Palisade Parenchyma

The palisade parenchyma is the elongated, tightly packed chlorenchyma cells in the upper region of the mesophyll of the leaf.  This is where most of the trapping of light energy occurs by the chloroplasts (photosystem I).  The chloroplasts circulate around the periphery (margin) of the cell by cytoplasmic streaming, carrying the chloroplasts up near the surface of the leaf and then back down again.  This seems to increase the efficiency of photosynthesis.

                   DIAGRAM:  Hydathode

                          PHOTO:  Leaf Cross Section / Leaf Cross Section
                                           Puccinia

 

Palm-like Leaves

Palmately Compound Leaves

Palmately compound leaves are compound leaves where the leaflets are all attached to the petiole at one point.  The leaflets of a pinnately compound leaf radiadiate out from that point like your fingers do from your hand.  This is how the palmately compound leaf got its name.

                    DIAGRAM:  Types of Leaves

                          PHOTO:

Palmately Lobed Leaves

                    DIAGRAM:  Pinnate/Palmately Lobed Leaves

                          PHOTO:  

 

Palmately Netted/Veined Leaves

Palmately netted leaves are leaves that have several main veins originating from the petiole. Each of the main veins will have secondary veins branching off.

                    DIAGRAM:  Leaf Veination

                          PHOTO:  

Pansies

Parallel

(anthoceros)

Parallel Veins

Parallel veined leaves have all the leaf veins running parallel to each other and lengthwise in the leaf.  The secondary veins that branch off these main veins are very small and difficult to see with the naked eye.  If you tear a parallel-veined leaf from apex to base, it will tear smooth, following a line between two parallel veins.  Corn leaves are good examples of parallel-veined leaves.

                    DIAGRAM:  Monocot Leaf

                          PHOTO:  

Paraphysis

                    DIAGRAM:  

                          PHOTO:  Fucus / Fucus / Fucus / Fucus / Fucus

                                           Mosses / Mosses

Parasitism

Parchment-like

Parenchyma

Parenchyma are isodiametric cells that are thin-walled and not extremely specialized.  It is found in the cortex, pith and pith ray of the dicot stem and in the ground parenchyma of the monocot stem.  It is the main lateral transport cell in the xylem and phloem.

                    DIAGRAM:  Stem Tangential Section
                                           Tissue Types
                                           Monocot Vascular Bundle
                                           Hydathode

                          PHOTO:  Pinus Stem Radial Section
                                           Monocot Vascular Bundle Cross Section
                                           Leaf Cross Section

Partition

(silique)

Passive Transport

Pathogenic

Pea Family

Peaches

Peanuts

Pears

Peas

Peat Bog

Pectin

Peduncle

                    DIAGRAM:  

                          PHOTO:  Narcissus / Narcissus / Narcissus / Narcissus
                                           Composite Flower / Composite Flower

Peltate

A peltate leave is a leaf with the petiole attached to the center of the leaf in the middle of the lamina.  A leaf that is not peltate has the petiole attached to the base of the leaf.

Pendulous

Penetrate

(light in ocean)

Pennales

Pepo

Peppermint

Peregrine Falcon

Perennial

                    DIAGRAM:  Growth Cycles

                          PHOTO:  

Perfect Flower

Perianth

                    DIAGRAM:  

                          PHOTO:  Narcissus / Narcissus / Narcissus

Pericarp

                    DIAGRAM:  Acorn

                          PHOTO:  Wheat Seed Longitudinal Section

Pericycle

                    DIAGRAM: Root Anatomy

                          PHOTO: Root Cross Section
                                          Fern Rhizome Cross Section

Periderm

Periderm cells are cork cells in the stems of dicots.  The periderm is produced by the phellogen (cork cambium) toward the outside of the stem.  The periderm contains suberin, a waxy substance, that seals the stem against water loss and invasion by insects, and infection by bacteria and fungal spores.  There are typically 4-6 layer of periderm cells.

                    DIAGRAM:  Growth of Woody Stem

                          PHOTO:  

Perigynous

Perigynous ovaries have the flower parts (calyx, corolla, and androecium) attached to a hypanthium.  The hypanthium is found only in dicots and is a fusion of the calyx, corolla, and androecium whorls forming a small cup-shaped structure that surrounds the ovary.  The base of the hypanthium is typically attached to the receptacle as is the case with the members of the rose family (Rosaceae) and is therefore said to by hypogynous.  The hypanthium can also be epigynous, that is, attached to the top of the ovary, as is the case with the fuschia flower.

