verwelking

Verwelking is the loss of turgor in plant tissues, causing drooping leaves and stems. It occurs when water uptake by the roots cannot meet the plant’s transpiration demand, or when the plant’s hydraulic system is impaired. Verwelking is a symptom rather than a single disease and can result from both abiotic and biotic factors.

Causes can be grouped into abiotic and biotic categories. Abiotic causes include insufficient soil moisture, high temperatures, rapid soil drying, drought stress, poor soil structure or drainage, compaction, and soil salinity. Biotic causes involve pathogens that block or degrade water transport within the plant, notably vascular wilts caused by Fusarium oxysporum, Verticillium dahliae, and Ralstonia solanacearum, among others. These pathogens clog xylem vessels, reducing water movement and leading to progressive wilting independent of short-term water status.

Physiology and signs: wilting reflects a drop in leaf turgor pressure. Stomata may close to conserve water, photosynthesis declines, and recovery after irrigation depends on the extent of tissue damage. Early wilting typically appears in outer leaves or growing points and may be reversible if water supply is restored promptly; prolonged stress or severe vascular damage can cause irreversible damage and necrosis.

Diagnosis and management: determine whether wilting is due to water shortage or a root/pathogen problem. Check soil moisture, drainage, and irrigation practices; inspect roots for damage or signs of disease; remove and rotate severely affected plants; improve soil structure, mulching, and irrigation scheduling; use resistant varieties when available and employ disease management practices in crops prone to vascular wilts.