Which is a symptom of magnesium deficiency in vines?

• A. Reduced yield and poor ripening.
• B. Deep green leaf color.
• C. Higher sugar concentration in juice.
• D. Increased resistance to drought.

Answer: (A)

Magnesium is central to chlorophyll and photosynthesis, and it is mobile within the plant, so deficiency appears first in older leaves as interveinal chlorosis. This reduction in photosynthetic capacity means the plant has less energy available for growth and fruit development, which in grapevines commonly shows up as reduced yield and poor ripening. The other options don’t fit because deep green leaves aren’t a deficiency sign (yellowing between veins is), higher sugar concentration in juice points to ripening or sugar accumulation rather than a deficiency, and magnesium deficiency doesn’t bolster drought resistance.