Question

Calcium influences the effect of several plant hormones. Why then, isn't Calcium considered a plant hormone?

Answer 1

Calcium is not a plant hormone instead it is a secondary messenger that plays an important role in signal transduction pathways of plants.
Role of calcium in action of plant hormone-
1.Calcium along with Abscisic acid (plant hormone) induces stomatal closure.
2.Increase in intracellular concentration of calcium along with Cytokinin (plant hormone) is associated with bud initiation.
3.Calcium along with Gibberellic acid (plant hormone) increases the activity of alpha-amylase enzyme in germinating seeds.