MODULE 4 LESSON 2: LEAVES Flashcards
What are the External structure of Leaves?
- BLADE or LAMINA
- PETIOLE or RACHIS
- STIPULES
- APEX
- MARGIN
- MIDRIB
- VEINS
EXTERNAL STRUCTURE
- All leaves originate as __________
- Immature leaf from the buds.
- The end of a plant (Apical meristems)
PRIMORDIA
EXTERNAL STRUCTURE
- Once it matures, each leaf would typically have a _______
- Broad portion of leaf
- It consists of Apex, Margin, Vein, Midrib, and Base
BLADE or LAMINA
EXTERNAL STRUCTURE
- Some leaves are attached to the plant stem by
- Thin stalk attached in the leaf to stem
PETIOLE (Rachis)
EXTERNAL STRUCTURE
- Leaves that do not have a petiole and are directly attached to the plant stem
SESSILE
EXTERNAL STRUCTURE
- Small green appendages usually found at the base of the petiole.
- Leaf like/ Thorn-like structures that are always present in the base
STIPULES
STIPULES TYPES
- SPONGY MESOPHYLL
- CUTICLE
- MESOPHYLL
EXTERNAL STRUCTURE
STIPULE TYPES:
- Where gas exchange takes place
SPONGY MESOPHYLLS
EXTERNAL STRUCTURE
STIPULE TYPES:
- It conserves water
- Epidermal cells secrete a waxy layer
CUTICLE
EXTERNAL STRUCTURE
PART OF THE BLADE:
- Most leaves have this, it travels the length of the leaf and the branches to each side to produce veins of vascular tissue
MIDRIB
EXTERNAL STRUCTURE
PART OF THE BLADE:
- This is the edge of a leaf
MARGIN
EXTERNAL STRUCTURE
PART OF THE BLADE:
- This is the tip of the leaf
APEX
EXTERNAL STRUCTURE
PART OF THE BLADE:
- Within each leaf, the vascular tissue forms _______
VEINS
EXTERNAL STRUCTURE
- The arrangement of veins in a leaf
VENATION PATTERN
This has parallel venation in which the veins runs in straight lines across the length of the leaf without converging.
MONOCOTS
The veins of the leaf have a net-like appearance, forming a pattern known as RETICULATE VENATION
DICOTS
- Complex organ composed of several tissues organized to optimize photosynthesis
- The solar energy and CO2 collectors of plants
- The principle structure, produced on stems, where photosynthesis takes place
- Some plants have become adapted for specialized functions
LEAF
INTERNAL STRUCTURE
TYPES OF EPIDERMIS
- This covers the upper surface
UPPER EPIDERMIS
INTERNAL STRUCTURE
TYPES OF EPIDERMIS
- This covers the lower surface
LOWER EPIDERMIS
INTERNAL STRUCTURE
- The upper epidermis of the leaves of certain grasses have large, thin-walled cells on both sides of the midvein
- These cells appear to be involved in the rolling or folding inward of the leaf during drought but when water is plentiful, they are Turgid (swollen with water) and the leaf is open
BULLIFORM CELLS
INTERNAL STRUCTURE
- The cuticle consists primarily of a waxy substance that varies in thickness in different plants, partly as a result of environmental conditions
CUTIN
INTERNAL STRUCTURE
- Openings in the surface of the leaf and stems for gas exchange
- Water vapor passes out through these holes
- Regulates the water entering
STOMA
INTERNAL STRUCTURE
- Two of these special cells surround each stoma and regulate the opening and closing of the stoma
- Changes the shape of each pair as it open and closes the stoma
- Usually the epidermal cells with chloroplasts
GUARD CELLS
INTERNAL STRUCTURE
- Photosynthetic ground tissue of the leaf that is sandwiched between the upper epidermis and the lower epidermis
- These are parenchyma cells packed with chloroplasts, and are loosely arranged with many air spaces between them that facilitate gas exchange
MESOPHYLL
INTERNAL STRUCTURE
TWO SUBLAYERS OF MESOPHYLL
PALISADE MESOPHYLL and SPONGY MESOPHYLL
INTERNAL STRUCTURE
TWO SUBLAYERS OF MESOPHYLL:
- Tall, tightly packed, and filled with chloroplasts for photosynthesis
-The upper epidermis, the columnar cells are stacked closely together in a layer
- Main site of photosynthesis in the leaf
PALISADE MESOPHYLL
INTERNAL STRUCTURE
TWO SUBLAYERS OF MESOPHYLL:
- Irregularly shaped, have large air spaces between them, and fewer chloroplasts
- The lower portion, the cells are more loosely and more irregularly arranged in a layer
- Also occurs photosynthesis but the Main function is to allow diffusion of gases, particularly CO2 throughout the leaf’s interior
SPONGY MESOPHYLL
INTERNAL STRUCTURE
- Leaf extend through the mesophyll
- Each veins contains two types of vascular tissue: Xylem and Phloem
VEIN or VASCULAR BUNDLES
INTERNAL STRUCTURE
TWO TYPES OF VASCULAR TISSUES:
- Conducts water and dissolved minerals upward
- Usually located on the upper side of a vein, toward the upper epidermis
XYLEM
INTERNAL STRUCTURE
TWO TYPES OF VASCULAR TISSUES:
- Conducts dissolved sugars throughout the plant
- Usually confined to the lower side of the vein
PHLOEM
INTERNAL STRUCTURE
- One or more layers of non-vascular cells surrounds the larger veins and make up the outer
BUNDLE SHEATH
LEAF FUNCTIONS
- PHOTOSYNTHESIS
- TRANSPIRATION
- RESPIRATION
- GUTTATION
LEAF FUNCTIONS
- This is the most important function of a leaf.