                    DIAGRAM:  Ovary Position

                          PHOTO:  

Periphery

Peristome Teeth

                    DIAGRAM:  

                          PHOTO:  Moss Capsule Cross Section

Permafrost

Permanent

Permeation

Persistent

(leaf bases)

Petals

Petiole

The petiole is the stalk upon which the leaf stands.  It is a stem-like structure that goes between the lamina and the stem.

pH

Phelloderm

The phelloderm is a single layer of cork cells to the inside of the phellogen (cork cambium). Phelloderm contains suberin, a waxy material that seals the stem against loss of water, invasion by insects, and infection by bacteria and fungal spores.

                    DIAGRAM:  

                          PHOTO:  Six-year Tilia Stem Cross Section

Phellogen

Phellogen is the cork cambium.  It generates 5-6 layers of periderm towards the outside of the stem and one layer of phelloderm toward the inside of the stem.  In the young stem the phellogen originates in the cortex. Because phellogen doesn't remain for the life of the tree, it dies after one to several years.  Thus, subsequent phellogens will from in the outer region of the living phloem.

                    DIAGRAM:  Growth of Woody Stem

                          PHOTO:  Six-year Tilia Stem Cross Section

Phloem

Phloem is a tissue that contain the vascular cells that carries photosynthetic products throughout the plant.  The conduction cells in the phloem are the sieve-tube members.

                    DIAGRAM:  Stem Sections
                                           Growth of Woody Stem

                                           Root Anatomy
                                           Vascular Cylinder

                          PHOTO:  One-Year Tilia Stem Cross Section
                                           Three-Year Tilia Stem Cross Section
                                           Three-year Tilia Stem Cross Section
                                           Three-year Tilia Stem Cross Section
                                           Six-year Tilia Stem Cross Section

                                           Leaf Cross Section

                                           Root Cross Section
                                           Root Cross Section
                                           Root Cross Section
                                           Root Cross Section
                                           Root Cross Section

                                           Psilotum Stem Cross Section
                                           Psilotum Stem Cross Section

                                           Equisetum Stem Cross Section
                                           Equisetum Rhizome Cross Section

                                           Fern Rhizome Cross Section
                                           Fern Rhizome Cross Section

Phloem Ray

                    DIAGRAM:  Stem Sections

                          PHOTO:  Three-year Tilia Stem Cross Section

Phloem Sap

(phloem transport)

Phosphorus

Photoperiodism

Photoreceptor

Photosynthesis

Photosynthesis is the process whereby light energy from the sun is trapped in the chloroplast of the plant.  This trapped energy is used to combine the carbon molecules from carbon dioxide into sugar molecules, the fuel that all cells use for energy.

Photosynthetic Lamellae

Phototropism

Phycocyanin

Phycoerythrin

Phyllaries

                    DIAGRAM:  

                          PHOTO:  Composite Flower / Composite Flower

Phyllotaxy

Physical Force

(water potential)

Physical Weathering

Physiological

Physiological Age

Phytochrome

Phytoplankton

Pigments

Pigweed

Pileus

                    DIAGRAM:  

                          PHOTO:  Coprinus / Coprinus

Pines

Pines are in the genus Pinus, the family Pinaceae, and the Division Coniferophyta.  Pines are characterized by needle-like leaves in bundles of 1-5 needles each depending upon the species of pine.  In addition, the cones are woody, and are pendulous on the tree.

Pinnae

                    DIAGRAM:  Fern Frond

                          PHOTO:  

Pinnately Compound Leaves

Pinnately compound leaves are leaves that have a rachis attached to the petiole and the leaflets are attached to the rachis.

Pinnately compound leaves may be once, twice, or three-times pinnate.  The once pinnate leaf is where the leaflets are attached to the rachis.  Twice pinnately compound leaves are leaves that have secondary rachises that are perpendicular to the rachis and the leaflets are attached to the secondary rachises.  A three-times pinnate leaf will have a single rachis with a secondary rachises perpendicular to the rachis and tertiary rachises perpendicular to the secondary rachises with the leaflets attached to the tertiary rachises.

