Bio 154- botany exam 2

Abaxial

Bottom surface

Epidermis

Single layer of cells covering the entire surface of leaf.

Devoid of chloroplasts.

Protects the leaf from pathogens and physical damage

Coated with waxy cuticle (cutin) that prevents dessication

Cutin

Waxy coating that protects leaves epidermis

Mesophyll

Ground tissue of the leaf between the two epidermal layers. Most photosynthesis takes place here

Adaxial

Top surface

Palisade mesophyll

Compactly stacked, barrel-shaped parenchyma cells, commonly in two rows.

Contains most of the leafs chloroplasts

Sponges mesophylls

Loosely arranged parenchyma cells w/ abundant air spaces for gas exchange

Veins

Vascular tissue spread throughout mesophyll

Sclerenchyma/ collenchyma primarily present

Prominent bundle sheath

Shade leaves

Leaves that receive less light

Tend to be larger And thinner

Have few well defined mesophyll layers and less chloroplasts

Simple leaves

Single, non-divided blades

Compound leaves

Divided into leaflets. Attached to the central rachis (petiole)

Pinnate leaf

Compound leaf that is divided into smaller leaflets in pairs along petiole. Can be even or odd

Palmate leaf

All leaflets attach at the Salem point at the END of the petiole

Phyllotaxy

Arrangement of mature leaves on a stem

Alternate

One leaf per node

Opposite

2 leaves per node

Whorled

3 or more leaves at a node

Microphylls

Leaves w/single vein

Megaphylls

Leaves w/a highly branched vascular system

Petiole

Stalk that attaches leaf to stem

Sessile

No petiole

Peltate

Petioles attach to center of blade (water lily)

Netted/ reticulate venation

Veinlets form a reticulum or network

Common in dicots

Etiolation

Lack of light causing long weak stems; smaller leaves due to longer internodes. White structure

Photoperiodism

The amount of daylight or darkness needed for plants to grow, bloom, or change color

Mesophyte

“Typical” plant

Xerophyte

Drought tolerant Plants w/ small thick leaves.

Succulents

Numerous stomata w/ trachomas. Lots of sclerenchyma & photosynthetic stem

Hydrophytes

Plants w/large thin leaves

Thin cuticle/cell walls

Little xylem, & sclerenchyma

Has astrosclereids

Spines

Modified leaves w/reduced surface to prevent water loss & protect from herbivores.

Leaf tissue replaced w/ sclerenchyma

Photosynthesis occurs in stems

Tendrils

Blade of leaves or leaflets are reduced in size, allows plant to cling to other objects

Leaf abscission

Shedding of leaves by plant during cold weather

Abscission

Process by which leaves are shed. Occurs as a result of changes in the abscission zone near the base of a leafs petiole

Separation layer

Weakened cells; pectin in the middle lamella of the cells is broken down

Protective layer

Suberized cells; cells are coated and impregnated w/suberin

Phytomeres

Repeating units of leaf and bud

Primordia

An organ in its early stage of development

Leaf primordia

Lateral outgrowths from apical meristem

Bud primordia

Develop into lateral shoots (branches)

Apical bud

Responsible for apical dominance

Controlling effect of shoot apex

Controls plant growth in a vertical e direction

Inhibits lateral branching

Produces growth hormone auxin (IAA)

Intercalary meristem

Located in internode regions in some plants

Regenerates tissue

Parenchyma

Ground tissue of monocots

Cortex

Ground tissue of dicots

Between epidermis and vascular ring and is primarily made of parenchyma

Pith

Also ground tissue of dicots

Center of the stem made primarily of storage parenchyma and sometimes lignified cells and sometimes secretory cells

Leaf trace

Continuous strand of vascular tissue

Leaf trace gap

Break in vascular tissue

Terminal bud

Contains apical meristem found at the tip of a stem. It increases the length of a stem (IAA)

Node

Area of stem where leaves are attached

Internode

Stem region between nodes

Lateral bud

Also called axilary. Develops into a branch or flower

Bud scales

Help the bud survive harsh climate changes. When the bud opens in the spring, they fall off leaving a scar

Leaf scars

Scars marking the location of last seasons leaves

Vascular bundle scars

Found inside leaf scars

These scars mark the location of the vascular bundle that passed from the stem, through the petiole, and into the blade

Lenticles

Dot-like structures on stems that consist of loosely packed cells

Small spots on stem that allow for gas exchange

Vascular rays

Consists of parenchyma cells that function in lateral conduction of nutrients and water

Springwood

Large, thin-walled xylem cells produced when water is abundant

Summerwood

Smaller, thicker-walled xylem cells produced during the time of year when water is limited

Heartwood

As xylem ages it become plugged with resins and other wastes. This causes the xylem (wood) to become stained darker.

