毛萼田菁的茎瘤形成于茎上蛰伏的不定根发生点。 当合适的根瘤菌从不定根发生点裂口入侵后，刺激不定根原基周围的皮层细胞分裂形成含菌组织而发育成茎瘤。

Rhizobium sesbania infected through the apical rupture of the growing site of adventitious root, multiplied in the fissure around the root primordium and stimulated the division of cortex cells.

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