Tip necrosis

Tip necrosis is primarily a physiological disorder in plants characterized by the localized death of tissue at the leaf tips and margins. It occurs due to an inadequate supply of calcium, which is essential for cell wall formation and stability. As a non-infectious condition, it is not caused by pathogens but rather by environmental and nutritional factors that disrupt the plant's vascular transport system.

This condition frequently affects a diverse range of crops, including Passiflora L., leafy greens, strawberries, and various greenhouse vegetables. Rapidly growing plants are particularly susceptible, as their physiological demand for calcium often exceeds the rate at which the plant can uptake and distribute this nutrient to newly developing leaves.

The primary symptom begins as small, light-colored spots on the tips or edges of young, expanding leaves. As the disorder progresses, these areas dry out, turn brown or black, and become necrotic. In severe cases, the leaf margins may curl or become brittle, leading to a stunted appearance and a reduced capacity for effective photosynthesis, which ultimately impacts the overall yield.

The development of tip necrosis is heavily influenced by environmental conditions that affect transpiration. High humidity levels, stagnant air, or extreme heat can reduce the flow of water through the xylem, preventing calcium from reaching the apex of the plant. Additionally, an imbalance in the root zone, such as excessive potassium or magnesium compared to calcium, can competitively inhibit calcium uptake by the roots.

Effective management and prevention of tip necrosis involve a proactive approach to irrigation and nutrient supply:

• Maintain consistent soil moisture levels to ensure steady nutrient uptake.
• Apply foliar calcium supplements during periods of rapid growth to bypass root transport limitations.
• Improve air circulation in greenhouses to promote uniform transpiration.
• Balance fertilization programs to avoid excessive levels of competing nutrients like nitrogen, potassium, or magnesium.