Which element deficiency may cause veins to turn purple in plant leaves?

A deficiency in phosphorus often leads to distinct symptoms in plants, notably the development of purple veins or purpling of the leaf blades. This is primarily due to the fact that phosphorus is critical for energy transfer and photosynthesis, and when plants do not have enough of it, they cannot produce the necessary energy for healthy growth. The purple coloration arises because anthocyanin pigments accumulate in the leaves as a response to inadequate phosphorus levels. This change can be more evident in cooler temperatures where the deficiency is pronounced.

While potassium, iron, and magnesium deficiencies can also manifest in various ways, they typically do not specifically cause purpling of the veins. Potassium deficiency may lead to yellowing or browning of the leaf margins, iron deficiency usually results in interveinal chlorosis (yellowing between the veins), and magnesium deficiency presents itself as leaf curling and older leaf yellowing. Understanding these specific symptoms can aid in diagnosing plant health and nutrient needs effectively.