DENDROLOGY

Detailed explanation-1: -Most of the flowering plants that belong to the family Fabaceae or Leguminosae have zygomorphic flowers. They are commonly known as legumes. Plants such as pea, bean, cassia, and gulmohar belong to Fabaceae. Therefore, four plants show a zygomorphic flower.

Detailed explanation-2: -Zygomorphic or bilateral is when the flower is divided into two equal halves only by one vertical plane, then it is called as a zygomorphic flower, e.g., pea, bean, gulmohur, Cassia. So, the correct answer is ‘Only one vertical section passing through its centre divides it into two equal halves’

Detailed explanation-3: -A. Pea is an example of a zygomorphic flower with diadelphous stamen and marginal placentation. Zygomorphic flower is a flower having only one plane of symmetry. Diadelphous stamens refers to the condition when stamens are fused together.

Detailed explanation-4: -Zygomorphic flower is a flower which can be divided into two equal vertical halves by only one plane. A zygomorphic flower has bilateral symmetry. For example, Pea, Salvia.