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

Explanation

It is mainly due to mobility of minerals. Based on this, they are classified into 1. Actively mobile minerals and 2. Relativity immobile minerals.
a. Actively mobile minerals: nitrogen , phosphorus, potassium, magnesium, chlorine, sodium, zinc and Molybdenum . Deficiency symptoms first appear on old and senescent leave due to active movement of minerals to younger leaves.
b. Relatively immobile minerals : calcium sulphur iron boron and copper shows deficiency symptoms first that appear on young leaves due to the immobile nature of minerals.