[Campbell Biology P.879] How do the distinct germination mechanisms of garden beans dicots a... | Practice Question
How do the distinct germination mechanisms of garden beans dicots and maize monocots protect their delicate shoot tips from mechanical damage as they push through the soil?
A: In garden beans, the cotyledons protect the shoot tip by being pulled first, while in maize, the radicle forms a protective cap.
B: Garden beans form a hypocotyl hook that, upon straightening, pulls the cotyledons and the delicate epicotyl (shoot tip) safely above ground. Maize encloses its shoot tip within a rigid coleoptile that pushes through the soil, acting as a protective tunnel.
C: Both species produce a sticky mucilage that lubricates the soil, reducing friction on the shoot tip.
D: Garden beans rely on rapid cell expansion to quickly emerge, whereas maize's shoot tip is inherently tougher.
Explanation
For garden beans, the hypocotyl forms a hook that pulls the delicate epicotyl containing the shoot tip and cotyledons through the soil. Once above ground, the hypocotyl straightens, exposing the epicotyl. For maize, the coleoptile acts as a protective sheath, pushing through the soil like a tunnel, through which the shoot tip grows safely.