What is the Difference Between Bract and Sepal

Bract and sepal are two parts of a flower, which is the reproductive structure of the flowering plants. The vegetative parts of the flower contain petals and sepals, whereas the reproductive parts of the flower contain stamen and pistil (stigma, style, and ovary).

The key difference between bract and sepal is their structure and location. bract is a shortened leaf-like structure found at the base of a pedicel of a flower while sepal is the outermost whorl of the flower present on the thalamus of a flower.

CONTENTS

1. Overview and Key Difference
2. What is Bract  
3. What is Sepal
4. Similarities – Bract and Sepal
5. Bract vs Sepal in Tabular Form
6. Summary – Bract vs Sepal
7. FAQ – Bract and Sepal

What is Bract?

A bract is a stalk of a flower or an inflorescence. It is also defined as a modified leaf. Bract usually grows from the axil of a leaf or leaf-like structure. They are present at the base of the inflorescence. Bracts can have a variety of colours, including green colour.

Figure 01: Bract of Bougainvillea

Some bracts are bright in colour and are often mistaken for petals of the flower. Therefore, bract serves the function of attracting pollinators, either together with the perianth or instead of it. Furthermore, their main function is to protect the inflorescence of plants.

What is Sepal?

Sepal is any of the outer parts of a flower that encloses and protects the unopened flower. A collection of sepals is known as calyx. Sepal is a sterile floral part. It may be either a green or leaf-like structure. It may be also composed of petal-like tissue. Sepals can remain separate or marginally fused.

Figure 02: Sepal

Sepals can fall off even before the flower is open (caduceus), sepals can fall off after fertilization (deciduous) or sepals can remain persistent. Sepal normally safeguards the inner structure of the flower buds. Furthermore, it defends and protects both flowers and fruits by producing chemicals that repel the predators. In addition, sepals protect the flower whorls against mechanical injuries and desiccation.

Similarities Between Bract and Sepal

1. Bract and sepal are two parts of the flower.
2. Both parts can be green in colour.
3. These parts can fall off or remain persist on the plant.
4. They are very important in flower protection.

Difference Between Bract and Sepal

Definition

1. Bract is a modified leave or scale of a flower.
2. Sepal is the outermost whorl of a part that forms a flower.

Colour

1. Bracts can be green, bright colours and other colours.
2. Sepals are usually green in colour.

Located on

1. Bract is located on the pedicel.
2. Sepal is located on the thalamus.

Function

1. Its main functions are to protect young flower buds from the elements by enclosing the floral organs and attract pollinators or protect fruits.
2. Its main functions are to protect the developing petals, and protect both flowers and fruits by producing chemicals that repel predators and flower whorls against mechanical injuries and desiccation.

The following table summarizes the difference between bract and sepal.

Summary – Bract vs Sepal

The main function of a flower is sexual reproduction. This part of the plant ensures the survival of the species. Bract and sepal are two parts of a flower. Sepal is the outermost whorl of flower present on the thalamus, while bract is a modified leaf or scale, especially associated with a flower located on the pedicel. This is the key difference between bract and sepal.

FAQ: Bract and Sepal

1. What is a bract also called?

• Bracts may be called chaff, paleas, or receptacular bracts. They are usually minute scales or bristles. Bracts are usually located at the base of each inflorescence.

2. What is the function of a bract?

• Bracts provide protection to flowers from extreme environmental conditions and protection from insects, attract pollinators toward the flower and favour pollination.

3. What does sepal mean?

• Sepal refers to any of the outer parts of a flower. It encloses and protects the unopened flower bud. The sepals on a flower are collectively known as the calyx. They are sterile floral parts and may be either green or leaf-like.

4. Why is sepal different from petal?

• Sepals are tougher outermost whorls, protecting the more fragile inner petals. Petals are each of the segments of the corollaof a flower. However, on some plants, the sepals and petals have no difference and hence these are called tepals.

5. What is the function of sepal?

• The sepals are an important part of the development of the flowers of angiosperms or flowering plants. Their main function is to protect the flower bud as it develops. The sepals on a flower, collectively known as the calyx of the flower, are the first layer of a flower bud to form on the stem.

Reference:

1. Baessler, Liz. “Learn about Plant Bracts: What Is a Bract on a Plant.” Gardening Know How.
2. “Sepal.” Encyclopædia Britannica, Encyclopædia Britannica, inc.

Image Courtesy:

1. “Bract of Bougainvillea” By Albarubescens – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Gossypium herbaceum sepal” By Calimo – Own work (CC BY-SA 3.0) via Commons Wikimedia

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