Download Stems and Roots (solutions)

STEMS Now that we understand leaves in detail, we move on to other plant organs.
The stem is a structural axis for plants above the ground. It is composed of alternating nodes and internodes. Nodes hold buds which can grow into leaves, flowers, cones or branches, while the internodes are the spaces between the nodes. Plant stems have multiple functions. Aside from support for flowers, leaves and fruit, stems have to transport nutrients and water, as well as store some nutrients and help the plant grow in size.
MORPHOLOGY Plant stems can be woody or herbaceous, depending on the plant. Plants that have herbaceous stems are replaced every year. Thay are not capable of withstanding harsh environments like that of a bitter Canadian winter. These plants include flowering plants like petunias.
Plants with woody stems can live for hundreds of years. These plants include trees and other plants that have grown a thick stem or trunk made of bark to be able to store nutrients and be protected from freezing temperatures.
CROSS­SECTION
Plant stems have multiple components to them. The vascular tissue is found in bundles throughout the stem. It transports water and nutrients throughout the plant. The epidermis is a single layer of cells that are densely packed together that protects the plant. It also has a waxy layer called the cuticle to prevent water loss.
The cortex (ground tissue) has multiple functions, but the major one is the storage of starch (closest to the innermost layer of the stem). It is mostly composed of unspecialized cells and does perform some photosynthesis.
The pith is the centremost section of the plant stem. It generally breaks down into a hollow section only for structural support.
The vascular cambium is a layer of meristematic tissue that continually divides to form phloem tissue towards the outer layer and xylem tissue towards the inner layer of the plant. It helps with plant stem growth.
CROSS­SECTION
ROOTS
Roots have two major functions in plants: they anchor plants to the ground, and they absorb water and inorganic nutrients. Roots also have an epidermis as the outer layer. This layer has many root hairs to increase the surface area for water absorption.
MORPHOLOGY
Roots have a conical covering on the tip known as the root cap. It is a protective layer that has the apical meristem in it. This is the region of the root that undergoes mitosis to push the root into the ground.
The vascular tissue is again the innermost layer. In a dicot, the vascular tissue looks like a cross or an "x", while monocots
MORPHOLOGY, CON'D