2nd Plant Exam

What is the Lateral Meristem and what is it responsible for?

Occur on axis of the plant, responsible for increases in width/circumference in plant.

two types are Vascular Cambium and Cork Cambium

What meristem is in F and what does it do?

arises between and

within the primary phloem/xylem

• produces the secondary vascular tissues

• secondary xylem tissue to inside & secondary phloem

tissue to outside

(see F) Vascular Cambium

What meristem is the needle pointing to and what does it do?

cork cambium

arises from parenchyma in

cortex (just under epidermis)

• produces periderm (secondary epidermal tissues)

• Cork cells to outside

• Parenchyma cells to inside

What is this tissue (Assuming it’s secondary), what system is it apart of, and what meristem? How can you tell and what is the function?

Tracheid, part of Axial system, Vascular Cambium meristem. Longer, thinner, ends taper. Function is water conduction

Tell-Tale Signs of Secondary Growth

1: Vascular Cambium

2: Rays and Ray Cells

3: Growth Rings

Identify all this shiz

What cell is this? Trace it back to its meristem and give the function

ray parenchyma → Ray System → Axial System → Secondary Xylem → Vascular Cambium Meristem

function: store and transport water, nutrients, and carbohydrates (NSCs) between the xylem and phloem

Lateral Meristems

Responsible for large increases in

width/circumference of plant

• Occur along the axis of the plant

Vascular Cambium:

arises between and

within the primary phloem/xylem

• produces the secondary vascular tissues

• 20 xylem tissue to inside & 20 phloem

tissue to outside2

Cork Cambium:

arises from parenchyma in

cortex (just under epidermis)

• produces periderm (20 epidermal tissues)

• Cork cells to outside

• Parenchyma cells to inside

Give me the Flow Chart for Lateral Meristems and the functions

Fiber tracheids:

, small pits small and thin shape

•

• Present in both angiosperms and

gymnosperms

Libriform fibers –

very elongated;

thick secondary walls with lignin,

small cell lumen

• have no pit cavity and the pit pair is

simple (no border). “slit like”

• Fiber tracheid walls become thicker

at end of season and libriform fibers

formed in early season can have

thinner walls

• Sometimes no sharp boundary

between fiber tracheids and

libriform fibers.

Septate fibers with ray function

These store materials (like

xylem parenchyma in function and

difficult to distinguish between them).

What are the two kinds of parenchyma and what is their funciton?

axial and ray

• Function: store starch, oils, ergastic substances such as

tannins, crystals.

• Walls may develop secondary thickenings and become

lignified.

• They can develop into sclereids.

Name all this, and give the signs

Diffuse singly. Example: Alnus [the parenchyma shows up as

dark dots in the wood]

b. Diffuse in aggregation.

c. In bands – may or may not be at margin of growth ring.

Marginal may be in early wood (initial parenchyma) or late

wood (terminal parenchyma).

Name all this shiz and tell me what the signs are

associated with vessels

a. Scanty – scattered, usually solitary, next to vessels.

b. Vasicentric – surround the vessel.

c. Aliform (with wings) – AP surrounds the vessel and extends

to either side in wings.

d. Confluent – wings connect adjacent vessels.

e. Boundary banded – in growth ring, forms sheath around

vessels and narrow bands that connect with other vessels.

Which is Spring Wood which one is Late Wood, how can you tell?

Early in growing season (pink) - lots of water,

light, cells have thinner walls larger

lumens

Late in growing season (green) – decreased

water availability, leaves are being

shed, cooler temps, cells produced

smaller cells with increased cell wall

thickness

What are these types of Porous arrangements? What are there differences?

Ring Porous vs. Diffuse porous:

arrangement of vessel members

(pores)

Ring Porous wood: large diameter

vessel members produced early in

spring wood (top)

Diffuse porous wood: diameter of

vessel members doesn’t change

and uniformly distributed thru-out

the growing season. (bottom)

Diffuse porous

Ring porous

Gymnosperms don’t produce vessels:

Nonporous Wood

What is this and what is the function?

Tyloses: defense mechanism against pathogens and stress

Storied vs Non Storied

Storied on the left, Non storied on the right

Hardwood vs. Softwood

Hardwood – angiosperms due to abundant presence of fibers

Softwood – gymnosperm wood due to absence of numerous fibers

What system is leaves part of?

