Which hormone redistributes across a young shoot and helps produce unequal elongation under one-sided light?

• Chlorophyll
• Auxin
• Glucose

A young shoot grows and curves towards light from a window. What is this response called?

• Positive phototropism
• Negative gravitropism
• Water loss causing wilting

In a horizontal root responding to gravity, extra auxin on the lower side makes that side elongate faster.

Circle one:   True   False

A growing seedling is placed horizontally in darkness. Its shoot later curves upwards. Which explanation fits?

• Light from below stimulated the upper side
• The shoot moved without any cell elongation
• Auxin promoted lower-side elongation

Light shines on the left side of a young shoot, and it bends left. Which side elongated more?

• Both sides elongated by the same amount
• The illuminated left side elongated more
• The shaded right side elongated more

Comparable young grass shoots bend under one-sided light with transparent tip caps, but not with opaque tip caps. What does this comparison support?

• Every cap stops growth by preventing the tip from expanding
• Light reaching the tip is needed for this response
• The lower shoot detects light without receiving any tip signal

A removed grass-shoot tip is replaced over permeable gelatin or an impermeable mica sheet. Under one-sided light, only the gelatin treatment bends. What does this support?

• The barrier comparison identifies the signal's exact chemical name as auxin
• A diffusible signal can pass through gelatin but not mica
• The barrier comparison shows that a tip is unnecessary for the response

A student says synthetic auxins cannot control weeds because auxin promotes growth. Which explanation resolves this?

• Excess auxin-like signalling can cause damaging, uncontrolled growth
• Auxin-like chemicals control weeds by blocking all sunlight from their leaves
• Any chemical that promotes growth must improve survival at every concentration