9: Stems (B)

shoot system

The aerial portion/system of a plant body, consisting of stems, leaves, flowers, and fruits (angiosperms)

shoot

above ground portion of plant

root system

all the roots of a plant

leaves

site of food production and photosynthesis

stem

support leaves to maximize light interception

Stem

important storage organs; Irish potato

Tuber

a swollen underground stem

epicotyl

the segment of an embryo or seedling stem above the point where the cotyledon is attached

Hypocotyl

the segment of an embryo or seedling stem below the point where the cotyledon is attached

False; from the epicotyl shea

Shoot growth is initiated in the embryo

from the hypocotyl, which may or may not

have one or more leaf primordia (True or False)

Nodes

the points at which leaves are attached

internodes

· the intervals between the nodes

axil

upper angle between a leaf stalk (or any lateral structure) and the stem

Axillary structures

anything that arises from the axil

Bud

an external meristem; can be protected by a bud scale

bud scales

modified leaves that protect buds

Lateral buds

a. buds along the side of the twig; may be for new leaves, flowers or branches (another stem)

Terminal buds

buds at the end of the twig; only for extending length of stem

leaf scar

all that remains on a branch after a leaf falls off

1. Support leaves and reproductive structures

2. Produce carbohydrates

3. Store materials

4. Transport water and solutes

Four Functions of Stems

True

Stems can be photosynthetic (True or False)

parenchyma cells

cells that play a role in stem storage

xylem and phloem

Tissues that carry food and water through the plant

herbaceous stem

Softer, more flexible, short-lived, and often green plant stems

woody stem

strong, long-lived, hard, usually brown stem that can support tall plants

Tunica

region of the shoot apex for surface growth to maintain their continuity over corpus

anticlinal division

Cell division that occurs in tunica when the cell wall plate is formed perpendicular to the circumference of the stem

corpus

region of the shoot apex that adds bulk to the apical meristem by increase in volume

primordia

Shoot apex produces ___________ that develop into all the above ground organs of a plant

leaf primordia and axillary buds

Shoot apex give rise to lateral appendages such as

leaf buttress

The initial outgrowth/bulge of the new leaf

leaf buttress: leaf primordium: mature leaf

3 levels of development of leaf

primary stem growth

type of stem growth that is a produce of the apical meristem

True

Primary stem tissues include three types of tissues: dermal, ground, and vascular (True or False)

False

All plants have primary growth and secondary growth (True or False)

1. epidermis

2. ground tissue

3. vascular bundles

Three main tissues of primary stem; be specific

protoderm, tunica

epidermis is formed from __________ via ____________

shoot apical meristem

meristem responsible to the increase in length of the shoot

secondary growth in stems; lateral meristem

meristem responsible for increase in thickness

Stele

primary vascular tissues plus the associated ground tissues (pith)

cortex

portion that is between the epidermis and stele

Protostele

The simplest type of stele, consisting of a solid column of vascular tissue.

Protostele

Solid core, phloem surrounds xylem

In primitive seed plants, whisk ferns, club mosses and ferns

in eudicot rooot

Protostele, siphonostele, atactostele, eustele

types of stele

Siphonostele

stele that is penetrated by a ground tissue in between (pith); continuous ring; in monocot roots

Eustele

A stele in which the primary vascular tissues are arranged in discrete bundles around a pith in a concentric manner; typical of gymnosperms and angiosperms.

Eustele

Stele in which vascular tissues are in bundles; concentric (pith); specialized siphonostele; in dicot stems

Atactostele; siphonostele

stele common in monocot stem and monocot root

Atactostele

stem contains a ring of vascular bundles, and then a spiral towards the center (specialized siphonostele); in monocot stem

Atactostele

highest level of development of the vascular system (stele)

cortex and pith

produced by ground meristem (specific)

True

cortex is mainly parenchyma with some collenchyma and sclerenchyma (True or False)

cortex

Which has lesser ground tissues? cortex or pith

Aerenchyma

a soft plant tissue containing air spaces, found in the cortex of many aquatic plants

pith

a typical parenchyma that is internal from vascular tissue

Epidermis (plant)

