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Leaves (Morphology and Anatomy of Other Leaf Types (Leaves with Kranz…
Leaves
Morphology and Anatomy of Other Leaf Types
Leaves of Conifers
Simple
Leaves are mostly perennial, remaining on the stem for many years
Succulent Leaves
Permits plants to survive in desert habitats
Lack of air spaces, leading to little evaporation (water loss) through stomata
Schlerophyllous Foliage Leaves
Produces more sugars by photosynthesis than used in construction of leaves
Plant makes schlerophyllous leaves because of hardness
Bud Scales
Most common modification of leaves
In perennial plants dormant shoot apical meristems are protected from low temperatures by bud scales
Small and rarely compound
primarily protection
Spines
Cacti have two types of leaves
The green body has microscopic green leaves and the cluster of spines are their axillary buds
Cactus spines are modified leaves of axillary buds
Tendrils
Another modified leaf in many plants
Cucumbers
Squash
Peas
Leaves with Kranz Anatomy
C4 photosynthesis
Lack palisade parenchyma and spongy mesophyll
Have prominent bundle sheaths composed of large chlorophyllous cells
Insect Traps
Has evolved in several families
In plants with habitats poor of nitrates and ammonia
External Structures of Foliage Leaves
Leaf Blade
Flat, light-harvesting portion of photosynthesis
Lamina
Dorsal Surface
Leaf blades lower side
Large, veins protrude like backbones
Ventral Surface
Upper side of the leaf blade
Usually smooth
Petiole
Stalk
Holds the blade out into the light
Leaf traces
Sessile leaf
Self-shading sometimes with no petiole
Abscission Zone
Perpendicular to the petiole
Its cells are involved in cutting off the leaf when its useful life is over
Internal Structures of Foliage Leaves
Veins
Bundles of vascular tissue
Distribute water from the stem
Collect sugars produced by photosynthesis and carry them for use or storage elsewhere
In angiosperm and eudicots they occur in netted patterns
Reticulate Venation
Epidermis
Water lost through the epidermis is known as traspiration
Must allow entry of carbon dioxide
Mesophyll
The ground tissues interior to the leaf epidermis
Palisade Parenchyma
Main photosynthetic tissue of most plants
In the lower portion of the leaf is the spongy mesophyll
Open, loose aerenchyma that permits carbon dioxide to diffuse rapidly away from stomata into all parts of leaf interior
Vascular Tissue
Midrib
Usually in eudicots
Lateral veins emerge
Branch into minor veins
Bundle sheath
Many fibers arranged as a sheath
Compound leaf
Divided into several parts
Has many small blades called leaflets
Each attached by petiolule to a rachis
Initiation and Development of Leaves
Basal Angiosperms and Eudicots
Leaf Primordium
Protrusion forming from protoderm
Monocots
Are initiated by the expansion of some shoot apical meristemce cells to form a leaf primordium
Simple leaf
Just one part
