# DBT JRF 2020 — Question 29

Exam: DBT JRF 2020 · Section: B · Topic: Immunology · Difficulty: Medium

## Question

All the vaccines mentioned below are attenuated or inactivated whole pathogen except

## Options

- **A.** Rotavirus vaccine
- **B.** Tetanus vaccine
- **C.** Hepatitis A vaccine
- **D.** oral polio vaccine

## Answer

Option B

## Explanation

The endothecium is the second layer of the anther wall (beneath the epidermis). It develops fibrous thickenings of cellulose and lignin bands on radial and inner tangential walls during pollen maturation — these are the 'fibrous bands' (NOT callose — callose is a transient wall material in young microspores). At pollen maturity, the endothecium cells desiccate and the hygroscopic fibrous thickenings shrink differentially, generating mechanical stress that causes the anther wall to rupture along the stomium — this is DEHISCENCE, allowing pollen release. The endothecium thus functions primarily as a mechanical actuator for pollen dispersal, not for nutrition or protection.

Source: https://mypyqbuddy.com/questions/all-the-vaccines-mentioned-below-are-attenuated-or-6a05a8a02adafec470293235