Pierce's disease causes the vine to be unable to produce which substance, leading to death within 1-5 years?

Pierce's disease causes the vine to be unable to produce which substance, leading to death within 1-5 years?

• A. Sugar
• B. Chlorophyll
• C. Tannins
• D. Anthocyanin

Answer: (B)

Pierce's disease is a xylem-blocking infection in grapes, so the vine cannot move water up from the roots. That disruption stresses the leaves to the point where chlorophyll production declines; without sufficient chlorophyll, photosynthesis collapses, so the plant cannot generate the energy and building blocks it needs, leading to death over several years. The other substances listed—sugars, tannins, anthocyanins—are not the essential deficit caused by this disease; chlorophyll loss directly undermines the vine’s ability to capture light energy and drive growth.

Pierce's disease is a xylem-blocking infection in grapes, so the vine cannot move water up from the roots. That disruption stresses the leaves to the point where chlorophyll production declines; without sufficient chlorophyll, photosynthesis collapses, so the plant cannot generate the energy and building blocks it needs, leading to death over several years. The other substances listed—sugars, tannins, anthocyanins—are not the essential deficit caused by this disease; chlorophyll loss directly undermines the vine’s ability to capture light energy and drive growth.