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35 Cards in this Set

  • Front
  • Back
Plant Form and Function
• A plant's body is devoted to
harvesting diffuse resources and
concentrating them in cells and
tissues. Although all plant bodies
function in this way, the 300,000
species living today are remarkably
diverse in size and shape.
The Diversity of Plant Form
• To perform photosynthesis, plants need large
amounts of light and carbon dioxide and a small
amount of water (Figure 35.1).
•They also need nutrients to synthesize the
macromolecules needed to build and run cells,
and large amounts of water to fill the cells and
maintain them at normal volume and pressure.
•The _____ system and the _____ system (Figure
35.2), the two basic systems for acquiring and
transporting nutrients, are connected by
vascular tissue.
Root and Shoot
What is an herb?
A seed plant that lacks wood and has a relatively short-lived
General Plant Anatomy
•Many root systems have a vertical section called a taproot and
numerous lateral roots that run more or less horizontally.
•The shoot system consists of one or more stems, which are
vertical aboveground structures. Each stem consists of nodes,
where leaves are attached, and internodes—segments between
nodes. A leaf is a lateral appendage, projecting from a stem, that
usually functions as a photosynthetic organ.
•Each node includes an intersection of a leaf and stem that is the
site of a lateral bud. The lateral bud may develop into a
branch—a lateral extension of the shoot system. At the top of
the stem is an apical bud.
The Diversity of Roots:
North American Prairie Plants
• Natural selection has favored a diverse array of root
systems in prairie plants to minimize competition for
water and nutrients (Figure 35.4).
•Even though root systems have similar
functions—in support, storage, and nutrient
absorption—they are highly diverse in structure.
The Diversity of Shoots:
Hawaiian Silverswords
• The silverswords are a group of closely
related plant species found only on the
Hawaiian Islands. They are incredibly diverse
in size, shape, and growth habit (Figure 35.6
and Figure 35.7).
•The adaptive radiation of silverswords may be
due to diversification of shoot systems.
Modified Shoots
• Modified stems are common. Examples are:
– the stems of cacti (for water storage and
–stolons (stems that run over the soil surface)
–rhizomes (stems that grow horizontally
–tubers (rhizomes modified to store
–thorns (stems that protect the plant (Figure
Modified Leaves
• In most plant species, the vast majority of
photosynthesis occurs in the leaves.
•Leaves differ in size and shape but have just
two major structures: a blade and a stalk called
a petiole (Figure 35.9).
•But, not all leaves function primarily in
photosynthesis (Figure 35.10).
• Plant cells have a cell wall and a vacuole, and
the cytoplasm of adjacent cells is connected by
structures called what?
The Diversity of Plant Cells
• Plant cells have many variations and are either
undifferentiated or mature.
What are Meristematic cells?
•Meristematic cells are the undifferentiated cells that are
responsible for plant growth.
–contain undifferentiated organelles called proplastids that can
differentiate into various organelles, such as chloroplasts, chromoplasts
and amyloplasts
What are Parenchyma cells?
•Parenchyma cells are alive at maturity and are totipotent,
meaning that they can divide and develop into a complete
mature plant.
–They can form a mass of undifferentiated cells called a callus, from
which roots develop and can be used to clone plants (Figure 35.13).
–Parenchyma cells perform a variety of functions: wound healing,
asexual reproduction, and starch storage, among others.
What are Collenchyma cells and what do they do?
• Collenchyma cells have thickened cell walls in some
areas (Figure 35.15)
–Serve to stiffen leaves and stems, support
–Can elongate even when mature
–Often found in stems
What are Sclerenchyma cells and name the different types?
• Sclerenchyma cells also stiffen stems and other structures
– distinguished by thickened secondary cell walls strengthened by
lignin (in addition to the primary cell walls that all plant cells
– There are several types of sclerenchyma cells:
• tracheids, vascular tissue for water and mineral transport
• vessel elements, vascular tissue for water and mineral
• fibers, elongated cells associated with vascular tissue (Figure
• sclereids, short cells with variable shapes that often function in
protection, such as thick nut shells (Figure 35.16b)
What is a tissue?
• A tissue is a group of cells that functions as a unit.
–Can be simple (one cell type) or complex (multiple cell
What are Meristematic tissues?
•Meristematic tissues are the rapidly dividing,
undifferentiated cells responsible for growth.
–Active in mitosis.
•Some cells remain meristematic cells
•Some cells differentiate into other cell types
What are the 3 major tissue systems in mature plants?