                    DIAGRAM:  Types of Leaves

                          PHOTO:  

Pinnately Lobed Leaves

                    DIAGRAM:  Pinnately/Palmately Lobed Leaves

                          PHOTO:  

Pinnately Netted

Pinnately netted leaves are dicot leaves where there is a single primary midvein with secondary veins branching off the midvein.  Pinnately netted veins can be  contrasted with palmately netted veins where there are several primary veins originating from the petiole. There are secondary veins that branch off these primary veins.

                    DIAGRAM:  Leaf Veination

                          PHOTO:  

Pinyon Nut

Pioneer Community

Pistil

Pistillate Flower

Pith

The pith is the parenchyma cells in the center of the primary dicot stem.

                    DIAGRAM:  Growth of Woody Stem

                          PHOTO:  One-year Tilia Stem
                                           Three-year Tilia Stem
                                           Three-year Tilia Stem
                                           Six-Year Tilia Stem

Pith Ray

Pith rays are the parenchyma cells between the vascular bundles in the primary dicot stem.

                    DIAGRAM:  Growth of Woody Stem

                          PHOTO:  One-year Tilia Stem
                                           Three-year Tilia Stem
                                           Three-year Tilia Stem
                                           Six-Year Tilia Stem

Pit Membrane

The pit membrane is the two primary cell walls and the middle lamella between the pit pair.

                    DIAGRAM:  Pits

                          PHOTO:  

Pit Pairs

Pit pairs are adjacent pits in adjacent pits on either side of the two adjacent cell walls.

                    DIAGRAM:  Pit Pairs

                          PHOTO:  

Pits

Pits are spots on the vascular cells in plant cells that contain no secondary cell wall which aids in the passage of water through the cells walls.  The pit membrane being impermeable to cavitation bubbles helps to localize cavitation during water stress in the plant.

                    DIAGRAM:  Pits
                                           Sclerenchyma

                          PHOTO:  

Placenta

                    DIAGRAM:  

                          PHOTO:  Cross Section of Ovary
                                           Cross Section of Ovary
                                           Narcissus / Narcissus

Plantae

Plantain

Plasmodesmata

Plasmodesmata are holes through the cell wall of adjacent plant cells though which the endoplasmic reticula pass.  This allows quick chemical communication between cells.

Plasmodesmata is the singular and plasmodesmata is the plural form of the word.

Plasmalemma

The plasmalemma is the name for the cell membrane in plants.  It is the membrane that contains the contents of the cell.  The primary and secondary cell walls are laid down by the cell outside the plasmalemma.

Plastids

Plastids are colorless structures in the plant cells that contain various products.  Chloroplastids contain chlorophyll and are responsible for photosynthesis in plant cells.

Plumes

Plumule

The plumule is a cluster of embryonic leaves at the tip of the embryonic shoot in the seed. This structure will become the first leaves to begin photosynthesis and turn green when the shoot tip reaches the sun.

                    DIAGRAM:  Cotyledons
                                           Acorn

                          PHOTO:  

Poaceae

Pod

Poinsettias

Polar Cell

Polar Nucleus

Polar

Polarity

Poles

(distribution)

Polished White Rice

Pollen

                    DIAGRAM:  

                          PHOTO:  Pollen Grains Whole Mount

Pollen Sac

Pollen Tubes

Pollinator

                    DIAGRAM:  Pollinators

                          PHOTO:  

Polyarch

Polymer

Polynomial

Polypodiaceae

                    DIAGRAM:  Fern Frond

                          PHOTO:  

Polysaccharides

Polysomes

                    DIAGRAM:  Ribosomes

                          PHOTO:  

Pome

Poppy

Populations

Pore

The pore is the opening in something.  In the stoma it is the opening that is bordered by the guard cells.  In the bordered pit, it is the opening in the border that lets the water through.

                    DIAGRAM:  Hydathode

                          PHOTO:  

Positive Regions

Positive Charge

Potassium

P-protein

P-protein is phloem protein.  It a spider web of protein strands in the sieve-tube member that will tear lose and pile up against the sieve plate when there is damage to the stem and pressure is suddenly lost in the sieve-tube.  It is a defense mechanism similar to the clotting of blood to prevent the loss of food products in the phloem tissue.

Prairie Dogs

Precipitation

Predators

Pressure

Pressure Potential

Primary Endosperm Nucleus

Primary Zoospore

Primary Tissues

The fully differentiated and mature cells originating from the primary meristem tissues are the primary tissues.  Primary tissues generally occur in the stem immediately below the apical meristem where all the cells have differentiated but where secondary growth has not yet begun to occur.  In the root, it is at the top end of the root hair zone.  The primary tissues may be thought of  as the end differentiation of the cells from the apical meristem before secondary growth begins.

