Deficiency diseases and symptoms - class-XII

Chlorosis is a symptom caused by the deficiency of various essential mineral elements, including Nitrogen, Potassium, Magnesium, Sulfur, Iron, Zinc, Manganese, and Molybdenum, which are all required for chlorophyll synthesis or stability.

Elements like N, K, and Mg are mobile in plants, so they are transported to young leaves when deficient, causing symptoms to appear first in old leaves. S and Ca are relatively immobile, so deficiency symptoms appear first in young leaves.

When essential elements are mobile (radially or systemically), the plant redistributes them from older tissues to younger, actively growing tissues. Therefore, deficiency symptoms for these elements appear first in older tissues.

Potassium deficiency in plants typically manifests as chlorosis (yellowing) starting at the leaf margins (edges) and tips, which eventually leads to necrosis.

Necrosis, or the death of plant tissue, is commonly caused by the deficiency of minerals like calcium, magnesium, copper, and potassium. Among the choices, calcium and magnesium are well-documented elements whose deficiency leads to localized tissue death.

Premature leaf fall is a classic symptom of phosphorus deficiency in plants. Phosphorus is mobile within the plant, and its lack disrupts energy transfer and metabolic processes, leading to early senescence and abscission.

When a living organism's cells or tissues die or degenerate, the condition is called necrosis. In a plant, necrosis causes leaves, stems and other parts to darken and wilt. Necrosis weakens the plant and makes it more susceptible to other diseases and pests. 

Nitrogen and potassium are mobile elements within the plant. When they are deficient, the plant translocates these nutrients from older, senescent leaves to younger, growing tissues, causing the deficiency symptoms to appear first in the older leaves.

Chlorosis is the loss of chlorophyll leading to yellowing of leaves. It is typically caused by deficiencies in essential mineral elements required for chlorophyll synthesis or maintenance, notably magnesium, iron, nitrogen, and potassium, with magnesium and iron being classic primary examples.

If there is a deficiency of mobile nutrients, the symptoms are first seen in the leaves. Mobile and immobile nutrients refer to the transportability of these (K), (Mg), (Cl), (Zn) and (Mo).