterns obtained in the epidermis account for the tendency of SO
follicles to group with P follicles, by initiating in-between members
of the trio group of P follicles as well as in between existing SO fol
licles. The prepatterns obtained did not account for the tendency of s
econdary follicles to initiate on the posterior side of the trio group
. Good agreement was obtained between the predicted increase in total
follicle density and the increase in follicle density observed during
follicle initiation by Carter and Hardy (1947), provided full account
was taken of the interaction between existing follicles and each new f
uture generations of follicles. The prepattern mechanism provides a fu
ndamental basis for an inverse genetic correlation between total P and
SO follicle density and fibre diameter.