10: Leaf

store water

succulent modified stem function

for climbing

tendrils

to deter herbivores + reduce water loss

function of thorns/spikes

- Blade or lamina

- Apex, Base, Margin

- Veins (vascular bundles)

- Petiole (Stalk)

- Stipules

leaves external anatomy

expanded petiole in monocots bc they have no stalk

leaf sheath definition

phyllotaxy

arrangement of leaves on a stem

opposite

phyllotaxy if 2 leaves on a node

alternate

phyllotaxy if 1 leaf on a node

whorled

phyllotaxy if multiple leaves on a node

basal

phyllotaxy if leaves are nasa baba

Decussate

special type of opposite phyllotaxy; 2 pairs of leaves 90 degrees to each other

undivided blade with a single axillary bud at the base of its petiole

simple leaf definition

pinnately-compound leaves

- leaflets in pairs

- rachis

extension of the petiole in pinnately-compound leaves

rachis definition

palmately-compound leaves

no rachis, leaflets attached at the same point at the end of the petiole

always at base of leaf (above the petiole)

location of axillary bud

only primary growth

type of growth of leaves

arrangement of tissues dictated by the physical environment (e.g. water availability, light intensity, ecological niche and herbivores)

how are leaves the most plastic/variable organs

1. Epidermis

2. Mesophyll

3. Vascular tissues

internal parts of leaf lamina

adaxial

closer to the internode above it; faces upward

Abaxial

faces downward

xeromorphic plants; modified structure when water is limited

saan common ang multiple epidermis

if all true epi, origin is protoderm

if may part of hypodermis (part of mesophyll) galing ground meristem

origins of multiple epidermis

- cuticle (hydrophobic)

- stomata (bc no intercellular spaces)

- trichomes (deters herbivory + reduces water loss)

features/parts of epidermis

parenchymatous ground tissues specialized for photosynthesis

mesophyll definition

Chlorenchyma

Parenchyma cells containing chloroplasts

Elongated; rod shaped in xs

Arranged in rows

Immediately below the epidermis (uni- or multi-seriate)

On adaxial surface

palisade mesophyll definition

Presence of lobes

Larger volume of intercellular spaces

spongy mesophyll definition

- Majority of the chloroplasts are found in palisade

- intercellular spaces for rapid gas exchange

- external (epidermal) and internal (mesophyll) surface area

reasons for photosynthetic efficiency

Dorsiventral or bifacial

Type of mesophyll in which the palisade is on one side and spongy mesophyll is on the other side

Isobilateral or isolateral or unifacial

Palisade present on both sides (Ficus)

Eudicot leaf - palisade developed

Monocot leaf - uniform

monocot vs eudicot mesophyll

Convergent or uniform

Mesophyll cells look the same; no distinct palisade and spongy parenchyma (Pinus)

- Vascular bundles or + assoc. non vascular tissues that surround it

- Usually have bundle sheath (parenchymatous)

veins definition

monocot

Vascular Bundles of similar dimensions

dicot

have a large central Vascular Bundle called a Midrib

C3 plants (normal photosynthesis)

where are bundle sheaths inconspicuous

C4 plants bc they store CO2 in bundle sheaths where calvin cycle happens

where are bundle sheaths enlarged

leaf - x outer, p inner

stem - x inner, p outer

leaf vs stem xy and phlo

venation

arrangement of veins in a leaf

common to eudicots and some nonflowering plants

where can u find netted venation (pinnately and palmately)

monocots

where can u find parallel venation

- epidermis

- Collenchyma close to the larger veins

- vascular bundles with fibers in monocots

- Sclereids in aqua plants

4 supporting tissues of the leaf

- Epidermis continuous with stem

- Parenchyma contains a few chloroplasts

- collenchyma and sclerenchyma

- Collateral vascular bundle

petiole description: type of ground tissue present? vascular bundle type?

v large vacuole to fold up + reduce water loss

bulliform/motor cells function

- Grow in arid habitats

- Decreased transpiration under conditions of water deficiency

xerophytes definition

- small + narrow leaves to lessen water loss

- Thick walls w cuticle and sclerenchyma

external specializations of xeromorphic plants

- multiseriate epidermis

- stomatal crypts

- abundant trichomes

- tendency to be isobilateral

- Involution of leaves through bulliform cells

5 internal specializations of xeromorphic plants

hide the stomata, invaginations in lower epi + maraming 3chomes

stomatal crypts definition

gymnosperms

examples ng xeromorphic

- consists of tracheids and elongated parenchyma cells

- characteristic of gymnosperms

- passage of water and nutrient substances between the bundle and the mesophyll

Transfusion tissue consists of what and its function

- Thick wall and thick cuticle

- Stomata are sunken and overarched by subsidiary cells

- Hypodermis

- Mesophyll walls have ridge-like invaginations into the cells; contain chloroplasts

