The deficiency symptoms of which of the following tends to first appear in young tissues?

Any mineral ion concentration is considered toxic to plants if it reduces the dry weight of tissues by:

Symptoms of excess of manganese may actually be the deficiency symptoms of all the following except:

Which one of the following statements can best explain the term critical concentration of an essential element?
1. Essential element concentration below which plant growth is retarded.
2. Essential element concentration below which plant growth becomes stunted.
3. Essential element concentration below which plant remains in the vegetative phase.
4. None of the above

A symptom common to the deficiency of Ca, Mg, Cu and K in plants is:
1. Chlorosis
2. Inhibition of cell division
3. Necrosis
4. Delay in flowering