Shoot System

Plants adapted to dry environments

Xerophytes.

Plants adapted to habitats that are neither too wet or too dry

Mesophytes.

Floating, emergent, or submergent plants

Hydrophytes.

Typical Mesophyte Characteristics

Bundle sheath extensions may be present (parenchyma or sclerenchyma)

• Bundle Sheath cells surround vascular bundle – composed of parenchyma

or sclerenchyma

• Most guard cells on abaxial (lower) surface of leaf

What is this and what is it generally a sign of and what’s the function?

bulliform cells, large, colorless cells that cause

the leaf to roll or fold to reduce water loss, found in mesophytes

Leaf with hydrophytic features characteristics

1. Well-developed aerenchyma (large air spaces) to facilitate gas exchange and

buoyancy.

2. Submerged leaves often lack stomata entirely & floating leaves are typically

epistomatic, with stomata confined to the upper epidermis.

Cross sections through a hydrophytic leaf from Nymphaea (water lily)

4. Veins run parallel and are connected by small veins. Vascular bundles are

generally small.

5. Possess poorly developed or reduced vascular bundles, particularly the

xylem, as water is readily available

Leaves with Xeromorphic features

1. Leaves with high volume / surface ratio (i.e. small and compact)

2. Palisade mesophyll strongly developed

3. Small intercellular spaces in mesophyll

What is this? What’s the function? What is it a sign of?

Hypodermis, made of collenchyma cells, Xeromorphic

Leaf structure in Pinus

1. Needles from short shoots in groups (fascicles); may be one or

several per fascicle.

2. Shape is either round or triangular.

3. Epidermis thick-walled, with a heavy cuticle, sunken stomata,

overarching subsidiary cells (Figure 7.8 in Esau). Stomata on all sides,

in rows.

4. Sclerified hypodermis below the epidermis

6. No palisade parenchyma - only spongy parenchyma.

7. Resin ducts (or canals). secreting antiseptic, aromatic, and sticky

resin to seal wounds, prevent fungal infections, and deter insects.

prevents freezing, and helps absorb heat.

8. Vascular bundles may be one or two side by side. Xylem consists

of protoxylem and metaxylem as well as xylem parenchyma

alternating with tracheids. The phloem appears in regular vertical

stacks.

9. Vascular bundles surrounded by transfusion tissue composed of

tracheids and parenchyma.

10. Vascular bundle and transfusion tissue surrounded by a thick-

walled endodermis with Casparian strip

Difference Between Sun and Shade leaves

Sun leaves (left) are often thicker, with a smaller blade

area and more developed palisade layer (shown left)

• Shade leaves (right) are generally larger, longer, wider with

a thinner palisade layer. They increase surface area to

capture light.

What is guttation?

At night-in some small plants roots continue to

take up water; as the water accumulates in the

leaf pressure builds and forces water out of

wide stomata called water pores (arrows). These

stomata are open-don’t close.

The process of secreting excess water is called

guttation. Typically see it in the morning and

only in small plants

All the Leaf Modifications

1. Asexual reproduction – produce clonal “plantlets”; genetically identical to

parent

2. Spines - Leaves are reduced to sharp structures to reduce water loss and defend

against herbivores, common in cacti

3. Tendrils - Thread-like structures that allow weak-stemmed plants to climb and

gain support, found in peas

Leaf Modification

4. Storage Organs - Water and Food Storage storage. Fleshy, succulent leaves that

store water or food, seen in onion, garlic, and Aloe.

Leaf Modification

5. Insect Traps - Specialized traps for capturing insects to overcome nitrogen

deficiency in soil, such as the pitcher plant, bladderwort, Venus flytrap.

How do Bladderworts work?

possess highly specialized leaves that function as

sophisticated, vacuum-powered, aquatic traps (bladders) to catch, digest, and absorb

nutrients from tiny prey.

How does Drosera (sundew) leaf work?

sticky trichomes that release volatiles to attract and

trap insects

• Once trapped leaves release digestive enzymes to absorb nutrients

What the shiz is this?

Glandular hair, traps insects

How does Darlingtonia (pitcher plant) pitcher work?

pitcher plant is lined with a slippery wax.