•There are three major tissue systems in mature plants:
Facts on Dermal Tissue
• Dermal tissue, or epidermis, consists of a single layer of cells
that covers the plant body
–secretes cuticle, which protects the leaves and reduces water loss
–forms the first line of defense against pathogens (disease-causing agents)
–often has specialized structure such as stomata and trichomes
•Stomata allow carbon dioxide to enter photosynthetically active
–Stomata consist of two guard cells, which change shape to open or close
an opening called a pore (Figure 35.17).
•Trichomes on epidermal cells minimize water loss, cool the leaf
surface, and protect the plant against attacks by herbivores
(Figure 35.18).
Facts on Ground tissue
• Ground tissue makes up the bulk of the plant
–is the primary location of photosynthesis and
carbohydrate storage.
Facts on Vascular tissue
•Vascular tissue is specialized for water and nutrient
What are the 2 types of vascular tissue?
xylem and phloem
Vascular Tissue: Xylem
• Xylem conducts water and dissolved ions
from the root system to the shoot system.
•Xylem contains two types of conducting
cells: tracheids (Figure 35.19a) and vessel
elements (Figure 35.19b).
–The sides and ends of tracheids have pits
(interruptions in the secondary cell wall).
–Vessel elements have perforations (openings
through both primary and secondary cells
–In angiosperms, tracheids and vessel
elements are found adjacent to each other
(Figure 35.19c).
Vascular Tissue: Phloem
• Phloem conducts sugar, amino acids, chemical
agents, and other substances throughout the plant
•Phloem contains:
– sieve-tube members that function in transport (long, thin
cells that have perforated ends called sieve plates)
•lack nuclei, chloroplasts, most organelles
–companion cells (Figure 35.20)
•contain all the organelles normally found in a plant
• are not conducting cells but provide materials to
maintain the cytoplasm and plasma membrane of sievetube
Distribution of Tissue Types
• The meristematic, dermal, ground,
and vascular tissues of plants are
distributed throughout the root and
shoot systems as shown in Figure
• Indeterminate growth occurs in meristematic
tissues and is the result of two processes:
–production of new cells by mitosis and cytokinesis
–cell enlargement.
Apical meristems are involved in what?
primary growth; which is growth in length
Lateral meristems do what?
Increase the width of the stem or trunk during secondary growth
•Many grassland species produce their leaves and
stems from _______ meristems, which are located
Primary Growth:The Root System
• There are three zones behind the root cap (a group of
protective cells that covers the growing region of the root)
(Figure 35.22).
1. The zone of cellular division contains the apical meristem,
where cells are actively dividing.
2. The zone of cellular elongation is made up of cells
recently derived from the apical meristem that are actively
increasing in length.
3. The zone of cellular maturation is where older cells
complete their differentiation into dermal, vascular, and
ground tissues. In this zone, epidermal cells produce
outgrowths called root hairs, which greatly increase the
surface area of the dermal tissue.
Primary Growth:The Shoot System
• Shoots grow at the shoot apical meristem (Figure 35.23).
On both sides of this region, newly developing leaves
emerge as leaf primordia.
• Stems (Figure 35.24) and leaves (Figure 35.25) contain a
variety of cells and tissues:
– The pith, or center of the stem, consists of ground tissue that stores
– Vascular bundles form strands around the pith running the length
of the stem through the ground tissue in the center of the leaf.
– Eudicots have a layer of ground tissue called the cortex between the
vascular bundles and the epidermis.
– Elongated palisade mesophyll cells are packed with chloroplasts
and are the site of most photosynthesis.
– Rounded spongy mesophyll cells are loosely packed and are often
surrounded by air spaces near stomata. The wet surfaces of spongy
mesophyll cells are the site of gas exchange in plants.
Secondary Growth
• Secondary growth increases root and shoot width and provides the structural
support necessary for extensive primary growth.
•Lateral meristems are also called secondary meristems or cambium. Lateral
meristems run the length of a root or stem and divide it in a plane parallel to
the long axis to increase the width of the structure.
•There are two types of lateral meristem, cork cambium and vascular
cambium (Figure 35.26a).
•Cork cambium produces cork cells that are a component of bark and form a
protective layer for the mature root or shoot.
•The parenchyma cells produced by the vascular cambium radiate laterally
across the xylem and form structures called rays (Figure 35.26b).
•Cells produced by the vascular cambium develop into secondary phloem and
secondary xylem. Secondary phloem contributes to bark, and secondary
xylem forms wood (Figure 35.27).
The Structure of a Tree Trunk
• During periods of rapid growth, secondary xylem
cells are large and thin-walled. During dormant periods,
the secondary xylem cells are small and thick-walled.
This variation in cell size results in annual growth rings
(Figure 35.28a).
The inner xylem of a trunk is called what?
The outer xylem of a trunk is called what?