Non-functional xylem but does strengthen tree trunk

Sapwood

Xylem that is functioning and is closest to cambium

Lighter in color

Softwood

wood of conifers

No fibers or vessel elements

Hardwood

Wood of dicot trees

Resin canals

Tubelike canals scattered through xylem and other tissues

Lined w/ specialized cells that secrete resin

Rootstock

General term used for underground stems or shoots that will later develop into aerial shoots

Suckers

Like stolen, however it grows upward and above ground and gives rise to a leafy shoot or new plant (banana)

Cladodes

Flattened stems & leaf-like in appearance

Stems have center nodes bearing small scale-like leaves w/ axillary buds (asparagus)

Cladophylls

Photosynthetic stem that resembles a leaf

Flat in appearance and reduces water loss (cactus)

Thorn

A modified, hard, straight, sharp-pointed stem, occurs where a branch would normally develop

Serves as a protective structure

Scape

‘Naked’ or lacking vegetative leaves (naked ladies)

Caulescent

A plant w/ an above ground stem w/ all the leaves arising from all or some of the nodes on the above-ground stems

Aculescent

Plants that have photosynthetic leaves at ground level (yucca)

Arborescent

Tree like in appearance (cycad (palm))

Photosynthesis

Process that converts solar light energy into chemical energy

Wavelength

Distance between crests of waves

Determines the electromagnetic energy

Absorption spectrum

Describes the wavelengths that are absorbed or the light wavelengths that are harvested

Action spectrum

Describes the wavelengths that are actually drive photosynthesis

Spectrophotometer

Determines absorption spectrum

Chlorophyll A

Only pigment that directly participates in photosynthesis.

Absorbs mostly violet and red

Found in everything photosynthetic

Undergoes oxidation in photosynthesis

Calvin cycle

Makes sugars from CO2

Thylakoids

Flattened sacs w/ pigments

Means ‘coin like’

Inside chloroplasts

Grana

Stacks of thylakoids

Inside of chloroplasts

Stroma

Interior region of chloroplasts

Photo system II

Functions 1st but was found second.

Contains ‘special pair’ of chlorophyll A molecules. Called p680, which donate an e- to the e- transport system

Linear or noncyclic photophosphorylation

E- move from h2o to PSII, to PSI, to NADPH

Photosystem I (PSI)

Also has chlorophyll A as a part of its special pair of e-

In this system chlorophyll A best absorbs wavelengths at 700nm

Cyclic phosphorylation

E- cycle w/in PSI

Calvin-benson cycle

Enzyme mediated rxns that build sugars in the the stroma or inner spaces of chloroplasts

Light independent rxn

Carbon fixation

Extraction of carbon atoms from inorganic sources 9atmosphere) and incorporating them into and organic molecule

C3 photosynthesis

“Normal” photosynthesis

85% of plants perform this pathway

Risk of photorespiration

Occurs in mesophyll cells

C4 photosynthesis

Spatial separation 2 carbon fixation paths

No risk of photorespiration

Moved into bundle sheaths

On hot days stomata’s are closed

CAM

Temporal separation of 2 carbon fixation paths

No risk of photorespiration

Requires PEPC

Hormones

“To excite” organic substances produced in small amounts that regulate and coordinate metabolism, growth, and morphogenesis

Either promote or inhibit

Auxins

“To increase”

Most common naturally occurring homo one in plants (IAA)

Provides chemical signals that communicate information over long distances

Apical dominance

Cytokinins

“Cell movement”

Stimulate cell division - speeds up transition from G2 to mitosis

Delays aging of plant organs (keeps cut flowers green)

Ethylene

Only gaseous hormone

Needs O2. CO2 inhibits

Ripening of fruits, roots, shoots, and flowers

Abscission Acid (ABA)

Made from carotenoid pigments in mature roots and leaves

Causes stomata to close and moves K+ out of guard cells so H2O flows

Prevents premature seed germination

Gibberellin (GA)

Causes dwarf plants to grow tall

Cause hyperelongation of shoots by stimulating cell division and elongation. Elongation between internodes

Stimulates seed germination in cereal grasses; interaction w/ light and temp

Brassinosteroids

Help w/ growth and defense

Facilities developmental processes and normal plant growth

Help w/ chemical signals and defense production

Salicylic acid

Brassinosteroid

Signal in defense responses to plant pathogens

Used in pain relievers

Jasmonates

Brassinosteroid

Plant growth regulation and defense to pathogens

Anti cancer qualities

Polyamines

Brassinosteroid

Growth and development; mitosis and meiosis

Help w/sperm production