85 Questions
What type of stem tissue pattern contains discrete vascular bundles?
Eusteles
Which type of stems do monocotyledons (monocots) have?
Monocotyledonous
What type of stem lacks a vascular cambium and cork cambium?
Monocotyledonous
In which type of stem does xylem lie closer to the center?
Protostele
What is the structure that surrounds a vascular bundle in a monocot stem?
Parenchyma Cells
Which type of stem pattern is tubular with a pith in the center?
Siphonosteles
What type of cells are found in the laticifers in the stem with secondary growth?
Latex-secreting cells
What do tyloses in the xylem do?
Prevent conduction of water
What is the function of resin canals found in woody dicotyledonous stems?
Secrete resin
In which part of the tree is heartwood typically found?
Center
How do tangentially cut boards differ from radially cut boards?
Show irregular bands of light and dark streaks
What accounts for about 50% of the wood weight in a living tree?
Water content
What is the primary function of the vascular cambium in a woody dicotyledonous stem?
To produce secondary xylem and secondary phloem
What is the primary difference in wood structure between trees that have active vascular and cork cambia all year round versus those with seasonal wood production?
The wood produced is more uniform and ungrained in trees with year-round active cambia
What is the primary function of the bark in a woody dicotyledonous stem?
To protect the inner tissues from damage and environmental stresses
In conifers, what is the primary difference in wood structure compared to angiosperms?
Conifers lack vessels and have only tracheids in their secondary xylem
What is the primary difference in wood structure between the spring wood and summer wood in woody dicotyledonous stems?
Spring wood has larger vessel elements, while summer wood has fewer and smaller vessel elements
What is the primary use of wood in the United States and Canada?
Lumber for construction
What is the second most widespread use of wood?
Pulp
What is the main function of the apical meristem at the stem tip?
To increase the stem length
What are rhizomes?
Horizontal stems that grow below-ground with long to short internodes
What is the main difference between a corm and a bulb?
Corms are composed almost entirely of stem tissue, while bulbs are composed of fleshy leaves
What are the three primary meristems formed from the apical meristem cells?
Protoderm, procambium, and ground meristem
What are the 'eyes' of a potato?
The nodes of the potato
What are leaf primordia and bud primordia?
Tiny embryonic leaves and buds that develop into mature ones
What is a leaf gap or bud gap?
A gap in the vascular tissue cylinder filled with parenchyma cells
What are cladophylls?
Flattened, leaf-like stems
What is a trace in the context of stem development?
A strand of xylem and phloem that enters a leaf or bud
What is the primary difference in wood structure between trees that have active vascular and cork cambia all year round versus those with seasonal wood production?
Trees with active cambia produce uniform, ungrained wood
What is the primary function of the vascular cambium in a woody dicotyledonous stem?
To produce secondary xylem (wood)
What is the primary difference in wood structure between the spring wood and summer wood in woody dicotyledonous stems?
Spring wood has larger vessel elements, while summer wood has fewer and smaller vessel elements
What is the primary function of the bark in a woody dicotyledonous stem?
To protect the stem from damage and infection
What is the main function of the apical meristem at the stem tip?
To produce new leaf and bud primordia
What structure is found at the angle between the petiole and the stem?
Axillary bud
What does the number of groups of bud scale scars indicate?
The age of the twig
What structure protects the buds on a woody twig?
Bud scales
What is the arrangement of leaves called when they are attached in groups of three or more?
Whorled
What are the paired, often leaflike appendages at the base of a leaf called?
Stipules
What is the term for the region of the stem between nodes?
Internode
Which tissue produces secondary xylem and secondary phloem in woody dicotyledonous stems?
Vascular cambium
What is the primary function of cork cells produced by the cork cambium (phellogen) in stems?
To reduce water loss and protect the stem against injury
What do the annual rings in a woody dicotyledonous stem indicate?
Both the age of the tree and the climate during its lifetime
What is the primary function of vascular rays in woody dicotyledonous stems?
To facilitate lateral conduction of nutrients and water
What type of stem tissue pattern is found in herbaceous dicotyledonous stems?
Discrete vascular bundles arranged in a cylinder
What is the primary function of lenticels in the stem?
To allow for the exchange of gases
What is the function of the protostele?
It is a solid core with phloem surrounding xylem, found in primitive seed plants, whisk ferns, club mosses, and ferns.
What is the primary difference between monocot and dicot stems?
Monocot stems have vascular bundles scattered throughout, while dicot stems have a central vascular cylinder.
What is the function of the sclerenchyma sheath surrounding vascular bundles in monocot stems?
It provides structural support and protection for the vascular tissues.
What is the primary function of the eustele in woody flowering plants and conifers?
It contains discrete vascular bundles that enable the stem to undergo secondary growth.
What is the primary function of the pith in the siphonostele?
It aids in the storage of food reserves for the plant.
What is the primary function of the cotyledons in a seed?
They store food needed by the young seedling during its initial growth.
What is the primary use of about half of the wood production in the United States and Canada?
Constructing buildings
In developing countries, what is approximately half of the cut timber used for?
Fuel
What is the primary function of veneer according to the text?
Decoration on furniture
Which specialized stem type is composed almost entirely of stem tissue with papery leaves and is used for storing food?
Bulbs
Which specialized stem is characterized by flattened, leaf-like structures and includes prickly pear cactus?
