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Leaves (Morphology: large scale features (Arrangement of leaves on the…
Leaves
Morphology: large scale features
Basic leaf types
Angiosperm: flowering leaves
Lycophytes: have microphyll leaves
Conifers: needle shaped or scale-like
Sheath: found in grasses
Ferns: have fronds
Other specialized leaves like Nepenthes
Arrangement of leaves on the stem
Cauline: leaf arises from arial stem
Rosulate: leaves from a rosette
Opposite: leaf attachment are paired at a node but opposing each other
Rows: leaves are arranged in a certain number of rows
Alternate: the leaves alternate directions
Verticillate: three of more leaves attached at a node
Basal: leaf arises from the base of the stem
Types of petiole
Phyllodes: petioles are expanded and broadened and function like leaf blades
Clasping: the blade partially surrounds the stem
Super petiolate: leaves are nearly petiolate and have extremely short petiole and may appear to be sessile
Perfoliate: leaves completely surround the stem
Stipule: leaves of many dicotyledons
Sessile leaves: have no petioles
Petiolate leaves: have petioles (leaf stalk)
Veins
Venation
Parallel: monocots have this kind of venation
Reticulate (net-like): eudicots have this type of venation
Levels of veins
Primary vein: vein entering the leaf
Secondary vein: vein branching from the primary vein
Lower order veins
Vascular structure of the organ
provides mechanical support
transport of water and nutrients between leaf and stem
Divisions of the blade
Simple leaf: has undivided blade
Compound lead
Pinnately compound: leaflets arranged along the main or mid-vein
Odd pinnate: with terminal leaflet
Even pinnate: lacking a terminal leaflet
Bipinnately compound: leaves are twice divided
Palmately compound: leaflets radiating from the end of the petiole
Trifoliate: a pinnate leaf with just three leaflets
Pinnatifid: pinnately dissected to the central vein but the leaflets not completely separated
Anatomy
Leaf development
Compound leaves are closer to shoot than simple leaves
Leaves are partial shoots being derived from primordia of shoot complex
Major Leaf Tissue
Mesophyll tissues: Parenchyma and chlorenchyma cells between lower and upper epodermis
most ferns and flowering plants mesophyll has two layers
Palisade layer
many chloroplasts than spongy layer
has intercellular spaces
lies beneath adaxial epidermis
Spongy layer
cells are not tightly packed
fewer chloroplasts than palisade layer
Epidermis
Functions
protection against water loss
regulation of gaseous exchange
Types of cells in epidermis
Epidermal hair cell (trichomes)
cells in stomatal complex
Guard cells
Subsidiary cells
Epidermal cell
Vascular tissue
Xylem: cells that bring water and minerals from the root to the leaf
Phloem: cells that move sap produced by photosynthesis in the leaf out of the cell
