[Campbell Biology P.835] Which of the following statements about phyllotaxy and the 137.5° a... | Practice Question

Which of the following statements about phyllotaxy and the 137.5° angle of leaf emergence in most angiosperms is correct?

  • A: Phyllotaxy refers to the branching pattern of stems, and the 137.5° angle maximizes shading of lower leaves.
  • B: The 137.5° angle is specific to species with opposite phyllotaxy, ensuring even light distribution.
  • C: Phyllotaxy describes the arrangement of leaves on a stem, and the 137.5° angle in alternate phyllotaxy is hypothesized to minimize shading of lower leaves.
  • D: The 137.5° angle is a constant across all plant species and is primarily for mechanical support.

Explanation

Phyllotaxy is defined as 'the arrangement of leaves on a stem.' The text further explains that 'Most angiosperms have alternate phyllotaxy, with leaves arranged in an ascending spiral around the stem, each successive leaf emerging about 137.5° from the site of the previous one. Why 137.5°? One hypothesis is that this angle minimizes shading of the lower leaves by those above.'