- The prepared food is transported to the other parts of the plant via Phloem tissue
- Takes carbon dioxide + H2O = Converts to sugar (food)
- Some sugar are used as Starches
- By product is Oxygen
- Produces energy
PHOTOSYNTHESIS
LEAF FUNCTIONS
PHOTOSYNTHESIS
- The pigment of chlorophyll that is responsible for helping in photosynthesis
CHLOROPLAST
LEAF FUNCTIONS
PHOTOSYNTHESIS
- The epidermis of the leaf contains guard cells that control, and regulate the small pores in the undersurface of the leaves. These pores are called STOMATA
GAS EXCHANGE
LEAF FUNCTIONS
PHOTOSYNTHESIS
- They are responsible for regulating water in and out of the cell.
- Responsible for the exchange of gases across the epidermis
STOMATA
LEAF FUNCTIONS
PHOTOSYNTHESIS
- The leaves are modified to store food
- These plants generally have succulent leaves as seen in xerophytic plants
STORAGE FOOD
LEAF FUNCTIONS
- The process of absorbing energy from sunlight and using it to produce food in the form of sugar
- They also generate oxygen during photosynthesis and are major contributors to the cycle of carbon and oxygen in the environment
PHOTOSYNTHESIS
LEAF FUNCTIONS
- Water movement in plant
- The water that a plant absorbs from the soil is lost by evaporation from the leaves and to a lesser extent, the stems.
- Loss of water vapor from aerial plant parts
- Occurs through open stomata
TRANSPIRATION
LEAF FUNCTIONS
- The secretion of droplets of water from the pores of plants
- Special opening at the tip of leaf veins that the root pressure would force liquid water out at night (when there is no transpiration)
HYDATHODES
LEAF FUNCTIONS
- It is the exudation of drops of xylem sap on the tips or edges of leaves of some vascular plants, such as grasses.
- Not to be confused with dew, it condenses from the atmosphere onto the plant surface.
GUTTATION
LEAF MODIFICATION
- They are larger than their counterparts in the sun
- They are thinner and have fewer well-defined mesophyll layers and fewer chloroplasts
- They also do not have as many hairs
SHADE LEAVES
LEAF MODIFICATION
- Thick, leathery leaves and fewer stomata, or stomata that are sunken below the surface in special depressions, to reduce loss of water through transpiration.
- May have succulent, water-retaining leaves or no leaves at all may have dense, hairy coverings
LEAVES OF ARID REGION
LEAF MODIFICATION
- Has less xylem than phloem, and the mesophyll, which is not differentiated into palisade and spongy layers, has large air spaces
LEAVES OF AQUATIC AREAS
LEAF MODIFICATION
- Helps the plant in climbing or supporting weak stems.
