Chapter 7:stems

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Questions and Answers

What type of stem tissue pattern contains discrete vascular bundles?

Protostele

Eusteles (correct)

Whisk Ferns

Siphonosteles

Which type of stems do monocotyledons (monocots) have?

Protostele

Cotyledons

Eusteles

Monocotyledonous (correct)

What type of stem lacks a vascular cambium and cork cambium?

Eusteles

Siphonosteles

Protostele

Monocotyledonous (correct)

In which type of stem does xylem lie closer to the center?

Protostele Signup and view all the answers

What is the structure that surrounds a vascular bundle in a monocot stem?

Parenchyma Cells Signup and view all the answers

Which type of stem pattern is tubular with a pith in the center?

Siphonosteles Signup and view all the answers

What type of cells are found in the laticifers in the stem with secondary growth?

Latex-secreting cells Signup and view all the answers

What do tyloses in the xylem do?

Prevent conduction of water Signup and view all the answers

What is the function of resin canals found in woody dicotyledonous stems?

Secrete resin Signup and view all the answers

In which part of the tree is heartwood typically found?

Center Signup and view all the answers

How do tangentially cut boards differ from radially cut boards?

Show irregular bands of light and dark streaks Signup and view all the answers

What accounts for about 50% of the wood weight in a living tree?

Water content Signup and view all the answers

What is the primary function of the vascular cambium in a woody dicotyledonous stem?

To produce secondary xylem and secondary phloem Signup and view all the answers

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 Signup and view all the answers

What is the primary function of the bark in a woody dicotyledonous stem?

To protect the inner tissues from damage and environmental stresses Signup and view all the answers

In conifers, what is the primary difference in wood structure compared to angiosperms?

Conifers lack vessels and have only tracheids in their secondary xylem Signup and view all the answers

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 Signup and view all the answers

What is the primary use of wood in the United States and Canada?

Lumber for construction Signup and view all the answers

What is the second most widespread use of wood?

Pulp Signup and view all the answers

What is the main function of the apical meristem at the stem tip?

To increase the stem length Signup and view all the answers

What are rhizomes?

Horizontal stems that grow below-ground with long to short internodes Signup and view all the answers

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 Signup and view all the answers

What are the three primary meristems formed from the apical meristem cells?

Protoderm, procambium, and ground meristem Signup and view all the answers

What are the 'eyes' of a potato?

The nodes of the potato Signup and view all the answers

What are leaf primordia and bud primordia?

Tiny embryonic leaves and buds that develop into mature ones Signup and view all the answers

What is a leaf gap or bud gap?

A gap in the vascular tissue cylinder filled with parenchyma cells Signup and view all the answers

What are cladophylls?

Flattened, leaf-like stems Signup and view all the answers

What is a trace in the context of stem development?

A strand of xylem and phloem that enters a leaf or bud Signup and view all the answers

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 Signup and view all the answers

What is the primary function of the vascular cambium in a woody dicotyledonous stem?

To produce secondary xylem (wood) Signup and view all the answers

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 Signup and view all the answers

What is the primary function of the bark in a woody dicotyledonous stem?

To protect the stem from damage and infection Signup and view all the answers

What is the main function of the apical meristem at the stem tip?

To produce new leaf and bud primordia Signup and view all the answers

What structure is found at the angle between the petiole and the stem?

Axillary bud Signup and view all the answers

What does the number of groups of bud scale scars indicate?

The age of the twig Signup and view all the answers

What structure protects the buds on a woody twig?

Bud scales Signup and view all the answers

What is the arrangement of leaves called when they are attached in groups of three or more?

Whorled Signup and view all the answers

What are the paired, often leaflike appendages at the base of a leaf called?

Stipules Signup and view all the answers

What is the term for the region of the stem between nodes?

Internode Signup and view all the answers

Which tissue produces secondary xylem and secondary phloem in woody dicotyledonous stems?

Vascular cambium Signup and view all the answers

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 Signup and view all the answers

What do the annual rings in a woody dicotyledonous stem indicate?

Both the age of the tree and the climate during its lifetime Signup and view all the answers

What is the primary function of vascular rays in woody dicotyledonous stems?

