Download Stems, Monocots and Dicots

Stems, Monocots and
Dicots
Types of Stems
Herbaceous stems – plants that have stems
that are soft and fleshy tissue.
• Vascular Tissue – specialized tissue that provides
support of plants and transport of materials up and
down the plant.
• Phloem [flow-em]- moves manufactured food down
the stem for storage.
• Xylem [zi-lim] – moves moisture and minerals up
the stem.
• Vascular plants are divided into 2 groups called
Gymnosperms and Angiosperms.
• Angiosperms also are divided into 2 groups:
• Monocotyledons
• Dicotyledons
Video - Monocot vs dicot
Characteristics of Monocots
• Parallel leaf veins
• Scattered vascular bundles
• Flowers in parts of 3's
• One cotyledon (seed leaf)
Characteristics of Dicots
• Branched leaf veins
• Continuous vascular bundles
• Flower Parts in 4's or 5's
• Two cotyledons (seed leaves)
Internal Stem Structure
Stems-Internal
• Monocot : examples: corn, grasses
• Dicot: example: trees
Internal Stem Structure
• Woody Dicot Plants have vascular tissue forming in
concentric rings.
• A corky outer layer called bark protects the vascular tissue. It
is:
• Phloem is located inside the corky bark.
• Cambium is the next layer. It is meristem tissue that produces
new cells for the phloem and the
• Xylem. This layer is also known as wood
Why do trees have rings?
• Because the cambium produces new cells for xylem and
phloem, a tree continues to increase in width year after year.
Internal Stem Structure
• Monocot plants form their internal stems in bundles of tubes
in random order in the stem.
• Each tube bundles both phloem and xylem tubes together.
• All cells are formed in the early stages of growth. No
cambium in a mature plant stem.
• A mature stem is achieved by cell enlargement. No new cells
are produced
Internal Stem Structure
• Herbaceous Dicot Stems have phloem, xylem and cambium
although the cambium disappears after maturity.
• The three parts of the system line up in a ring form but not
as strong as the woody stem.
• Herbaceous means soft fleshy tissue.
Summary
• The ring system of tissue in woody dicots can support a large
amount of weight.
• The random order of tubes in moncot and dicot herbaceous
stems cannot support large amounts of weight;
• They cannot therefore, get very large.