35
Vegetative Organs of the Flowering Plant Body
• Most flowering plants belong to one of two major
lineages.
• Monocots are generally narrow-leaved flowering
plants such as grasses.
• Eudicots are broad-leaved flowering plants such
as roses.
• Monocots and eudicots account for 97 percent of
the species of flowering plants.
Figure 35.1 Monocots versus Eudicots
35
Vegetative Organs of the Flowering Plant Body
• The shoot system of a plant consists of the stems
and the leaves, as well as flowers.
• Leaves are the main sites of photosynthesis in
plants.
• Stems hold and display the leaves to the sun and
provide connections for the transport of materials
between roots and leaves.
• A node is the point where a leaf attaches to a
stem.
• Regions of stem between nodes are the
internodes.
• The root system provides support and nutrition.
Figure 35.2 Vegetative Organs and Systems
35
Vegetative Organs of the Flowering Plant Body
• There are two main types of root system: taproot
and fibrous root.
• Most eudicots have a taproot system..
• Monocots and some eudicots have a fibrous root
system.
Figure 35.3 Root Systems
35
Vegetative Organs of the Flowering Plant Body
• A bud is an embryonic shoot.
• A stem bears leaves at its nodes, and where each
leaf meets the stem, there is a lateral bud.
• At the tip of each stem or branch there is an
apical bud, which produces the cells for the
growth and development of that stem or branch.
35
Vegetative Organs of the Flowering Plant Body
• Leaves are well adapted for gathering light.
• The blade of a leaf is a thin, flat structure,
attached to the stem by the petiole.
• A simple leaf has a single blade.
• A compound leaf has multiple blades (or leaflets)
arranged along an axis or radiating from a central
point.
Figure 35.5 The Diversity of Leaf Forms
35
Plant Cells
• Plant cells have all the organelles common to
eukaryotes.
• Every plant cell is surrounded by a cellulosecontaining cell wall.
35
Plant Cells
• On division each daughter cell secretes cellulose
and other polysaccharides to form a primary wall.
• Some plant cells may deposit more layers,
sometimes impregnated with material such as
lignin or suberin to form a secondary wall.
Figure 35.6 Cell Wall Formation
35
Plant Cells
• Plasmodesmata are pore-like structures that
pass through primary cell walls, allowing
substances to move freely from cell to cell without
crossing the plasma membrane.
• Animal Cells have similar structures called gap
junctions.
Figure 35.7 Plasmodesmata (Part 2)
35
Plant Cells
• Parenchyma cells are the most numerous type
of cell in young plants.
• Parenchyma cells usually have thin walls and
large central vacuoles.
• The photosynthetic cells in leaves are
parenchyma cells filled with chloroplasts.
• Some parenchyma cells store lipids or starch.
35
Plant Cells
• Collenchyma cells are supporting cells that lay
down primary cell walls that are thick in the
corners.
• Collenchyma cells provide support to leaf petioles,
nonwoody stems, and growing organs.
35
Plant Cells
• Sclerenchyma cells are the main supporting
cells of a plant.
• There are two types of sclerenchyma cells: fibers
and sclereids.
• Sclereids form the grit found in many fruits like
pears.
Figure 35.9 Plant Cell Types (Part 1)
Figure 35.9 Plant Cell Types (Part 2)
35
Plant Cells
• The xylem conducts water from roots to above
ground plant parts. It contains conducting cells
called tracheary elements, Tracheids and Vessel
elements.
• Both tracheary elements and tracheids undergo
apoptosis and do their jobs as empty cells (only the
cell walls remain).
Figure 35.10 Evolution of the Conducting Cells of Vascular Systems
35
Plant Cells
• Cells of the phloem are alive when they do their job,
unlike those of the xylem.
• The characteristic cell of the phloem is the sieve
tube member.
• The sieve tube members have adjacent companion
cells.
• Companion cells retain all their organelles and may
regulate the performance of the sieve tube members.
35
Plant Tissues and Tissue Systems
• A tissue is an organization of cells that work
together as a functional unit.
• Parenchyma cells make up parenchyma tissue,
which is a simple tissue.
• Xylem and phloem are complex tissues; they are
composed of a number of different cell types.
• Tissues are grouped into tissue systems that
extend throughout the body of the plant from
organ to organ.
• There are three plant tissue systems: vascular,
dermal, and ground.
35
Plant Tissues and Tissue Systems
• The vascular tissue system includes the xylem
and phloem; it is the conductive or “plumbing”
system of the plant.
• The phloem transports carbohydrates from sites
of production (sources such as leaves) to sites of
utilization (sinks) elsewhere in the plant.
• The xylem distributes water and mineral ions
taken up by the roots to the stem and leaves.
35
Plant Tissues and Tissue Systems
• The dermal tissue system is the outer covering
of the plant.
• The epidermis contains epidermal cells and other
specialized cells such as guard cells.
• The shoot epidermis secretes a layer of waxcovered cutin, the cuticle, which helps retard
water loss from stems and leaves.
35
Plant Tissues and Tissue Systems
• The ground tissue system makes up the rest of a
plant and consists primarily of parenchyma tissue.
• Ground tissue functions primarily in storage,
support, and photosynthesis.
35
Forming the Plant Body
• In animals, the body grows as an individual
develops from embryonic stages but ceases to
grow once adulthood is reached (determinate
growth).
• In plants the growth of roots and stems is
indeterminate and is generated from specific
regions of active cell division.
35
Forming the Plant Body
• The localized regions of cell division in plants,
called meristems, are forever embryonic. They
have the ability to produce new cells indefinitely.
• The cells of meristematic tissues are analogous to
the stems cells found in animals.
35
Forming the Plant Body
• There are two types of meristems:
 Apical meristems give rise to the primary
plant body, which is the entire body of many
plants.
 Lateral meristems give rise to the secondary
plant body.
35
Forming the Plant Body
• Shoot apical meristems supply the cells that
extend stems and branches.
• Root apical meristems supply the cells that extend
roots.
• Apical meristems are responsible for primary
growth, which leads to elongation and organ
formation.
35
Forming the Plant Body
• Vascular cambium produces the secondary
xylem and phloem.
• The cork cambium produces cells that protect
the outermost layers of the stem.
35
Forming the Plant Body
• The root cap protects the delicate growing area
of the root as it pushes through the soil.
• The root cap also detects the pull of gravity and
controls the downward growth of roots.
• Tissues of the root are divided into three zones:
cell division, cell elongation, and cell
differentiation.
35
Forming the Plant Body
• Vascular tissue in the stem is arranged in
vascular bundles.
• The eudicot stem also contains pith and cortex
storage tissues.
35
Leaf Anatomy Supports Photosynthesis
• Leaf anatomy is adapted to carry out
photosynthesis, limit evaporative water loss, and
transport the products of photosynthesis to the
rest of the plant.
• The two zones in leaf parenchyma that
photosynthesize are the palisade mesophyll and
the spongy mesophyll.
• Within the mesophyll is air space through which
CO2 can diffuse to the photosynthesizing cells.
Figure 35.23 (a) The Eudicot Leaf
35
Leaf Anatomy Supports Photosynthesis
• Veins supply mesophyll cells with water and
minerals, and they transport the products of
photosynthesis to the rest of the plant.
• The epidermis of the leaf is the outermost cell
layer, which is covered by a waxy cuticle. The
epidermis functions to keep water and
photosynthetic products in the leaf.
• Guard cells allow controlled gas exchange
through pores in the leaf (the stomata).
Figure 35.23 (b,c) The Eudicot Leaf