Plant Physiology

Cell division

The process by which a parent cell divides into two or more daughter cells.

Cell enlargement

The process by which a cell increases in size.

Cell differentiation

The process by which a cell changes from one cell type to another.

Shoot apical meristem

Region at the tip of a shoot responsible for the growth of stems and leaves.

Root apical meristem

Region at the tip of a root responsible for the growth of the root.

Lateral bud meristem

Meristematic tissue located at the nodes of the shoot that gives rise to branches.

Internode

The section of stem between two nodes.

Lateral root meristem

Meristematic tissue located along the length of the root that produces lateral roots.

Primary growth

Growth that results in the lengthening of plants.

Embryophytes

Land plants that have adaptations for survival on land.

Bryophytes

Nonvascular plants, commonly known as mosses.

Tracheophytes

Vascular plants, which include seed and non-seed plants.

Alternation of generations

A life cycle that alternates between diploid (sporophyte) and haploid (gametophyte) stages.

Megaspores

Spores that develop into female gametophytes.

Microspores

Spores that develop into male gametophytes.

Angiosperms

Flowering plants that produce seeds. Monocots & Eudicots. About 370 000 known species, 17 000 unknown species.

Monocotyledons

Plants with one seed leaf in the embryo.

Eudicotyledons

Plants with two seed leaves in the embryo.

Secondary growth

Growth that results in an increase in the girth of plants. Gymnosperms go through this.

Indeterminate growth

Growth that occurs continuously throughout a plant's life.

Determinate growth

Growth that ends at a certain point.

Monoecious

Plant species that have both male and female reproductive structures on a single individual.

Dioecious

Plant species that have male and female reproductive structures on separate individuals.

Conifers

A group of gymnosperms that produce cones.

Primary cell wall

The outermost layer of a plant cell that allows growth and flexibility. All plant cells have.

Secondary cell wall

A thicker cell wall found in some plants that provides additional strength. Contains lignin (provides greater strength). No further cell growth can occur once this is present.

Plasmodesmata

Microscopic channels that connect plant cells, allowing for communication and transport. Tubular structures. Intercellular movement of proteins, nucleic acid and macromolecules.

Symplast

Region of the plant body enclosed by plasma membrane (interior of plant cells). Includes plasma membrane and cytosolic connections (plasmodesmata) between adjacent cells. Movement through plasmodesmata is called ____mic transport.

Apoplast

consists of the region outside the plasma membrane (intercellular air space). Transport through the permeable cell wall space outside the cells is called _____ic transport

Parenchyma tissue

Thin primary wall and large central vacuole. Wide range of functions in the plant, depending on their location, from food storage to carrying out photosynthesis.

Collenchyma tissue

Often present in young actively growing parts of the plant requiring mechanical support. Parenchyma-like cells, often more elongated and thicker which provides mechanical support while still allowing for cell expansion in these growing parts

Sclerenchyma tissue

This tissue is found in mature plant parts and also provides mechanical support. Thick secondary cell wall. Dead at maturity. Two types of cells. Fibers (elongate cells, vascular tissue), and Sclereids (more variously shaped cells, common in seed coats).

Xylem tissue

Vascular tissue responsible for water and nutrient conduction from root to shoot. In gymnosperms → tracheid. In angiosperm → vessel elements. Both withstand extreme negative pressure (tension).

Tracheid

Elongate, hollow, dead cells in xylem. The plasma membrane, nucleus, and cytosolic contents have been lost. Has pits in their walls - movement from one cell to another

Vessel elements

Hollow dead cell at maturity. form a continuous hollow tube for efficient water conduction. Larger over evolutionary time. Lower water resistance, breaking down walls

Phloem tissue

Vascular tissue responsible for transporting the products of photosynthesis. From leaves to stems, roots, flowers, and fruits. Major conducting cells are the sieve tube elements. Cells form long tubes (sieve tubes) for conduction of substance. Contain cytosol and some organelles but lack nucleus. Movement is aided by pores in the end walls between cells.

Dermal tissue system

Outer protective layer of the plant (epidermal or corky tissue)

Vascular tissue system

Tissue system specialized for the transport of substances from one part of the plant to another (xylem and phloem). Conducting, parenchyma cells. Thick-walled fibers.

Ground tissue system

Tissue system that fills the spaces between dermal and vascular tissues. Includes pith and cortex of primary stems and roots, and the mesophyll in leaves.

Root cap

Structure that protects the root apical meristem as it grows.

