Patterns of Regeneration in Mutilated Seedlings of Garden Balsam, Impatiens balsamina L.

Seedlings of garden balsam, Impatiens balsamina, form an encirclingswollen ring, the collet, basal to the hypocotyl. From this,four lateral roots emerge promptly after germination. When thisstructure is excised, it regenerates as a basal encircling swellingfrom which four lateral roots with root hairs emerge. Repetitionof the removal of this structure results again in the regenerationof a similar complex. Eventually, after 3–4 excisions,the pattern is broken and lateral roots occur sporadically alongthe hypocotyl. Mutilations of seedlings of the garden balsamindicate that the regeneration will not occur in the absenceof cotyledonary tissue. This suggests a control site for thisregenerative phenomenon but no mechanism for this control isadvanced. Impatiens balsamina, balsam, lateral roots, regeneration, collet