Which among the following is not a part of the shoot system?

• Stipules are small lateral outgrowths of the leaf base.
• Leaves are the parts of a plant that arise from the nodes of a stem.
• A rhizome is an underground stem modification.
• Pneumatophores are negatively geotropic roots that grow upward. These roots contain air spaces that help in gaseous exchange in the mangrove plants.

Thus, option C is the correct answer.