Primary root

Primary Consumers

Primary Succession

Primary Growth

Primary growth is growth in length of the stem as a result of the activity of the apical meristem contained within the terminal bud.  Primary growth produces herbaceous stems only.

                    DIAGRAM:  Growth of Woody Stem

                          PHOTO:  

Primary Cell Wall

The primary cell wall is composed of cellulose and is the first, rather thin, cell wall that is laid down by the plant cell just after it divides.

                    DIAGRAM:  Pits

                          PHOTO:  

Primary Meristem Tissues

The primary meristem tissues are differentiated from the apical meristem.  The primary meristem tissues include three different tissues:  protoderm, ground meristem, and procambium.  The protoderm differentiates into the epidermis; the ground meristem differentiates into the cortex, pith ray, and pith; and  the procambium differentiates into the vascular tissue.  

Primary Tissues

Primary tissues are fully differentiated and mature tissues that result from primary growth. Their ultimate origin can be traced from the apical meristem to the primary meristem tissues to the primary tissues.  These tissues are fully functional when differentiated.  Some of the cells in the cortex (those between the vascular bundles in the pith ray region) will de-differentiate to become the interfascicular cambium portion of the vascular cambium.

Primordia

Primordia are structures that are formed on the flanks (outer margin) of the apical meristem. Typical primordial structures are leaf primordia, flower buds, and lateral buds.

Procambial Strands

The procambial strands are the strands of procambium that are embedded in the ground meristem in both the monocot and dicot stems.  These procambial strands will differentiate into vascular bundles of xylem and phloem in both monocots and dicots.

Procambium

The procambium is one of the primary meristem tissues that is differentiated form the apical meristem.  The procambium differentiates into the vascular bundle and vascular tissues.

Prochloron

Producers

Productivity

(energy production in ecosystem)

Proembryo

Profundal Zone

Prokaryota

Prokaryote Flagella

Proliferates

Promotion

Propagation

Protein Synthesis

Protein

Prothallus

Protists

The protists are a group of organisms that belong to the Kingdom Protista.  These include all the single-celled organisms that may cluster together into colonies, or filaments, or remain single cells. The algae, amoeba, paramecium, euglena, etc. belong to this group.

Protoderm

The protoderm is one of the primary meristem tissues that is differentiated from the apical meristem.  The protoderm differentiates into the epidermis.

Proton

Proton Pump

Protonema

                    DIAGRAM:  

                          PHOTO:  Mosses / Mosses

Protoplasm

The protoplasm is the entire contents of the cell inside the plasmalemma (cell membrane).

Protoplasmic Extension

In some cells, such as the epidermis of roots, the cell pushes out a long filament or hair-like structure.  This hair-like structure is all part of the original cell and the protoplasm of the cell extends out into the hair.  In fact, the nucleus of the epidermal cells is at the tip of the hair-like structure, causing it to elongate.

Protoplast

Protoxylem

                    DIAGRAM:  Vascular Cylinder

                          PHOTO:  Root Cross Section / Root Cross Section

Protoxylem Poles

                    DIAGRAM:  Root Anatomy

                          PHOTO:  Root Cross Section / Root Cross Section 

Protozoans

Pseudotsuga

Psilotum

                    DIAGRAM:  Psilotum

                          PHOTO:  Psilotum Stem Cross Section
                                           Psilotum Stem Cross Section
                                           Psilotum Sporangium

Ptarmigan

Pterophyta

                    DIAGRAM:  Pterophyta/Ophioglossales
                                           Pterophyta/Salvineales
                                           Pterophyta/Marsileales

                          PHOTO:  

Puccinia

                    DIAGRAM:  

                          PHOTO:  Puccinia / Puccinia / Puccinia / Puccinia / Puccinia
                                           Puccinia / Puccinia / Puccinia / Puccinia / Puccinia
                                           Puccinia / Puccinia / Puccinia

Puma

Pumpkin

Pure Water

Purslane

Pustules

                    DIAGRAM:  

                          PHOTO:  Puccinia / Puccinia

Pycnia

                    DIAGRAM:  

                          PHOTO:  Puccinia / Puccinia / Puccinia / Puccinia

Pyramid of energy

Pyramid of Numbers

Pyramid of Biomass

Pyrenoids