Question

Which of the following is/are cyanogenic plant(s) ?
A. Prunus amygdalus
B. Zea mays
C. Sorghum halepense
D. Beta vulgaris
Choose the correct answer from the options given below:

• A. A, B and D only
• B. A, B and C only
• C. B and D only
• D. D only

Hint:

Remember that the family Rosaceae (Prunus) and the grass family Poaceae (Sorghum, young Zea mays) are the two primary plant groups associated with cyanogenic glycosides like amygdalin and dhurrin.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Cyanogenic plants contain specialized secondary metabolites called cyanogenic glycosides.
When the plant tissue is damaged (due to chewing, crushing, trampling, drought, or frost), intracellular enzymes (such as $\beta$-glucosidases) come into contact with these glycosides.
This enzymatic reaction hydrolyzes the glycosides, releasing free hydrogen cyanide ($\text{HCN}$), which is highly toxic to grazing animals.
$\text{HCN}$ inhibits cytochrome oxidase in the mitochondrial respiratory chain, causing cellular hypoxia and rapid death.

Step 2: Detailed Explanation:
Let us analyze each plant's toxic potential:
1. Prunus amygdalus (A):
Commonly known as the almond tree, members of the genus Prunus are classic cyanogenic plants.
They contain the cyanogenic glycoside amygdalin, primarily concentrated in their seeds and leaves.
Ingestion of damaged leaves can cause rapid cyanide poisoning in livestock.
Therefore, A is a cyanogenic plant.
2. Zea mays (B):
Commonly known as maize or corn, young or stressed maize plants contain cyanogenic glycosides (principally dhurrin).
While mature maize is safe, immature stalks or those damaged by frost or drought can accumulate toxic levels of cyanide.
Therefore, B is a cyanogenic plant.
3. Sorghum halepense (C):
Commonly known as Johnson grass, members of the genus Sorghum are notorious for causing cyanide poisoning in ruminants.
They contain high concentrations of the cyanogenic glycoside dhurrin, especially in young tillers, wilted leaves, or frost-damaged tissues.
Therefore, C is a cyanogenic plant.
4. Beta vulgaris (D):
Commonly known as beetroot, sugar beet, or mangels, this plant is not cyanogenic.
Instead, it is a well-known accumulator of nitrates/nitrites and oxalates, which cause methemoglobinemia and calcium oxalate crystalluria, respectively.
Therefore, D is not a cyanogenic plant.
Thus, the cyanogenic plants are A, B, and C.

Step 3: Final Answer:
Prunus amygdalus, Zea mays, and Sorghum halepense are cyanogenic plants, while Beta vulgaris is not.
Therefore, the correct option is (B).