State three physiological roles and two deficiency symptoms of potassium.

Physiological Roles:

1. Anion-cation balance: Maintains ionic equilibrium and electrical neutrality in cells.
2. Protein synthesis: Activates enzymes involved in protein biosynthesis pathways.
3. Stomatal regulation: Essential for guard cell turgor changes controlling stomatal opening/closing.

Deficiency Symptoms:

1. Chlorosis: Yellowing of leaves due to impaired chlorophyll synthesis and degradation.
2. Necrosis: Death of leaf tissue, particularly at margins and tips, due to cellular breakdown.