# DBT JRF 2020 — Question 28

Exam: DBT JRF 2020 · Section: B · Topic: Plant Biology · Difficulty: Hard

## Question

The mature anther wall comprises an epidermis followed by a layer of radially elongated cells with fibrous bands of callose called endothecium whose function is

## Options

- **A.** nutrition
- **B.** mechanical
- **C.** protection
- **D.** dehiscence

## Answer

Option C

## Explanation

Specific growth rate $\mu$ and doubling time $t_d$ relationship: $\mu = \dfrac{\ln 2}{t_d} = \dfrac{0.693}{t_d}$ . Given $t_d = 0.231 \text{ h}$ : $\mu = \dfrac{0.693}{0.231} = 3.0 \text{ h}^{-1}$ . This is an unusually high growth rate (E. coli typically has $\mu_{\max} \approx 1.0–1.7 \text{ h}^{-1}$ in rich media). The formula assumes negligible endogenous metabolism (maintenance energy), so $\mu_{\text{observed}} = \mu_{\text{growth}}$ (no correction for maintenance coefficient $m$ ).

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