Purplish coloration on stems and leaves with slow growth is most commonly due to which nutrient deficiency?

• A. Nitrogen deficiency
• B. Potassium deficiency
• C. Phosphorus deficiency
• D. Magnesium deficiency

Answer: (C)

Purplish coloration on stems and leaves combined with slow growth points to a phosphorus deficiency. Phosphorus is essential for energy transfer in the plant (ATP) and for making DNA and RNA, so when it’s short, growth slows and the plant often increases production of anthocyanin pigments, which gives tissues a purple hue. Because phosphorus is relatively mobile within the plant, the deficiency signs can appear as stunted growth with visible purpling as the limited phosphorus is redistributed to developing areas. This pattern is distinct from nitrogen deficiency (yellowing and overall poor vigor), potassium deficiency (marked leaf edge scorch and weak stems), or magnesium deficiency (interveinal chlorosis), making the purplish coloration with slow growth a classic indicator of phosphorus shortage.