Nutrients are the main course of ingredients for plant growth. And micronutrients are the one which is required in moderate quantities. If the consumptions are below moderate causes the deficiency symptoms and a moderate increase causes toxicity.
Any mineral ion concentration in tissues that reduces the dry weight of tissues by about 10 per cent is considered toxic.
Nutrient toxicities in plants are more frequent for manganese (Mn) and boron (B) than for other nutrients.