Difference between Sieve Cells and Sieve Tubes

Vascular plants contain conducting elements such as xylem and phloem for the transport of water and food respectively in plants. Phloem is the conducting element that transports food produced in the plant from their source to the sink. They are composed of sieve elements, companion cells, phloem fibres and phloem parenchyma. Sieve cells and sieve tubes are two types of sieve elements found in phloem, let us differentiate between them.

What Are Sieve Cells?

Sieve cells are long, conducting cells with narrow diameter that do not have sieve plates. They are associated with albuminous cells that help in the transportation of organic materials. Albuminous cells have long unspecialised ends that overlap with other sieve tubes; they store food and nutrients for tissue nourishment. The albuminous cells connect the sieve cells to parenchyma which enables easy transportation of food and nutrients.

Because they lack companion cells, sieve cells are mostly associated with gymnosperms and other seedless vascular plants. They are evenly distributed throughout the sieve area. Sieve cells have narrow pores called sieve pores at their ends that ensures proper transportation of food.

What Are Sieve Tubes?

Sieve tubes, found in angiosperms, are living cells that are associated with companion cells. The association with companion cells helps in distant transportation within the plant cells. The sieve tubes are made up of longitudinal arrangement of sieve tube members from end to end. The sieve tube members do not have ribosomes and nucleus and thus need the help of companion cells.

The sieve tubes are largely dispersed with plasmodesmata in groups in their walls that later develop into sieve plates. The sieve tubes are very long and have horizontal end walls. The sieve plates contain sieve pores that help in regulating the size of the opening and thus the exchange of nutrients in the plant. The multiple vertical connections of the sieve tube members direct the transport of nutrients with minimum resistance.

Sieve Cells vs Sieve Tubes

Sieve Cells

Sieve Tubes

Definition

Sieve cells are long elongated cells found in gymnosperms and other seedless vascular plants.

Sieve tubes are short specialised cells that are found only in angiosperms.

Morphology

Long cells with narrow pores.

Short cells with wider pores.

Found in

Gymnosperms and other seedless vascular plants.

Only in angiosperms.

Associated with

Sieve cells are associated with albuminous cells.

Sieve tubes are associated with companion cells.

Presence of Sieve Plates

No

Yes

Aggregation

Sieve cells are single cells.

Sieve tubes are longitudinal arrangements of sieve tube members.

Pores

The sieve pores are present on both lateral and end walls.

Sieve pores are present only on the sieve plates.

Specialisation

Less specialised cells.

Much specialised cells.

Visit BYJU’S Biology for more information.

Also see:

Frequently Asked Questions

Q1

Are sieve tubes made of sieve cells?

Sieve tubes are not made of sieve cells but made up of longitudinal arrangement of sieve tube members.
Q2

Why does the sieve tube have no nucleus?

The sieve tubes have no nucleus because they are associated with companion cells that control their functional activities.
Q3

What is the shape of a sieve tube?

The sieve tubes are elongated cells.
Q4

Is a sieve cell a single cell?

Yes, sieve cells are single cells.
Q5

Where are sieve tube cells found?

Sieve tube cells that are associated with companion cells are found only in flowering plants.
Q6

Why are sieve tubes called so?

In angiosperms the sieve tube members along with companion cells are arranged end to end in a linear row and are hence known as sieve tubes.