Botany Exam 3

Where do woody species have their secondary tissues?

Stem and root

What does the accumulation of wood and bark do?

Widens plants, allowing greater conducting capacity

What are the disadvantages of secondary growth?

Greater need for sturctural and chemical defenses, must use energy and nutrient resources for winterizing in temperate climates, expesnive metabolically to construct wood and bark, may not reproduce until several years old (energy is limited)

What does the vascular cambium of woody dicotyledonous stems produce?

Secondary xylem toward the inside of cambium and phloem toward outside (usually less formed)

What is bark?

All tissues outside the cambium

Where does the meristematic vascular cambium lie?

Between metaxylem and metaphloem

What happens to the cells in the meristematic vascular cambium in herbaceous plants?

These cells stop dividing

What happens to the cells in the meristematic vascular cambium in woody plants?

The cells continue to divide and produce the fasicular cambium

What forms between vascular bundles?

Interfascicular cambium

What happens in the interfascicular cambium?

Some mature parenchyma cells resume mitosis, connects with the fasicular cambia to either side

What is the vascular cambium like?

Continuous ring

What are the two types of cells in the vascular cambia?

Fusiform initials and ray initials

What are fusiform initials?

Long, tapered cells in the vascular cambia that form xylem and phloem

What are ray initials?

Short, cuboidal vascular parenchyma cells in the vascular cambia that act as storage

How do fusiform initials divide?

Longitudinally with a pariclinal wall

What do fusiform initals produce when they divide?

Two elongate cells, one that remains a fusiform initial and one that differentiates into a secondary xylem or secondary phloem

When secondary xylem cells increase greatly in diameter, what happens?

The cambial cells are pushed outward

How are ray initials arranged?

Grouped together in short vertical rows

What are one-cell-wide rows of ray initials called?

Uniserate

What are two-cells-wide rows of ray initials called?

Biseriate

What are rows of ray initals that are many cells wide called?

Multiseriate

How may fusiform initals occur (arrangement-wise)?

In regular horizontal rows (storied cambium) and irregularly, without any horizontal pattern (nonstoried cambium)

What can the fusiform initial divide transversely to become?

A row of ray initials

What is the ratio of fusiform initials to ray initials within a species like?

Quite constant and apparently under precise developmental control

What kind of cell types do secondary xylem “wood cells” have?

All that occur in primary xylem

What is an axial system derived from?

Fusiform initials

What is a radial system developed from?

The ray initials

What do tracheary elements do?

Carry out vertical conduction of water through the wood

What wood angiosperms contain large amounts of fibers?

Hardwoods

What wood angiosperms contain few or no fibers?

Softwoods

What is an axial xylem parenchyma?

Temporary reservoir of water

What do most gymnosperms only contain in their axial system?

Tracheids (fibers and parenchyma are sparse or absent)

Where do vascular rays radiate from?

Center across annual rings

What is the cell type of vascular rays?

Parenchyma, usually 2-3 cells wide and 2-50 deep

What is the function of vascular rays?

Lateral nutrient, water conduction

What does the radial system only contain in woody angiosperms?

Parenchyma

How can the rays in the radial system be arranged?

Uniseriate, biseriate, or multiseriate

What can the radial system store?

Carbohydrates and other nutrients

What is conduction in the radial system like?

Over short distances, radially

What are the xylem rays in gymnosperms usually like?

Uniseriate, but multiseriate only if resin canal is present

In addition to ray parenchyma cells, what may xylem rays in gymnosperms contain?

Ray tracheids

Growth rings appear due to what?

Spring/summer wood growth

What does spring wood have a high proportion of?

Wide vessels or tracheids

What are the tracheids in summer wood like?

Fewer vessels or narrower, thick-walled tracheids

What are the characteristics of spring wood?

First activity of vascular cambium, produces secondary xylem, large vessel elements

What are the characteristics of summer wood?

Vessel elements become smaller each division OR fewer vessel elements and more tracheids made

What is ring porous?

Wood with vessels found mostly in early wood

What is diffuse porous?

Wood with vessels found throughout

What is heartwood?

Center of a log that is almost darker, drier, and more fragrant

How does wood become heartwood?

Tracheary elements no longer function for water transport and are sealed off by tyloses

What is sapwood?

