Phosphorus deficiency-Tobacco

Reasons
Phosphorus deficiency Excess nitrogen fertilisation also leads to dark green leaves, but these are not small nor have a lanceolate form. With potassium deficiency, the younger leaves become dark green, but do not have a lanceolate form. Zinc deficiency causes lanceolate leaves and rosette-like growth of the plants, but these have a light green or yellow colour rather than dark green.

Tobacco - Growth retardation

Symptoms
The small, relatively narrow lanceolate leaves of tobacco plants show a dark green to bluish colour and dark, sunken spots. Severe deficiency causes poor, stunted growth.

Reasons
Phosphorus deficiency (right plant) Excess nitrogen fertilisation also leads to dark green leaves, but these are not small and have a lanceolate form. With potassium deficiency, the younger leaves become dark green, but do not have a lanceolate form. Zinc deficiency causes lanceolate leaves and rosette-like growth of the plants, but these have a light green or yellow colour rather than dark green.

Phosphorus deficiency made worse by

Acidic or very alkaline (calcareaus) soils
Low organic matter
Cold or wet conditions
Crops with a poorly developed root system
Soils with low P reserves
Soils with a high phosphate capacity
Iron rich soils

Phosphorus is important for

Energy transfer
Nucleic acid formation
Protein synthesis
Cell membrane component
Carbohydrate metabolism