The inflorescence which is a compact unisexual spike which matures and falls down as a single unit is

Options

A. spike
B. spadix
C. catkin
D. typical raceme

Answer

To solve the question regarding the inflorescence that is a compact unisexual spike which matures and falls down as a single unit, we can follow these steps:

### Step 1: Understand the Definition of Inflorescence
Inflorescence refers to the arrangement of flowers on a plant. Different types of inflorescence can be classified based on their structure and the nature of the flowers they bear (unisexual or bisexual).

**Hint:** Remember that inflorescence can be categorized into different types based on flower arrangement and type.

### Step 2: Identify the Characteristics of the Inflorescence
The question specifies that the inflorescence is:
- Compact
- Unisexual
- Spike-like
- Matures and falls down as a single unit

**Hint:** Focus on the terms "compact," "unisexual," and "falls down as a single unit" to narrow down the options.

### Step 3: Compare Different Types of Inflorescence
Two types of inflorescence that may come to mind are:
- Spike: A type of inflorescence with flowers attached directly to the stem without pedicels, usually bearing bisexual flowers.
- Catkin: A type of inflorescence that is elongated, usually unisexual, and often droops or hangs down.

**Hint:** Consider the differences between spike and catkin, especially in terms of flower type (unisexual vs. bisexual).

### Step 4: Identify the Correct Inflorescence
Given the characteristics outlined in the question, the inflorescence that fits the description is the **catkin**. Catkins are typically unisexual and can mature and fall as a single unit.

**Hint:** Recall that catkins are often associated with trees like willows and mulberries, which can help in identifying them.

### Step 5: Provide Examples
An example of a plant that produces catkins is **Morus alba** (the mulberry tree). This reinforces the identification of catkin as the correct answer.

**Hint:** Think of common plants that produce catkins to solidify your understanding.

### Final Answer
The inflorescence which is a compact unisexual spike that matures and falls down as a single unit is called a **catkin**.