Leaves

Leaves

• constitutes the shoot of the plant body

• principal function is to act as the main site of photosynthesis in a plant

epidermis

outermost layer of cells

Epidermal Cells

secrete a waxy substance that forms a covering over the outer dermal cells rendering these cells impermeable to water

Cuticle

waxy covering in a leaf

dorsiventral

There is an upper epidermis and a lower epidermis in a leaf with ________ orientation.

Stomates

openings in the epidermis

guard cells

The stomates are formed in between specialized epidermal cells called

trichomes (hairs)

found on the undersurface of the leaves and herbaceous stems

help reduce the evaporation of water from plants or protect young shoots from herbivores

Function of trichomes (hairs) in leaves

mesophyll tissue

comprises all of the cells between the upper and lower epidermis and is usually divided into two parts

vascular bundles

The mesophyll tissue comprises all of the cells between the upper and lower epidermis except…

palisade layer

cells toward the upper epidermis, which are elongated, make up the

spongy layer

zone below the palisade layer, composed of irregularly shaped cells

Inter-cellular air spaces

What is found between mesophyll cells?

isobilateral

In some monocots, there are no distinct palisade and spongy layers because the leaves are _______

True

True or False

All the parenchyma cells with chloroplast between the upper and lower epidermis comprise the mesophyll layer.

supporting and conducting tissue

Function of vascular bundles

xylem and phloem

What is the vascular bundle composed of?

Vein

collective name for the conducting tissues that are surrounded by vascular bundle sheath cells

shoot apical meristem

Where is the leaf derived from?

Blade

The leaf consists of a flattened laminar portion called

Petiole

stalk of the leaf that is attached to the blade of the stem

sessile

If the blade is attached directly to the stem, the leaf is described as what?

Apical or lateral bud

Where do leaves arise from in dicots?

bud scales

In dicots, leaves arise from an apical or lateral bud that is often protected by _______

Stipules

small leaf-like structures that develop in pairs on each side of the leaf during the growing season.

Twigs

What can some plants have that is similar to stipules?

Narrow

What is the usual shape of the blade in monocots?

Sheath

What is the base of a monocot leaf that wholly or partly encloses the stem

auricles and ligules

appendages between the blade and sheath of monocots

True

True or False

There is usually a persistent meristem at the base of the leaf that allows it to grow indefinitely.

Veins

The blade and lamina of a leaf is line with what?

midrib

middle portion of the blade usually has a prominent central vein

netted

venation of dicots

parallel

venation of monocots

margin

edge of a blade

apex

leaf tip

leaf base

part near the petiole

simple and compound

types of leaves

simple leaf

has a single blade or lamina, opposite arrangement, petiole or leaf stalk, axillary buds or growth node, and pulvirus or swelling

compound leaf

composed of two or more separate leaflets.

pinnately compound and palmately compound

subtypes of compound leaf

pinnately compound leaf,

leaflets occur in a linear sequence lined up along both sides of a central axis

rachis

sides of a central axis in leaves

palmately compound leaf

one in which three, five, seven or more leaflets are all attached at one point near the tip of the petiole and they radiate out from this ti

False

True or False

The branch will have a terminal bud and a compound leaf will also have a terminal branch.

Phyllotaxy

Leaf arrangement

alternate or spiral arrangement

one leaf occurs at each node

distichous

A variation of alternate is _______ in which the leaves occur only on two rows.

opposite arrangement

two leaves at a node facing each other.

decussate

A variation of opposite is _______ in which two opposite leaves are perpendicular to the two opposite leaves below or above them.

whorled arrangement

has three or more leaves at one node.

Leaf Attachment

how a leaf connects to the stem of a plant

Reproductive

• Modified leaves where plantlets are produced along the margins of its leaves.

• New plants fall off and become separate from the main plant

Asexual reproduction

Is this asexual or sexual reproduction

• Modified leaves where plantlets are produced along the margins of its leaves.

• New plants fall off and become separate from the main plant

False

True or False

New plants of modified leaves under reproduction are different from the mother plant

Storage

Modified leaves that function to store water and/or nutrients for the plant

Tendrils

modified leaves used for climbing or support.

Carnivorous

These type of leaves have evolved due to low nutrient availability in the soil where it grows, so plants with these leaves are able to gather nitrogen and other nutrients from the bodies of the insects they trap

Sundrews (Drosera sp.)

Example of a carnivorous modified leaf where its glands secrete mucilage used for trapping insects

Spines

• A sharp-pointed , hardened structure derived from leaf or stipule 

• used for protection against herbivores. 

• They have also evolved as a water-saving strategy in some plants.

Axillary buds

• develop at the axils of leaves

• bring forth more leaves and branches (vegetative shoots) as well as flowers (reproductive shoots).

Lower part of the plant since new leaves grow upwards

Where would you find older leaves on a stem, near the tip or near the lower part?

orderly

Is the formation of leaf primordia and stem tissues orderly or random?

Monocot leaf

What kind of leaf is this?

Dicot leaf

What kind of leaf is this?

scaly leaves

what is the modified leaf of onions and garlic?

colored bracts

what is the modified leaf of poinsettia?

carnivorous

what is the modified leaf of the pitcher plant?

reproductive

what is the modified leaf of kalanchoe?

phylloclade

what is the modified leaf of cacti?

cotyledon

what is the modified leaf of bean seeds?

aquatic

what is the modified leaf of Hydrilla?

epiphyte

what is the modified leaves of ficus/balete?

thorns

what is the modified leaves of roses?

tendrils

what is the modified leaves in squash?

for light absorption in photosynthesis

Why are the blades of most leaves flat?

they are attached directly to the stem without a petiole

What is the counterpart of the petiole of the dicot leaf in monocots?

allows the upper epidermis to properly face the sun

How does the petiole aid in the photosynthetic function of the leaves?

big or broad-leaved species

Which leaf shape predominates in rainy regions?

smaller leaf shapes

Which leaf shape predominates in dry regions?  Why?

Bulliform cells

facilitate the curling of the leaf to reduce evaporation process and avoid excessive water loss, especially in extremely high temperatures

Adaxial portion

Where can you find bulliform cells?

Chlorenchyma

What is the type of parenchyma cells for the palisade layer?

aerenchyma

What is the type of parenchyma cells for the spongy layer?

Humid conditions because there is more water for the plants to utilize in photosynthesis

which has higher stomata? dry or humid conditions?

Present on the lowerside only of the leaf, away from direct sunlight

what is the position of the stomata during dry conditions?

Present on both lowerside and upperside of the leaf

what is the position of the stomata during humid conditions?

Smaller and almost closed to conserve water

what is the size of the stomata during dry conditions?

Larger and open since there is less risk of water loss

what is the size of the stomata during humid conditions?

amphistomatic

what do you call leaves with equal amounts of stomata on the upper and lower side of the leaf

Bulliform cells

What is present in monocots that cannot be seen in dicots?