Zone of cell division

Root apical meristem and the cells immediately behind it undergo rapid cell division. Can begin to see blocking out of dermal, vascular and ground tissue → mature epidermis, xylem and phloem, and the cortex and pith

Zone of cell elongation

In this zone, cells produced by the root apical meristem undergo a period of rapid growth in length

Zone of cell differentiation

Now fully expanded cells differentiate into particular cell types. Proceeding from the outside toward the middle of the root there are different parts

Epidermis

Outer layer of cells, dermal tissue system of the root. Many epidermal cells grow long extensions called root hairs. They increase the absorptive surface of the root, aiding uptake of water and minerals

Cortex

Region usually made up of thin-walled parenchyma cells often involved in the storage of food within the root

Endodermis

Single layer of cells, the cell walls of which contain suberin (called the casparian strip), which provides a barrier preventing any further movement of water or solute within the apoplast.

Sieve cells (gymnosperm), and sieve tube elements stack and create sieve tubes (angiosperms). Made in phloem cells

Stele

Central region of the root that contains vascular tissues.

Pericycle

Layer of cells that can produce lateral roots in plant roots.

Axillary buds

Meristems developed at the nodes of leaves that can form branches.

Rays of parenchyma cells

Within xylem and phloem tissues are arranged like the spokes of a tire.

Cork cambium

Layer of cells that produces cork, providing protection.

Palisade mesophyll

Layer of elongated cells in leaves where photosynthesis primarily occurs.

Spongy mesophyll

Layer of loosely packed cells in leaves that facilitates gas exchange.

Stomata

Pores in the leaf surface that allow for gas exchange.

Vacuoles

Organelles that store substances and help maintain turgor pressure in plant cells.

Chloroplast

Plant cell organelle responsible for photosynthesis.

Middle Lamella

Region “cementing” one cell wall to its neighbour. Pectin holding in place. Staple, don’t move around.

Primary plasmodesmata

forms during cytokinesis, connections between clonally related cells.

Secondary plasmodesmata

Form after cell wall deposition, requires localized digestion of existing wall between cells, allows communication between clonally unrelated cells. Cell walls are too difficult to get through. Cell really needs to locally digest cell wall

Pit fields

Depressions in the primary cell walls where numerous plasmodesmata cluster. Secondary wall does not form over these fields, leaving pits in the secondary wall.

Vacuoles

Single membrane bound (one bilayer), tonoplast membrane. Store water, inorganic ions, organic acids, sugars, enzymes, secondary metabolites (diverse functions)

Peroxisomes

Involved in photorespiration in mesophyll cells. glycolate oxidation in this pathway produces hydrogen peroxide, a reactive oxygen species (reactive, potentially damaging). High levels of catalase breaking down H₂O₂. Single membrane. Uses rubisco to react with oxygen rather than CO₂ which then uses CO₂ to make sugar (3-PGA)

Glyoxysomes

Lipid-storing seeds, enzymes for glyoxylate cycle which converts triacylglycerols to sugar during germination.

Microtubules and actin filaments

Components of the plant cytoskeleton that provide structural support and facilitate transport.

Polymerization

Building up the highway. Sheet-like positive end, curling into a tubule as the GTP is hydrolyzed.

Depolymerization

Taking down the highway. Frayed positive end, with individual protofilaments separating and curling

Specific heat capacity

Heat energy required to raise the temperature of one unit of mass by one unit of temperature

Latent heat of vaporization

Energy needed to separate molecules from the liquid phase and move to a gas phase. Occurs during transpiration. Latent heat the energy released.

Hydraulic conductivity

The ease of water movement through plant membranes.

Turgor pressure

Pressure exerted by water in the vacuole against the cell wall.

Diffusion

Net movement of particles down concentration gradient (driving force). Comes to equilibrium (no more net movement) Initial → intermediate → equilibrium. Rate of ____ (Fick’s 1st Law) = -____ coefficient (total concentration / total distance).

Osmosis

The diffusion of solvent (water) across a selectively permeable membrane (ie. a membrane where solutes can’t readily cross). The driving force is a difference in water potential. Movement across the membrane is facilitated by integral membrane proteins (aquaporins)

Flux density

rate of transport = (diffusion coefficient)(concentration gradient / distance or size)

Photosynthesis

Process by which plants convert light energy into chemical energy.

Light reactions

Phase of photosynthesis that captures energy from sunlight.

Calvin cycle

Phase of photosynthesis that synthesizes glucose from carbon dioxide.

Photosystems

Clusters of chlorophyll and proteins involved in the light reactions of photosynthesis.

Photon

A particle of light that carries energy.

Fluorescence

Emission of light by a substance that has absorbed light.

Emerson enhancement effect

The rate of photosynthesis when red and far-red light are given together is greater than the sum of their rates when given separately. More effective light use when both wavelengths were given. Two photosystems cooperate and work more efficiently.

• 700 nm and 600 nm then add = photosynthetic rate is higher than just the sum.