Question

Why is that in certain plants, deficiency symptoms appear first in younger parts of the plants while in others, they do so in mature organs?

Answer 1

When deficiency symptoms appear first, we can notice the differences in old and younger leaves. It is mainly due to mobility of minerals. Based on this, they are classified into

1. Actively mobile minerals and
2. Relatively immobile minerals

• Actively mobile minerals:
  Nitrogen, Phosphorus, Potassium, Magnesium, Chlorine, Sodium, Zinc and Molybdenum. Deficiency symptoms first appear on old and senescent leaves due to the active movement of minerals to younger leaves, than the older leaves.
• Relatively immobile minerals:
  Calcium, Sulphur, Iron, Boron and Copper. Here, deficiency symptoms first appear on young leaves due to the immobile nature of minerals.