- It curls in the direction of the contact (solid support) growth is continuous
- Example: Cucurbits family
TENDRILS
LEAF MODIFICATION
TENDRILS:
- The rachis serve effectively as tendrils
CLEMATIS
LEAF MODIFICATION
- Less water loss
- Protects the plant from browsing animals
- Leaf tissue replaced with sclerenchyma
- Example: Mesquite, Black locust
SPINES
LEAF MODIFICATION
- Less water loss
- Protects the plant from browsing animals
- Pine-like objects arising in the axils of leaves
THORNS
LEAF MODIFICATION
- Less water loss
- Protects the plant from browsing animals
- Neither leaves nor stems, but are outgrowths from the epidermis or cortex
- Example: Roses and Raspberries
PRICKLES
LEAF MODIFICATION
- Succulent leaves (modified for water retention)
- Parenchyma cells with large vacuoles
STORAGE LEAVES
LEAF MODIFICATION
- DISCHIDIA is an epiphyte that grows non-parasitically on other plants develop urn like pouches that become home to ant colonies
FLOWER POT LEAVES
LEAF MODIFICATION
- Leaves buried in ground/sand
- There is mass of tightly packed, transparent water storage cells below the exposed end
- These allow light coming through the ‘windows’ to penetrate to the chloroplasts in the mesophyll, located all around the inside of the shell of the leaf
- Example: Carpetweed family
WINDOW LEAVES
LEAF MODIFICATION
- Walking fern: New plants at leaf tips
- Air plant: Tiny plantlets along leaf margins
REPRODUCTIVE LEAVES
LEAF MODIFICATION
- Specialized leaves known as Bract, are found at the bases of flowers or flower stalks
- In poinsettia (Euphorbia pulcherrima), the flowers themselves have no petals, but the brightly colored floral bracts that surround the small flowers function as petals in attracting pollinators.
FLORAL LEAVES (Bract)
LEAF MODIFICATION
INSECT TRAPPING LEAVES:
- Known as ‘Passive trap’
- It has nectar-secreting glands around the rim
- The distinctive odor produced by these glands attracts insects, which, while foraging, often fall into the watery fluid at the bottom
PITCHER PLANTS (Serracenia)
LEAF MODIFICATION
INSECT TRAPPING LEAVES:
- Mechanically/actively trap insects.
- Leaves covered with Glandular hairs and have sticky digestive enzymes
SUNDEWS (Drosera)
LEAF MODIFICATION
INSECT TRAPPING LEAVES:
- Known as ‘Active trap’
- Two halves of the blade have the appearance of being hinged along the midrib, with stiff, hairlike projections along their margins
VENUS FLYTRAP (Dionaea muscipula)
LEAF MODIFICATION
INSECT TRAPPING LEAVES:
- Found in margins of lakes and streams
- Have finely dissected leaves with tiny bladders
- When triggered, the trapdoor springs open, and water rushes into the bladder, trapping the insect inside.
BLADDERWORTS (Utricularia)
STOMA
- Have stomata on both surfaces
ALFALFA and CORN
STOMA
- Does not have stoma
- Placed on the upper surface
- Submerged leaves of aquatic plants
WATER LILY
- These are the early leaves produced
JUVENILE LEAVES
INTERNAL STRUCTURE OF LEAF
- CUTICLE
- UPPER EPIDERMIS
- LOWER EPIDERMIS
- PALISADE MESOPHYLL
- SPONGY MESOPHYLL
- XYLEM
- PHLOEM
- STOMA
INTERNAL STRUCTURE
- A layer of cells one cell thick that provides protection for the inner tissues
EPIDERMIS
How stomata open and close
- Rigid inner surface remains stiff
GUARD CELLS
- INFLATE = OPEN
- DEFLATE = CLOSE
LEAF FUNCTIONS
- Plants take simple inorganic molecules (carbon dioxide and water) and convert them to sugar
- Involves trapping and storing of energy in sugar molecules that are constructed from ordinary water and CO2 in the atmosphere
PHOTOSYNTHESIS
Carbon dioxide + Water + Heat energy = Oxygen + Glucose
PHOTOSYNTHESIS
LEAF FUNCTIONS
- Essentially the release of energy from glucose molecules that are broken down to individual carbon dioxide molecules
RESPIRATION
LEAF FUNCTIONS
Oxygen + Glucose = Carbon dioxide + Water
+ Heat energy
RESPIRATION
LEAF FUNCTIONS
- The process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers
TRANSPIRATION
LEAF FUNCTIONS
- The loss of water through hydathodes.
- Expelled water may contain ions secreted by root cells
GUTTATION
- When water is abundant:
Temporal regulation if stomata is used
1. Open during the day
2. Closed at night
STOMATAL CONTROL
- When water is limited:
1. Stomata will open less or even remain closed even on a sunny morning
2. Plant can avoid dehydration
STOMATAL CONTROL
Kataka-taka (Kalanchoe sp)
REPRODUCTION
Buoyancy (Water hyacinth)
AERATION
Tendrils (Banana, Rattan, Patola, Squash, Garden pea)
SUPPORT
Cacti, Century plant, Ficus
PROTECTION
Succulents (Aloe, Cacti), Food (Onion bulb, Lily)
STORAGE
Petaloid, brightly-variegated leaves (Dona aurora, Bougainvillea, Anthurium)
ATTRACTION
Insectivorous leaves, Aquatic plants: leaves (-) cutin (Pitcher plant, Digman)
ABSORPTION
