Botany: Origin and Development of Stems

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is formed by the vascular cambium throughout the year in tropical trees?

Ungrained, uniform wood (correct)

Summer wood

Spring wood

Annual rings of wood

What primarily constitutes the bulk of a tree trunk?

Annual rings of wood (correct)

Secondary phloem

Vascular rays

Darkened wood from heartwood

What type of wood is produced during the spring, which consists of relatively large vessel elements?

Tropical wood

Spring wood (correct)

Summer wood

Heartwood

What role do vascular rays serve in the structure of woody stems?

Functioning in lateral conduction of nutrients and water Signup and view all the answers

What happens to conductance in xylem due to the formation of tyloses?

Prevents conduction of water through xylem Signup and view all the answers

What is the primary function of cork cells produced by cork cambium?

Reduce water loss and protect the stem Signup and view all the answers

What type of stele consists of a solid core with phloem surrounding the xylem?

Protostele Signup and view all the answers

Which of the following is NOT a characteristic of annual plants?

Have primarily secondary growth Signup and view all the answers

What is the role of lenticels in stems?

Facilitate gas exchange Signup and view all the answers

What separates the primary xylem from the primary phloem in stems?

Vascular cambium Signup and view all the answers

Which type of flowering plants develop from seeds with a single cotyledon?

Monocotyledons Signup and view all the answers

In herbaceous dicotyledonous stems, how are the vascular bundles typically arranged?

In a ring formation Signup and view all the answers

Which plant group is characterized by the development from seeds having two cotyledons?

Dicots Signup and view all the answers

What is the area of the stem where leaves are attached called?

Node Signup and view all the answers

Which part of the stem contributes to the increase in stem length during growth?

Apical meristem Signup and view all the answers

What is the role of the procambium in stem development?

Produces primary xylem and phloem Signup and view all the answers

What indicates the age of a woody twig?

Number of bud scale scars Signup and view all the answers

Which structure protects the apical meristem?

Bud scales Signup and view all the answers

Which of the following describes a whorled leaf arrangement?

Leaves grow in groups of three or more Signup and view all the answers

What type of plant has dormant axillary buds located below leaf scars?

Deciduous trees and shrubs Signup and view all the answers

What develops into mature leaves and buds from the stem?

Leaf and bud primordia Signup and view all the answers

Which type of specialized stem grows below ground and has long to short internodes?

Rhizome Signup and view all the answers

What is the primary function of tubers?

Store food Signup and view all the answers

Which of the following wood components is responsible for the durability of wood?

Tannins and oils Signup and view all the answers

What is the primary characteristic of heartwood?

It is older and darker wood found in the center. Signup and view all the answers

What characteristic distinguishes radially cut boards from tangentially cut boards?

They show annual rings in side view Signup and view all the answers

Which tissue type is responsible for producing latex in plants?

Laticifers Signup and view all the answers

What type of specialized stem is characterized by flattened, leaf-like structures?

Cladophyll Signup and view all the answers

Which part of wood contributes approximately 60-75% of its dry weight?

Cellulose Signup and view all the answers

Which statement accurately describes softwood?

It is the wood of conifers with no fibers or vessel elements. Signup and view all the answers

Which specialized stem is produced beneath the surface of the ground and tends to grow in various directions?

Rhizome Signup and view all the answers

What occurs in the bark of woody dicotyledonous stems?

It is made of secondary phloem and cork. Signup and view all the answers

What two components primarily make up the vascular bundles in monocot stems?

Xylem and phloem Signup and view all the answers

What is the primary use of veneer in wood products?

To glue thin sheets of desirable wood to cheaper lumber Signup and view all the answers

What happens to first formed xylem cells in a typical monocot vascular bundle?

They collapse and leave irregularly shaped air spaces. Signup and view all the answers

In monocotyledonous stems, where is the xylem typically located in relation to the phloem?

