Growth Disturbance, Mineral Nutrient Imbalance, Specific Symptoms and Leaf Characteristics Changes in Two Pomegranate Cultivars Induced by Deficiencies and Excess of Ca, Mg, Zn and Fe

Meso-elements (Calcium and Magnesium), and Micronutrients heavy metals (Zinc and Iron) are needed for crop optimal growth. This study aims to evaluate the response of two pomegranate cultivars (Gabsi and Kalaii) to a nutritional stress; deficit and excess of these nutrients. As an attempt to understand this response: vegetative growth, some physiological traits, leaf mineral content, and the symptomology, using’’ the missing element technique ‘’ or the application of ‘’overdoses’’ of a specific element in greenhouse, were assessed. The absence of those elements reduced shoot elongation, while their excess did not enhance the growth. The nutritional stress affected the Surface Leaf Area mainly in Gabsi cultivar. For the Leaf Tissue Density, the lack of those elements showed similar results as control, while the excess increased this parameter. Absence of calcium, magnesium, zinc and iron decreased chlorophyll Index in both cultivars. However the effect of excessive treatments was different depending on the element and the cultivar. The maximum quantum efficiency of photosystem II was affected only by Iron treatments in Gabsi and Mg in Kalaii. Some Leaf water characteristics were disturbed by the treatments, and some remained indifferent. Leaf mineral content was significantly affected by the treatments for both cultivars. Overall the deficiencies induced a drop of concentration either by the end of the experimentation or all along the monitoring period, while the excess increased mineral concentration. A common visual symptom related to the deficiency of the studied nutrients was a chlorosis appearing at different dates depending of the element. Plants exposed to an excessive supply of those nutrients showed strong greenish color with thick leaves. Both cultivars presented the same symptoms. These results may be applied to develop an appropriate fertilization program for efficient nutrient uptake.