Identify the CORRECT combination of statements with respect to chemical defense in plants.
P. Pisatin, a phytoalexin produced by Ricinus communis is a constitutive defense compound
Q. Phaseolus vulgaris produces Phaseolus agglutinin I, which is toxic to the cowpea weevil
R. A single step non-enzymatic hydrolysis of cyanogenic glycoside releases the toxic hydrocyanic acid (HCN) to protect plant against herbivores and pathogens
S. Avenacin, a triterpenoid saponin from oat prevents infection by Gaeumannomyces graminis, a major pathogen of cereal roots
Plant Chemical Defense Analysis
This question assesses the understanding of different chemical defense mechanisms in plants.
Statement P Analysis
Incorrect. Pisatin is a phytoalexin (an inducible defense compound) produced by peas (Pisum sativum), not a constitutive compound from Ricinus communis. Ricinus communis produces ricin.
Statement Q Analysis
Correct. Phaseolus vulgaris (common bean) produces lectins, such as Phaseolus agglutinin I. These lectins can act as defense compounds by interfering with insect digestion, including toxicity towards pests like the cowpea weevil.
Statement R Analysis
Incorrect. The release of toxic hydrocyanic acid ($\text{HCN}$) from cyanogenic glycosides is typically triggered by enzymatic hydrolysis, catalyzed by specific enzymes like $\beta$-glucosidase, usually when the plant tissue is damaged. Non-enzymatic hydrolysis is not the primary protective mechanism.
Statement S Analysis
Correct. Avenacin, a type of triterpenoid saponin found in oats (Avena sativa), plays a crucial role in protecting the plant against root pathogens. It is known to inhibit the growth of Gaeumannomyces graminis var. avenae, which causes take-all disease.
Conclusion
Based on the analysis, statements Q and S are correct descriptions of chemical defense mechanisms in plants.
The correct combination is Q and S.
Important Questions from Plant Biochemistry Secondary Metabolites
- Correctly match the following secondary metabolites in Group-I with their chemical classes in Group-II.
Group-I Group-II (P) Codeine (1) Flavones (Q) Podophyllotoxin (2) Alkaloids (R) Resveratrol (3) Lignans (S) Linamarin (4) Monoterpenes (T) Limonene (5) Cyanogenic glycosides (6) Stilbenes Identify the CORRECT statements in plant secondary metabolism.
P. Tropane alkaloids in Atropa belladonna are synthesized from tyrosine
Q. Antioxidative food ingredient rosmarinic acid is obtained from cell suspension cultures of Coleus blumei
R. Thiophenes are produced from hairy root cultures of Tagetes patula
S. Cyanidin, the principal anthocyanin responsible for red color in Rosa hybrida is produced from cinnamaldehyde
- Which of the following plant hormones is a carotenoid-cleavage product?
- Identify the INCORRECT statement with relation to plant secondary metabolites.
- Horseradish peroxidase and alkaline phosphatase are the two enzymes commonly utilized as reagents in ELISA, because these enzymes
