The pattern becomes more regular if the pattern forming reaction works already during growth. In Fig. 5 pattern formation is shown on a cylinder that grows by proliferation at it upper end. New maxima appear during growth at regular distances on alternating sides. This is a simple model for the initiation of leaves on a growing shout. This leads also to a limitation of the inhibitor production.
More cells become activated at a lower level until sufficient inhibitor is produced.
In other word, the activated regions have the tendency to enlarge, However, in order to become activated, a close neighbourhood to non-activated cells is essential into which the inhibitor can be dumped. Both requirements, large activated patches and a direct neighbourhood of non-activated cells, seems to contradict each other. This is, however, not the case. Stripe formation is a very frequent phenomenon at very different developmental situations. Usually the size of a morphogenetic field increases during the growth of the embryo.