Usually a single layer of cells on the upper and lower surfaces of a leaf

Trichomes

projections on the epidermis for protection

False

epidermis do have chloroplasts (true or false)

stomatal apparatus

found in the epidermis which regulates transpiration and gas exchange

Epidermis

outside layer of plant that serves as protection from outside environment and prevents water dessication

procambium

The vascular tissue in primary stem are formed from

Endarch and Exarch

two types of primary xylem differentiation

Protoxylem

the part of the primary xylem that has thicker walls and differentiates early, while adjacent cells are still elongating

Metaxylem

The part of the primary xylem that has thinner walls and differentiates late, after adjacent cells have completed their elongation.

Endarch

protoxylem is internal to metaxylem; xylem differentiation is centrifugal or toward the periphery of stem, derived character

Endarch

The direction of xylem maturation in shoots of seed plants, where the direction of maturation is from the inner portion of the stem (protoxylem) to the outside (metaxylem).

Exarch

The direction of xylem maturation in roots of seed plants, where the direction of maturation is from the outer portion of the root (protoxylem) to the inside (metaxylem).

Exarch

pattern of differentiation in which the direction of maturation is centripetal; toward the center

Exarch

Xylem differentiation that is usually star-shaped and present in roots

Collenchyma

A flexible plant cell type that occurs in strands or cylinders that support young parts of the plant without restraining growth

concentric cylinders

Arrangement of xylem and phloem that is common in ferns

secondary growth

growth of plants that allow for much greater size and volume

vascular cambium

A cylinder of meristematic tissue in woody plants that adds layers of secondary vascular tissue called secondary xylem (wood) and secondary phloem.

vascular cambium

arise from interfascicular cambium and procambium

interfascicular cambium

originates from the dedifferentiation of parenchyma cells

True

interfascicular cambium is a secondary meristem (true or false)

secondary growth

which growth in stems provide great commercial value

True

Vascular cambium is a partial secondary meristem (True or False)

epidermis, phloem, or cortex

Cork cambium arises from?

False

Vascular cambium does not necessarily need to be formed before secondary growth can occur (True or False)

fascicular cambium

Cambium that develops within the vascular bundles in the stem of a plant.

True

In herbaceous stems, the interfascicular cambial area does not activate; thus does not produce new phloem and xylem (True or False)

xylem cells

new ___________ are formed inwardly

phloem cells

new __________________ are formed outwardly

periclinal division

parallel division in vascular cambium resulting in xylem and phloem

True

primary phloem is near the epidermis (may be crushed)

pith

In secondary growth, primary xylem is near the?

periderm

The protective coat that replaces the epidermis in plants during secondary growth, formed of the cork cork cambium, and phelloderm.

cork and phelloderm

cork cambium produces

Phellogen

another name for cork cambium

Phellem

also known as cork; external to the cork cambium, cells are densely arranged as protective layers

Phellem

non-living suberized cells for waterproofing

Phelloderm

thin layer of parenchyma cells that forms to the interior of the cork cambium

Cork cells

Which are more produced often, cork cells or phelloderm?

1. Increase in diameter of the stem occurs due to activity of vascular cambium

2. Causes the protective epidermis to crack and split open

3. Layer of cork cambium forms outside of the phloem

4. Cylinder of cork cambium increases in diameter as stem increases in diameter

State the formation of periderm

bark

All tissues external to the vascular cambium, consisting mainly of the secondary phloem and layers of periderm.

Phase 1: As the layers of cells outside the vascular cambium die, they are sloughed off as bark

Phase 2: In the young stem the bark contains: epidermis, cork, cork cambium, phelloderm, cortex, and phloem

Phase 3: In the old stem the bark contains: cork, cork cambium, phelloderm, and phloem

State the phases of bark formation

cortical cells

For the cork formation, in the young stem (1-year-old or less), _____________ just under the epidermis become meristematic

1-2 cells thick

How thick is the layer of cork cambium produced by meristematic cortical cells?

cork cells

flattened and cell walls contain suberin, a waxy substance