In ovule, exostome is

Options

A. Area just outside the micropyle
B. Area at the tip of nucellus
C. Part of micropyle enclosed by inner integument
D. Part of micropyle enclosed by outer integument.

Answer

To answer the question "In ovule, exostome is," we need to understand the structure of the ovule and the definitions of the terms involved. Here’s a step-by-step breakdown:

### Step 1: Understanding the Ovule Structure
- The ovule is a structure found in seed plants that develops into a seed after fertilization. It consists of several parts, including the integuments, which are protective layers surrounding the ovule.

### Step 2: Identifying the Micropyle
- The micropyle is an opening in the ovule that allows the entry of the pollen tube for fertilization. It is located at the tip of the ovule.

### Step 3: Differentiating Between Endostome and Exostome
- The term "endostome" refers to the opening formed by the inner integument of the ovule. Conversely, "exostome" refers to the opening formed by the outer integument.

### Step 4: Analyzing the Options
- Now, let's evaluate the provided options:
- **Option A**: Area just outside the micropyle - This is incorrect as it does not define exostome.
- **Option B**: Area at the tip of the mucilus - This is also incorrect; it does not relate to exostome.
- **Option C**: Part of micropyle enclosed by inner integument - This describes endostome, not exostome.
- **Option D**: Part of micropyle enclosed by outer integument - This correctly describes exostome.

### Step 5: Conclusion
- Based on the definitions and the analysis of the options, the correct answer is **Option D**: part of micropyle enclosed by outer integument.

### Final Answer
In ovule, exostome is part of micropyle enclosed by outer integument (Option D).

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