Cladophylls
The apical meristem at the stem tip contributes to increase in stem ______
length
Leaf primordia are tiny embryonic ______ that develop into mature leaves
leaves
The apical meristem cells form three primary ______
meristems
Traces branch off from the cylinder of xylem and phloem, and enter the leaf or ______
bud
A ______ is a strand of xylem and phloem that leaves a gap filled with parenchyma in the cylinder of vascular tissue
trace
The region of the stem between nodes is called the ______.
internode
The angle between the petiole and the stem is called the ______.
axil
The ______ protects the buds on a woody twig.
bud scales
The arrangement of leaves attached in groups of three or more is called ______.
whorled
The paired, often leaflike appendages at the base of a leaf are called ______.
stipules
The number of groups of ______ scars tells the age of the twig.
bud scale
Rubber, chicle, and morphine are examples of latex-secreting cells found mostly in the phloem called ______
laticifers
In woody dicotyledonous stems, the wood of conifers without fibers or vessel elements is known as ______
softwood
Tyloses are protrusions of adjacent parenchyma cells into conducting cells of xylem that prevent the conduction of water and accumulate resins, gums, and tannins, forming ______
heartwood
Radially cut boards show annual rings in side view, while tangentially cut boards show annual rings as irregular bands of light and dark streaks in a cut known as ______
plainsawed
In a living tree, about 50% of the wood weight comes from water content, with the dry part composed of about 60-75% cellulose and about 15-25% ______
lignin
Tannins and oils in wood repel decay organisms, contributing to its ______ against decay
durability
The ______ is a solid core, with phloem surrounding xylem, found in primitive seed plants, whisk ferns, club mosses and ferns.
protostele
In monocot stems, the ______ surrounds the vascular bundles.
parenchyma
The ______ consists of sieve tubes and companion cells in a monocot vascular bundle.
phloem
A ______ of sclerenchyma cells surrounds the vascular bundle in a monocot stem.
sheath
In monocot stems, the ______ is closer to the center of the stem than the phloem.
xylem
Monocot stems do not have a ______ nor a cork cambium.
vascular cambium
Veneer - Thin sheet of desirable wood glued to cheaper ______
lumber
In developing countries, about half of cut timber is used for ______
fuel
Tubers - Swollen, fleshy, underground ______ Store food
stem
Bulbs - Large buds surrounded by numerous fleshy leaves, with a small ______ at lower end Store food
stem
Corms - Resemble bulbs, but composed almost entirely of ______ tissue, with papery leaves Store food
stem
Cladophylls Flattened, leaf-like ______ Greenbriars, some orchids, prickly pear cactus
stems
Study Notes
Stem Structure
- Stem is comprised of three main components: xylem, phloem, and pith
- Xylem is responsible for water transport, phloem for food transport, and pith for storage
- Xylem consists of tracheids, vessels, and parenchyma cells
- Phloem consists of sieve tubes, companion cells, and parenchyma cells
Tissue Patterns in Stems
- Steles: central cylinder of primary xylem, primary phloem, and pith (if present)
- Protostele: solid core, phloem surrounds xylem (primitive seed plants, whisk ferns, club mosses, and ferns)
- Siphonosteles: tubular with pith in center (ferns)
- Eusteles: discrete vascular bundles (woody flowering plants and conifers)
- Cotyledons: seed leaves attached to embryonic stems, storing food for young seedling
- Dicotyledons (Dicots): flowering plants developing from seeds with two cotyledons
- Monocotyledons (Monocots): flowering plants developing from seeds with a single cotyledon
Monocotyledonous Stems
- No vascular cambium or cork cambium
- Produce no secondary vascular tissues or cork
- Primary xylem and phloem in discrete vascular bundles scattered throughout the stem
- Xylem closer to center of stem, phloem closer to surface
- Parenchyma (ground tissue) surrounds vascular bundles
- In a typical monocot vascular bundle:
- Two large vessels with several small vessels
- First formed xylem cells stretch and collapse, leaving irregularly shaped air space
- Phloem consists of sieve tubes and companion cells
- Vascular bundle surrounded by sheath of sclerenchyma cells
Wood and Its Uses
- Wood: secondary xylem produced by vascular cambium
- Types of sawing:
- Radially cut (quartersawed) boards show annual rings in side view
- Tangentially cut (plainsawed or slab cut) boards show annual rings as irregular bands of light and dark streaks
- Wood composition:
- 50% of wood weight comes from water content
- Dry part of wood composed of about 60-75% cellulose and about 15-25% lignin
- Density: weight per unit volume
- Durability: ability to withstand decay, influenced by tannins and oils
Specialized Stems
- Rhizomes: horizontal stems that grow below-ground and have long to short internodes (irises, some grasses, ferns)
- Runners: horizontal stems that grow above ground and have long internodes
- Stolons: produced beneath the surface of the ground and tend to grow in different directions (potato)
- Tubers: swollen, fleshy, underground stem storing food (potatoes, eyes of potato are nodes)
- Bulbs: large buds surrounded by numerous fleshy leaves, with a small stem at lower end storing food (onions, lilies, hyacinths, tulips)
- Corms: resemble bulbs, but composed almost entirely of stem tissue, with papery leaves storing food (crocus and gladiolus)
- Cladophylls: flattened, leaf-like stems (greenbriars, some orchids, prickly pear cactus)
Origin and Development of Stems
- Apical meristem at stem tip contributes to increase in stem length
- Dormant before growing season begins, protected by bud scales and leaf primordia
- Leaf primordia and bud primordia develop into mature leaves and buds
- Traces branch off from cylinder of xylem and phloem, and enter leaf or bud
- Each trace leaves a gap filled with parenchyma in the cylinder of vascular tissue, forming leaf gap or bud gap
Test your knowledge on the origin and development of stems in plants, including the role of apical meristem, primary meristems, and protective structures like bud scales and leaf primordia.
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