Final answer:
Non-heme iron from vegetables needs to be converted to Fe2+ for absorption. This conversion occurs by cytochrome B and/or Vitamin C in the duodenum/proximal jejunum, but it can also occur in the stomach due to low pH and vitamin C.
Step-by-step explanation:
Non-heme (Fe3+) iron (vegetable-derived) must be converted to Fe2+ in the duodenum / proximal jejunum by cytochrome B and/or Vitamin C for absorption. However, reduction from Fe3+ to Fe2+ occurs in the stomach as well (via low pH and vitamin C).