Insects crawling on the lip slip and fall into a pool of water in the bottom of the

pitcher, where they are digested by bacteria. The plant then absorbs the smaller

molecules.

Two Processes of Photosynthesis

1) Light reactions:

• Light absorption by chlorophyll is able to

hydrolyze water into protons, electrons &

oxygen (2H20 → 4e- + 4H+ + 02)

• Electron transport thru a series of distinct

carriers results in the synthesis of ATP and

NADPH

2) Calvin Cycle (aka dark reactions)

• ATP and NADPH is used to reduce C02 to

CH20 (carbon dioxide is converted into

sugars/food for the plant)

Light Reactions

1) light absorption by chlorophyll is able to hydrolyze water & 2)

electron transport of the electrons results in the synthesis of NADPH & ATP

The Calvin Cycle (aka the dark reactions):

Uses the ATP and NADPH made in light reactions to reduce CO2 to

carbohydrate (CH20)

• Occurs primarily within chlorenchyma tissue in the stroma of chloroplasts

• The C-H bonds produced provides almost all of the energy for life on earth

Calvin Cycle: three distinct processes

Carboxylation, Reduction, Regeneration

Carboxylation

1. Carboxylation (“fixation”) Phase:

• CO2 is added to a 5-carbon sugar called RuBP (ribulose 1,5-bisphosphate)

• RuBisCO (RuBP carboxylase/oxygenase) catalyzes the reaction.

• The 6-carbon molecule is unstable and quickly splits into two 3-carbon

molecules: 3-phosphoglycerate (3PG)

In C3 plants the first stable product produced is this 3-carbon substrate

(3-phosphoglycerate).

Reduction Phase:

the products of the light rxs are used to reduce C02 to carbohydrate

• ATP phosphorylates 3-phosphoglycerate (3PG) to form 1,3 bisphosphoglycerate (1,3 bPG)

• NADPH will reduce 1,3 bPG to Glyceraldehyde 3-phosphate (G3P)

• Glyceraldehyde 3-phosphate is THE SUGAR that is made during the Calvin Cycle

RuBisCO can bind to

O2 as well of CO2

• RuBisCO can bind CO2 (functions as a carboyxylase)

• RuBisCO can also bind O2 (functions as an oxygenase)

• RuBisCO binding to oxygen is known as photorespiration

Unstable 5C 2C + 3C (glyceraldehyde 3-phosphate)

re-used in Calvin Cycle – but it will take

some extra energy to return it to the

Calvin Cycle

photorespiration)

Two 2C molecules combine to reform a 3C sugar while one C is oxidized

to CO2 (i.e. photorespiration)

Under normal spring temp, RubisCo will

bind to 1 02 for

every 2 C02 bound

Under warm, dry conditions – the pore of the stomatal complex

becomes

smaller to limit water loss-but it also doesn’t allow C02 to enter the leaf

• In addition 02 levels increase inside the leaf due to photosynthesis

H20

Guard cell closure leads to

increased oxygen levels within leaf

and decreased CO2 concentrations.

This leads to increased

photorespiration

Conifer phloem

Simple, less variable than dicot secondary phloem.

Variety of cells including: Sieve Cells with associated Rays

Parenchyma cells singly or in strands

Albuminous cells at ends of rays

Fibers and sclereids may be present

Stems are extremely varied in plants, with many modifications.

Aspects that affect this variation include:

1. leaf arrangement (around the stem)

2. leaf insertion (angle, position, attachment)

3. presence of axillary buds

4. where (at what level) does branching occur

5. is the shoot vertical or horizontal, free-standing or climbing,

etc.

6. where does the shoot system grow? (above ground,

underground, in water)

two leaves arise at a single node in the same vertical

plane but in opposite directions.

Phyllotaxy: • If successive pairs of leaves are parallel it is termed Superposed,

• if successive pairs of leaves are at right angles it is termed

Decussate.

single leaves arise at each node in an

alternating manner.

• Alternate: A single plane where they appear to go from side

to side (Distichous), or a

• Spiral where the leaves are arranged around the stem. Leaves

arise at repetitions of an angles until one eventually arises over

the first.

three or more leaves arise at a node and radiate in

different directions

Whorled

Vegetative SAM produces

stems (nodes, internodes), leaves,

axillary buds

Reproductive SAM produces

flowers

SAM locations:

1. Terminal bud-end of primary shoot

2. Axillary buds in the axils of the leaf

petiole/stem

• Will produce lateral branches with

their own terminal bud.

