Question

In plants a common symptom caused by deficiency of P, K, Ca and Mg is the
A. Bending the leaf tip
B. Formation of anthocyanin
C. Poor development of vasculature
D. Appearance of dead necrotic areas

Answer 1

Hint: It is not a disease but a symptom of distress in plants. This occurs in many ways from dark, marine spots on leaves and fruit to dried, tanned or black papery spots.

Complete answer:
When plants struggle to survive, this can be a symptom of a nutrient shortage, despite sufficient soil preparation, irrigation and mulching. Fruit and vegetables, as well as plants grown in extremely acidic and alkaline soils, are especially susceptible. Macronutrients and micronutrients may be classified into the basic components. Macronutrients are referred to as nutrients that require plants in greater quantities. Around half of the fundamental elements are known as the macronutrients. These are phosphorus, carbon, oxygen, hydrogen, nitrogen, calcium, potassium, magnesium and sulphur. The typical signs of a lack of nitrogen, magnesium and potassium are yellow or reddish leaves, a stunted growth and poor flowering.
Nitrogen, potassium, phosphorus, and magnesium deficiencies contribute to chlorosis of old mature leaves and subsequent necrosis. These nutrients are mobile components that are transferable from older to new leaves when their soil source is reduced and their young leaves fail. The older leaves with these vital nutrients are reduced, resulting in chlorosis and necrosis. A region of the grey or brown necrotic tissue referred to in a spot. Spots on leaves and fruits are very common and perhaps the most well-known necrotic symptom. Sometimes the necrotic tissue in the blade will split and spill away from the green tissue that covers and leaves an empty space. The so-called shot-hole is this symptom.

Hence, the correct answer is option (D)

Note: The absence of any element in plants will cause several symptoms, and the defects of one of the various elements can also trigger the same symptoms. A deficiency of many elements such as K, Mg, Ca and P will lead to necrosis.