[Campbell Biology P.899] Based on Figure 39.8 and its accompanying text, what is the primary... | Practice Question

Based on Figure 39.8 and its accompanying text, what is the primary reason why removing the apical bud leads to increased growth of lateral branches?

  • A: The apical bud is a major source of cytokinins, and its removal reduces cytokinin levels, thus promoting lateral growth.
  • B: Removal of the apical bud increases sugar availability to remaining buds and reduces the inhibitory effects of auxin and strigolactones.
  • C: The presence of the apical bud actively produces a hormone that promotes lateral bud growth, and its removal enhances this effect.
  • D: Apical bud removal directly stimulates gibberellin production, which is the sole hormone responsible for lateral branching.

Explanation

Figure 39.8's accompanying text explicitly states: "Removal of the apical bud allows remaining buds to receive more sugars for growth. Auxin and strigolactone levels also decline, particularly near the cut surface. This decline allows the topmost axillary buds in particular to grow and take over as the new apical bud." This encompasses both increased nutrient availability and reduced hormonal inhibition.