Question

Typically, vascular tissue is organized as _________ in stems and as ___________ in roots. a. multiple vascular bundles; one vascular cylinder b. one vascular bundle: multiple vascular cylinders c. one vascular cylinder; multiple vascular bundles d. multiple vascular cylinders; one vascular bundle

Short answer

a. multiple vascular bundles; one vascular cylinder

Step-by-step solution

Identify Vascular Tissue in Stems

In stems, vascular tissue is typically organized into multiple structures known as vascular bundles. Different bundles contain xylem and phloem, which transport water, nutrients, and food throughout the plant.

Identify Vascular Tissue in Roots

In roots, vascular tissue is organized into a single structure called the vascular cylinder or stele. This central core contains the xylem and phloem surrounded by the pericycle and endodermis.

Select the Correct Answer for Stems and Roots

Based on the identification, stems have multiple vascular bundles, and roots have one vascular cylinder. Therefore, the correct option for this arrangement is: 'multiple vascular bundles; one vascular cylinder,' which corresponds to option a.

Key concepts

Understanding Vascular Bundles

Vascular bundles are the organizational structures found primarily in plant stems. These bundles act as conduits for the plant’s transport system, which includes both xylem and phloem. Xylem is responsible for transporting water and minerals from the roots to the rest of the plant, while phloem distributes sugars and other nutrients produced by photosynthesis. In a typical stem, multiple vascular bundles are present and arranged in a specific pattern that provides structural support and efficiency in nutrient distribution.
Each vascular bundle is like a mini highway for fluids and nutrients within a plant. Their presence not only ensures that all parts of the plant receive the necessary sustenance but also provides mechanical support, helping the plant remain upright. The organization and distribution of these bundles can vary among different plant types, including monocots and dicots, influencing both their physical characteristics and growth patterns.

The Vascular Cylinder: A Central Core

The vascular cylinder, also referred to as the stele, is the main structure organizing vascular tissues within plant roots. Unlike the multiple vascular bundles seen in stems, roots feature a single vascular cylinder. This singular structure is strategically centered and serves as the main channel for transport in roots.
Within the vascular cylinder, you’ll find the xylem and phloem surrounded by the pericycle and endodermis. The pericycle plays a key role in the growth of secondary roots, while the endodermis acts as a selective barrier, regulating water and nutrient flow into the vascular cylinder. Thus, the vascular cylinder not only supports transport but also manages the critical processes involved in nutrient uptake and plant growth.
This arrangement ensures that the roots maintain a direct and effective conduit to bring water and nutrients from the soil and distribute them upward into the plant.

Roles of Xylem and Phloem

Xylem and phloem are the two most essential components of a plant's vascular system. They work in tandem to transport resources throughout the plant. These two tissues serve distinct but complementary functions within both vascular bundles in stems and the vascular cylinder in roots.
**Xylem:** Its primary function is to transport water and dissolved minerals absorbed by the roots up through the plant. Xylem vessels are typically wider and have thickened cell walls to withstand the pressure involved in lifting water against gravity. In addition to their transport role, xylem also contributes to the structural integrity of the plant.
**Phloem:** In contrast, phloem tissue transports organic compounds, mainly sugars produced during photosynthesis, from the leaves to other parts of the plant requiring energy. Phloem cells are generally living, and their structure allows for the effective transport of nutrients via a process called translocation.
Together, xylem and phloem ensure a plant's survival by maintaining a steady flow of essential resources, facilitating growth and development, and aiding in recovery after damage.