Plant Structure
Overview of Plant Structure
• Plants are Earth’s Primary Producers
– Producers harvest energy from sunlight by
converting light energy into chemical energy
• Chemical Energy is stored in bonds formed when
Carbohydrates are synthesized from Carbon Dioxide
and Water.
• Plants are Non- motile
– They have evolved to grow towards resources
throughout their life span.
Overview of Plant Structure
• The vegetative body of
the plant consists of:
• Leaf: Photosynthesis
• Stem: Support
• Roots: anchorage and
absorption of water &
minerals.
• Nodes: where the leaf is
attached to stem.
• Internode: Region of stem
between two nodes
The Leaf
The leaf is the primary photosynthetic organ of
the plant.
The leaf consists of
Cuticle a thin waxy outer covering
Epidermis layer of cells supplying
nutrients to the cuticle
Xylem and Phloem are the
vascular tissue, found within the
veins of the leaf
Bundle Sheath is the outer layer
of the veins.
Mesophyll are the cells in middle
of the leaf.
Stomata are the tiny holes within
the epidermis used for breathing
Guard Cells are specialized cells,
that surround the stomata and
are shaped like lips.
The Stem
The stem is the support and transport
system of the plant.
The internal structure of the stem consists of
Pith: Large central area for storage & support.
Cambium: Found as a circle around inner stem
& outer surface. Forms woody secondary tissue
for support.
Cortex: Storage area between cambium and
epidermis.
Epidermis: Thin layer of skin cells. For
protection.
Xylem: Water movement up the plant.
Phloem: Sap (sugar) movement down to roots.
The Root
Primary functions of the root are anchorage of the plant,
absorption of water and dissolved minerals and movement of
water to the stem, and sap to storage as reserve foods.
The internal structure of the root consists of
Epidermis: the outermost layer of layer of
living cells that are arranged closely and
compactly
Cortex: between the epidermis and the
endodermis
Endodermis: inner most layer of the cortex
composed of a single row of barrel shaped
cells
Pericycle: creates lateral roots
Vascular bundles: contains xylem and phloem
Overview of Plant Structure
• Two general types of plants:
• Angiosperms: Flowering plants
About 250,000 species of angiosperms known
Major innovation is the Flower
• Gymnosperms: naked seeds/ evergreens
Much older species than angiosperms
Only about 700 species of gymnosperm known
Largest group is the conifer (cone bearer)
Ex. pine, fir, spruce, and redwood
Xylem
• Xylem: One type of vascular
tissue found in a plant
– Main water-conducting
tissue of vascular plants.
– Made from individual
cylindrical cells placed end
to end.
– When xylem cells mature
they die.
– The result is the xylem
vessel, a continuous
nonliving duct.
– Xylem can carry water and
some dissolved solutes,
such as inorganic ions, up
the plant
Phloem
• Phloem: one type of vascular tissue
found in plants
– conducts sugars and amino acids from the leaves, downward to the
rest of the plant
– Phloem consists of living cells. The
cells that make up the phloem are
adapted to their function.
– Sieve tubes are specialized cells
for transport and have no nuclei.
– Each sieve tube has a perforated
end so its cytoplasm connects one
cell to the next.
3 questions before we go.
1) What is the structure of the plant
that is responsible for support and
transport?
2) What structure carries water and
dissolved minerals (solutes) up the
plant?
3) What is the name for the waxy outer
layer of the leaf?