Final answer:
Iron deficiency can cause interveinal chlorosis in older leaves. It is the first mineral to show this symptom.
Step-by-step explanation:
In older leaves, iron deficiency can cause interveinal chlorosis. This is because iron is necessary for the production of chlorophyll, which is responsible for the green color of leaves.
When there is an inadequate supply of iron, new leaves can still produce enough chlorophyll, but older leaves start to show signs of chlorosis, which is the yellowing of the areas between the veins.
Other minerals like manganese, zinc, and copper can also cause interveinal chlorosis in older leaves if there is a deficiency, but iron is usually the first mineral to show this symptom.