• Will produce leaves with their

own apical meristems

Shoot apical meristems: are protected by the newest formed leaves

(leaf primordia)

Arise initially as small “bumps” (leaf buttresses) along the meristem

and then grow into leaf primordia that surround the meristem

(leaf buttresses), Their development will reflect the phyllotaxy you see in the plant

What is this and what type of organization is it and what does it do?

1. Apical Meristem with a single Apical Cell (ferns, mosses)

• a prominent, single tetrahedral (four-sided) pyramidal cell

located at the shoot apex

• serves as the main site of cell division

What is this and what type of organization is it and what does it do?

2. Apical Meristem with a Conspicuous Cyto-Histological Zonation

• Produce zones rather of cell division (rather than layers)

• Surface meristem has occasional periclinal divisions and

contribute cells to the central mother cells (arrow). Since the

Tunica does not-this is one way to tell the two meristems apart

CMC: central mother cells. Don’t

divide as often as other cells in apical

meristem. Often larger and more

vacuolate.

RM: Pith (rib) Meristem: produces pith

PM: Peripheral Meristem:

produces cortex, leaf primordia,

vascular tissues, sometimes the outer

part of the pith

SAM in Pine

SM: Surface Meristem

What is this, what type of organization is it, what is the function

Tunica (L1, L2): Comprises the

peripheral outer layer(s) that divide

perpendicular to the meristem

surface (anticlinal divisions). This

increases surface area, allowing for

surface expansion. L1 typically

forms the epidermis, while L2

contributes to subepidermal tissues.

Corpus (L3 and below): Located

beneath the tunica, this mass of cells

divides in multiple planes (periclinal,

anticlinal), increasing the volume

and bulk of the shoot. Look for the

periclinal divisions to help you

identify the corpus

This slide is looking at which part of the plant? Which belongs to which class of plant?

red is dicot, blue is monocot

Phloem to the outside of the xylem (“typical”)

Collateral:

phloem to the inside and to the outside of xylem

• Result of two cambia!

Bicollateral:

xylem is concentric and surrounds phloem

Concentric, Amphivasal

phloem is concentric and surrounds xylem

Concentric, Amhicribral:

Anomalous Growth

Anomalous Growth are deviations from the normal, predictable

pattern of development in plants

• often resulting from irregular cambial activity, accessory cambia,

or unusual vascular bundle arrangements

Example: Cucurbita:

• No interfasicular cambium

produced

• Isolated phloem strands inside

of the perivascular fibers

• Bicollatoral bundles

Example of anomalous growth:

Aristolochia & Clemaatis produce

medullary rays (during secondary growth-the bundles look like they

are being maintained)

• secondary parenchyma is produced from the vascular cambium that

formed between the original bundles.

Stems as storage organs:

2. Storage Organ: store excess carbohydrate-numerous kinds

a. Rhizomes: horizontal stem just under soil

• Daffodils, lillies, ginger

Stems as tubers

enlarged end of a rhizome

Stems as bulbs

vertical underground shoot

• lots of enlarged leaves that

store carbohydrates/food;

• i.e. onions, garlic

Stems as water storage

Water Storage-organs are often adapted for

dry habitat (xerophytic)

• Adaptions include: photosynthetic stem with

chlorenchyma, often with sunken stomata,

thick cuticle, cells that store water, Reduced

Surface Area to minimize transpiration,

stems may be cylindrical, spherical, or

reduced in length

• Leaves are modified (spines)

What are the adaptations seen in aquatic

plant stems (hydrophytic environment)?

Adaptations provide buoyancy,

flexibility, gas exchange, direct nutrient

absorption

• aerenchyma (spongy, air-filled tissue)

for flotation, light weight

• reduced, structures for direct nutrient

absorption-structure maximizes contact

with water

• lack the need for rigid support or

extensive, woody vascular systems.

Monocots do not have true ”secondary growth” since they don’t have

vascular or cork cambia.

They do however unique meristems that increase their width

1. Primary Thickening Meristem – occurs close to shoot apex

2. Secondary Thickening Meristem – occurs in area of plant

where cell elongation has stopped.