- Transfusion tissue

- Endodermis

features of pinus leaves

- Epidermal cell thick walled and thick cuticle

- Stomata are sunken and abaxial surface

- Hypodermis

- Vein surrounded by endodermis

features of cycas leaves

- Reduction of supporting (water supports) and protective tissues

- Decrease vascular tissue esp xylem

- Presence of air chambers for filtration

- very thin cuticle

- Aerenchyma

5 features of hydrophytes

Epistomatic (floating)

hydrophytes stomata

very reduced

hydrophytes root system

- periclinal

- sides of the apex/peripheral zone

- come from apical meristem

leaf initiation

Protrusion in the peripheral zone that will turn into leaf primordia

leaf buttress definition

at sites that are correlated with the phyllotaxis of the shoot

where do leaf primordia arise

1. Photosynthesis
2. Transport
3. Transpiration
4. Modified Functions

Functions of Leaves

blade or lamina

the flattened, green, expanded portion of a leaf

Apex, Base, Margin

Sections of leaf

Veins

The vascular bundles of the leaf traversing because of the thin surface

petiole

The stalk of a leaf, which joins the leaf to a node of the stem.

Stipules

a pair of leaf like appendages at the base of the petiole that protect the developing bud

leaf sheath

the base of a leaf that wraps around the stem; typical in grasses and some other monocots; no stalk and an expanded petiole

phyllotaxy

arrangement of leaves on a stem

blade divided into leaflets

compound leaf defimition

True

Leaflets lack an axillary bud but each compound leaf has a single bud at the base of its petiole (True or False)

Rachis

extension of the petiole in which several leaves are attached

False, above petiole

Axillary bud is always at base of leaf below the petiole (True or False)

True

Leaves generally have primary growth (True or False)

True

The arrangement of tissues is dictated by the physical environment such as water availability, light intensity, ecological niche, and herbivores (True or False)

Epidermis, Mesophyll, Vascular Tissues

Three main components of the leaf lamina

adaxial epidermis

This leaf layer is generally protective and contains trichomes, cuticle, epidermal cells and sometimes stomata. It is closer to the internode above it.

abaxial epidermis

lower epidermis

Protoderm

Origin of true epidermis

Ground Meristem

Origin of hypodermis (a part of mesophyll)

True

Epidermis has cuticle and is devoid of intercellular spaces (True or False)

Stomata

Openings of the epidermis for photosynthesis

Trichomes

Tiny, spike-like projections on some leaves for protection

mesophyll

The ground tissue of a leaf, sandwiched between the upper and lower epidermis and specialized for photosynthesis.

True

Mesophyll is parenchymatous !!!! (True or False)

palisade mesophyll

Layer of tall, column-shaped mesophyll cells just under the upper epidermis of a leaf

spongy mesophyll

Loose tissue beneath the palisade layer of a leaf; has many air spaces between its cells

Chlorenchyma

Parenchyma cells containing chloroplasts that function in photosynthesis

palisade parenchyma

elongated photosynthetic cells; rod shaped in cross section that are arranged in rows

Spongy parenchyma

Presence of lobes and larger volume of intercellular spaces

1. Majority of the chloroplasts are found in palisade
2. Palisade mesophyll are located at the adaxial portion
3. Well-developed intercellular spaces for rapid gas exchange

What are the reasons for increase in photosynthetic efficiency?

Convergent/Uniform

In monocot and gymnosperms, what is the common type of mesophyll?

Veins (Leaf)

Vascular bundles or associated non-vascular tissues that surround it.

Midrib vein

single large vein of the leaf

True

Monocots have similar dimensions for veins (True or False)

bundle sheath

A protective covering around a leaf vein, consisting of one or more cell layers, usually parenchyma.

True

In C3 plants, bundle sheath is inconspicuous (True or False)

C3 plants

A plant that uses the Calvin cycle for the initial steps that incorporate CO2 into organic material, forming a three-carbon compound as the first stable intermediate. (mesophyll)

perform calvin cycle in their bundle sheath

C4 plants differ from C3 and CAM plants in that C4 plants _____.

True, photorespiration

In C4 plants like corn, they have specialized structure called bundle sheath where they store carbon dioxide in which it happens to combat what?

True

Larger bundles usually lack bundle sheath or they have sclerenchymatous sheath (True or False)

parallel venation

a parallel arrangement of veins; typical of the leaves of monocots