Xylem is closer to the center of the stem. Signup and view all the answers

What differentiates hardwood from softwood?

Hardwood contains fibers and vessel elements. Signup and view all the answers

Study Notes

Origin and Development of Stems

A narrow band of cells between the primary xylem and phloem may become vascular cambium
Cells produced by the vascular cambium become components of secondary xylem towards the center and secondary phloem towards the surface.
In many plants, cork cambium produces cork cells with suberin and phelloderm cells.
Parenchyma cells in cork facilitate gas exchange.

Tissue Patterns in Stems

Stele is the central cylinder of primary xylem, primary phloem, and pith (if present).
Protostele has a solid core with phloem surrounding the xylem.
Siphonosteles are tubular with pith in the center.
Eusteles have discrete vascular bundles.
Cotyledons, seed leaves attached to embryonic stems, store food for the young seedling.
Dicotyledons have two cotyledons, while monocotyledons have a single cotyledon.
Most monocots are annuals, but many dicots are also annuals.

Herbaceous Dicotyledonous Stems

Herbaceous dicots have discrete vascular bundles arranged in a cylinder.
Vascular cambium arises between primary xylem and phloem.

Woody Dicotyledonous Stems

Wood is secondary xylem.
Vascular cambium and cork cambium are active year-round, producing ungrained, uniform wood.
Differences in wood production occur seasonally:
- Spring wood has relatively large vessel elements.
- Summer wood has fewer, smaller vessel elements.
Conifers have larger tracheids in the spring.
One year's growth of xylem forms an annual ring.
Indicates age of a tree and climate during its lifetime.
Vascular rays consist of parenchyma cells for lateral conduction of nutrients and water.
Tyloses are protrusions of adjacent parenchyma cells into conducting cells of xylem, preventing water conduction and darkening wood.
Heartwood is older, darker wood in the center.
Sapwood is lighter and still-functioning xylem closest to the cambium.
Softwood is wood of conifers, lacking fibers and vessel elements..
Hardwood is wood of dicot trees.
Resin canals are tubelike canals containing resin secreted by specialized cells, found in conifers and some tropical flowering plants.
Bark is tissues outside the vascular cambium, including secondary phloem.
Laticifers are ducts found mostly in phloem with latex-secreting cells.

Monocotyledonous Stems

Monocot stems lack a vascular cambium and a cork cambium.
Primary xylem and phloem in discrete vascular bundles are scattered throughout the stem.
Vascular bundles are oriented with xylem closer to the center and phloem closer to the surface.
Parenchyma tissue surrounds the vascular bundles.
Vascular bundles in monocots have:
- Two large vessels with several small vessels.
- First formed xylem cells stretch and collapse, leaving irregularly shaped air spaces.
- Phloem consists of sieve tubes and companion cells.
- A sheath of sclerenchyma cells surrounds the vascular bundle.

Specialized Stems

Rhizomes are horizontal stems that grow belowground with long to short internodes.
Runners are horizontal stems that grow aboveground with long internodes.
Stolons are produced beneath the surface of the ground and grow differently.
Tubers are swollen, fleshy, underground stems that store food.
Bulbs are large buds surrounded by fleshy leaves with a small stem at the base, storing food.
Corms resemble bulbs, but are mostly stem tissue with papery leaves that store food.
Cladophylls are flattened, leaf-like stems.

Wood and Its Uses

In a living tree, 50% of the wood weight comes from water content.
Dry wood is composed of 60-75% cellulose and 15-25% lignin.
Wood products include lumber, particle board, pulp, veneer, and sawdust.
Knots are bases of lost branches covered by new annual rings.
Radially cut boards show annual rings in side view.
Tangentially cut boards are cut perpendicular to rays.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the intricate processes involved in the origin and development of plant stems. This quiz covers the role of vascular cambium, the different tissue patterns in stems, and the characteristics of herbaceous dicotyledonous stems. Test your knowledge on plant anatomy and development.