• It can be continuous with primary thickening meristem

Primary Thickening Meristem

occurs close to shoot apex

• Occurs primarily in short compact plants; often immediately &

greatly increases the width of the apex

• Diffuse primary meristem, narrow zone of meristematic cells with

radial derivatives

• Produces lots of parenchyma towards the inside; may produce

vascular bundles

Secondary Thickening Meristem

occurs in area of

plant where cell elongation has stopped.

• Arises in the cortex-produces radial derivatives

• Produces “secondary” vascular bundles that are

often amphivasal (xylem surrounds phloem) to

the inside and parenchyma to the outside

Intercalary meristems:

Specialized region in monocot stems

• Small undifferentiated cells at the base of some internodes (or

above a node)

• Cells retain capacity for cell elongation

• Particularly important when plant is dislodged (falls over)

• Stem senses gravity and elongates the cells on bottom side of

stem so shoot rights itself.

Fusiform initials

Elongated to isodiametric in shape, fusiform = spindle shaped, really

prismatic, wedge-shaped ends.

• rectangular in radial section, fusiform shape in tangential section,

smaller rectangle in transverse (cross) section.

Cell divisions

1) Ain angiosperms, cambial initials are usually bifacial, which means they

produce cells off of two sides.

• They divide periclinally to produce xylem to the inside and phloem to

the outside, sometimes alternating.

• Also called additive divisions

Cell divisions

2) To keep up with the increasing girth of the plant a fusiform initial must

produce more of themselves

• Divisions that add to the cambial cells are called multiplicative

divisions

3. Radial anticlinal divisions gives more vascular cambium cells that are

arranged in stacks, gives rise to storied wood (considered an advanced

condition). The oblique divisions result in non-storied wood, no tiers of

cells.

Robinia- storied vascular cambium

Will produces a storied wood Pyrus- non storied vascular cambium

produces non storied wood

4. After the anticlinal cell divisions, the derivatives can enlarge tangentially,

elongate via apical intrusive growth (remember this type of growth with

fibers). Intrusive growth also causes forking and invasion of rays (Figure

10.5 H-L, Figure 10.6 C) which may result in the ray splitting.

Ray initials

Transverse divisions of the fusiform

initial results in several cells, only some

of which may survive and become ray

initials.

• Rays begin as a group of only 1-2 cells

but they increase in height through later

transverse divisions and by fusion with

other rays.

• To become multiseriate, radial anticlinal

divisions and fusions occur.

Robinia Vascular cambium

Initials may divide again before their derivative cell has matured, so a zone of

undifferentiated cells accumulates.

• Sometimes hard to distinguish between the fusiform initial and its

derivative, which is why some call the entire cambial zone the

"cambium".

produced by the cork cambium (phellogen)

Periderm

Relatively simple, rectangular, radially

flattened cells. Produce derivatives in radial files.

Phellogen = cork cambium.

Phellem

cork layer. Tissue that differentiates to the outside of

cork cambium variable in in shape. Lack intercellular spaces.

Nonliving but may have solid or liquid contents. In these photos,

tannins were deposited into the phellem cell vacuoles of Quercus

and Clusia.

a. Walls are suberized. Suberin and wax forms a lamellar layer on

top of primary wall (that may or may not be lignified).

b. Walls of Quercus suber (cork oak) phellem are thin, cells filled with

air, thus lightweight and insulating. Form a barrier that is

impervious to water and resistent to oil.

Cork cells

Quercus suber

c. May also have phelloid cells – non-suberized, may become

sclereids.

• Layering of cork and sclerified cells can also occur in seasonal

increments (layers). Similar phenomenon in this cactus

(Oreocereus celsianus) root.

Phelloderm

living parenchyma that differentiates to the

inside of the cork cambium. Usually 1-4 cell layers thick, if

present at all

Cork cambium (phellogen) typically produces less

phelloderm (parenchyma) than phellum (cork)

Development of Periderm

A. Typically - the first periderm develops in the outside portion of the

cortex in stems and roots.

• Often directly under the epidermis but sometimes a bit deeper.

• The phellogen can derive from various different living, potentially

meristematic cells, e.g. epidermis, subepidermal parenchyma or

collenchyma, pericycle (roots), phloem and phloem rays.

