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