The whorl of bracts present below the inflorescence of Helianthus (sunflower) is

Options

A. epicalyx
B. spathe
C. involucel
D. involucre.

Answer

To answer the question regarding the whorl of bracts present below the inflorescence of Helianthus (sunflower), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Plant Family**: Recognize that Helianthus, commonly known as sunflower, belongs to the family Asteraceae (also known as Compositae). This family is known for its unique floral structures.

**Hint**: Remember that the family Asteraceae is characterized by composite flowers.

2. **Understand Inflorescence Structure**: Note that what we refer to as a sunflower is actually an inflorescence, which is a cluster of many small flowers (florets) rather than a single flower.

**Hint**: Think of the sunflower as a collection of many tiny flowers grouped together.

3. **Identify the Parts of the Inflorescence**: In the sunflower, the outer flowers are called ray florets, while the inner ones are called disc florets. The structure that supports these florets is the receptacle.

**Hint**: The ray florets are the colorful parts you see, while the disc florets are found in the center.

4. **Recognize the Role of Bracts**: Below the inflorescence, there is a whorl of bracts. These bracts are modified leaves that can serve various functions, including protection of the flowers.

**Hint**: Bracts are often mistaken for petals but are actually leaf-like structures.

5. **Identify the Correct Term**: The specific term for the whorl of bracts found below the inflorescence in Helianthus is called the "involucrum."

**Hint**: Involucrum is a key term in botany related to the structure of inflorescences.

6. **Eliminate Incorrect Options**: Other terms like epicalyx and spathe do not refer to the whorl of bracts in this context, confirming that "involucrum" is the correct answer.

**Hint**: Be cautious of similar-sounding botanical terms that may not apply to the specific structure in question.

### Final Answer:
The whorl of bracts present below the inflorescence of Helianthus (sunflower) is called the **involucrum**.