B. The first cork cambium often forms at the same time or after the

vascular cambium (first year).

C. Later (sequent) periderms are initiated deeper, either the same

year or many years later

Sequential periderms

1. Forms each year and in successively deeper

layers beneath the first.

2. Originate from parenchyma cells of secondary

phloem and ray cells, which on the outside is

no longer functional.

3. The first phellogen may form in isolated areas

that later become contiguous by lateral

spread and meristematic activity.

• Most cell divisions are periclinal but

anticlinal divisions are involved in the

phellogen keeping pace with the stem’s

increase in circumference.

4. Sequent periderms appear as discontinuous

but overlapping layers (Figure 12.4, 12.7B for

Quercus).

Rhytidome

is the technical term for the outer, dead layer of

bark on trees and woody plants.

• It is primarily composed of dead, suberized cork cells,

cortical tissue, and phloem formed by successive

periderms.

• This protective, often cracked outer layer insulates the tree,

prevents water loss, and shields it from insects and disease

Rhytidome

The outermost bark. Layers of tissue isolated by the

periderm and layers of the non growing periderm.

2. When periderm arises in successively deeper tissue,

accumulation of old periderms have a variety of tissues (cortex,

1 ̊ phloem, 2 ̊ phloem). All of these tissues are no longer

functional – just a barrier to movement of water and gases

3. Eventually the new periderms will arise from living cells within

the secondary phloem

Key Aspects of Rhytidome:

Structure: It consists of multiple layers of dead tissue that

accumulate over time.

• Formation: It is produced by the phellogen (cork cambium).

• Function: It protects the inner, living bark (phloem).

• Appearance: Often rough and fissured, it varies in thickness

from thin (e.g., birch) to very thick (e.g., redwoods).

• Separation: Unlike the inner, living bark, the rhytidome can be

shed, as seen in trees like sycamores or birches.

What is Bark and what is it composed of?

all the tissues outside the

vascular cambium, i.e. secondary

phloem, any primary tissues that are

still there, periderm, and dead tissue

outside the periderm.

Composed of an inner living part and

an outer dead part (rhytidome)

What the shiz is the green and red? What are they doing?

Lenticels in green,

companion cells in red

First appear under stomata (in the stem) Nwhere phellogen is more

active.

• Phellogen is bent downward, and in this “cup” is produced loose

cells called filling (complementary) tissue.

• The outer layers of the lenticel are pushed and the whole structure

ruptures the surface.

As subsequent cork cambia form deeper inside the stem,

they will

form lenticels in the same region as the pre-existing lenticels –

there will be an oxygen diffusion pathway through all layers.

Crassulacian Acid Metabolism:

in cacti, • Primary function of CAM metabolism

is to limit water loss and survive!

• Characterized by an inverted guard

cell cycle (open at night/closed during

the day

• Make 4-carbon acids (with PEP

carboxylase) at night and store them

in vacuole

• IN the morning; Decarboxylate the 4-

carbon acid and use C02 for

photosynthesis (when the light

reactions can make ATP/NADPH)

• GC don’t need to be open-ready

supply of C02

General Functions of Root System

Absorption of water and minerals from

substrate.

• Storage of photosynthates.

• Anchorage of the plant to the soil.

• Control and distribute the the flow of

water throughout the plant.

Tap Roots

The primary root originates from the radicle (embryonic

root) of an embryo and gives rise to the taproot.

• One central root with smaller lateral roots branching off of the main

root.

• Generally, penetrate deeper in the soil for anchorage

• Common in Dicots and Gymnosperms.

Fibrous Roots

Embryonic root dies and all roots arise from base of shoot

• A type of Adventitious root

• Adventitious-arise in unusual place

• What makes them a root and not a leaf is their anatomy!

• Anchorage is shallow but more laterally extensive than tap roots

• Common root system in Monocots

The root cap

protects the meristem and is the site for gravity perception

• Statoliths (starch dense amyloplasts) sediment to new lower wall when

plant is reoriented-this change in pressure redirects growth

• Remove the root cap-roots unable to perceive gravity

stele)

Vascular tissues occur as a solid cylinder in the center (aka stele)

• xylem is “armed” – phloem between arms

Vascular Tissues in Dicots vs Monocots

“many arms in monocots

Central core of parenchyma is

also present in the center of the

stele