The active layer that continues to form new layers every year; has intact water conduction and almost constant thickness

On average, how long will the working sapwood function before it converts to heartwood?

1 year

Which type of wood is not essential for survival?

Heartwood

What do tyloses in heartwood help do?

Prevent bacterial/fungal growth

What produce tyloses in heartwood?

Parenchyma cells

What is the result of tyloses?

Accumulation of resins, gums, and tannins, and a darkening of wood color

What are examples of hardwoods?

Beech, oak, ash, teak

What does hardwood come from?

Deciduous trees

What are deciduous trees?

Broad-leaved trees which lose their leaves in the winter

What are examples of softwoods?

Pine, spruce, cedar, fir

What does softwood come from?

Coniferous trees

What are coniferous trees?

Evergreen, needle-leaved, cone-bearing trees

What are ray cells like in hardwoods?

Radial parenchyma

What are ray cells like in softwoods?

Radial parenchyma and radial tracheids (in some species)

What are longitudianal cells in softwoods like?

Axial tracheids and axial parenchyma (in some species)

What are longitudinal cells in hardwoods like?

Fibres, axial tracheid (rare), axial parenchyma (usually), thick wall, pits

What kinds of bark do woody dicotyledonous stems have?

Inner and outer

What is contained in the inner bark of woody dicotyledonous stems?

Primary and secondary phloem

What is contained in the ouer bark (periderm) of woody dicotyledonous stems?

Cork tissue and cork cambium

Why is the outer layer of bark mostly dead?

It’s cut off from water supply, sugar supply, etc.

What is the inner bark?

Older layers of phloem that have been crushed by new cells and made functionless, and cortex parenchyma cells that function briefly before getting crushed

What may the outer bark be?

Alternating layers of crushed phloem and cork

What does the axial system of phloem in secondary phloem contain?

Sieve tube members and companion cells in angiosperms, sieve cells in gymnosperms, and fibers and nonconducting parenchyma cells in both

How are phloem rays formed?

The same as xylem rays

What do phloem rays consist of?

Parenchyma storage cells (albuminous cells in gymnosperms)

How long do sieve tube members and sieve cells usually conduct?

Less than a year

What is the only layer of secondary phloem that is capable of conduction?

Innermost phloem layer

What do the youngest phloem layers near the cambium have?

Sieve tubes to transport nutrients and a sugar recognized by Native Americans

What role do the youngest phloem layers near the cambium have?

Transporting materials from leaves to other parts

What is the cork cambium also called?

Phellogen

What is the cork cambium?

A lateral meristem that comes from different layers of tissue (cortex, epidermis, or phloem depending on age and species)

What does the periderm layer do?

Produces boxlike cork cells that contain suberin, continually make layers each year, and die quickly

What are phelloderm cells?

Parenchyma-like cells in the cork cambium region that die quickly but act as protection; deposit suberin and other maxy materials

Why does all plant material exterior to the periderm die?

Lack of water and nutrients

How does the impermeability of cork affect the plant?

Conserves water, increases pathogen/pest resistance, blocks the absorption of oxygen

When does bark become permeable?

When rounded cork cells are produced and through breakages in the epidermal layers

How do young stems use gas exchange?

Stomata in epidermis allow very regulated gas exchange

How do woody stems use gas exchange?

Lenticils in cork tissue appear in fissures of bark help get oxygen to lower layers

What tissues can initiation of cork cambia occur in?

Epidermis, cortex, primary phloem, secondary phloem

Where would you normally see cork cambia in secondary phloem?

Older trees

What can root secondary growth include that develops between the xylem and the phloem?

Vascular cambium

What can also be activated to cause root secondary growth?

Pericycle cells

What kind of roots would bark form in?

Perennial roots

Where does the first cork cambium usually arise?

Pericycle

What can cause shedding of endodermis, cortex, and epidermis?

Root secondary growth

When lenticels occur in secondary roots, where are they usually especially prominent?

Near lateral roots

Can roots make wood?

Yes

What happens when roots make wood?

Storage capacity is increased and structure strength is increased

Why is storage capacity often increased in woody roots?

Rays may become larger, increasing the number of storage ray parenchyma, axial parenchyma in the wood can be used as storage

In many storage roots, what is wood almost purely made of?

Parenchyma