Vascular Plants with SeedsC9L3P5Leaves

External Structures of LeavesBlade: the flat portion of a leafPetiole: the stalk of a leaf; attaches leaf to stemMargin: the edge of a leafs bladeVeins: the pipelines that carry food & waterNode: place on stem where leaves are attachedMargin

Stipule: a small leaf like or scale like structure on a plant that helps to cover a leaf while it is developingExternal Structures of Leaves

Leaf VenationTwo basic patterns of leaf venation: Parallel Venation Netted Venation

Parallel VenationA series of veins which originate at the stem and proceeds to the tip of the leafOccurs in monocots corn, grass, irises, orchids

Netted VenationPalmate: two or more main veins coming from a single pointExamples: maple, ivy, geraniumsPinnate: if the veins branch off one large central vein called a midribExamples: oaks, apple trees, African violets

Classification of LeavesSimple leavesCompound leaves

Simple or Compound?Simple Leaves: one blade on each petiole

Simple or Compound?Compound: more than one blade on each petioleEach small blade on a compound leaf is referred to as a leaflet

Sessile LeavesSessile leaves lack petioles

Sessile LeavesGrasses and certain other monocots have sessile leaves that attach to the stem by way of a sheath that seems to wrap around the stem

Leaf MosaicAlternateOppositeWhoredLeaf mosaic: the arrangement of leaves on a stem

Leaf MosaicAlternate Mosaic: leaves alternate from opposite sides of the stem (one petiole per node)

Leaf MosaicOpposite Mosaic: two leaves grow from the same point on the stem (two petioles per node)

Leaf MosaicWhorled Mosaic: three or more leaves grow from a single point on a stem (3 or more petioles per node)

Leaf Mosaic

Leaf ShapesLinearCordateDeltoidLobedCircular

Linear Leaf Shapelong and narrow

Lobed Leaf Shape

Cordate Leaf Shapekidney or heart-shaped

Deltoid Leaf Shapedeltoid-shaped

Circular Leaf Shape

Leaf MarginsEntireSerrateUndulateDentate

Entire Leaf Marginsmooth margin with no teeth

Serrate Leaf Margintoothed margins

Undulate Leaf Marginwavy margins

Dentate Leaf Marginteeth point out

The internal structures of leaves.

Most leaves are the major site of photosynthesis for the plant. The top and bottom layers of a leaf are made of epidermal tissue.Leaves

The Covering of a LeafThe Epidermis

The Epidermis the top and bottom layer one cell layer in thickness lacks chlorophyll serves as protection often secrets a waxy substance that forms a cuticle usually transparent

The CuticleCuticleEpidermiswaxy substance made by some epidermal cells for protection

The Lower Epidermis tiny openings called stomata (stoma, sing.)(or leaf pores) permit the exchange of gases between atmosphere and spaces in leaf main purpose - to allow air to move in and out of the leaves

Most leaves have a small opening in the epidermis called stomata.Dr. Gerald Van Dyke/Visuals Unlimited/Getty Images

When the stomata open, carbon dioxide, oxygen, and water vapor can pass through them.StomataDr. Gerald Van Dyke/Visuals Unlimited/Getty Images

The Lower Epidermis may be very abundant (apple tree leaf - 47,000 stomata per square inch; oak tree 100,000) guard cells - two crescent-shaped cells around each stomata; open and close the stomata

The Lower EpidermisGuard CellsStoma

The Lower EpidermisStomata & Guard CellsGuard CellsStomata

The Lower EpidermisStomata & Guard Cells

The Lower EpidermisGuard CellsGuard Cells

Stomata & Guard Cells

Internal Leaf StructuresBetween the upper and lower epidermis is the mesophyll.It is in the mesophyll where most of the photosynthesis takes place.It is structural tissue called parenchyma.Mesophyll is divided into two layers:Palisade MesophyllSpongy Mesophyll

Internal Leaf Structures

Below the upper epidermis are rows of tightly packed cells called palisade mesophyll cells where photosynthesis mainly occurs.Palisade Mesophyll

Palisade Mesophyll located toward the upper side of the leaf consists of elongated, column like cells there may be several layers abundance of chloroplasts move in a circle

Spongy Mesophyll located toward the lower side of the leaf sometimes sandwiched in the middle consists of large, irregularly shaped cells separated by large air spaces form a system of passages throughout the leaf that permits air to come in contact with the individual cells

Veins (Fibrovascular Bundles) run through the mesophyll contain the vascular tissue xylem and phloem contain thick-walled strengthening collenchyma tissue

Scanning Electron Microscopic Picture of a Freeze-Dried Cross-Section Through a Bean Leaf E: Upper and lower epidermis, Sz: Guard cell, P: Cells of the palisade parenchyma, S: Cells of the spongy parenchyma, I: Intercellular space.

Cross Section of a Leaf

Cross Section of a Leaf

Cross Section of a Leaf

Cross Section of a Leaf

Cross Section of a Leaf

Cross Section of a Leaf

Cross Section of a Leaf

GAS EXCHANGE IN PLANTS(1) The cycle of oxygen and carbon dioxide takes place in green parts of plantsO2 from photosynthesisCO2 from cellular respiration(2) stomata takes place in leaves

GAS EXCHANGE IN PLANTS(3) lenticels takes place in the woody parts of plantslenticels: small openings in the woody parts of plants

GAS EXCHANGE IN PLANTSepidermis takes place in underground parts; gases exchanged through the thin coverings; helped by burrowing of worms, insects, and other organisms (helps bring air; helps soil to drain)

GAS EXCHANGE IN PLANTSPlants with roots always in H2O and sometimes leaves - special networks of air tubes in fibrovascular bundles

What Plants Do With Glucose (the sugar they make)? glucose - contains in a stored form the energy captured from the sunCells that carry on photosynthesis make more sugar than they need and they pass glucose along to other plant parts through the phloem.

What Plants Do With Glucose (the sugar they make)? Some glucose molecules are not used for energy but are hooked together to make cellulose.Some glucose molecules are stored as starch (potatoes, wheat, bananas, corn) and some convert the glucose to lipids (corn oil, peanut oil, olive oil).

Leaves

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