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Leaves (Morphology and anatomy of other leaf type (Sclerophyllous foliage…
Leaves
External structure of foliage leaves
Lamina (Leaf blade)
Dorsal surface
Ventral surface
Leaf apex
Helps in photosynthesis and gas exchange
Terminal part of leaf
Midrib veins
Lateral veins emerge that branch to narrow minor veins
Minor vein release water from xylem and sugar into phloem
Helps to keep leaf in upright position
Margin
Smooth
No teeth nor lobes
Toothed
Saw like margin with small tooth
Lobed
Indentation towards midrib, go less than halfway to midrib
Parted
Indentation towards midrib, go more than halfway to midrib
Internal structure of foliage leaves
Mesophyll
Palisade parenchyma
Main photosynthetic tissue, upper portion of leaf
Separated cells, more intracellular spaces
Spongy parenchyma
Lower portion of cell
Loose Aerenchyma, Diffuse CO2 into leaves interior
Vascular tissue
Lateral veins
Involve mostly in conduction
Minor veins
Release water from xylem
Load sugar into pholem
Epidermis
Cutin and wax on outer walls
Water loss called Transpiration
Outermost layer
Petiole
Transition between stem and lamina
Usually tiny but larger in plants like palm, celery and water lilies.
Initiation and development of leaves
Basal Angiosperms and Eudicots
Produced through apical meristem
Primordium increases its thickness to become midrib
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Protoderm grow outward to form leaf primordium
Monocots
Initiated by expansion of shoot apical meristem
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Lamina grows by meristem, where it attaches to the top of sheathing leaf base
Morphology and anatomy of other leaf type
Sclerophyllous foliage leaves
Leaves must produce more sugar by photosynthesis
Leaves are tough and hard
Examples- Barberry, Holly, Agave
Plant invest more glucose to make secondary walls of sclerenchyma cells
Leaves of conifers
Have thick cuticle, epidermis and hypodermis cells have thick walls
Contains unpalatable chemical
Leaves are sclereophylls
Examples-Larches, Bald cypress, Dawn Redwood
Bud scales
Its role is primary protection not photosynthesis
Leaves are tougher and waxier, produce thin layer of corky barks
Form tight layer to protect from low temperatures and drying
spines
Deposition of lignin in their walls makes them hard
Protects the plants from herbivorous
Spines are modified leaves of axillary buds
Example- Araucaria araucana
Succulent leaves
Thick and fleshy leaves to retain water in arid climate
They can store water for long period of time, grows in high temperatures
Examples:- Jade plants,Echeveria elegans
Kranz Anatomy
Lack palisade parenchyma and spongy mesophyll but have prominent bundle
Leaves of plants with C4 photosynthesis
Insect traps
Has the ability to trap and digest insect
Grows in habitats poor in nitrates and ammonia
Examples-: Nepenthes, Darlingtonia, Sarracenia, Sundew
Tendrils
Modification of leaves to spiral structure
Have sense to of contact, and use it for support
Examples:- Peas, cucumbers, squash
Photosynthesis without leaves
Occurs in
Bark
Occurs exclusively in desert- adapted trees
Example- Palo Verde
Stem cortex
Young stem have chlorophyll and can undergo photosynthesis
Stem- succulent plants, produce large, thin ordinary leaves
Reduce the distance of diffusion of gases between the atmosphere and innermost leaf cells.