To facilitate lateral conduction of nutrients and water Signup and view all the answers

What type of stem tissue pattern is found in herbaceous dicotyledonous stems?

Discrete vascular bundles arranged in a cylinder Signup and view all the answers

What is the primary function of lenticels in the stem?

To allow for the exchange of gases Signup and view all the answers

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. Signup and view all the answers

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. Signup and view all the answers

What is the function of the sclerenchyma sheath surrounding vascular bundles in monocot stems?

It provides structural support and protection for the vascular tissues. Signup and view all the answers

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. Signup and view all the answers

What is the primary function of the pith in the siphonostele?

It aids in the storage of food reserves for the plant. Signup and view all the answers

What is the primary function of the cotyledons in a seed?

They store food needed by the young seedling during its initial growth. Signup and view all the answers

What is the primary use of about half of the wood production in the United States and Canada?

Constructing buildings Signup and view all the answers

In developing countries, what is approximately half of the cut timber used for?

Fuel Signup and view all the answers

What is the primary function of veneer according to the text?

Decoration on furniture Signup and view all the answers

Which specialized stem type is composed almost entirely of stem tissue with papery leaves and is used for storing food?

Bulbs Signup and view all the answers

Which specialized stem is characterized by flattened, leaf-like structures and includes prickly pear cactus?

Cladophylls Signup and view all the answers

The apical meristem at the stem tip contributes to increase in stem ______

length Signup and view all the answers

Leaf primordia are tiny embryonic ______ that develop into mature leaves

leaves Signup and view all the answers

The apical meristem cells form three primary ______

meristems Signup and view all the answers

Traces branch off from the cylinder of xylem and phloem, and enter the leaf or ______

bud Signup and view all the answers

A ______ is a strand of xylem and phloem that leaves a gap filled with parenchyma in the cylinder of vascular tissue

trace Signup and view all the answers

The region of the stem between nodes is called the ______.

internode Signup and view all the answers

The angle between the petiole and the stem is called the ______.

axil Signup and view all the answers

The ______ protects the buds on a woody twig.

bud scales Signup and view all the answers

The arrangement of leaves attached in groups of three or more is called ______.

whorled Signup and view all the answers

The paired, often leaflike appendages at the base of a leaf are called ______.

stipules Signup and view all the answers

The number of groups of ______ scars tells the age of the twig.

bud scale Signup and view all the answers

Rubber, chicle, and morphine are examples of latex-secreting cells found mostly in the phloem called ______

laticifers Signup and view all the answers

In woody dicotyledonous stems, the wood of conifers without fibers or vessel elements is known as ______

softwood Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

Tannins and oils in wood repel decay organisms, contributing to its ______ against decay

durability Signup and view all the answers

The ______ is a solid core, with phloem surrounding xylem, found in primitive seed plants, whisk ferns, club mosses and ferns.

protostele Signup and view all the answers

In monocot stems, the ______ surrounds the vascular bundles.

parenchyma Signup and view all the answers

The ______ consists of sieve tubes and companion cells in a monocot vascular bundle.

phloem Signup and view all the answers

A ______ of sclerenchyma cells surrounds the vascular bundle in a monocot stem.

sheath Signup and view all the answers

In monocot stems, the ______ is closer to the center of the stem than the phloem.

xylem Signup and view all the answers

Monocot stems do not have a ______ nor a cork cambium.

vascular cambium Signup and view all the answers

Veneer - Thin sheet of desirable wood glued to cheaper ______

lumber Signup and view all the answers

In developing countries, about half of cut timber is used for ______

fuel Signup and view all the answers

Tubers - Swollen, fleshy, underground ______ Store food

stem Signup and view all the answers

Bulbs - Large buds surrounded by numerous fleshy leaves, with a small ______ at lower end Store food

stem Signup and view all the answers

Corms - Resemble bulbs, but composed almost entirely of ______ tissue, with papery leaves Store food

stem Signup and view all the answers

Cladophylls Flattened, leaf-like ______ Greenbriars, some orchids, prickly pear cactus

stems Signup and view all the answers

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

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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.